Release of gonadotropin-releasing hormone by veratrine in a hypothalamic-pituitary coincubation

The effects of veratrine and veratridine on the release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) from incubations of pituitary alone, hypothalamus alone, and coincubations of hypothalamus and pituitary were examined. Veratrine produced only small increases in LH secretion from pituitaries alone relative to that produced by exogenous GnRH. Veratrine caused a calcium-dependent release of GnRH from the hypothalamus. When a pituitary and hypothalamus were coincubated veratrine produced increases in LH secretion that were much larger than its direct pituitary effects. Veratridine also produced large increases in the release of GnRH and LH from hypothalamic-pituitary coincubations. The direct effect of veratridine on pituitary LH release, however, was greater than that of veratrine. The results indicate that veratrine is capable of releasing hypothalamic GnRH with relatively small direct effects on pituitary LH secretion. Hypothalamic-pituitary coincubations coupled with veratrine depolarization may be quite useful for studying hypothalamus factors controlling pituitary hormone release.