Effect of anterior hypothalamic lesions on neurohypophysial and peripheral tissue concentrations of somatostatin in the rat.

Somatostatin (SRIF) is present in nerve endings in the median eminence (ME) and posterior pituitary. Hypothalamic SRIF containing neuronal perikarya are predominantly located in the anterior hypothalamic area (AHA), a region implicated in the inhibitory control of GH secretion. The effect of AHA lesions on SRIF in the ME, posterior pituitary, pancreas, stomach, and small intestine was studied in the rat in order to elucidate the source of ME and posterior pituitary SRIF and to determine if depletion of hypothalamic SRIF affects peripheral organ concentrations of the peptide. Lesioned animals showed a highly significant (P less than 0.01) 83% and 82% reduction in ME and posterior pituitary SRIF and to determine if depletion of hypothalamic SRIF affects peripheral organ concentrations of the peptide. Lesioned animals showed a highly significant (P less than SRIF concentrations in the pancreas, stomach, and small intestine of the lesioned animals. Plasma and pancreatic insulin and pancreatic glucagon were likewise unchanged. These data suggest that the hypothalamic SRIF pathway begins in the AHA, from where axons of somatostatinergic neurosecretory neurons project to both ME and posterior pituitary. AHA lesions have no effect on gut and pancreatic SRIF or pancreatic insulin and glucagon.