Showing papers by "Rajesh Kumar published in 1968"
TL;DR: “ADDICTION” to morphine and morphine-type drugs can be shown in laboratory animals in several ways, including experiments in which rats and monkeys are induced to administer the drug to themselves either by drinking solutions of it or by pressing levers which release intravenous injections through an implanted catheter.
Abstract: “ADDICTION” to morphine and morphine-type drugs can be shown in laboratory animals in several ways Among the most convincing1 are experiments in which rats and monkeys are induced to administer the drug to themselves either by drinking solutions of it2,3 or by pressing levers which release intravenous injections through an implanted catheter4,5 Standard experimental procedures involve a period of premedication: daily injections of increasing doses of morphine are given for 2–3 weeks in order to make the animals “passively” dependent on the drug Injections are then stopped and the animals have withdrawal symptoms6,7 which are only relieved by more morphine; so they learn to seek and self-administer the drug Monkeys will, however, learn to press levers for intravenous injections even without premedication, though such learning is much slower Some monkeys will also voluntarily drink morphine solutions, which are bitter, but others persistently reject them unless pre-medicated (personal communication from Seevers) In rats, premedication has usually been considered essential for learning either kind of self-administration, but even premedicated rats will initially reject morphine solutions if given a choice between them and water, probably because of the bitter taste
53 citations
TL;DR: Two doses of dexamphetamine and also of amylobarbitone stimulate the “exploratory” activity of rats in a new environment such as a Y-shaped maze and some mixtures of these drugs produce far greater increases in activity than do the separate constituents.
Abstract: SUITABLE doses of dexamphetamine and also of amylobarbitone stimulate the “exploratory” activity of rats in a new environment such as a Y-shaped maze. In addition, some mixtures of these drugs produce far greater increases in activity than do the separate constituents. One of the suggested explanations was that amphetamine increased activity directly, and that barbiturates acted indirectly by reducing the fear evoked by new environments, and that appropriate mixtures exerted both effects1,2.
19 citations