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Brain Research 07/1980; 191(1):265-72. · 2.73 Impact Factor
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Brain Research 02/1980; 181(1):191-7. · 2.73 Impact Factor
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ABSTRACT: The present study compares the effects of d-amphetamine (d-AMP) and the potent non-amphetamine CNS stimulant, amfonelic acid (AFA), on the firing rate of single midbrain dopaminergic (DA) neurons and on neostriatal DA metabolism (dihydroxyphenylacetic acid--DOPAC). The results indicate that AFA, like d-AMP, reduces the firing rate of DA neurons, although unlike d-AMP, AFA does not cause a decrease in neostriatal DOPAC content and, in fact, enhances that produced by haloperidol (HALO). The AFA-induced decrease in firing rate, like d-AMP, is reversed by the DA receptor blocker HALO, but again unlike d-AMP, the decrease in firing rate is not prevented by catecholamine synthesis inhibition with alpha-methyl-para-tyrosine. Thus, both amphetamine and amfonelic acid have identical electrophysiological effects on DA neurons but act by different mechanisms.
Acta Neurovegetativa 02/1979; 44(1-2):39-49. · 2.73 Impact Factor
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ABSTRACT: Morphine blocked decremental bar pressing of rats to escape electrical stimulation of aversive midbrain sites. These sites included the dorsal central gray area (DCG), the ventral reticular formation (VRF) and the lateral tegmentum (LT). Naloxone, which had no effect alone, blocked the morphine effects of all three aversive sites.
Neuroscience Letters 12/1978; 10(1-2):197-202. · 2.11 Impact Factor
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ABSTRACT: In these experiments we have examined the role of brain monoamines in the fearlike aversive responses produced by the electrical stimulation of the dorsal midbrain tegmentum (DMT). Chronic bipolar stimulating electrodes were bilaterally implanted into the DMT of 77 rats. Electrical stimulation via 34 of these electrodes produced fearlike, escape seeking responses. These animals were then trained for stable stimulus escape using a decremental bar pressing paradigm. In this paradigm, each bar press reduced the stimulation current by a predetermined fraction (5 percent) of the initial current level. Perceived aversive strength of the initial stimulus current was thereby represented by an increasing function of the number of bar presses to escape. Administration of the catecholamine depleting drug alpha-methyl-para-tyrosine yielded no change in bar pressing relative to saline-injected controls. However, the serotonin depleting drub para-chlorophenylalanine produced a marked increase in decremental bar pressing compared to saline-injected controls. These results suggest that fearlike responses to DMT stimulation may be dependent upon brain serotonin levels and relatively insensitive to levels of brain catecholamines.
Physiology & Behavior 08/1975; 15(1):47-53. · 2.87 Impact Factor
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ABSTRACT: Low doses of d-amphetamine (d-AMP) produced a 50% or greater decrease in the firing rates of both dopamine (DA) neurons (substantia nigra zone compacta) and norepinephrine (NE) neurons (locus coeruleus). However, pretreatment with the tyrosine hydroxylase inhibitor α-methyl-para-tyrosine (α-MT) blocked the d-AMP-induced reduction in DA neuron firing rate, but had no effect on the d-AMP-induced reduction in NE cell firing rate. Similarly, α-MT administered subsequent to d-AMP readily reversed the d-AMP-induced decrease in the firing rates of DA cells, but caused no significant reversal in NE cell firing rates. These electrophysiological findings, in conjunction with biochemical and behavioral data, support the hypothesis that there is a difference in the DA and NE neurotransmitter storage mechanism. In the DA neuron, there appears to be a slow transfer between stored and readily-releasable (newly synthesized) amine pools so that, following synthesis inhibition, there is little DA available for release. However, in the NE neuron, there is a more rapid mobilization of stored amine to readily releasable sites, such that d-AMP continues to cause the release of NE even though synthesis of transmitter is blocked.
Brain Research Bulletin. 4(2):217-221.
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ABSTRACT: Low doses of d-amphetamine (d-AMP) produced a 50% or greater decrease in the firing rates of both dopamine (DA) neurons (substantia nigra zone compacta) and norepinephrine (NE) neurons (locus coeruleus). However, pretreatment with the tyrosine hydroxylase inhibitor alpha-methyl-para-tyrosine (alpha-MT) blocked the d-AMP-induced reduction in DA neuron firing rate, but had no effect on the d-AMP-induced reduction in NE cell firing rate. Similarly, alpha-MT administered subsequent to d-AMP readily reversed the d-AMP-induced decrease in the firing rates of DA cells, but caused no significant reversal in NE cell firing rates. These electrophysiological findings, in conjunction with biochemical and behavioral data, support the hypothesis that there is a difference in the DA and NE neurotransmitter storage mechanism. In the DA neuron, there appears to be a slow transfer between stored and readily-releasable (newly synthesized) amine pools so that, following synthesis inhibition, there is little DA available for release. However, in the NE neuron, there is a more rapid mobilization of stored amine to readily releasable sites, such that d-AMP continues to cause the release of NE even though synthesis of transmitter is blocked.
Brain Research Bulletin 4(2):217-21. · 2.82 Impact Factor
