The Effects of Interruption of the Ventral Noradrenergic Pathway on the Proestrous Discharge of Prolactin in the Rat

Abstract

Summary

6-Hydroxydopamine was mi-croinjected bilaterally into the ventral nor-adrenergic tract at the level of the interpe-duncular nucleus. Effective injections into the tract as indicated by the lesions induced and by a decline in the catecholamine fluo-resence in the anterior hypothalamus were associated with a complete blockade of the rise in prolactin which occurs on the afternoon of proestrus and, in fact, a decline in prolactin ensued. Lesions which were asymmetrical or missed the ventral noradrenergic tract had only a slight effect in inhibiting the release of prolactin on the afternoon of proestrus. All lesions were capable of blocking the release of LH on the afternoon of proestrus. It is postulated that increased impulse traffic along the ventral noradrenergic tract induces the proestrous discharge of prolactin and LH or that, alternatively, tonic activity in this tract is required for this release to occur.