Robert E. Jewett

Effect of tranquilizing drugs on postnatal behavior

Abstract Chlorpromazine 6 mg/kg and reserpine 0.1 mg/kg were given subcutaneously to pregnant albino rats on days 4–7 of gestation in order to investigate in more detail previous reports of long-term behavioral modification of offspring by these drugs. Reserpine did not cause significant differences from controls. Chlorpromazine was shown to decrease motor activity and increase audiogenic seizure susceptibility in offspring. Those animals below average in weight and in motor activity were most likely to exhibit convulsive responses. These associated factors are interpreted as representing an altered behavioral complex. These abnormal responses were found in some animals of every chlorpromazine litter. No histological differences in the brains and no differences in susceptibility to amphetamine toxicity could be demonstrated in offspring of chlorpromazine-treated mothers.

Measurement of behavior of rats under isolation and observations on preliminary drug effects

Summary1.Rats were maintained under chronic isolation except for weekly testing with another rat in an open field situation. Such chronic isolates were more active than chronically grouped rats during testing.2.Activity in the open field increased with duration of isolation, a maximum being reached at 35 days. Thereafter activity gradually decreased until, after 20 weeks of isolation, activity of grouped and isolated rats was not significantly different. Other behavior changes observed in the isolated rats were increased episodes of aggression and “following” the other rat.3.Chlorpromazine, 5 mg/kg, decreased activity of isolated animals without affecting grouped animals.4.Methamphetamine, 0.5 mg/kg, increased activity of grouped animals but not of isolates.5.Higher doses of both drugs (chlorpromazine, 7.5 mg/kg, and methamphetamine, 1 mg/kg) significantly altered activity of both isolated and grouped rats, the first depressing and the second increasing activity.6.Although all these rats were tested under identical conditions of pairing, the previous environment (isolation or grouping) before testing had a marked effect on the response to centrally acting drugs.7.It is concluded that the sensitivity of the open field test for measuring some behavioral effects of isolation can be increased by using pairs of rats during testing and that differential effects of drugs can be detected with this method.

An analysis of visual evoked potential wave forms in unrestrained cats.

SummaryMarked alterations in the wave forms of the visual evoked potential were found during repeated observations in 7 unrestrained cats. These changes were usually, but not always, associated with behavioral and electroencephalographic correlates of sleep and wakefulness.The different evoked potentials could be characterized as belonging to one of 8 possible wave forms. All wave forms were obtained from each cat although the frequency of occurrence of different wave forms varied between cats.During alert behavior the most common wave form consisted of two rapid, diphasic peaks, starting at about 20 msec with a positive wave following the flash. A more rhythmic wave form of six diphasic peaks was also common during the alert state.With increasing behavioral drowsiness and sleep spindles the wave form usually showed an increase in amplitude of negative waves.At times a wave form was present in which the early waves were missing. This wave form consisted only of two late, low-amplitude, diphasic waves and was always associated with a desynchronized EEG. Usually the animal was in activated sleep (r.e.m.-sleep) when this form of the evoked potential was observed.The observed variations in the form of the evoked potential may result from peripheral delays and activation of different pathways to different cortical neuron groups. Alternatively, the wave forms may be produced by alterations in latency of the second of two oscillating pathways to the cortex.

Effects of prolonged EEG suppression by a pyrrolopyrimidine on learned behavior

Abstract It was found that BW 58-271, a pyrrolopyrimidine, produced a CNS effect in rats resembling cortical spreading depression with suppression of spontaneous electrical activity and production of repeated high voltage slow waves. The effects of anesthetization of rats were studied in an operant conditioning situation with short (SI) and long (LI) fixed intervals for food rewards. Anesthetization with ether or thiopental 24–30 hr after the last training session had no demonstrable effect on this conditioning. Anesthetization with BW 58-271 caused an increase in lever pressing rate during both portions of the LI but did not affect the SI rate. The rats relearned the LI, the rate dropping back to control levels after three weekly trials. Using a photocell activity cage it was found that anesthetization with BW 58-271 also caused an increase in locomotor activity for several subsequent trials in experienced rats but not in inexperienced rats. The effects on learned behavior were postulated to be a consequence of the prolonged spreading depression.