Effects of a lesion in the dorsal raphe nuclei performed during the juvenile period of the female rat, on puberty

The present study examined the effect of thermic lesions on the dorsal raph e nuclei (DRN) of the female rat, performed at various ages during the prep ubertal period (21, 24, or 27 days), on puberty, and at first ovulation. In comparison with sham-operated animals, the age of vaginal opening and firs t vaginal oestrus was delayed in rats with a DRN lesion performed at the en d of the infantile period (day 21) (45.6 +/- 0.94 vs. 89.9 +/- 1.03, p < 0. 05), whereas differences were not observed in animals with lesions performe d during the juvenile period (day 24 or 27). The number of ova shed by ovul ating animals was greater in those rats with lesions performed on day 24 or 27 (9.7 +/- 0.4 vs. 7.4 +/- 0.4; 9.5 +/- 0.5 vs. 7.7 +/- 0.4, p < 0.05). O varian follicular atresia in these animals was significantly lower than in control and sham-operated ones. On the day of first vaginal oestrus and 48 h after the lesion, the serotonin-hypothalamic concentration decreased in a ll lesioned animals. Present results support the idea of the participation of the serotoninergic system, arising from the DRN, in the neuroendocrine m echanisms regulating the onset of puberty and the first ovulation, with var iations depending on animal maturity. (C) 1998 Elsevier Science Inc.