Developmental increase in 3H-muscimol binding to the γ-aminobutyric acid A receptor in hypothalamic and limbic areas of the rat: why is the ventromedial nucleus of the hypothalamus an exception?

Abstract

Using in vitro autoradiography to measure binding of the γ-aminobutyric acid A (GABA A) receptor agonist, muscimol, we examined male and female rats on postnatal days 1, 5, 10, and 20. There were no sex differences in muscimol binding in any hypothalamic or limbic regions examined. However, all regions exhibited a developmental increase in the density of binding, except the ventromedial nucleus (VMN) of the hypothalamus. We have previously shown that the adult VMN is the only hypothalamic nucleus containing an abundance of the α2 subunit of the GABA A receptor and lack of the α1 subunit. We hypothesize that the lack of α1 may be causally related to the lack of increase in muscimol binding.