EFFECT OF ENVIRONMENTAL STRESSORS ON TIME-COURSE, VARIABILITY AND FORM OF SELF-GROOMING IN THE RAT - HANDLING, SOCIAL CONTACT, DEFEAT, NOVELTY, RESTRAINT AND FUR MOISTENING

Grooming is often related to dearousal following stressors. Interestin gly, electrical and chemical stimulation of the paraventricular nucleu s of the hypothalamus (PVH), at levels that are known to activate the hypothalamus-pituitary adrenal axis (HPA), also elicits grooming. At t he level of the PVH, the neuroendocrine stress response is apparently still linked to the behavioural response to stressors. However the pre cise nature of this relation is not fully understood. Here we report o n grooming in rats following exposure to different stressors which are known to activate the HPA axis. Stressors such as handling, restraint , novelty, encounters with aggressive or non-aggressive conspecifics, or moistening the fur, change the amount and time course of grooming u pon return in the home cage, as compared with controls that are just h andled. However the amount of grooming is not directly related to the strength of the stressor. Defeated intruders groom less upon return in their home cage. Novelty and non-aggressive encounters with conspecif ics reduce the variation in the amount of grooming between rats. The t ime course of grooming over the 20-min observation period also differs between treatments. Following restraint, or exposure to non-aggressiv e conspecifics, grooming first increases and then decreases. Moistened rats immediately start grooming which subsequently decreases. Rats us ed as intruders in the territory of another rat maintain a constant lo w level of grooming. Rats placed in a novel cage steadily increase gro oming during the 20-min observation period. These results suggest that grooming cannot be simply understood as an immediate response necessa ry to reduce arousal following stressors. Following exposure to a stre ssor, grooming rather seems temporary suppressed. If grooming has a re storative function, it is a delayed function, which is not directly re lated to the strength of the stressor.