ABSTRACT
This is a selected review of oral and intravenous models of the reinforcing effects of ethanol in non-human primates and rodents. The point of view is that studies of the reinforcing effects of ethanol in experimental animals must include demonstrations of high, sustained, voluntary ethanol intake of 8 to 12 g kg
d
and blood levels in the range of 200 to 300 mg% with clear behavioral intoxication in order to substantiate claims to measure an aspect of the reinforcing effects of ethanol relevant to the human condition of alcoholism. These criteria have clearly been met when nonhuman primates are trained to respond and receive intravenous ethanol. Thus far, however, using an oral route of administration, no rodent preparation and few primate preparations have provided these data. Although animals drink ethanol in patterns that closely resemble those shown with intravenous administration and demonstrate a reinforcing effect of ethanol, they do not drink as much, they do not develop marked intoxication, and, when access is continuous, they do not show sustained intakes. It is not clear why there is a marked difference in the amount of ethanol consumed under oral as compared with intravenous administration, but limits on fluid ingestion, delayed feedback effects, and different behavioral requirements are suggested as possible avenues to explore. The possibility that alcoholism in animals as in humans tends to be a slowly developing process, with a number of environmental as well as genetic constraints that limit the rapid establishment of symptomatic behavior, must be entertained.
