ISSN:
1432-2072
Keywords:
Rat
;
Place preference
;
Extinction
;
Conditioning
;
Naloxone
;
Heroin
;
Clonidine
;
Pimozide
;
Memory
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract These experiments examined the neurochemical mechanisms involved in the development and expression of place conditioning produced by heroin. Conditioned place preferences (CPP) lasting up to 8 weeks were obtained with doses of 50–1000 μg/kg heroin, using a regimen shown not to produce physical dependence. Naloxone pretreatment (50 μg/kg) during conditioning prevented the acquisition of heroin-induced CPP, but when given only on the test day, naloxone (50 or 1000 μg/kg) did not prevent the expression of heroin CPP. Clonidine disrupted the establishment of heroin CPP at 20 μg/kg, but disrupted its expression only at debilitating doses (100 and 200 μg/kg). Pimozide attenuated the acquisition (100 μ/kg) and expression (250 μg/kg) of heroin CPP. Together, these results support a role for opioid and catecholamine systems in the acquisition of heroin reinforcement, but they suggest that once heroin CPP is established, its expression in opiate-free subjects is not opiate receptor mediated and is relatively refractory to pharmacological treatments which disrupt acquisition. The data challenge the notion that the conditioned effects of opiates in drug-free animals are related to the release of endogenous opioids, and they also may help to explain why naloxone and clonidine are ineffective in the treatment of opiate addiction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00442007
