Joseph A Schroeder

Connecticut College · Psychology

The β-lactam antibiotic ceftriaxone (CTX) is a glutamate transporter subtype 1 (GLT-1) enhancer that reduces cocaine reinforcing efficacy and relapse in rats, but pharmacokinetic liabilities limit translational utility. An attractive alternative is clavulanic acid (CLAV), a structurally related β-lactamase inhibitor and component of FDA-approved Au...

Background Despite the efficacy of ceftriaxone (CTX) in animal models of CNS diseases, including drug addiction, its utility as a CNS-active therapeutic may be limited by poor brain penetrability and cumbersome parenteral administration. An alternative is the β-lactamase inhibitor clavulanic acid (CA), a constituent of Augmentin that prevents antib...

A brief summary of teleost spatial navigation research is followed by a description of a paradigm for the evaluation of egocentric-based, or viewpoint-dependent, spatial learning and memory function in zebrafish. The three-axis maze and testing protocol are used to evaluate the effects of nicotine and methylphenidate on spatial lionizing and memory...

The factors influencing sensitization to cocaine are complex and likely include both cellular and neural systems factors. Upregulation of the striatal dopamine cAMP-signaling pathway and enhanced accumbens adenosine tone are two mechanisms that have been proposed to underlie the development of cocaine sensitization. Isobutylmethylxanthine (IBMX) is...

Analgesic tolerance is partially mediated by enhanced glutamatergic transmission in the CNS. β-lactam antibiotics, through glutamate transporter subtype 1 (GLT-1) activation, reduce extracellular glutamate levels and attenuate tolerance to morphine analgesia in rats. Similar to opioids, nicotine has potent analgesic properties that are subject to t...

Sleep is often a topic of avid interest to college students, yet it is one that does not yield itself well to hands-on, interactive learning modules. Supplementing classroom learning with interactive "real world" laboratory activities provides students with a deeper understanding of behavior and its neural control. The project described here was de...

Philosophers and scientists have been attempting to understand how humans sense, perceive, and respond to their environment for thousands of years. Psychophysicists have relied upon self-report, threshold measurements, perceptual accuracy, and epidemiological comparisons to define the limits and norms of our sensory abilities. A significant portion...

Exposure to cocaine causes many neuroadaptations including alterations in several neurotransmitter receptors and transporters. This study investigated potential mechanisms of cocaine-induced receptor and transporter regulation by measuring levels of two proteins involved in receptor and transporter trafficking, dynamin 2 and G protein-coupled recep...

Chronic administration of cocaine has been shown to attenuate the functional capacity of delta opioid receptors to inhibit adenylyl cyclase activity. Abuse and withdrawal from cocaine in humans is associated with increases in anxiety and depression. Since recent research supports the role of delta opioid receptors in anxiety- and depression-like be...

Considerable evidence suggests that the endogenous opioid system plays a role in mediating the behavioral effects of psychostimulants. Opioidergic drugs have been shown to have profound effects on cocaine-induced behavioral sensitization and conditioned reward. However, the role specifically of the mu opioid receptor in this regard is unclear as mo...

The present study used the endpoint of hypothermia to investigate cannabinoid and nociceptin/orphanin FQ (N/OFQ) interactions in conscious animals. Prior work has established that cannabinoids produce hypothermia by activating central cannabinoid CB(1) receptors. The administration of N/OFQ into the brain also causes significant hypothermia. Those...

Numerous studies support a role for the endogenous opioid system in cocaine-influenced behavior. Few of these studies, however, selectively delineate a role for the mu opioid receptor (MOR) in this regard. This investigation examined if the MOR modulates cocaine-induced behavior in mice using a 17-base antisense oligodeoxynucleotide (AS ODN) direct...

The Indian herb Gymnema sylvestre has been used in traditional Ayurvedic medicine for 2000 years, most recently for the treatment of diabetes. Loose leaf Gymnema sylvestre can be prepared as a tea and will impair the ability to taste sugar by blocking sweet receptors on the tongue. This report describes a laboratory exercise easily applied to an un...

Behavioral sensitization is a characteristic sequelae of repeated cocaine exposure. It likely occurs due to long-lasting neuroadaptations produced by cocaine, although the exact nature of these adaptations has yet to be defined. The goal of the present study was to determine if behavioral sensitization to cocaine is accompanied by alterations in G-...

Intra-accumbens infusion of pertussis toxin (PTX) results in a progressive and persistent locomotor hyperactivity and sensitizes rats to the locomotor-activating effects of cocaine. The present study further defined the hyperactivity resulting from inactivation of accumbens Gi/Go proteins and tested the hypothesis that PTX-induced hyperactivity is...

Repeated cocaine exposure produces behavioral sensitization expressed as an increased locomotor response to subsequent drug administration. Chronic cocaine administration also results in increased activity of adenylyl cyclase and cyclic-AMP (cAMP) dependent protein kinase (PKA) in the nucleus accumbens. To investigate the relationship between cocai...

Chronic cocaine administration produces alterations in mu and kappa opioid receptor density as well as striatal and accumbens opioid-regulated adenylyl cyclase activity, suggesting a psychostimulant responsive interaction between opioidergic and dopaminergic systems. Stimulation of G-protein-coupled opioid receptors inhibits adenylyl cyclase produc...

The expression of parkinsonian motor symptoms may be partly attributed to an increase in GABAergic neurotransmission from hyperactive GABA/enkephalinergic striatopallidal efferents. The present study measured pallidal GABA(A) and mu-opioid receptor binding in normal cats and cats symptomatic for and recovered from MPTP-induced parkinsonism. GABA(A)...

The motor signs of Parkinson's disease have been partly attributed to an overinhibition of the external globus pallidus (GP) that results from hyperactivity of striatopallidal GABA/enkephalinergic neurons. The goals of this study were to measure basal levels of extracellular fluid GABA in the GP of normal cats, 1-methyl-4-phenyl-1,2,3,6-tetrahydrop...

1-Methyl-4-phenyl-1,2,3,6-tetrahyrdropyridine (MPTP)-exposed cats develop severe Parkinsonism that spontaneously resolves in 4-6 weeks. The present study examined the extent to which compensatory changes in tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene and protein expression may underlie this behavioral recovery. In normal cats, TH...

Glutamic acid decarboxylase (GAD65, GAD67) mRNA expression was measured in the globus pallidus (GP) and entopeduncular nucleus (ENTO) of normal, and MPTP-lesioned cats symptomatic for and recovered from MPTP-induced Parkinsonism. In the ENTO of symptomatic cats, GAD65 and GAD67 mRNA expression were both significantly increased, while only GAD67 gen...

Loss of striatal dopamine has been associated with an increase in striatal enkephalin expression. However, the relationship between increased striatal enkephalin expression and the manifestation of parkinsonian motor deficits is not clear. Administration of MPTP to cats produces a severe parkinsonian condition from which the animals spontaneously r...

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to cats results in a parkinsonian syndrome characterized by rigidity, akinesia, bradykinesia, decreased response to external sensory stimuli and depletion of nigrostriatal dopamine. Cats spontaneously recover gross sensorimotor functions despite little recovery of the dopaminergi...

The spontaneous mouse waved 1 (wa1) mutation is allelic with the transforming growth factor alpha (TGF-alpha) gene and produces phenotypes similar to those of TGF-alpha knockout mice. Here, we show that TGF-alpha mRNA and protein levels are measurable in wa1 tissues but reduced 5- to 30-fold relative to wild type. Because the wa1-coding sequence is...

Studies of teleost spatial cognition have revealed that fish possess an impressive array of navigational abilities and are capable of spatial memory based tasks utilizing both egocentric and allocentric cues. The emergence of zebrafish as an optimal animal model for developmental, genetic, and chemical screening investigations necessitates a better...