Behavioural and electrocortical spectrum power effects of growth hormone releasing factor in rats

The effects on behaviour and electrocortical spectrum power of intracerebroventricular, intrahippocampal and intracaudate injections of human pancreatic growth hormone releasing Factor-40 (hpGRF) (10-100 ng) were studied in rats. The hpGRF, given into the third cerebral ventricle or into the dorsal hippocampus (50-100 ng), in freely-moving rats, produced behavioural sedation accompanied by electrocortical synchronization and an increase in the total voltage power with a predominant increase in the lower frequency bands. On the contrary, unilateral injection of hpGRF (75 ng) into the head of the caudate nucleus produced an increase in locomotor activity, marked postural changes, episodes of contralateral circling and an intense pattern of stereotyped movements. In all, these results indicate that, besides its specific endocrinological effects, hpGRF possesses, in small doses, marked behavioural and electrocortical actions, the mechanism(s) of which still remain to be elucidated.