Abstract
Long-term adult castrated rats of either sex were used. The preopticsuprachiasmatic (POA-SCH) region was stimulated bilaterally with 200-μA monophasic pulses of 0.5-ms width, in trains of 30 s on :30 s off, and at 10 or 50 Hz during 30 min under pentobarbital anesthesia. Sequential blood samples were taken starting immediately before stimulus onset and thereafter every 30 min during a 90-min period. Plasma luteinizing hormone (LH) and prolactin were measured by radioimmunoassay in the same sample. LH concentrations in control samples in both sexes were significantly reduced compared to values obtained in trunk blood after decapitation of unanesthetized rats. Stimulation at 10 Hz induced a significant rise in LH values in both sexes, with similar response profiles. Stimuli of 50 Hz delivered only in females resulted in LH values comparable to those obtained after stimuli applied at 10 Hz. Maximum average responses had values similar to those obtained in decapitated animals. In male rats, 10-Hz stimulation resulted in a significant prolactin increase. A similar stimulation in females was not effective in inducing significant prolactin changes, but stimuli delivered at 50 Hz resulted in a significant, brief increase, with a response profile different from that obtained in males. Current results indicate (a) the efficiency of “low”-frequency stimulation of the POA-SCH region to induce the release of LH and/or prolactin in castrated animals; (b) the similarity in the LH response profiles in both sexes; (c) the existence of sex differences in the prolactin release response to electrical stimulation of the POA-SCH region; and (d) the possibility of affecting differentially LH and prolactin release control mechanisms based on the temporal pattern of electrical stimuli.
Published Version
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