Hypothalamic paraventricular nucleus is a privileged site for brain-pituitary interaction in long-term tissue culture.

Abstract

It is generally accepted that hypothalamic factors are released from the median eminence into the hypophysial portal vessels and exert a powerful control on the secretion of anterior pituitary hormones1. The brain sites involved in the synthesis of hypothalamic factors—particularly those that control ACTH secretion2,3—are, however, not yet established. It is also not known whether these sites are targets for pituitary hormone action, although recent anatomical4 and physiological studies5,6 suggest that pituitary hormones may reach the brain. For these reasons, we co-cultured7,8 various hypothalamic explants from rat brain for 4 weeks with anterior pituitary. We report that during the third and fourth week in vitro, there is an approximately 10-fold increase in bioactive ACTH9,10 in the medium of co-cultures prepared from the paraventricular nucleus and anterior pituitary, and that this increase is highly correlated with an increase (up to 10-fold) in concentrations of immuno-reactive11,12 arginine vasopressin (AVP). Hormone levels did not increase when basal hypothalamus was co-cultured with anterior pituitary, paraventricular nucleus with posterior pituitary, or supraoptic nucleus with anterior pituitary. Thus, we propose a specific interaction between anterior pituitary and paraventricular nucleus that results in a mutual enhancement ofeach other's peptide production.