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Wenyuan Yin,
Samarpan Majumder,
Terry Clayton,
Steven Petrou,
Michael L VanLinn,
Ojas A Namjoshi,
Chunrong Ma,
Brett A Cromer,
Bryan L Roth,
Donna M Platt,
James M Cook
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ABSTRACT: A series of 3,6-disubstituted β-carbolines was synthesized and evaluated for their in vitro affinities at α(x)β(3)γ(2) GABA(A)/benzodiazepine receptor subtypes by radioligand binding assays in search of α(1) subtype selective ligands to treat alcohol abuse. Analogues of β-carboline-3-carboxylate-t-butyl ester (βCCt, 1) were synthesized via a CDI-mediated process and the related 6-substituted β-carboline-3-carboxylates 6 including WYS8 (7) were synthesized via a Sonogashira or Stille coupling processes from 6-iodo-βCCt (5). The bivalent ligands of βCCt (32 and 33) were also designed and prepared via a palladium-catalyzed homocoupling process to expand the structure-activity relationships (SAR) to larger ligands. Based on the pharmacophore/receptor model, a preliminary SAR study on 34 analogues illustrated that large substituents at position-6 of the β-carbolines were well tolerated. As expected, these groups are proposed to project into the extracellular domain (L(Di) region) of GABA(A)/Bz receptors (see 32 and 33). Moreover, substituents located at position-3 of the β-carboline nucleus exhibited a conserved stereo interaction in lipophilic pocket L(1), while N(2) presumably underwent a hydrogen bonding interaction with H(1). Three novel β-carboline ligands (βCCt, 3PBC and WYS8), which preferentially bound to α1 BzR subtypes permitted a comparison of the pharmacological efficacies with a range of classical BzR antagonists (flumazenil, ZK93426) from several different structural groups and indicated these β-carbolines were 'near GABA neutral antagonists'. Based on the SAR, the most potent (in vitro) α(1) selective ligand was the 6-substituted acetylenyl βCCt (WYS8, 7). Earlier both βCCt and 3PBC had been shown to reduce alcohol self-administration in alcohol preferring (P) and high alcohol drinking (HAD) rats but had little or no effect on sucrose self-administration.(1-3) Moreover, these two β-carbolines were orally active, and in addition, were anxiolytic in P rats but were only weakly anxiolytic in rodents. These data prompted the synthesis of the β-carbolines presented here.
Bioorganic & medicinal chemistry 09/2010; 18(21):7548-64. · 2.82 Impact Factor
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ABSTRACT: The first stereospecific synthesis of polyneuridine aldehyde (6), 16-epivellosimine (7), (+)-polyneuridine (8), and (+)-macusine A (9) has been accomplished from commercially available d-(+)-tryptophan methyl ester. d-(+)-Tryptophan has served here both as the chiral auxiliary and the starting material for the synthesis of the common intermediate, (+)-vellosimine (13). This alkaloid was available in enantiospecific fashion in seven reaction vessels in 27% overall yield from d-(+)-trytophan methyl ester (14) via a combination of the asymmetric Pictet-Spengler reaction, Dieckmann cyclization, and a stereocontrolled intramolecular enolate-driven palladium-mediated cross-coupling reaction. A new process for this stereocontrolled intramolecular cross-coupling has been developed via a copper-mediated process. The initial results of this investigation indicated that an enolate-driven palladium-mediated cross-coupling reaction can be accomplished by a copper-mediated process which is less expensive and much easier to work up. An enantiospecific total synthesis of (+)-polyneuridine aldehyde (6), which has been proposed as an important biogenetic intermediate in the biosynthesis of quebrachidine (2), was then accomplished in an overall yield of 14.1% in 13 reaction vessels from d-(+)-tryptophan methyl ester (14). Aldehyde 13 was protected as the N(a)-Boc aldehyde 32 and then converted into the prochiral C(16)-quaternary diol 12 via the practical Tollens' reaction and deprotection. The DDQ-mediated oxidative cyclization and TFA/Et(3)SiH reductive cleavage served as protection/deprotection steps to provide a versatile entry into the three alkaloids polyneuridine aldehyde (6), polyneuridine (8), and macusine A (9) from the quarternary diol 12. The oxidation of the 16-hydroxymethyl group present in the axial position was achieved with the Corey-Kim reagent to provide the desired beta-axial aldehydes, polyneuridine aldehyde (6), and 16-epivellosimine (7) with 100% diastereoselectivity.
The Journal of Organic Chemistry 04/2010; 75(10):3339-49. · 4.45 Impact Factor
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ABSTRACT: Herein, the full details of the synthesis of the 9-methoxy-substituted Corynanthe indole alkaloids mitragynine (1), 9-methoxygeissoschizol (3), and 9-methoxy-N(b)-methylgeissoschizol (4) are described. Initially, an efficient synthetic route to the optically active 4-methoxytryptophan ethyl ester 20 on a multigram scale was developed via a Mori-Ban-Hegedus indole synthesis. The ethyl ester of D-4-methoxytryptophan 20 was obtained with a radical-mediated regioselective bromination of indoline 12 serving as a key step. Alternatively, the key 4-methoxytryptophan intermediate 22 could be synthesized by the Larock heteroannulation of aryl iodide 10b with the internal alkyne 21a. The use of the Boc-protected aniline 10b was crucial to the success of this heteroannulation. The alpha,beta-unsaturated ester 6 was synthesized via the Pictet-Spengler reaction as the pivotal step. This was followed by a Ni(COD)(2)-mediated cyclization to set up the stereocenter at C-15. The benzyloxy group in 31 was removed to provide the intermediate ester 5. This chiral tetracyclic ester 5 was employed to accomplish the first total synthesis of 9-methoxygeissoschizol (3) and 9-methoxy-N(b)-methylgeissoschizol (4) as well as the opioid agonistic indole alkaloid mitragynine (1).
The Journal of Organic Chemistry 01/2009; 74(1):264-73. · 4.45 Impact Factor
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ABSTRACT: An enantiospecific method for the synthesis of 4-methoxytryptophan has been developed via a regiospecific Larock heteroannulation and employed for the first total syntheses of 9-methoxygeissoschizol and 9-methoxy-Nb-methylgeissoschizol, as well as the total synthesis of the opioid agonistic alkaloid mitragynine. The asymmetric Pictet-Spengler reaction and a Ni(COD)2-mediated cyclization served as key steps.
Organic Letters 09/2007; 9(18):3491-4. · 5.86 Impact Factor
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ABSTRACT: The first enantiospecific total synthesis of the alkaloids 16-epi-vellosimine (1), (+)-polyneuridine (2), (+)-polyneuridine aldehyde (3), and macusine A (4) is reported. The key oxidation was accomplished with the Corey-Kim reagent to provide the important biogenetic intermediates, 16-epi-vellosimine (1) and polyneuridine aldehyde (3), the latter of which is required for the conversion of the sarpagan skeleton into the ajmalan system in the biosynthesis of quebrachidine. [reaction: see text].
Organic Letters 02/2007; 9(2):295-8. · 5.86 Impact Factor
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Harry L June,
Katrina L Foster,
William J A Eiler,
Joshua Goergen,
Jason B Cook,
Nathan Johnson,
Boikai Mensah-Zoe,
Jothan O Simmons, Wenyuan Yin,
James M Cook,
Gregg E Homanics
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ABSTRACT: The present study investigated the role of the alpha1-containing GABA(A) receptors in the neurobehavioral actions of alcohol. In Experiment 1, mice lacking the alpha1 subunit (alpha1 (-/-)) were tested for their capacity to initiate operant-lever press responding for alcohol or sucrose. Alcohol intake in the home cage was also measured. In Experiment 2, the alpha1 (-/-) mice were injected with a range of alcohol doses (0.875-4.0 g/kg; i.p.) to evaluate the significance of the alpha1 subunit in alcohol's stimulant actions. In Experiment 3, we determined if the alcohol-induced stimulant effects were regulated via dopaminergic (DA) or benzodiazepine (BDZ)-dependent mechanisms. To accomplish this, we investigated the capacity of DA (eticlopride, SCH 23390) and BDZ (flumazenil, betaCCt) receptor antagonists to attenuate the alcohol-induced stimulant actions. Compared with wild-type mice (alpha1 (+/+)), the null mutants showed marked reductions in both EtOH and sucrose-maintained responding, and home-cage alcohol drinking. The null mutants also showed significant increases in locomotor behaviors after injections of low-moderate alcohol doses (1.75-3.0 g/kg). betaCCt, flumazenil, eticlopride, and SCH 23390 were able to attenuate the alcohol-induced stimulation in mutant mice, in the absence of intrinsic effects. These data suggest the alpha1 receptor plays an important role in alcohol-motivated behaviors; however, it also appears crucial in regulating the reinforcing properties associated with normal ingestive behaviors. Deleting the alpha1 subunit of the GABA(A) receptor appears to unmask alcohol's stimulatory effects; these effects appear to be regulated via an interaction of both DA- and GABA(A) BDZ-dependent mechanisms.
Neuropsychopharmacology 02/2007; 32(1):137-52. · 7.99 Impact Factor
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ABSTRACT: The stable conformations of both the trans- and cis-1,3-disubstituted Nb-benzyl stereoisomers of the Pictet - Spengler reaction have been determined by NMR spectroscopy and X-ray crystallography in order to better understand the C(1) -N(2) cis- to trans-isomerization process. In the Na-H series, the chair conformation was preferred for the trans-isomer 3a, while the cis-isomer 3b existed predominantly in the boat form. However, in the Na-methyl series (1a, 1b, 2a, 2b), both the cis (1b, 2b) and trans (1a, 2a) diastereomers existed in the chair conformation to relieve the A(1,2)-strain between the Na-methyl function and the substituent at C(1). The difference in the preferred conformations of the cis-isomers in the Na-H and Na-methyl series (as compared to the preferred conformations in the trans-isomers) can be employed to understand the reduced rate of epimerization of cis-2b into trans-2a as compared to 3b into 3a. This provides the structural basis for the carbocation-mediated intermediate in the C(1) - N(2) scission process.
Journal of Natural Products 02/2007; 70(1):75-82. · 3.13 Impact Factor
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Organic Letters - ORG LETT. 01/2007; 9(18):3491-3494.
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ABSTRACT: Benzodiazepine agonists characteristically increase food intake in humans and non-human subjects, and the underlying mechanisms of this effect are not understood completely.
Compounds with selectivity for GABAA receptor subtypes were used to evaluate the role of GABAA receptors containing alpha1 and alpha5 subunits (alpha1GABAA and alpha5GABAA receptors, respectively) in benzodiazepine-induced increases in sucrose pellet consumption.
Adult male squirrel monkeys (N=4-6), maintained under free-feeding conditions, were administered with intramuscular injections of the nonselective benzodiazepines diazepam and alprazolam, the alpha1GABAA-preferring compounds zolpidem and zaleplon, or the alpha5GABAA-preferring agonist QH-ii-066 before daily 10-min periods when sucrose pellets were available. In a separate experiment, observable behavioral effects (e.g., ataxia and procumbent posture) were quantified after administration of alprazolam, zaleplon, and QH-ii-066. To further assess the roles of GABAA receptor subtypes, zolpidem-induced increases in pellet consumption were re-evaluated after pretreatment with nonselective antagonist flumazenil, the alpha1GABAA-preferring antagonist beta-carboline-3-carboxylate-t-butyl ester (BCCT), or QH-ii-066.
Alprazolam, diazepam, zolpidem, and zaleplon but not QH-ii-066 significantly increased sucrose pellet consumption. In addition, all agonists decreased locomotion and environment-directed behavior as well as engendered ataxia and procumbent posture. For all compounds except QH-ii-066, these behaviors occurred at doses similar to those that increased pellet consumption. Flumazenil and BCCT, but not QH-ii-066, antagonized zolpidem-induced increases in pellet consumption in a surmountable fashion.
These results suggest that the alpha1GABAA receptor subtype plays a key role in benzodiazepine-induced increases in consumption of palatable food, whereas the alpha5GABAA receptor subtype may not be involved in this effect.
Psychopharmacology 09/2006; 187(3):321-30. · 4.08 Impact Factor
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ABSTRACT: Benzodiazepine site inverse agonists may increase or decrease locomotor activity in rodents, depending on the experimental settings. We have compared the behavioral responses to environmental novelty of rats treated with the non-selective inverse agonist DMCM (2 mg/kg) and the alpha1-subunit affinity-selective inverse agonist 3-EBC (15 mg/kg). The behavior in spontaneous locomotor assay (during 45 min) and elevated plus maze (EPM) was automatically recorded. In the EPM, general activity-related parameters were similarly decreased, whereas only DMCM inhibited open-arm activity. In the locomotor assay, both compounds depressed locomotion in the first 15 min and activity in the central zone of the chamber. However, the influence of 3-EBC was less pronounced. The alpha1-subunit selective antagonist beta-CCt (15 mg/kg) attenuated locomotor depression, but not the central-zone avoidance elicited by DMCM. When habituated to the chamber, DMCM-treated animals emitted a plateau phase of activity, which disappeared by adding beta-CCt. Hence, inhibition of activity in exposed areas may be mediated by non-alpha1-subunits, whereas both alpha1 and non-alpha1-subunits may participate in suppression of activity in more protective areas of an apparatus. Hyperlocomotion in habituated animals may depend primarily on the alpha1-subunit. Moreover, the bimodal influence of inverse agonists on locomotion can be biphasic, observable in the same experiment.
Pharmacology Biochemistry and Behavior 06/2006; 84(1):35-42. · 2.53 Impact Factor
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Harry L June,
Katrina L Foster,
William J A Eiler,
Joshua Goergen,
Jason B Cook,
Nathan Johnson,
Boikai Mensah-Zoe,
Jothan O Simmons, Wenyuan Yin,
James M Cook,
Gregg E Homanics
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ABSTRACT: The present study investigated the role of the 1-containing GABAA receptors in the neurobehavioral actions of alcohol. In Experiment 1, mice lacking the 1 subunit (1 (-/-)) were tested for their capacity to initiate operant-lever press responding for alcohol or sucrose. Alcohol intake in the home cage was also measured. In Experiment 2, the 1 (-/-) mice were injected with a range of alcohol doses (0.875–4.0 g/kg; i.p.) to evaluate the significance of the 1 subunit in alcohol's stimulant actions. In Experiment 3, we determined if the alcohol-induced stimulant effects were regulated via dopaminergic (DA) or benzodiazepine (BDZ)-dependent mechanisms. To accomplish this, we investigated the capacity of DA (eticlopride, SCH 23390) and BDZ (flumazenil, CCt) receptor antagonists to attenuate the alcohol-induced stimulant actions. Compared with wild-type mice (1 (+/+)), the null mutants showed marked reductions in both EtOH and sucrose-maintained responding, and home-cage alcohol drinking. The null mutants also showed significant increases in locomotor behaviors after injections of low–moderate alcohol doses (1.75–3.0 g/kg). CCt, flumazenil, eticlopride, and SCH 23390 were able to attenuate the alcohol-induced stimulation in mutant mice, in the absence of intrinsic effects. These data suggest the 1 receptor plays an important role in alcohol-motivated behaviors; however, it also appears crucial in regulating the reinforcing properties associated with normal ingestive behaviors. Deleting the 1 subunit of the GABAA receptor appears to unmask alcohol's stimulatory effects; these effects appear to be regulated via an interaction of both DA- and GABAA BDZ-dependent mechanisms.Keywords: GABAA, dopamine, 1 subunit, KO mice, EtOH, locomotor activity
Neuropsychopharmacology 05/2006; 32(1):137-152. · 7.99 Impact Factor
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ABSTRACT: [structures: see text] The enantiospecific synthesis of 7-methoxy-D-tryptophan ethyl ester was completed by combination of the Larock heteroannulation process with a Schöllkopf-based chiral auxiliary in good yield. This ester was then employed in the first regiospecific, stereospecific total synthesis of (+)-12-methoxy-N(a)-methylvellosimine, (+)-12-methoxyaffinisine, (-)-fuchsiaefoline, and 12-methoxy-N(b)-methylvoachalotine in excellent overall yield. The asymmetric Pictet-Spengler reaction and enolate-driven palladium-catalyzed cross-coupling processes served as key steps. The quaternary center at C16 of 12-methoxy-N(b)-methylvoachalotine was established via the Tollens reaction between (+)-12-methoxy-N(a)-methylvellosimine and formaldehyde to form diol 17. The two prochiral primary alcohols in diol 17 were differentiated by the oxidative cyclization(DDQ) of the hydroxyl group at the axial position of 17 with the benzylic postion at [C6] to form a cyclic ether [C6-O17]. After oxidative formation of the alpha-ester at C16, the ether bond was reductively cleaved with TFA/Et3SiH in high yield. The DDQ-mediated oxidative cyclization and TFA/Et3SiH reductive cleavage served as protection/deprotection steps in order to provide a versatile entry into the voachalotine alkaloids.
The Journal of Organic Chemistry 02/2006; 71(1):251-9. · 4.45 Impact Factor
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ABSTRACT: Ethanol's ability to enhance GABA neurotransmission via GABA(A) receptors has been implicated as an important mechanism underlying its discriminative stimulus (DS) effects in animals and subjective effects in humans. The present study assessed the contribution of alpha(1)GABA(A) and alpha(5)GABA(A) receptors to the DS effects of ethanol. Squirrel were monkeys trained to discriminate i.v. ethanol from saline under a fixed-ratio schedule of food delivery. Under test conditions, ethanol engendered a dose-dependent increase in drug-lever responding, reaching an average maximum of >80%. In substitution experiments, the alpha(1)GABA(A) agonists zolpidem, zaleplon, and CL 218,872 (3-methyl-6-[3-(trifluoromethyl)phenyl]-1,2,4-triazolo[4,3-b]pyridazine), the alpha(5)GABA(A) agonists QH-ii-066 (1-methyl-7-acetyleno-5-phenyl-1,3-dihydro-benzo[e]-1,4-diazepin-2-one) and panadiplon [3-(5-cyclopropyl-1,2,4-oxadiazol-3-yl)-5-(1-methylethyl)imidazo(1,5-a)quinoxalin-4(5H)-one], and representative nonselective agonists partially to fully reproduced the ethanol DS. In antagonism studies, the alpha(1)GABA(A) antagonist beta-carboline-t-butyl ester did not attenuate the DS effects of ethanol or the ethanol-like effects of zolpidem and zaleplon. In contrast, pretreatment with the alpha(5)GABA(A) inverse agonist L-655,708 (ethyl[S]-11,12,13,13a-tetrahydro-7-methoxy-9-oxo-9H-imidazo[1,5-a]pyrrolo[2,1-c][1,4]benzodiazepine-1-carboxlate) dose-dependently attenuated the DS effects of ethanol and the ethanol-like effects of QH-ii-066. RY-23 (tert-butyl 8-[(trimethylsilyl)ethynyl]-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5a]-[1,4]benzodiazepine-3-carboxylate), another alpha(5)GABA(A) inverse agonist, similarly attenuated the ethanol-like DS effects of QH-ii-066. Antagonism of both QH-ii-066 and ethanol by the alpha(5)GABA(A) inverse agonists occurred at doses that did not alter the rate of responding suggesting that this blockade was pharmacologically specific and not the result of a nonspecific disruption of operant behavior. These findings suggest a key role for alpha(5)GABA(A), but not alpha(1)GABA(A), receptor mechanisms in the DS effects of ethanol and the ethanol-like DS effects of benzodiazepine agonists.
Journal of Pharmacology and Experimental Therapeutics 05/2005; 313(2):658-67. · 3.83 Impact Factor
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ABSTRACT: Positive modulators of the benzodiazepine/GABA(A) receptor complex can heighten aggressive behavior; the GABA(A)/alpha(1) subunit may play a critical role in benzodiazepine-modulated aggressive behavior.
The carboline derivatives, beta-CCt and 3-PBC, antagonists with preferential action at the GABA(A) receptors with alpha(1) subunits, may antagonize benzodiazepine-heightened aggression, thus implicating the alpha(1) subunit in heightened aggression.
The GABA(A) receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4c]-pyridin-3-ol (THIP) (0.01-3.0 mg/kg), and the benzodiazepine receptor agonists midazolam (0.3-3.0 mg/kg) and triazolam (0.003-3.0 mg/kg) were administered to adult male resident rats to assess the drugs' effects on their aggressive behavior toward an intruder. Then beta-CCt (0.3-10.0 mg/kg) and 3-PBC (0.3-17.0 mg/kg) were each administered in conjunction with midazolam. The salient elements of aggressive and non-aggressive behavior were measured by analyzing video recordings and encoding each behavioral act and posture in terms of its frequency and duration of occurrence.
Midazolam significantly increased the duration of aggressive behaviors at 1.0 and 1.7 mg/kg, and triazolam increased attack bite frequency at 0.03 mg/kg, both implicating GABA(A) receptors with benzodiazepine binding sites in aggressive behavior. In the present dose range, THIP did not affect any behaviors. The broad-spectrum benzodiazepine antagonist, flumazenil (1.0 mg/kg), antagonized the aggression-heightening effects of midazolam. beta-CCt (0.3-10.0 mg/kg) and 3-PBC (0.3-17.0 mg/kg) also antagonized the aggression-heightening effects of midazolam (1.0 mg/kg).
These results implicate both the GABA(A) gamma and alpha(1) subunits in benzodiazepine-heightened aggression.
Psychopharmacology 04/2005; 178(2-3):232-40. · 4.08 Impact Factor
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ABSTRACT: Recent research on genetically modified mice has attributed the amnesic effect of benzodiazepines mainly to the alpha1-containing GABA(A) receptor subtypes. The pharmacological approach, using subtype selective ligands, is needed to complement genetic studies. We tested the effects of the non-selective antagonist flumazenil (0-20.0 mg/kg), the preferential alpha1-subunit selective antagonist beta-carboline-3-carboxylate-t-butyl ester (beta-CCt) (0-30.0 mg/kg), the non-selective agonist midazolam (0-2.0 mg/kg), the preferential alpha1-subunit selective agonist zolpidem (0-3.0 mg/kg), and the non-selective inverse agonist methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) (0-2.0 mg/kg) in the one-trial step-through passive avoidance task in rats. The compounds were administered intraperitoneally, before the acquisition test. Flumazenil and beta-CCt did not affect retention performance. Midazolam and zolpidem induced amnesia in a dose-dependent manner. The complete reversal of amnesia was unattainable. The effects of zolpidem were significantly attenuated by the both, flumazenil (10.0 mg/kg) and beta-CCt (30.0 mg/kg); by contrast, only flumazenil was considerably effective when combined with midazolam. DMCM exerted promnesic effects at 0.2mg/kg, in an inverted U-shape manner. Both antagonists tended to abolish this action. The results indicate that some other alpha-subunit(s), in addition to the alpha1-subunit, contribute to the amnesic actions of non-selective benzodiazepine site agonists in the passive avoidance task. On the other hand, a significant part of the DMCM-induced promnesic effect could involve the alpha1-subunit and/or other putative beta-CCt-sensitive binding site(s).
Behavioural Brain Research 04/2005; 158(2):293-300. · 3.42 Impact Factor
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ABSTRACT: Recent research using genetically modified mice has pointed to the specific contribution of individual receptor subtypes to the various effects of benzodiazepines. The aim of this study was to examine the relative significance of alpha(1)-containing GABA(A) receptors in the effects of modulators at the benzodiazepine site in the elevated plus-maze (EPM) under dim red light in rats. We tested the effects of the non-selective antagonist flumazenil (0-20.0 mg/kg), the preferential alpha(1)-subunit selective antagonist beta-carboline-3-carboxylate-t-butyl ester (beta-CCt, 0-30.0 mg/kg), the non-selective agonist midazolam (0-2.0 mg/kg), the preferential alpha(1)-subunit selective agonist zolpidem (0-2.0 mg/kg) and the non-selective inverse agonist methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM, 0-2.0 mg/kg). The influence of flumazenil (10.0 mg/kg) and beta-CCt (30.0 mg/kg) on the effects of both kinds of agonists were also examined. The standard spatio-temporal parameters reflecting anxiety (percentage of open arm entries and time) and locomotion (closed and total arm entries) were analyzed. beta-CCt did not affect behavior, while flumazenil at the highest dose (20.0 mg/kg) decreased indices of open arm activity and total arm entries. Midazolam at the dose of 1.0 mg/kg significantly increased the percentage of open arm time, whereas at 2.0 mg/kg both anxiety-related parameters were increased. In contrast to the open arm entries, the open arm time was independent of the decreased closed arm entries, observed at 2.0 mg/kg. Flumazenil abolished these effects, whereas beta-CCt partially potentiated the anxiolytic actions of midazolam. Zolpidem significantly increased both open-arm indices at 1.0 mg/kg, but the effect was dependent on the decreased closed arm entries. The selectivity of the anxiolytic-like effects of zolpidem was further checked under brighter white illumination. In these settings, the influence on anxiety-related, but not activity-related parameters, was absent. All of the activity-related effects of midazolam and zolpidem were mainly counteracted by both antagonists. DMCM produced significant anxiogenic effects at 1.0 mg/kg (open arm time) and 2.0 mg/kg (both parameters). beta-CCt (30.0 mg/kg) and flumazenil at higher dose (20.0 mg/kg) antagonized the effects of DMCM. The results indicate the anxiolytic effects of a non-selective benzodiazepine site agonist involve a predominant role of subunits other than alpha(1), whereas the behavioral indices of the anxiolytic-like properties of an alpha(1)-selective ligand, if observed, depend on the experimental settings and the changes in locomotor activity, and hence were behaviorally non-specific. The present results generally correspond well to the behavioral findings with the genetically modified mice. On the other hand, the relative significance of the alpha(1)-subunit in the anxiogenic effects of DMCM could not be clearly deduced.
Pharmacology Biochemistry and Behavior 11/2004; 79(2):279-90. · 2.53 Impact Factor
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ABSTRACT: The positive modulation of gamma-aminobutyric acid type-A (GABAA) receptors is a putative mechanism via which alcohol escalates aggressive behavior. Broad-spectrum benzodiazepine antagonists block alcohol-heightened aggression in rats and monkeys. However, the degree to which GABAA subunit composition plays a role in heightened aggressive behavior induced by self-administration of a moderate alcohol dose remains unresolved.
Beta-carboline-3-carboxylate-t-butyl ester (beta-CCt) and zolpidem act preferentially at GABAA receptors containing the alpha1 subunit as antagonist and agonist, respectively, and serve as useful tools to evaluate the role of GABAA receptor subtypes in self-administered alcohol on aggression.
Male resident mice, housed in breeding pairs, were conditioned to nose-poke in a removable panel in their home cage, with each fifth poke being reinforced by the delivery of 0.05 ml of 6% ethanol (EtOH). After consuming EtOH, the resident mice were given the antagonists beta-CCt and flumazenil or agonists zolpidem and triazolam, and then confronted an intruder male in their home cage for a 5-min period.
Following self-administration of EtOH (1.0 g/kg, 1.7 g/kg), 14 of 37 resident mice displayed unusually large increases in the frequency of attack bites and sideways threats. Flumazenil or beta-CCt decreased alcohol-heightened and non-heightened aggression in a dose-dependent manner. Administration of 3 mg/kg beta-CCt lowered the aggression-heightening effects of 1 g/kg and 1.7 g/kg EtOH, but did not antagonize the sedative effects of 3.0 g/kg EtOH. Triazolam and zolpidem decreased alcohol-heightened and non-heightened aggressive behavior, and these antiaggressive effects were accompanied by reduced motor activity, indicating sedation.
Benzodiazepine antagonists, particularly those acting preferentially at GABAA/alpha1 subunit-containing receptors, decrease alcohol-heightened and species-typical aggressive behavior, but are ineffective in attenuating the sedative effects of alcohol.
Psychopharmacology 04/2004; 172(3):255-63. · 4.08 Impact Factor
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ABSTRACT: The present study tested the hypothesis that GABA(A) and opioid receptors within the central nucleus of the amygdala (CeA) regulate ethanol (EtOH), but not sucrose-maintained responding. To accomplish this, betaCCt, a mixed benzodiazepine (BDZ) agonist-antagonist with binding selectivity at the alpha1 subunit-containing GABA(A) receptor, and the nonselective opioid antagonist, naltrexone, were bilaterally infused directly into the CeA of alcohol-preferring rats. The results demonstrated that in HAD-1 and P rat lines, betaCCt (5-60 microg) reduced EtOH-maintained responding by 56-89% of control levels. On day 2, betaCCt (10-40 microg) continued to suppress EtOH maintained responding in HAD-1 rats by as much as 60-85% of control levels. Similarly, naltrexone (0.5-30 microg) reduced EtOH-maintained responding by 56-75% of control levels in P rats. betaCCt and naltrexone exhibited neuroanatomical and reinforcer specificity within the CeA. Specifically, no effects on EtOH-maintained responding were observed following infusion into the caudate putamen (CPu), a locus several millimeters dorsal to the CeA. Additionally, responding maintained by sucrose, when presented concurrently with ethanol (EtOH) or presented alone, was not altered by betaCCt. Naltrexone reduced sucrose-maintained responding only under the 5 microg dose condition when sucrose was presented alone, however, it did not alter sucrose responding when given concurrently with EtOH. These results support the hypothesis that GABA(A) and opioid receptors within the CeA can selectively regulate EtOH-maintained responding. The CeA may represent a novel target site in the development of prototypical GABA(A) and opioidergic receptor ligands, which selectively reduce alcohol abuse in humans.
Neuropsychopharmacology 03/2004; 29(2):269-84. · 7.99 Impact Factor
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Harry L June,
Katrina L Foster,
Peter F McKay,
Regat Seyoum,
James E Woods,
Scott C Harvey,
William J A Eiler,
Collette Grey,
Michelle R Carroll,
Shannan McCane,
Cecily M Jones, Wenyuan Yin,
Dynesha Mason,
Rancia Cummings,
Marin Garcia,
Chunrong Ma,
P V V S Sarma,
James M Cook,
Phil Skolnick
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ABSTRACT: It has been hypothesized that alcohol addiction is mediated, at least in part, by specific gamma-aminobutyric acid(A) (GABA(A)) receptors within the ventral pallidum (VP). Among the potential GABA(A) receptor isoforms regulating alcohol-seeking behaviors within the VP, the GABA(A) alpha1 receptor subtype (GABA(A1)) appears pre-eminent. In the present study, we developed beta-carboline-3-carboxylate-t-butyl ester (betaCCt), a mixed agonist-antagonist benzodiazepine (BDZ) site ligand, with binding selectivity at the A1 receptor to explore the functional role of VP(A1) receptors in the euphoric properties of alcohol. The in vivo actions of betaCCt were then determined following microinfusion into the VP, a novel alcohol reward substrate that primarily expresses the A1 receptor. In two selectively bred rodent models of chronic alcohol drinking (HAD-1, P rats), bilateral microinfusion of betaCCt (0.5-40 microg) produced marked reductions in alcohol-reinforced behaviors. Further, VP infusions of betaCCt exhibited both neuroanatomical and reinforcer specificity. Thus, no effects on alcohol-reinforced behaviors were observed following infusion in the nucleus accumbens (NACC)/caudate putamen (CPu), or on response maintained by saccharin. Parenteral-administered betaCCt (1-40 mg/kg) was equally effective and selective in reducing alcohol-reinforced behaviors in P and HAD-1 rats. Additional tests of locomotor activity revealed that betaCCt reversed the locomotor sedation produced by both chlordiazepoxide (10 mg/kg) and EtOH (1.25 g/kg), but was devoid of intrinsic effects when given alone. Studies in recombinant receptors expressed in Xenopus oocytes revealed that betaCCt acted as a low-efficacy partial agonist at alpha3beta3gamma2 and alpha4beta3gamma2 receptors and as a low-efficacy inverse agonist at alpha1beta3gamma2, alpha2beta3gamma2, and alpha5beta3gamma2 receptors. The present study indicates that betaCCt is capable of antagonizing the reinforcing and the sedative properties of alcohol. These anti-alcohol properties of betaCCt are primarily mediated via the GABA(A1) receptor. betaCCt may represent a prototype of a pharmacotherapeutic agent to effectively reduce alcohol drinking behavior in human alcoholics.
Neuropsychopharmacology 01/2004; 28(12):2124-37. · 7.99 Impact Factor
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ABSTRACT: The discriminative stimulus effects of zolpidem in squirrel monkeys trained at doses greater than or equal to 3.0 mg/kg differ from those of conventional benzodiazepines (BZs), but the extent to which these effects reflect the selectivity of zolpidem for GABA(A)/alpha(1) receptors is not known.
The present study investigated the ability of GABA(A)/alpha(1)-preferring agonists to substitute for training doses of zolpidem greater than or equal to 3.0 mg/kg and the ability of GABA(A)/alpha(1)-preferring antagonists to block zolpidem's discriminative stimulus effects.
Squirrel monkeys were trained to discriminate intravenous injections of zolpidem (3.0 or 5.6 mg/kg) from saline and tested with BZ agonists differing in selectivity and efficacy at GABA(A)/alpha(1) receptors. Antagonism of the effects of zolpidem was studied using the GABA(A)/alpha(1)-preferring antagonists beta-carboline-3-carboxylate-t-butyl ester (beta-CCT) and 3-propyloxy-beta-carboline (3-PBC).
Zolpidem and quazepam (GABA(A)/alpha(1)-preferring agonist) engendered full substitution for zolpidem, whereas CL 218,872 (GABA(A)/alpha(1)-preferring partial agonist) and the non-selective BZ agonists alprazolam and flunitrazepam engendered low and variable levels of zolpidem-lever responding (35-58%). Both beta-CCT and 3-PBC antagonized the discriminative stimulus effects of zolpidem in a surmountable fashion.
Our findings provide evidence for a key role of GABA(A)/alpha(1) receptors in the discriminative stimulus effects of zolpidem at relatively high training doses, and suggest that selectivity and relatively high efficacy at GABA(A)/alpha(1) receptors is required for BZ agonists to reproduce these discriminative stimulus effects.
Psychopharmacology 02/2003; 165(3):209-15. · 4.08 Impact Factor
