Short-term isolation increases social interactions of male rats: A parametric analysis

Abstract

NIESINK, R. J. M. AND J. M. VAN REE. Short-term isolation increases social interactions of male rats: A parametricanalysis. PHYSIOL. BEHAV. 29(5) [819][820][821][822][823][824][825] 1982.--Frequencies of social interactions were higher in pairs of short-term individually housed male Wistar rats as compared to group-housed animals. This was most pronounced when an individually housed rat and a group-housed conspecitic were tested together in the morning under red light conditions. Then, in particular the behavioral elements exploration partner, anogenital investigation, crawl over/mount and social grooming were enhanced. The increases in social interactions was dependent on the duration of the period of individual housing and appeared to be maximal after 4 to 7 days of individual housing. The effect extinguished after repeated testing. The observed behavioral changes were hardly affected by habituation to the test cage and were also present in young animals. The increase in social interactions is apparently not due to a general increase in locomotor or exploratory behavior, since no differences in ambulation between individually-and group-housed animals were observed when they were tested together in the social interaction test, and locomotor activities hardly differed in an open field test procedure. Social interactionHousing In most of these studies long-term individually housed animals were used and the differences with group-housed animals were apparent only after weeks or sometimes even months of individual housing. However, other studies showed that also short-term social deprivation induces disturbances, for instance, a delayed adaptation to painful stimuli when rats were repeatedly tested on a hotplate (Van Ree, unpublished observations), an increase in systolic blood pressure and heart rate [12] and increased social activity when the rats were put back in a social situation [11, 20, 28].In the present study we have studied in detail the increas~Requests for reprints should be sent to Dr. J. M. van Ree at the ing effect of short-term isolation on social interactions of pairs of rats. Additional experiments showed that this effect is specific for social interactions and is not due to a more general change in locomotion or exploratory behavior of isolated rats. METHOD AnimalsMale rats of a Wistar strain, weighing between 180 and 220 grams were used, unless otherwise indicated (see experiment d below). The rats were obtained from TNO-Zeist, The Netherlands and housed in wire cages in groups of approximately 20 animals. Prior to experimentation the rats were either individually housed (isolated, I) or in groups of 5 animals per cage (non-isolated, S) for 7 days, except as otherwise indicated. Home cages were of plastic, 22 x 13 cm and 26x40 cm, respectively. During the isolation period the cages of isolated and non-isolated rats were in the same room, so the isolated animals could hear and probably smell other rats, but did not have physical contact with them. During this period the animals were kept in...

Disrupting circadian rhythms in rats induces retrograde amnesia

“…Extinction of active avoidance behavior appeared to be facilitated in phase-shifted rats as compared to controls, indicating that the amnesia induced by phase-shifting is not restricted to passive avoidance behavior. Previous studies have shown that changes in the environment before (isolation for 4-7 days) or during (intense light) testing markedly affect the level of social behaviors of rats tested in dyadic encounters [7,8]. However, neither reversal of the illumination cycle nor continuous exposure to light changed the various aspects of social interactions and explorative behavior.…”

“…Testing was performed by placing two rats (an experimental rat and a rat exposed to the normal light/dark cycle) together in a perspex observation cage illuminated with red lights for 10 minutes [7,8]. The behavior of rats was analysed later from video tapes by individuals who did not know the illumination schedule of the rats.…”

“…In addition, the frequencies of ambulation, rearing wall, rearing field and self-grooming of the individual rats were deterimined. A detailed description of the behaviors is described elsewhere [7].…”

Long-term impoverished housing effects on morris maze performance after a fimbria lesion

“…This is in contrast with the expectations, based on t~te report by Wade and Mater, that impoverishment for 2-3 weeks impaired Morris maze performance of rats without a lesion, and these deficits grew more severe as the period of impoverishment increased [28]. After long-term impoverished housing rats develop an array of behavioural changes, including, amongst others, increased aggression [ 14,26], high locomotor activity [112] and altered social behaviour [ 17]. Several authors have contributed the impoverishment effect to a 'hyperreactivity to environmental stimuli' or 'hyperarousal' [6,10,14].…”

“…Einon has shown that IC effects on object contact and radial arm maze learning could not be induced when rats were first introduced to the impoverished condition after 45/50 days of age [5,6], but emergence from cover in an open field could be affected by impoverishment at any time [6]. Some behaviours seem to be susceptible to impoverishment starting well after weaning; rats impoverished at young adult age are slower to extinguish conditioned taste aversion [13], and upon resocialization after a period of impoverishment rats show an increase in social grooming and approach the other animal more [17]. When impoverishment lasts for weeks or even months several behavioural differences can be distinguished: rats become more aggressive [18], explore more in a holeboard task [7] and are hyperactive when introduced into a novel environment [ 11].…”