Biomedical subjects

J D Belluzzi

Publications and source records attributed to J D Belluzzi.

38 records · Page 3Linked to original sources

PubMedDate not supplied

Rats choose cocaine over dopamine agonists in a two-lever self-administration preference test.

Rats will self-administer dopamine D(1) and D(2) agonists, alone or in combination. Response rates and patterns for the D(1):D(2) combinations are nearly identical to those induced by cocaine. Here we examine whether rats prefer cocaine over D(1) or D(2) agonists presented alone or in D(1):D(2) combinations. During daily 3-h tests in a two-lever box, cocaine was available at either the right or left lever and the active side was alternated daily. After response rates had stabilized (+/-10% for 2 days), different groups were offered cocaine (800 microg/kg/injection) at one lever and either another dose (267, 1600, or 2400 microg/kg/injection) of cocaine or a dopamine agonist at the other lever. Animals consistently chose the higher of the presented cocaine doses over the low cocaine dose (267 microg). In choices between cocaine and dopamine agonists, the preferred cocaine dose (800 microg) was chosen over doses of the D(1) (SKF 82958) or D(2) ((+)-PHNO) agonist. However, no preference was shown between 800 microg cocaine and D(1):D(2) agonist mixtures, and the high-dose agonist mixture was preferred to the low cocaine dose. These results suggest that neither D(1) nor D(2) agonists alone fully duplicate the reinforcing actions of cocaine, but agonist combinations may approximate cocaine's reinforcement strength.

Animals↗

PubMedDate not supplied

Cellular investigations of behavioral reinforcement.

Using the hippocampal-slice preparation, we attempted to demonstrate operant conditioning of pyramidal cell activity using local micropressure applications of transmitters and drugs as reinforcement; the same injections administered independently of bursting provided a control for direct pharmacological stimulation or facilitation of firing. The results suggested that the spontaneous bursting of individual CA1 pyramidal neurons may be reinforced with activity-contingent injections of dopamine and cocaine, whereas, CA3-bursting responses may be reinforced with contingently-applied dynorphin A. We sought to confirm these indications of cellular reinforcement at the behavioral level in studies of hippocampal self-administration (despite the fact that the hippocampus has been ignored as a brain site for chemical self-administration experiments). The results suggested that dynorphin A is a powerful reinforcer of hippocampal self-administration behavior when injected in the CA3 field; experiments still in progress suggest that dopamine can reinforce self-administration behavior when injected in the CA1 field. Successful prediction of new behavioral data from operant-conditioning data at the cellular level helps to validate the cellular data by providing suggestive evidence of interrelationship between cellular and behavioral operant conditioning processes.

Animals↗