Abstract
A comparison was made of the effects of administering luteinizing hormone-releasing hormone (LH-RH) by the intravenous (i.v.) vs. intraventricular routes to ovariectomized estrogenprimed rats. LH-RH was effective by either route in causing an increase in serum LH as measured by radioimmunoassay, but i.v. injection induced the greater LH discharge. The time courses of the LH responses were identical by the two approaches. A cross-transfusion technique failed to demonstrate the uptake of intraventricularly injected LH-RH into the general circulation. These results support the feasibility of direct uptake and transport of LH-RH from the ventricle to the hypophyseal portal system. However, the direct pathway appears at best to be of questionable physiological significance, since intraventricularly administered LH-RH was less potent in causing LH release than i.v. LH-RH, even though the latter was diluted by the systemic circulation.
