[Demonstration of pulsatile secretion of somatostatin in the third cerebral ventricle of unanesthetized rats].

Using a specially designed push-pull cannula stereotaxically implanted into the 3rd ventricle, a pulsatile secretion of IR-SRIF with a circhoral periodicity was detected in male rats. At 30 min. to 1 h 1/2 intervals the secretion rate of the neuropeptide rose from a baseline rate of 14.5 +/- 0.5 pg/10 min., corresponding to a baseline concentration of 60 +/- 2 pg/ml to peaks of 50 +/- 5 pg/10 min. or 210 +/- 22 pg/ml, respectively. This pulsatile pattern was restricted to rats where histological examination showed no dilation pictures of the ventricle. The possible origin and function of intra-ventricular IR-SRIF are discussed.