A study was made of the influence of agonists and antagonists of catecholamine action on LH and FSH secretion during the second rise of FSH secretion at the early hours of the estrous stage (E). Administration of phentolamine (a blocker of alpha-adrenoceptors) did not change the level of gonadotropins. On the contrary, haloperidol (a blocker of dopamine receptors) lowered the level of FSH at 3 o'clock of the estrous stage but made no effect on the blood concentration of LH. Administration of a stimulator of dopamine receptors increased the blood concentration of FSH at 1 and 3 o'clock of the estrous stage. Acute administration of haloperidol decreased the number of nuclear estradiol-binding sites in the adenohypophysis at 3 o'clock of the estrous stage but did not change the concentration of nuclear receptors of testosterone at either of the above time intervals. The results suggest that estrogenic and androgenic receptors and dopamine cerebral systems are involved in the stimulation of the second wave of FSH secretion. The interrelation of the dopamine activity and level of hypophyseal estradiol receptors, influencing FSH secretion in the early estrus, was established.
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