Showing papers by "Trevor W. Robbins published in 1978"

Effects of 6-hydroxydopamine lesions of the nucleus accumbens septi and olfactory tubercle on feeding, locomotor activity, and amphetamine anorexia in the rat.

Abstract: Bilateral 6-hydroxydopamine lesions of the nucleus accumbens septi (NAS) and olfactory tubercle (OT) caused enhanced intake of wet mash in 23-hr-food-deprived rats tested in photocell activity cages during restricted 30-min sessions. This mild hyperphagia was accompanied by a significant hypoactivity in the group with NAS/OT lesions. No hyperphagia was observed during a prolonged 120-min test session or in free-feeding tests conducted in the home cage. Anorexia induced by d-amphetamine (.5 and 1.5 mg/kg) was unaltered by the lesion, although the locomotor stimulant action of the drug was attenuated. A second experiment showed that the NAS/OT lesion also enhanced food intake in the photocell cages during 30-min sessions with dry food pellets but that food-associated drinking was concomitantly reduced. The results are consistent with the hypothesis that the behavioral changes caused by mesolimbic neuron destruction result in part from an inability to switch from one behavioral activity to another.

The acquisition of responding with conditioned reinforcement: effects of pipradrol, methylphenidate, d-amphetamine, and nomifensine.

Abstract: The effects of pipradrol (5–15 mg/kg), methylphenidate (5–15 mg/kg), d-amphetamine (0.5–3.0 mg/kg), and nomifensine (5–15 mg/kg) on the acquisition of responding with conditioned reinforcement (CR) were examined. In preliminary training (phase 1), a panel-push was required for water-deprived rats to obtain access to a water-dipper. The presentation of the dipper occurred at variable intervals, independently of responding, and was preceded by a light stimulus. In phase 2, no water was available and presentation of light and empty dipper (CR) was contingent upon pressing one of two levers present (CR lever), according to a variable-ratio 2 schedule. Pressing the other lever had no effect (NCR lever). In Experiment I, pipradrol produced a dose-dependent increase in responding on the CR lever, but a dose-dependent decrease on the NCR lever. Methylphenidate and d-amphetamine produced inconsistent results, and nomifensine produced a general reduction in responding. The stimulation of responding by pipradrol transferred to the undrugged state, but previous experience with pipradrol outside the experimental setting did not increase responding during control sessions. Experiment II showed that the effects of repeated doses of pipradrol changed over sessions. Experiment III showed that 15 mg/kg pipradrol did not increase responding for the light and dipper stimuli when these had not previously been paired with water. The results suggest that pipradrol enhances the effects of conditioned reinforcers, and are discussed in terms of the other behavioral effects of ‘psychomotor stimulant’ drugs.

Pipradrol enhances reinforcing properties of stimuli paired with brain stimulation.

Abstract: The hypothesis that a psychomotor stimulant drug (pipradrol) enhances the reinforcing effects of stimuli paired with reinforcing brain stimulation was tested using a conditioned reinforcement paradigm. Rats were trained to discriminate between two stimuli (S+ and S−) to obtain ICS in the lateral hypothalamus by pushing a panel in the presence of S+. In a subsequent preference test, ICS was no longer available, but responding on one of two novel levers now produced S+, whereas responding on the other lever produced S−. Four groups of four rats received 0, 5, 10 or 15 mg/kg pipradrol. Doses of 5 and 10 mg/kg significantly enhanced the preference for S+ over S−. These doses increased responding for S+, but had no effect on responding for S−. These results support the hypothesis tested, and suggest that pipradrol potentiates the effects of conditioned reinforcement.