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Biomedical subjects

R Plotnik

Publications and source records attributed to R Plotnik.

12 recordsLinked to original sources
PubMed1982

Chronic amphetamine: effects on defensive flight in the rat.

Hooded rats were injected with physiological saline or d-amphetamine sulfate for 13 days on a schedule designed to mimic patterns of abuse: one injection on days 1-11, two injections on day 12, and three injections on day 13; amphetamine dosage for the first three injections was 3.5 mg/kg and for all subsequent injections was 5.0 mg/kg. Amphetamine-treated rats (Amphet) showed a dramatic flight reaction in response to a novel stimulus (mechanical robot) that did not elicit flight from saline control animals. Tested on a slow-moving treadmill that carried them toward the stimulus, Amphet rats accumulated only 15% of the trial time at the front of the apparatus nearest the stimulus and accumulated approximately 75% of the trial time at the extreme rear of the apparatus, farthest from the stimulus. Control tests of Amphet rats in the absence of the stimulus ruled out interpretations in terms of motor behavior. In fact, a major advantage of the present procedure is that animals are able to execute the relatively simple defense response despite the occurrence of motor stereotypy. These results suggest that the defense-response paradigm is suitable for the study of chronic amphetamine and may provide a useful adjunctive to existing models of amphetamine psychosis.

Aggression↗
PubMed1979

Physostigmine: effects on fear or defense responses in the rat.

Previous research had shown that the anticholinergic drug, scopolamine, decreased innate defensive responses of rats to a live cat or mechanical robot, and that the effects of scopolamine were attributable to actions of the drug on the central nervous system. In the present research, the anticholinesterase, physostigmine, which increases central cholinergic activity, caused an increase in the defense responses of male hooded rats. Physostigmine caused significantly more freezing and significantly more suppression of feeding and suppression of time near the aversive stimulus (ROBOT). Dose-response curves showed a positive, linear relationship between dose (0.025, 0.05, 0.1 and 0.2 mg/kg) of physostigmine and defense responses. The present results could not be attributed to general response suppression since the effects of physostigmine were situation-specific, i.e., the drug had no significant effect on behavior in the non-aversive or NO ROBOT condition. The present results were taken as further evidence of the involvement of cholinergic activity in the mediation of defense responses. The effects of cholinergic and anticholinergic drugs on the observable defense response of freezing were thought to have important implications for the large literature relating these drugs and avoidance responding.

Aggression↗
PubMed1979

Amphetamine: effects on defensive flight or avoidance in the rat.

Treatment with a moderately high dose of amphetamine caused rats to retreat from a stimulus they would normally approach and explore (mechanical robot or live white rabbit). While saline-treated rats spent approximately equal amounts of time in the area of the apparatus near the stimulus, amphetamine-treated rats spent a high percentage of trial time in the area of the apparatus farthest from the stimulus. The drug effects were dose related (range: 1.75, 3.5 and 7.0 mg/kg) with higher avoidance time at higher doses, and significant linear trends accounting for much of the variance. The highest dose of amphetamine elicited response stereotypy. However, control conditions ruled out the possibility that the present results could be explained by competing motor responses of stereotypy or increased activity. Thus, apart from its actions on motor behavior, amphetamine treatment resulted in rats avoiding or retreating from an otherwise neutral stimulus.

Animals↗
PubMed1976

Scopolamine: effects on fear or defense responses in the rat.

In previous research scopolamine reduced fear or defense responses of rats to a cat, and removal of the rats' olfactory bulbs had the same effect. This suggested that scopolamine might have affected defense responses by blocking olfactory perception of the stimulus cat. The present experiments studied this possibility and explored further the effects of scopolamine on defense responses of the hooded rat. In Experiment 1 rats treated with scopolamine were found to be responsive to olfactory cues from a cat. When cat smell, but not a cat, was present in the apparatus, scopolamine-treated rats showed a large and significant suppression of food consumption. In Experiment 2 the effects of scopolamine on defense responses were shown to be generalizable to an inanimate stimulus, mechanical robot. Scopolamine caused significantly less freezing and avoidance and significantly shorter latencies to drink in the presence of the robot. One of the primary findings of the present research is that scopolamine has now been shown to reduce the defensive response of freezing in a variety of stimulus situations. This finding was thought to have important implications for the literature relating anticholinergic drugs and avoidance behavior.

Animals↗
PubMedDate not supplied

Comparing the effects of scopolamine on operant and aggressive responses in squirrel monkeys.

The anticholinergic drug, scopolamine, causes disinhibition or an increase in responses that an animal normally suppresses. Experiment 1 confirmed this effect in squirrel monkeys. Experiment 2 explored the implications of drug-produced disinhibition on aggressive interactions. In Experiment 1, scopolamine produced increased unreinforced responding on a DRL schedule and increased responding during unreinforced (Time Out) periods. In contrast, the peripheral control drug, methyl scopolamine, caused decreased responding in both situations. In Experiment 2, social rank and drug treatment interacted. When space was restricted so that the opportunity for social interactions was maximized, scopolamine consistently increased aggressiveness in the dominant monkey and decreased aggressiveness in a submissive monkey. When space was increased so that the opportunity for social interactions was minimized, scopolamine caused decreased aggressive responses in all monkeys. Neither the effective dosage nor the drug's effect on the operant task could be easily generalized to aggressive responses.

Aggression↗