Central site of action of somatostatin (SRIF): Role of hippocampus

The direct cerebral administration of somatotropin release inhibiting factor (SRIF) into two loci of the hippocampal formation induced a variety of behavioural, motor and electrophysiological changes. These were characterized by several patterns of stereotyped behaviour, alteration of the sleepwaking cycle and frequent dissociation of the EEG from behaviour. Both behavioural and electrophysiological phenomena were found to be dose-related. The administration of SRIF analogues via the same route failed to produce comparable effects, thus suggesting the specificity of SRIF action within the central nervous system. The results indicate that the hippocampus is involved in mediating the central, nonendocrine action of SRIF and are consistent with the hypothesis proposing the existence of a limbic pacemaker controlling stereotyped behaviour.