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

The developmental changes of hypothalamic, pituitary, striatum and pineal gland tachykinin concentrations, as well as the response to estradiol-benzoate (EB) administration, were studied in offspring of control and melatonin (MEL) treated mother rats. Female rats were studied throughout different phases of the sexual development: infantile, prepubertal and pubertal periods, in the four following groups; control-offspring+vehicle; control-offspring+EB; MEL-offspring+vehicle; MEL-offspring+EB. Hypothalamic NKA in control-offspring+ vehicle was significantly increased only at 27 days of age and in control-offspring+EB at 27 days of age and during the infantile period. Hypothalamic SP levels increased similarly in control-offspring+EB during the infantile period but the EB influence was more pronounced with significantly increased concentrations at 32 days of age. Prenatal melatonin treatment produced major alterations in these patterns of postnatal development. In MEL-offspring+EB tachykinins concentrations in the hypothalamus during infantile and prepubertal periods did not increase, however at 37 days of age, they showed significantly higher values than in control-offspring+EB groups. The developmental pattern of pituitary NKA and SP concentrations in both; control-offspring+vehicle and control-offspring+EB groups, showed similar values from the infantile period to puberty, indicating that NKA and SP concentrations remained at similar levels independently of the sexual stage, only at 27 days of age in control-offspring+EB significantly increased 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 concentrations showed a similar developmental pattern. In control-offspring, EB treatment produced NKA and SP decreased concentrations at the infantile period than in control-offspring+vehicle and significantly increased concentrations during the prepubertal period, then during the pubertal period NKA and SP concentrations decreased in control-group+EB. However, prenatal melatonin treatment reduced the levels of striatal NKA and SP during the prepubertal period after EB treatment and delayed until pubertal period the increase previously observed in control group during the prepubertal period. In MEL-offspring+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 throughout sexual development. Plasma estradiol concentrations were significantly higher in the groups that received EB treatment than in those that received vehicle during prepubertal and juvenile periods in control-offspring+EB group and during the pubertal period in MEL-offspring+EB group. These data indicate that prenatal MEL treatment may influence NKA and SP developmental pattern from the infantile period until adulthood in the female rat.