The present experiments were undertaken to throw light on the physiological role played by α-MSH in the advent of female puberty. The serum and pituitary α-MSH concentrations were determined in prepubertal rats 5, 15, 25, 30, 33 days old and at vaginal opening. The serum levels showed a significant increase on day 30 and the pituitary α-MSH levels increased steadily from day 5 to day 33. To determine if a relation exists between the increase in α-MSh levels and the peak of LH prior to vaginal opening, prepubertal rats of the same age range as above received an injection of α-MSH or saline solution and were sacrificed 30 min later. The peptide increased LH serum levels only at 30 days of age. To examine the hypothesis that α-MSH was involved in determining the timing of puberty, prepubertal rats pretreated with estradiol benzoate received an injection of α-MSH or saline solution on day 28. This treatment advanced the time of vaginal opening by 2 days in the experimental animals. With the same experimental procedure, an increase in serum levels of LH and progesterone was also observed at 29 days of age. The action of α-MSH on GnRH was analysed by incubating median eminence from prepubertal rats 20, 25 and 30 days of age, with the peptide. α-MSH increased GnRH release only in 25-day-old rats. The above results show that acute treatment with α-MSH induces modifications in the hormones related to puberty and hence allows us to include α-MSH in the chain of neuroendocrine events involved in reproductive maturation.
|Original language||English (US)|
|Number of pages||6|
|State||Published - Jan 1 1989|
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