Leon S. Otis

On the role of endogenous opioid peptides: Failure of naloxone to influence shock escape threshold in the rat

Abstract Rats treated with doses of naloxone sufficient to block morphine analgesia showed no change in the threshold for escape from foot shock. The data offer no support to the hypothesis that an endogenous opioid modulates responsiveness to pain and discomfort.

Persisting effects of chronic electroshock seizures on brain and behavior in two strains of rats

Abstract Fischer rats were given minimal, maximal, or sham electroshock seizures daily, 5 times each week for 6 weeks beginning at 30 days of age. Groups were sacrificed 48 hr, 2 or 6 weeks after the last treatment. The initial depression in body weight and increase in cortical brain weight by the maximally convulsed group recovered to control values by 6 weeks. Monoamine oxidase activity was elevated throughout the brain 48 hr after the last treatment and remained so in the ventral cortex for 6 weeks. Buffalo rats exhibited only the decreased body weight and elevated monoamine oxidase activity after 6 weeks of treatment; treatment for 10 or 12 weeks produced some of the other changes observed in Fischer and Wistar strains. Treatment for 6 weeks did not affect acquisition of a successive brightness discrimination in an underwater T-maze in either strain when tested 48 hr or 4 weeks after the last treatment. Acquisition of a pole-displacement conditioned avoidance response was depressed in both strains at both test intervals.

Disruption of size discrimination in squirrel monkeys (Saimiri sciureus) by LSD-25

A “difficult” size discrimination (ratio 1.12:1) was disrupted in four of five squirrel monkeys by 10 to 40 μg/kg LSD-25 whereas an “easy” discrimination (ratio 1.96:1) was relatively unaffected. Disruption lasted from 4–6 months postinjection in two of the monkeys. Neither the difficult nor the easy discrimination was affected in three monkeys by up to 100 μg/kg BOL-148.

Chronic electroshock: Effects on brain weight, brain chemistry, and behavior

Minimum or maximum electroshock convulsions administered chronically to rats resulted in increased brain weight, total brain cholinesterase activity, total protein, and total acetylcholinesterase activity depending upon whether or not full convulsions were induced and on the frequency of their induction over a 17–20 week period. Convulsed rats made more errors in an underwater T-maze than rats given subconvulsive shocks or sham controls.

Brain biochemical and behavioral effects of 1, 2, 4 or 8 weeks′ electroshock treatment☆

Abstract In experiment 1, littermate male Wistar rats were given minimal, maximal, or sham seizures 3 or 5 times per week for 4 or 8 weeks, beginning at 30 days of age. The treatment resulted in increased cortical brain weight; body weight was reduced in the maximally convulsed S s but not in the minimally convulsed S s. Acetylcholinesterase (AChE) activity was increased slightly in the ventral cortex. Monoamine oxidase (MAO) activity was increased throughout the cortex. In Experiment 2, S s were treated 5 or 10 times per week for 1, 2, or 4 weeks. Body weight was reduced after only one week, whereas were four weeks required for the increase in brain weight to be detected. AChE activity was slightly increased in the cortex after two weeks. MAO activity was significantly increased in some parts of the cortex after only one week and throughout most of the cortex after two or four weeks. Performance in a two-trial spatial discrimination in an underwater T-maze tended to be poorer in maximally convulsed groups, but the differences were not significant at these short treatment durations.

Effects of stress during infancy on tumor development and tumor growth.

A number of investigators have reported that stressing a variety of mammals by repeated electric shocks resulted in decreased resistance to cancer-producing agents, as well as an increase in the rate of development of spontaneous tumors. Other investigators have reported the opposite findings. By-and-large, however, these studies have lacked adequate controls and have depended on results from small groups of subjects. We used sufficiently large groups to minimize sampling error. Rigid controls were instituted and each study was repeated at least twice to check the reliability of the findings. Mice and rats were stressed for short periods daily by electric shock to the body surface or convulsive shock to the brain. The stress treatments were given during early infancy (birth to weaning) or for an equal period during young adulthood (Days 24 to 47). Tumors were either transplanted or induced by chemical or viral agents. Out results failed to support the reports of other investigators that stress applied to the infant or young adult organism alters its susceptibility to develop cancer.

Lack of effect of TCAP on conditioned avoidance learning in rats

TCAP has been reported to enhance the retention of a discriminated lever-pressing avoidance response in rats, presumably by increasing the rate of RNA synthesis during the learning trials. In three experiments using a pole-climb avoidance response and multiple injections, we were unable to demonstrate enhancement. In two additional experiments designed to confirm the original report, results were also negative.

EMG Training and Headache Reduction: Some Methodological Issues

We’ve been running experiments on voluntary control of tension headaches since 1971, and our results have done nothing but cause problems for us. They simply are not orthodox. More specifically, they raise questions about the relationship of head and neck muscle tension to the etiology, onset, and control of tension headaches. And what is learned by our subjects does not appear to fit either the operant learning model or the skills learning model—not, at least, in any obvious way. This is, perhaps, not quite correct. Some skills are being learned and reinforcement of operant behavior does occur. The skills being learned, however, do not appear to be the ones we think we are training, and the reinforcement we are paying attention to docs not appear to be the one that is responsible for making the subject headache-free.