COEXISTENCE OF NEUROPEPTIDE-Y AND PROGESTERONE-RECEPTOR IN NEURONS OFGUINEA-PIG ARCUATE NUCLEUS

Double-label immunocytochemistry has been employed to determine whethe r progesterone receptor (PR)-containing neurons in the arcuate nucleus (AR) of female guinea pig contain neuropeptide Y (NPY). Animals were ovariectomized, primed by estradiol and microinjected intracerebrovent ricularly with colchicine to visualize NPY-immunoreactive (IR) neurons . Only a very small population of NPY-IR perikarya (2.5% approximately ) were found to be also PR-IR. NPY-IR varicosities appeared in close p roximity to neurons with PR-containing nuclei. This restricted coexist ence provides morphological evidence that most NPY neurons in the AR a re not directly regulated by progesterone.