DISTRIBUTION OF SOMATOSTATIN IMMUNOREACTIVITY IN SHEEP HYPOTHALAMUS -A COMPARISON WITH THAT OF THE RAT

The distribution of somatostatin immunoreactivity was determined throu ghout the hypothalamus of the sheep and comparisons were made with the known distribution of somatostatin immunoreactivity in the rat. Immun opositive perikarya were present in the sheep periventricular region f rom as far rostral as the supraoptic recess of the third ventricle to the posterior optic chiasm. In the basal hypothalamus, a thick shell o f immunopositive neurons surrounded the ventromedial nucleus (VMH), an d there were also neurons in the caudal arcuate nucleus. Somatostatin immunoreactive fibres were concentrated in the dorsal VMH and arcuate nucleus as well as in the median eminence. The distribution in sheep w as similar to that in rats, but immunoreactive neurons around sheep VM H were distinctive, a characteristic that might relate to differences in growth hormone physiology in this species.