Prenatal melatonin influences developmental changes of tachykinins in response to estradiol benzoate

The developmental changes of hypothalamic, pituitary, striatum and pineal g land tachykinin concentrations, as well as the response to estradiol-benzoa te (EB) administration, were studied in offspring of control and melatonin (MEL) treated mother rats. Female rats were studied throughout different ph ases of the sexual development: infantile, prepubertal and pubertal periods , in the four following groups; control-offspring+vehicle; control-offsprin g + EB; MEL-offspring + vehicle; MEL-offspring + EB. Hypothalamic NKA in co ntrol-offspring + vehicle was significantly increased only at 27 days of ag e and in control-offspring+EB at 27 days of age and during the infantile pe riod. Hypothalamic SP levels increased similarly in control-offspring+EB du ring the infantile period but the EB influence was more pronounced with sig nificantly increased concentrations at 32 days of age. Prenatal melatonin t reatment produced major alterations in these patterns of postnatal developm ent. Ln MEL-offspring+EB tachykinins concentrations in the hypothalamus dur ing infantile and prepubertal periods did not increase, however at 37 days of age, they showed significantly higher values than in control-offspring+E B groups. The developmental pattern of pituitary NKA and SP concentrations in both; control-offspring + vehicle and control-offspring+EB groups, showe d similar values from the infantile period to puberty, indicating that NKA and SP concentrations remained at similar levels independently of the sexua l stage, only at 27 days of age in control-offspring +EB significantly incr eased values were found as compared to MEL-offspring+EB, Prenatal melatonin did not produce marked modifications, only significantly lower NKA and SP concentrations in MEL-offspring+EB group were observed at 25 days of age in comparison to control-offspring+EB group. Striatal NKA and SP concentratio ns showed a similar developmental pattern. In control-offspring, EB treatme nt produced NKA and SP decreased concentrations at the infantile period tha n in control-offspring+vehicle and significantly increased concentrations d uring the prepubertal period, then during the pubertal period NKA and SP co ncentrations decreased in control-group+EB. However, prenatal melatonin tre atment reduced the levels of striatal NKA and SP during the prepubertal per iod after EB treatment and delayed until pubertal period the increase previ ously observed in control group during the prepubertal period. In MEL-offsp ring+vehicle group striatal concentrations of both tachykinins remained at low levels from infantile period until pubertal period. Prenatal melatonin and EB did not produce major alterations in SP pineal concentrations throug hout sexual development. Plasma estradiol concentrations were significantly higher in the groups that received EB treatment than in those that receive d vehicle during prepubertal and juvenile periods in control-offspring+EB g roup and during the pubertal period in MEL-offspring+EB group. These data i ndicate that prenatal MEL treatment may influence NKA and SP developmental pattern from the infantile period until adulthood in the female rat. (C) 19 99 by Elsevier Science Inc.