Conscious ovariectomized rats were administered either saline or an ethanol (ETOH)-saline solution via a permanent intragastric cannula, and plasma LH, FSH and PRL were measured by RIA of jugular blood samples drawn every 10 min through an indwelling silastic catheter. Control injections of saline into the gastric cannula did not modify any of the plasma hormone concentrations. Animals which were administered ETOH, showed marked decreases in the plasma concentrations of LH. Compared to basal levels, a significant decrease in the area under the secretion curve of LH occurred during the initial hour after ETOH administration. This decline continued with the lowest levels of plasma LH being detected at approximately 1.5 hours following the ETOH injection. Additionally, no LH pulses were detected in any of the ETOH-treated animals during the second hour after ETOH; thus, reducing the number of LH pulses observed in ETOH vs. saline-injected animals. Comparable increases in the area under the LH curve occurred following a challenge dose of LHRH in both saline and ETOH-injected rats, indicating that pituitary responsiveness was the same for both groups. In contrast to LH, ETOH did not significantly alter the pattern of FSH secretion, as represented by the area under the curve and the number of FSH pulses. In addition to the differential effects of ETOH on the pulsatile release of LH and FSH, the present data also indicate that these two gonadotropins have different secretory patterns. With regard to PRL, ETOH-injected animals showed a significant elevation in plasma PRL levels during the first hour following ETOH administration.(ABSTRACT TRUNCATED AT 250 WORDS)