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R Stretch

Publications and source records attributed to R Stretch.

26 records · Page 2Linked to original sources
PubMed1967

Methylphenidate and stimulus control of avoidance behavior.

The introduction of a warning signal that preceded a scheduled shock modified the temporal distribution of free-operant avoidance responses. With response-shock and shock-shock intervals held constant, response rates increased only slightly when the response-signal interval was reduced. The result is consistent with Sidman's (1955) findings under different conditions, but at variance with Ulrich, Holz, and Azrin's (1964) findings under similar conditions. Methylphenidate in graded doses increased response rates, modifying frequency distributions of interresponse times. Drug treatment may have disrupted a "temporal discrimination" formed within the signal-shock interval. More simply, methylphenidate influenced response rates by increasing short response latencies after signal onset; this effect was more prominent than the drug's tendency to increase the frequency of pre-signal responses. When signal-onset preceded shock by 2 sec, individual differences in performance were marked; methylphenidate suppressed responding in one rat as a function of increasing dose levels to a greater degree than in a second animal, but both subjects received more shocks than under control conditions.

Animals↗
PubMed1966

Some effects of methylphenidate on stimulus control of ratio avoidance behavior in the rat.

After exposure to an avoidance schedule which included a warning signal, a rat was placed on a multiple schedule in which the first component was the same as before, i.e., a single response reset the response-shock interval, delaying shock, and the second component differed only in that four bar-presses were required to postpone shock. A fixed ratio requirement of four responses (FR 4) generated behavior resembling a fixed ratio requirement of one response (FR 1) since responding was controlled by the warning signal but more shocks were received. At a dosage of 2 mg/kg, methylphenidate given intraperitoneally decreased shock frequency during FR 4 periods while FR 1 behavior was not affected; at 4 mg/kg, stimulus control of avoidance responding was impaired during both components. Results at 4 mg/kg were partially confirmed by two animals exposed to an FR 4 avoidance schedule which included a warning signal but with different parameters. Response distributions showed that methylphenidate increased response rates in the absence of the warning signal, i.e., stimulus control of ratio-avoidance behavior was impaired although the increased response rates reduced shock frequency. One hour later responses again occurred more frequently during the signal than in its absence but shocks were less frequent than during control (non-drug) periods.

Animals↗
PubMedDate not supplied

Drug-induced reinstatement of extinguished self-administration behavior in monkeys.

Responding was established in squirrel monkeys under a modified progressive ratio schedule of IV d-amphetamine or cocaine self-administration. Subsituation of saline for the drug solutions resulted in extinction of the self-administration behavior. IV injections of certain doses of d-amphetamine or cocaine, immediately prior to test sessions in which response-contingent saline infusions were delivered, reinstated the rate and pattern of responding observed during sessions in which drug was self-administered. Presession IV injections of several doses of pentobarbital or chlorpromazine failed to consistently reinstate responding. These results were interpreted in terms of the discriminative control of drug self-administration behavior by the current drug state of the subject.

Animals↗