Lack of effect of intracerebroventricular infusion of H1 or H2 histamine receptor antagonists on luteinizing hormone secretion in fed or fasted rats

Abstract

The effects of intracerebroventricular infusion of histamine receptor antagonists on pulsatile secretion of luteinizing hormone (LH) were examined in ovariectomized, estradiol-primed rats under conditions of normal feeding or fasting for 48 h. Blood samples for determination of the plasma LH concentration by radioimmunoassay were collected every 6 min for 3 h through an atrial indwelling catheter. Ten microliters of either the H1 receptor antagonist chlorpheniramine (3 mM), the H2 receptor antagonist ranitidine (3 mM), or artificial cerebrospinal fluid (vehicle) were infused into the third ventricle during the second 1-h period of blood sampling. The infusion of either receptor antagonist failed to restore the pattern of pulsatile LH release in fasted animals to that observed in fed rats. The plasma LH concentration as well as the pulse frequency and pulse amplitude of LH secretion in fed rats were also not affected by either receptor antagonist. These results indicate that H1 or H2 receptor antagonists did not affect on tonic LH secretion in fed or fasted rats.