Cold restraint-induced gastric lesions in individual- and group-stressed rats

The aim of the present study was to 1) determine the intensity of cold restraint-induced gastric lesions and core body temperature in single- and group-stressed rats, and establish a correlation between them; and 2) determine the influence of visual contact among animals during cold restraint on development of gastric stress ulcer. Therefore, adult male Wistar rats were put into individual or group restraint boxes (composed of two, three, six or nine single boxes) with or without possibility of visual contact and then exposed 2 hr to the cold (4 degrees C). Core body temperature was measured just before and after cold restraint using a digital rectal thermometer. The results showed that: 1) single stressed animals expressed significantly higher ulcer index than those stressed in group of three, six and nine rats; 2) there was no significant difference in degree of hypothermia among rats exposed to various group paradigms; and 3) there was no significant difference in ulcer index among animals stressed in conditions with or without visual contact. An absence of significant difference in ulcer index between single and paired stressed rats implies that three is the lowest number of animals per group at which an influence of group size on behavioral and adaptive mechanisms in rats exposed to cold restraint becomes manifest.