Influences of the Pineal and Adrenal Glands on the Proestrous Release of Hormones in Rats Maintained in a Reduced Photoperiod

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Abstract
The influence of pinealectomy (Px) and/or adrenalectomy (Adx) on reproductive processes was examined in female rats maintained in a reduced photoperiod (8 h L:16 h D). Estrous cycle length, number of ova ovulated and organ weights (ovaries, uterus or pituitary gland) were not significantly altered by either surgical procedure. Moreover, the critical period for LH release as defined by Nembutal blockade was unaffected by these treatments. In contrast, serum LH levels on proestrus (third proestrus subsequent to surgery) were reduced overall by Px. In Px-Adx rats either the magnitude of the LH surge was subnormal or the onset of the LH rise was delayed. The time periods selected for blood sampling did not allow us to distinquish between these 2 effects. In any case, serum LH values were markedly depressed at 1700 h in Px-Adx animals. At this time serum progesterone concentrations were also reduced in this group of rats. Both Px and/or Adx significantly altered the time course of serum prolactin on proestrus and at 1700 h in Px-Adx animals, serum concentrations were significantly elevated above control levels. Our data demonstrate that both the pineal and adrenal glands influence the release of pituitary hormones in animals maintained in a reduced photoperiod.

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