A comparative study of the effects of neonatal androgenization and estrogenization on vasoactive intestinal peptide levels in the anterior pituitary and the hypothalamus of adult female rats.

Abstract

We compared the effects of neonatal androgenization (NA) and estrogenization (NE) on vasoactive intestinal peptide (VIP) levels in the anterior pituitary (AP) and the hypothalamus and on prolactin (PRL) secretion in adult female rats. Twenty-four hours after birth, a total of seven groups were treated as follows. Three NA groups received a single subcutaneous injection of 10, 100, or 1,000 micrograms of testosterone, respectively. Similarly, three NE groups received 1, 10, or 100 micrograms of 17 beta-estradiol, respectively. The remaining one group was injected with oil vehicle only, and served as controls. At 8 weeks of age, animals were sacrificed by rapid decapitation. NA (1,000 micrograms) and NE (100 micrograms) resulted in a similar degree of hyperprolactinemia and hyperestrogenemia, but this effect ratio between NA and NE (about 1:10) was not true with the lower doses, indicating a qualitative difference in the effects of the two treatments. This is in agreement with our previous study. VIP content determined in the suprachiasmatic nucleus, the paraventricular nucleus and the median eminence did not significantly correlate with plasma PRL. In contrast, there were significant correlations among AP VIP, plasma PRL and estradiol. These results suggest the possibility that the NA- and NE-induced hyperprolactinemia may be mediated, at least in part, by a paracrine and/or autocrine effect of the increased AP VIP on the lactotroph which may probably be mediated by hyperestrogenemia. However, the possibility was also suggested that the observed changes in AP VIP were related more to NA and NE's imprinting effects on the developing brain than to the PRL secretion.(ABSTRACT TRUNCATED AT 250 WORDS)