Polydrug self-administration in rats:
cocaine-heroin is more rewarding than cocaine-alone
by
Ranaldi R, Munn E
Center for Studies in Behavioral Neurobiology,
Concordia University, Montreal, Quebec, Canada.
Eur J Pharmacol 1997 Oct 15; 337(1):1-10

ABSTRACT

The i.v. self-administration by rats of a polydrug combination of cocaine and heroin was explored. The rewarding efficacies of a range of cocaine doses (0.25-8 mg/kg/injection) alone or in combination with heroin (12.5 or 25 microg/kg/injection) were compared using a progressive ratio (PR) schedule of reinforcement. Breaking points (BP) for one group of rats were determined at each dose of cocaine alone and for two other groups at each of the same cocaine doses plus one of the heroin doses, respectively. The cocaine-heroin combination was associated with higher BPs than cocaine alone at all doses of cocaine. These data demonstrate that cocaine-heroin combinations (speedballs) are more rewarding than the identical doses of cocaine alone. Some possible mechanisms by which heroin increases cocaine reward are discussed.

Reward
Cocaine
Tobacco
Cannabis
Anhedonia
Speedballs
Drug addiction
Opium timeline
NMDA antagonists
Rats on speedballs
Nicotine and heroin
The nucleus accumbens
Cocaine highs and lows
The neural basis of addiction
Dopamine levels in speedballing rats

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