SEX DIFFERENCE IN THE NEUROTENSIN-IMMUNOREACTIVE CELL-POPULATIONS OF THE PREOPTIC AREA IS QUAIL (COTURNIX JAPONICA)

The distribution of neurotensin-immunoreactive cells and fibers was an alyzed by immunocytochemistry in the forebrain of male and female Japa nese quail (Coturnix japonica) by using an antibody directed against t he C-terminal part of the molecule. Immunoreactive perikarya were loca ted almost exclusively in the medial preoptic area with small populati ons also being present in the nucleus paraventricularis and in the tub eral region. Immunoreactive fibers were observed not only throughout t he preoptic area-hypothalamus, but also in the septal region, nucleus intercollicularis, substantia grisea centralis and the classical catec holaminergic areas of the mesencephalon, such as the area ventralis of Tsai and the nucleus tegmenti pedunculo-pontinus, pars compacta. The preoptic neurotensin-immunoreactive cells were exclusively located wit hin the boundaries of the sexually dimorphic medial preoptic nucleus. They were significantly more numerous in females than in males. in fem ales, the number of neurotensin cells varied during the ovulatory cycl e: fewer cells were observed in birds that were about to lay an egg (t hey had a calcified egg in the oviduct) than in those that had already laid or were not going to lay on that day. These data indicate major variations in the expression of neurotensin in response to neurochemic al or neuroendocrine changes associated with ovulation.