Effects of d-amphetamine and chlordiazepoxide on spaced responding in pigeons

The effects of d-amphetamine and chlordiazepoxide were studied in pigeons on performance (1) under a schedule that reinforced responses on a key (food key) if they were more than 20 sec apart, (2) under the same schedule when responses also were required on a collateral key during the interresponse time on the food key, and (3) under the same schedule when responses were required on a collateral key during the interresponse time on the food key and collateral-key responses could produce a stimulus correlated with the availability of food. Under all three spaced-responding schedules, d-amphetamine and chlordiazepoxide at low dose levels slightly increased the frequency of short interresponse times on the food key for about half the birds, and either did not affect the interresponse time patterns of the other birds, or lengthened the durations slightly. At higher dose levels, d-amphetamine and chlordiazepoxide increased the frequency of long interresponse times or abolished responding in all birds. Changes in the pattern of interresponse times on the food key did not seem to depend on changes in the rate or pattern of collateral-key responses.

Experimental effects of amphetamine: supplementary report

As a supplement to a previous review, generalizations related to the experimental effects of amphetamine on food-motivated operant behavior, bodily activity and avoidance conditioning are evaluated in terms of recent evidence. Acceptance of generalizations related to the drug's action on such behaviors requires that one also accept numerous qualifications or limitations in terms of drug-dose factors, S variables, and task characteristics. However, the desirability of such generalizations is stressed.

Effects of chlorpromazine in the pigeon under a second-order schedule of food presentation

Chlorpromazine was studied for its effects on responding under a second-order schedule in which food was presented following a sequence of 20 one-minute fixed-interval components. A brief visual stimulus occurred at the completion of each fixed interval including the one that terminated with food presentation. Chlorpromazine showed rate-dependent effects in that it increased low rates in the early components of the second-order schedule and, to a lesser extent, decreased high rates in the later components. Chlorpromazine also increased rates in the early quarters within the 1-min fixed-internal components and to a smaller extent decreased rates in the final quarter. The alteration in the patterns of responding within 1-min fixed-interval components terminating in a brief stimulus presentation was substantially less than that which occurred throughout the succession of 1-min fixed-interval components terminating in food presentation, thus suggesting that the presentation of the brief stimulus exerted more control over responding within components than did food presentation over the sequence of components. This result and others suggest that studies using drugs may be useful in elucidating the factors controlling patterns of responding in second-order schedules.

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.

Effects of d-amphetamine on observing behavior in the squirrel monkey

Four squirrel monkeys were trained to press a lever, which produced stimuli indicating availability or non-availability of reinforcement for pushing a key. Food reinforcements were available for the key response at random intervals with an average rate of 1 per min. When food was available, a single lever response produced a red light behind the key. Reinforcement availabilities and red keylights remained until terminated by a reinforced key response. When reinforcement was not available, each lever response produced a 0.5-sec green light on the key. Except after lever responses, the key remained dark. Under this procedure, lever responses functioned as observing behavior in that they produced discriminative stimuli correlated with the availability or non-availability of reinforcement for key responses. The procedure generated a high rate of responding on the lever, short latencies of the key response after onset of red lights and few responses to the key in the absence of red lights. Intra-muscular d-amphetamine, in doses from 0.125 to 1.0 mg/kg, abolished both observing behavior and key responding for periods that increased as a function of dose. However, both observing and key rates were increased at the smallest dose in two subjects whose performances included responding to the key in the absence of red lights. Results are discussed in relation to previous findings regarding effects of amphetamines on operant behavior and on observing and monitoring performance.

Modification of the autonomic component of the conditioned emotional response

A series of experiments was conducted to clarify the role of the autonomic nervous system in the acquisition and maintenance of the conditioned emotional response (CER). In Exp. 1 the reactivity of either the sympathetic or the parasympathetic system was altered by drugs during maintenance testing of the CER. 12 rats were trained to bar-press for sugar water on a VI 30-sec. schedule; 6 CER trials were administered during each 2-hr. session. The intensity of the unconditioned stimulus (electric shock) was adjusted for each S so as to suppress responding during the CER signal (tone) to approximately 50% of normal pressing rate. Neither the sympathetic agents (adrenalin, Chlorpromazine, Dibenzyline), nor the parasympathetic agents (methacholine chloride, propantheline, atropine sulfate) reliably altered bar-press rates during the CER trials. Exp. 2 demonstrated that the autonomic agents, in the dosages used, were in fact altering autonomic reactivity as indexed by heart-rate measures. In Exp. 3 acquisition of the CER by 18 rats was found not to be affected by autonomic alteration as produced by drugs.