PERIAQUEDUCTAL GRAY LESIONS DO NOT AFFECT GROOMING, INDUCED ELECTRICALLY IN THE HYPOTHALAMIC PARAVENTRICULAR AREA IN THE RAT

Electrical stimulation inducing behavioral responses from the hypothal amus seems to activate systems involved in the execution phase of the behaviour rather than in the introductory or decision-making phase. Ho wever, the pathways involved are not fully understood. Projections ori ginating from hypothalamic areas involved in specific behavioral respo nses are rather complex. The periaqueductal gray (PAG) has been propos ed to be an essential output station of hypothalamic behavioral mechan isms. Here we report that lesions of the periaqueductal gray area have no effect on grooming responses evoked by electrical stimulation of t he hypothalamic paraventricular area. Neither threshold current intens ities needed to evoke grooming, nor latencies were affected 7 or 14 da ys after lesioning. The lesions caused severe behavioural deficits. An imals did not drink or eat spontaneously, had problems with motor coor dination and sometimes showed strong defensive reactions upon touch. H owever, their grooming responses induced by hypothalamic stimulation w ere not changed. The PAG may have a modulatory role on grooming behavi our; however, this modulatory effect apparently is overruled during el ectrical stimulation of the hypothalamus.