Peter L. Carlton

Contingent tolerance to the anorexigenic effects of amphetamine

Abstract Rats given pretest injections of amphetamine and post-test injections of saline develop tolerance to the anorexigenic effects of the drug. Rats given the same number of injections, but in the reverse order, fail to develop tolerance during the same period of time. Thus, the development of tolerance is contingent on the relationship between time of injection of amphetamine and eating.

Attenuated habituation due to parachlorophenylalanine

Abstract The effect of parachlorophenylalanine (PCPA), and the presumed depletion of serotonin due to it, was studied for its effect on the habituation of a startle response in rats. Parachlorophenylalanine was found to increase overall levels of startle amplitude. Detailed examination of the data from individual animals indicated that this effect was entirely due to an attenuation of the rate of habituation.

Potentiation of the behavioral effects of amphetamine by imipramine.

SummaryThe effects of imipramine in combination with amphetamine were studied in two operant-behavior situations. In one of these, rats were required to press a response lever in order to avoid brief electric shocks; in the other, rats were reinforced for displacing a small response “key” only if such responses were emitted at a rate no greater than one per 15 seconds.In general, imipramine was found to potentiate the tendency of amphetamine to increase responding in these situations. The relationship of imipramine to atropine, which has a similar action in combination with amphetamine, is discussed.

Behavioral Restraint and Symptoms of Attention Deficit Disorder in Alcoholics and Pathological Gamblers

Adult alcoholics as well as pathological gamblers reported that, as children, they had higher than control levels of attention deficit disorder-related behaviors. On the other hand, alcoholics and only a subset of gamblers showed deficits in a test of behavioral restraint.

Retrograde Amnesia Produced by Hippocampal Spreading Depression

Injection of potassium chloride into the hippocampus produces a disruption of electrical activity; a concomitant of this disruption is a deficit in retention of conditioned suppression learned 24 hours before injection.

Studies of the amnesic properties of scopolamine

Prior exposure to a stimulus results in a long-term loss of the effectiveness of that stimulus. Administration of scopolamine before such exposure attenuates this loss of effectiveness in animals subsequently tested without drug. These animals behave much as if they have not had prior exposure at all.

Dopamine and schizophrenia: an analysis of the theory.

The postulated relationship of dopamine to schizophrenia ranks among the most important contemporary theories pertinent to the biological bases of behavior. However, as an examination of the relevant research literature makes clear, the theory has not yet been convincingly validated. This lack of validation is due, in part, to a failure to address the following questions: Is dopamine hyperactivity an etiological and/or a symptom factor in schizophrenia; do laboratory measures used to test the theory truly parallel the relevant clinical phenomena; is attenuated dopamine activity a necessary and/or sufficient condition for remission of schizophrenic symptoms? Analysis of these questions not only provides a departure point for examining the theory, but sets the stage for a reformulation of the theory itself.

Augmentation of the behavioral effects of amphetamine by scopolamine.

SummaryNon-effective doses of scopolamine were found to augment the tendency of amphetamine to increase the response rates of rats working in an operant, shock-avoidance situation. This finding is presumably related to our earlier observation that the related parasympatholytic, atropine, also had this augmenting action.

Increased conditioned gustatory aversion following VMH lesions in rats

Abstract Rats with ventromedial hypothalamic (VMH) lesions and sham operated animals were allowed 20 min of access to a solution of sweetened condensed milk. After drinking the substance, the animals received intraperitoneal injections of either saline or methylatropine (1.0 mg/kg). The rats injected with methylatropine demonstrated reduced intake of the test solution when it was next presented. This conditioned gustatory aversion was more pronounced and more resistant to extinction in the rats with VMH lesions. The results support the hypothesis that VMH lesions increase responsivity to interoceptive cues associated with illness as well as to exteroceptive cues associated with consummatory responding.

Scopolamine, amphetamine and light-reinforced responding

Behavior maintained by response-contingent illumination declines within the session. This decline is reversed by the anticholinergic, scopolamine, but not by the stimulant, amphetamine. These data may be related to earlier findings implicating acetylcholine (ACH) in habituation and in certain functions of the hippocampus.