The research described in this proposal is intended to characterize the neuropharmacology of opiate drugs in the hippocampus, nucleus accumbens, medial prefrontal cortex, and ventral tegmental area (area A10) of rats. We will use electrophysiological and electrochemical techniques to measure functional responses to opiate drugs and opioid peptides. Our primary hypothesis is that opiates act through multiple receptor mechanisms, but that the cellular mechanism by which any one receptor produces its effects is consistent in different brain regions and on different cellular elements. By identifying the receptor subtypes that mediate opiate effects in different regions, and by determining which neurons within a region are opiate-sensitive, we hope to explain the """"""""anomalous"""""""" excitations that are observed in regions such as the ventral tegmental area. In addition, we intend to determine the extent to which pre- synaptic modulation of transmitter release, and postsynaptic interactions with other transmitters contribute to the overall actions of opioid peptides. We will use electrophysiological techniques to characterize the direct actions of these drugs in in vitro brain slices, single and double in oculo brain grafts, in human xenografts to the anterior chamber of the rat eye, and in situ in rats with brain stem transections. We will measure electrophysiological responses with intracellular recording from both in vitro brain slices and in oculo transplants, with in vivo electrochemical detection of the release of endogenous norepinephrine and dopamine from brain slices and transplants, and with extracellular recording of spontaneous and evoked activity. In terms of long-range objectives, we hope to characterize the specific ways in which opiates affect the electrophysiology of neuronal systems that may be involved in the rewarding effects of these drugs. Be determining the receptors that are involved, and the ways in which their activation contributes to changes in activity in dopamine-containing regions and their targets, we hope to provide an understanding of the changes in cellular activity that may underlie behavioral responses to drugs of abuse.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA002702-09
Application #
3207518
Study Section
Pharmacology I Research Subcommittee (DABR)
Project Start
1980-08-01
Project End
1992-07-31
Budget Start
1988-08-01
Budget End
1989-07-31
Support Year
9
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of Colorado Denver
Department
Type
Schools of Medicine
DUNS #
065391526
City
Aurora
State
CO
Country
United States
Zip Code
80045
Smith, D A; Browning, M; Dunwiddie, T V (1993) Cocaine inhibits hippocampal long-term potentiation. Brain Res 608:259-65
Dunwiddie, T V; Taylor, M; Heginbotham, L R et al. (1992) Long-term increases in excitability in the CA1 region of rat hippocampus induced by beta-adrenergic stimulation: possible mediation by cAMP. J Neurosci 12:506-17
Lupica, C R; Proctor, W R; Dunwiddie, T V (1992) Dissociation of mu and delta opioid receptor-mediated reductions in evoked and spontaneous synaptic inhibition in the rat hippocampus in vitro. Brain Res 593:226-38
Finger, T E; Dunwiddie, T V (1992) Evoked responses from an in vitro slice preparation of a primary gustatory nucleus: the vagal lobe of goldfish. Brain Res 580:27-34
Lupica, C R; Proctor, W R; Dunwiddie, T V (1992) Presynaptic inhibition of excitatory synaptic transmission by adenosine in rat hippocampus: analysis of unitary EPSP variance measured by whole-cell recording. J Neurosci 12:3753-64
Lupica, C R; Dunwiddie, T V (1991) Differential effects of mu- and delta-receptor selective opioid agonists on feedforward and feedback GABAergic inhibition in hippocampal brain slices. Synapse 8:237-48
Heginbotham, L R; Dunwiddie, T V (1991) Long-term increases in the evoked population spike in the CA1 region of rat hippocampus induced by beta-adrenergic receptor activation. J Neurosci 11:2519-27
Dunwiddie, T V; Taylor, M; Cass, W A et al. (1990) Arachidonic acid metabolites do not mediate modulation of neurotransmitter release by adenosine in rat hippocampus or striatum. Brain Res 527:76-80
Lupica, C R; Dunwiddie, T V (1990) Release of endogenous adenosine does not mediate electrophysiological responses to morphine in the hippocampus in vitro. Neuropharmacology 29:1131-9
Lupica, C R; Cass, W A; Zahniser, N R et al. (1990) Effects of the selective adenosine A2 receptor agonist CGS 21680 on in vitro electrophysiology, cAMP formation and dopamine release in rat hippocampus and striatum. J Pharmacol Exp Ther 252:1134-41

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