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 secretion^2,3—are, however, not yet established. It is also not known whether these sites are targets for pituitary hormone action, although recent anatomical⁴ and physiological studies^5,6 suggest that pituitary hormones may reach the brain. For these reasons, we co-cultured^7,8 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 ACTH^9,10 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-reactive^11,12 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.