Twenty-four hour pattern of @entity3695 levels in female XXXX subjected to transection of the mesencephalic raphe or ablation of the suprachiasmatic nuclei.

@entity55812 @entity8943 @entity3695 @entity18489 @entity35
The present study was undertaken to evaluate the 24-hour periodicity in serum @entity3695 levels subsequent to transecting the ascending serotonergic system or ablating the suprachiasmatic nuclei ( @entity8943 ) of adult (185 g) female @entity35 . The ascending serotonergic system was transected at the level of the rostral mesencephalon using a 1.5 mm wide knife and the @entity8943 was ablated with a modified @entity55812  sz-Pupp knife. The effect of @entity18489 ( @entity18489 ) or @entity8943 ablation on the circadian rhythm in nonstress serum @entity3695 levels was assessed 45 days after surgery by measuring with radioimmunoassay the serum @entity3695 concentration in serial blood samples obtained from the tail vein of lightly restrained rats. Serum @entity3695 concentration in control and @entity18489 animals showed circadian periodicity; peak levels occurred during the midafternoon, 4 h prior to the dark phase of the lighting regime (lights on at 4 a.m., off at 6 p.m.). The amplitude of the fluctuations of both groups varied markedly and were related to the estrous cycle. However, @entity18489 animals showed a reduced amplitude in the rhythm. In controls peak @entity3695 levels on days of proestrus and estrus were 15-20 times higher than on days of diestrus. In contrast, serum @entity3695 levels in @entity8943 -ablated @entity35 did not vary with a circadian periodicity but rather showed random, low amplitude fluctuations. Reproductive cyclicity was also abolished by @entity8943 ablation, i.e., @entity8943 -ablated @entity35 presented persistent vaginal cornification. These data indicate that circadian periodicity in serum @entity3695 levels is not compromised by sectioning the ascending serotonergic fibers but is abolished after ablating the @entity8943 .
