Effects of d-amphetamine, WIN 35,428, pentobarbital and morphine on schedule-controlled responding in two inbred rat strains that differ in locomotor stimulatory effects of cocaine.
Behavioral effects of d-amphetamine, the cocaine analog, WIN 35,428, morphine, and pentobarbital were compared in NBR/NIH and F344CR1BR rats. Either nose-poke or lever-press responding was maintained under 3-min fixed-interval schedules of food presentation. The effects of morphine, WIN 35,428 and pentobarbital depended upon the rat strain studied: morphine increased nose-poke responding in NBR but not F344 rats; significant strain x dose interactions were observed with WIN 35,428; and pentobarbital was more potent in decreasing nose-poke responding in NBR than in F344 rats. No strain differences were observed in the behavioral effects of d-amphetamine. There were also prominent differences in the effects of drugs that were related to the nature of the response requirement. In both rat strains, nose-poke responding was affected differently than lever-press responding by morphine, d-amphetamine, and WIN 35,428. Pentobarbital produced effects that were independent of the specified response topography. A global underlying difference in these rat strains cannot be identified at present to account for the diversity of findings. The behavioral effects of these drugs appear to be influenced by a host of interactive factors including the drug, strain of animal, the baseline response rate and physical dimensions of the response.
Preclinical Pharmacology Branch, Addiction Research Center, National Institute on Drug Abuse, Baltimore, Maryland, USA.
J.M.
JM
Witkin
S.R.
SR
Goldberg