Biochemical mapping of somatostatinergic systems in rat brain: Effects of periventricular hypothalamic and medial basal amygdaloid lesions on somatostatin-like immunoreactivity in discrete brain nuclei

Immunohistochemical studies have demonstrated the presence of somatostatin (growth hormone release-inhibiting factor)-positive cell bodies in the periventricular nucleus of the hypothalamus and in the medial-basal amygdala. In order to map biochemically the projections of these cell groups, electrolytic lesions were made in these structures and somatostatin was measured by radioimmunoassay in microdissected brain nuclei. Bilateral destruction of the periventricular nucleus significantly decreased somatostatin-like immunoreactivity (SLI) in the median eminence, and in the rostral periventricular, medial preoptic and arcuate nuclei. Bilateral lesions placed in the medial-basal amygdala significantly decreased SLI in the median eminence and suprachiasmatic nucleus. Similar depletions were observed following lesions of the stria terminalis. These results suggest that both the periventricular and amygdaloid somatostatin systems may participate in the regulation of growth hormone secretion via their projections to the median eminence and other hypothalamic nuclei.