The research described in this proposal is intended to investigate the mechanism(s) of action of opiate drugs and cocaine in the central nervous systems of rodents. We will use electrophysiological techniques to characterize the direct and indirect actions of these drugs in various brain regions in in vitro brain slices, single and double in oculo brain grafts, in situ in acutely anaesthetized preparations, and in unanaesthetized chronically implanted animals. We will measure electrophysiological responses with intracellular recording techniques, and with extracellular recording of spontaneous unit activity and evoked field responses. Our primary hypothesis is that animals self-administer these drugs because of some reinforcing aspect of drug administration, and that such reinforcement depends upon a monoaminergic substrate in the central nervous system. Therefore, we will attempt to determine whether opiate drugs such as morphine and cocaine appear to have a common electrophysiological action on this putative monoamine """"""""reward"""""""" system which might provide a basis for their common neuropharmacological actions. In terms of long-range objectives, we hope to define the mechanisms of action of opiates and cocaine in reinforcement-related systems, as opposed to their actions in other neuronal systems (e.g., those involved in analgesia, etc.). If we can establish that these drugs have a common mechanism of action in a particular brain region, or in relation to a specific neurotransmitter, then we would have a basis for predicting the abuse potential of drugs based upon some pharmacological criterion. Ultimately, this might lead to a better understanding of the phenomenon of drug abuse in general, and in particular what kinds of biological bases which might underlie individual differences in the use of abused drugs.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA002702-07
Application #
3207517
Study Section
(DABA)
Project Start
1980-08-01
Project End
1987-07-31
Budget Start
1986-08-01
Budget End
1987-07-31
Support Year
7
Fiscal Year
1986
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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