PROGESTERONE-RECEPTOR IMMUNOREACTIVITY IN AROMATIC L-AMINO-ACID DECARBOXYLASE-CONTAINING NEURONS OF THE GUINEA-PIG HYPOTHALAMUS AND PREOPTIC AREA

A double-labeling immunofluorescence procedure was used to determine w hether progesterone receptor (PR)-immunoreactive (IR) neurons in the p reoptic area and hypothalamus of female guinea pigs also contained aro matic L-amino acid decarboxylase (AADC), an enzyme involved in the syn thesis of both catecholamines and serotonin. Immunostaining was perfor med on cryostat sections prepared from ovariectomized guinea pigs prim ed by estradiol to induce PR. The nuclear presence of PR was visualize d by a red fluorescence while the AADC-containing perikarya showed a y ellow-green fluorescence. The topographic distribution of AADC-IR neur ons was investigated by using a specific antiserum obtained by immuniz ation of rabbits with a recombinant protein beta-galactosidase-AADC in the two regions known to contain the densest populations of estradiol -induced PR-IR cells: the preoptic area and the mediobasal hypothalamu s. The localization of PR-IR and AADC-IR cell populations showed consi derable overlap in these areas, mainly in the medial and periventricul ar preoptic nuclei and in the arcuate nucleus. A quantitative analysis of double-labeled cells estimated that about 15% to 23% of AADC-IR ce lls in the preoptic area and about 11% to 21% of AADC-IR cells in the arcuate nucleus possessed PR. This colocalization persisted throughout the rostrocaudal extent of these areas and represented 3% to 9% of th e population of PR-IR cells. These findings provide neuroanatomical ev idence that a subset of AADC neurons is directly regulated by progeste rone. The exact physiological role of this enzyme in target cells for progesterone is not understood. AADC may be involved in functions othe r than that for the synthesis of the classical neurotransmitters. (C) 1996 Wiley-Liss, Inc.