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Biomedical subjects

C R Schuster

Publications and source records attributed to C R Schuster.

At least 163 records · Page 9Linked to original sources
PubMed1973

Fixed-interval schedule of cocaine reinforcement: effect of dose and infusion duration.

Rhesus monkeys were trained on a fixed-interval 9-min limited-hold 3-min schedule of intravenous cocaine reinforcement. A 15-min timeout followed each reinforcement or limited-hold expiration. An identical schedule of food reinforcement was interspersed in the session to assess rate-modifying effects of the drug infusions not specific to drug reinforcement. In one experiment, response rate for cocaine reinforcement was shown to be a positive function of reinforcement magnitude for a dose range from 0 to 800 ug/kg/inj. At these doses, there was little effect on food reinforced responding except at the highest dose, where responding decreased. Results of the second experiment indicated that increasing the duration of the cocaine infusion produced a change in response rate similar to decreasing unit dose. The response rate change for a given increase in infustion duration was less at a unit dose of 400 ug/kg than at 200 ug/kg.

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PubMed1970

Conditioned nalorphine-induced abstinence changes: persistence in post morphine-dependent monkeys.

Every tenth lever-press of three morphine-dependent rhesus monkeys was reinforced with food. A red light, initially a neutral stimulus, was presented every third or fourth session for 5 min before and 5 min after an intravenous injection of nalorphine, a morphine antagonist that produces an immediate abstinence syndrome in morphine-dependent monkeys. After several pairings, conditioned suppression of lever pressing, heart-rate decrease, vomiting, and excessive salivation were observed during the red-light period before nalorphine injection. No conditioned electrocardiogram, respiration or temperature changes occurred. After 10 red light-nalorphine pairings, morphine administration was completely discontinued and monkeys were then tested monthly for persistence of the conditioned responses. The red light paired with saline injection continued to suppress lever pressing and to produce heart-rate decreases after 60 to 120 days of complete abstinence from morphine. Subsequently, daily presentations of the red light-saline injection complex rapidly extinguished these conditioned responses. Nevertheless, they could be rapidly reinstated by additional nalorphine injections.

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PubMed1969

Morphine: conditioned increases in self-administration in rhesus monkeys.

Operant responding in three monkeys was maintained by intravenous presentations of morphine. Nalorphine produced reliable increases in morphine-reinforced responding. With successive daily nalorphine injections there was a decreased latency of self-administration responding for morphine, and substituted saline injections produced conditioned increases in morphine-reinforced responding.

Animals↗
PubMed1967

Conditioned suppression by a stimulus associated with nalorphine in morphine-dependent monkeys.

Three rhesus monkeys, physically dependent on morphine, were trained to press a lever for food on a fixed ratio of 10 responses. A tone, initially a neutral stimulus, was aperiodically presented every third or fourth session, 5 min before and after the intravenous injection of nalorphine, a morphine antagonist which produces an immediate withdrawal syndrome in morphine-dependent monkeys. After several sessions, conditioned suppression of food-lever response rate was observed. Conditioned bradycardia, emesis, and excessive salivation also occurred. In 40 to 45 sessions the conditioned suppression of food-lever response rate and the conditioned autonomic changes were extinguished by presenting pairings of a tone and saline injection. The monkeys were then reconditioned by presenting the tone aperiodically, every third or fourth session, 5 min before and after the intravenous injection of nalorphine. Results were similar to the initial conditioning sessions. Two rhesus monkeys not dependent on morphine were stabilized on a food schedule similar to that used for the first three monkeys. These monkeys showed no change in food-lever response rate during or after nalorphine injections.

Animals↗
PubMed1966

Second-order avoidance behavior in monkeys.

Two monkeys were trained on a three-component multiple schedule using discrete trials. In one component (food), a response terminated a red stimulus and produced food and S(Delta). In the second component (avoidance), a response terminated a green stimulus and avoided shock. In the third component (optional), a response terminated a blue stimulus and produced S(Delta). The consequence of not responding in the blue stimulus, however, was the production of either a food or an avoidance trial. Manipulation of these consequences showed that when food trials were available only a small percent of the time after optional trials, the subjects tended not to respond in the blue, even though this led to an increase in the total number of avoidance trials per day. If only avoidance trials followed as a consequence of not responding in the optional component, the animals terminated the blue stimulus and avoided the avoidance trials. Throughout the experiment both subjects maintained consistently low shock rates (about 10 per day) and these were not affected by the various manipulations. The data suggest that a stimulus associated with avoidance can be a conditioned aversive stimulus and will maintain a more remote avoidance response under certain conditions.

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