Small-dose intravenous heroin facilitates hypothalamic self-stimulation without response suppression in rats

Intravenous heroin at 10 and 30 μg/kg produced an immediate increase in rates of lever pressing for electrical stimulation of the lateral hypothalamus, while 100 μg/kg produced brief suppression in some rats followed by reliable response rate increases in all rats. The duration of response facilitation increased with dose and corresponded to the duration of the inter-infusion interval found in self-administration experiments. These data indicate correspondence between the reinforcing and the self-stimulation facilitating effects of heroin in relation to dose and time course parameters, and fit with the view that narcotic facilitation of self-stimulation reflects the reinforcing value of the drugs.