OPIOID-DOPAMINERGIC INTERACTIONS IN PRIMARY EMPTY SELLA

Previous studies have indicated different abnormalities of PRL secreti on in patients with primary empty sella (PES). Since it is known that endogenous opiates and dopamine interact in modulating PRL secretion, we have studied the effect of an opiate receptor blockade (with Naloxo ne, NAL, 1.6 mg/h as a continuous infusion) on anterior pituitary horm ones and on PRL responsiveness to metoclopramide (MCP), in 10 premenop ausal normoprolactinemic patients with PES, studied in follicular phas e, in order to investigate neurotransmitter abnormalities present in s uch a syndrome. NAL failed to significantly affect LH and FSH basal le vels; on the contrary, slight but significant increases in PRL and GH secretion were observed. NAL partially blunted the PRL responsiveness to the dopaminergic blockade, which was very marked when tested after MCP alone. These data confirm that the modulation of anterior pituitar y hormone secretion is different in PES patients, when compared with n ormal subjects. The infusion of NAL induced a ''paradoxical'' increase in hormones (PRL and GH) which are normally stimulated by endogenous opiates; but, on the other side, it blocked the marked PRL responsiven ess to the dopaminergic blockade, which is characteristic of PES syndr ome. This phenomenon seems to indicate that the relationships between dopaminergic and opiatergic neurons could be modified by the neuroanat omic alteration which is present in this complex syndrome.