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Biomedical subjects

C R Schuster

Publications and source records attributed to C R Schuster.

16 recordsLinked to original sources
PubMed1979

The effects of chlorpromazine and pentobarbital on behavior maintained by electric shock or point loss avoidance in humans.

Human volunteer subjects were trained to press a lever to avoid or escape electric shock or loss of points which could be redeemed for money at the termination of the study. The effects of pentobarbital and chlorpromazine on avoidance and escape behavior were compared. Both aversive stimuli maintained behavior which was differentially sensitive to these two drugs. Chlorpromazine caused a decrease in avoidance responding at doses which had little effect on escape responding. Pentobarbital, in contrast, suppressed avoidance responding at doses which also had a suppressant effect on escape responding.

Adult↗
PubMed1979

The effects of methamphetamine on fine motor control in rhesus monkeys.

Six rhesus monkeys were trained to extend their arms through a tube to press a lever with between 25 and 40 g of force for 3 or 5 sec. Responding was maintained by the delivery of 1.5 cc of water. Stimulus lights indicated whether the exerted force was below 25 g. between 25 and 40 g (i.e., correct) or above 40 g. Sessions were terminated after 50 water deliveries or 30 min had elapsed. Performance was well-maintained in all monkeys. Allowing the animals access to water prior to the session had no effect on performance. Discontinuing sessions for two weeks disrupted some aspects of performance but responding improved within 5 sessions. Single injections of methamphetamine (0.06-0.5 mg/kg) were given IM 20 min prior to the session. The highest dose of 0.5 mg/kg totally eliminated responding. Lower doses decreased rate of responding somewhat and increased phasic activity (i.e., tremors) in a dose-dependent manner. The procedure seems ideally suited for investigating the effects of psychotropic drugs on fine motor control in rhesus monkeys.

Animals↗
PubMed1979

Methamphetamine-induced changes in brain catecholamines in rats and guinea pigs.

Repeated administration of methamphetamine was found to cause long-term changes in caudate dopamine levels in the rat and guinea pig. Methamphetamine was administered twice a day for thirty days. Two weeks following the last injection, the animals were killed and brains assayed for catecholamine content. These long-term depletions of dopamine, when combined with similar observations previously reported in rhesus monkeys, indicate a species generality of the effects of methamphetamine on caudate dopamine levels.

Animals↗
PubMed1978

Synthesis and biological activity of cocaine analogs I: N-alkylated norcocaine derivatives.

N-Allylnorcocaine, N-dimethylallylnorcocaine, and N-cyclopropylmethylnorcocaine were prepared and examined for cocaine-like activity. The compounds were prepared by alkylation of norcocaine, which was obtained by demethylation of cocaine with 2,2,2-trichloroethyl chloroformate followed by zinc--acetic acid reduction. The compounds were evaluated by comparison with cocaine in causing disruption of milk intake in rats, behavioral modification in squirrel monkeys, and inhibition of 3H-serotonin uptake by rat synaptosomes. The compounds showed cocaine-like activity less potent than cocaine in the latter two tests and were inactive in the milk intake test.

Animals↗
PubMed1978

Effects of passive immunization against morphine on heroin self-administration.

Antimorphine antibodies produced in Rhesus monkeys immunized with morphine-6-hemisuccinate-BSA were passively administered to recipient monkeys trained to self-administer heroin and cocaine. Following antibody administration, changes in heroin self-administration behavior were observed which were similar to those achieved with low doses of naloxone. Both manipulations increased heroin self-administration without affecting cocaine responding.

Animals↗
PubMed1978

The effects of naloxone on behavior maintained by cocaine and heroin injections in the rhesus monkey.

The effects of repeated administration of naloxone on heroin and cocaine self-administration in non-dependent rhesus monkeys were investigated. Animals lever pressing for intravenous heroin (6 micron/kg) and cocaine (100 or 200 micron/kg) were treated for 7--10 days with naloxone at a fixed dose prior to each session. Low pretreatment doses of naloxone increased rate of responding maintained by herion. The pattern of responding over the 10-day period of treatment with the higher doses of naloxone was similar to that observed when saline was substituted for heroin. Naloxone was without effect on responding maintained by injections of cocaine.

Animals↗
PubMed1977

An investigation of nalorphine and perphenazine as negative reinforcers in an escape paradigm.

Rhesus monkeys were trained to self-administer morphine intravenously at dose levels sufficient to develop physical dependence. The monkeys were then trained to press a lever to escape a continuous infusion of the morphine antagonist, nalorphine. When saline was substituted for the nalorphine, escape responding extinguished. After morphine self-administration was eliminated, responding to escape from nalorphine was maintained in the postdependent monkeys, showing no difference from escape responding during morphine dependence. Finally, perphenazine was substituted for the nalorphine and the monkeys reliably escaped continuous infusions of this phenothiazine. The escape procedure appears useful for analyzing the aversive properties of drugs.

Animals↗
PubMed1977

Second-order schedules of intravenous drug self-administration in rhesus monkeys.

Lever-pressing behavior was generated and maintained in 3 rhesus monkeys by intravenous infusions of morphine or cocaine under a second-order schedule of reinforcement. Under this schedule, every tenth lever-press response (FR 10) during a fixed interval of time produced a 2 sec stimulus light. The first FR 10 completed after a 60 min interval had elapsed produced the stimulus light and an intravenous infusion of morphine or cocaine. The stimulus light remained on for the duration of the drug infusion (50-60 sec). Sessions of morphine or cocaine presentation, each with distinct stimulus light conditions, alternated on a daily basis. Under this schedule, single doses of morphine from 0.125 to 1.0 mg/kg maintained high overall response rates (maximum of 40 Rs/min) in the pattern characteristic of fixed interval (FI) schedules of reinforcement. There was no functional relationship between the response-rates and the doses of morphine tested. The simultaneous infusion of naloxone (0.125 mg/kg/) with morphine (0.25 mg/kg) markedly decreased response rates. However, the infusion of the same dose of naloxone five min after the presentation of morphine failed to suppress self-administration behavior. Naloxone had no effects on cocaine-reinforced responding.

Animals↗
PubMed1977

Long-term behavioral changes in the rhesus monkey after multiple daily injections of d-methylamphetamine.

The effects of multiple daily injections of d-methylamphetamine on spaced lever-press responding were investigated in the rhesus monkey. Responding was measured after single injections of d-mehtylamphetamine (0.0625-1.0 mg/kg) both before and after the monkeys were maintained on a multiple daily d-methylamphetamine injection regimen in doses ranging from 0.5 to 16 mg/kg/day. Tolerance developed to the suppressant effects of this drug on responding. As evidenced by a shift in the dose-response curve measuring number of responses and number of reinforcements per session, this tolerance persisted for at least three months after cessation of the multiple drug injection regimen. In order for tolerance to develop, it was necessary for the animals to perform the task while maintained on drug. When saline was substituted for d-methylamphetamine, no evidence of a withdrawal syndrome was seen.

Animals↗