RAT OXYTOCIN RECEPTOR IN BRAIN, PITUITARY, MAMMARY-GLAND, AND UTERUS - PARTIAL SEQUENCE AND IMMUNOCYTOCHEMICAL LOCALIZATION

Partial complementary DNAs of an oxytocin (OT) receptor were cloned fr om rat brain and uterus. The complementary DNAs encoded for the same a mino acid sequence, which showed a high degree of homology with the hu man and porcine uterine OT receptors, except for a region in the third intracellular loop. Antibodies were raised against nonoverlapping seq uences of the third intracellular loop of this rat OT receptor. Using these antisera, OT receptor expression was demonstrated in the brain, pituitary, mammary gland, and uterus by immunocytochemistry. In the br ain, several areas including the ventromedial hypothalamus, the bed nu cleus of the stria terminalis, the ventral pallidum, the paraventricul ar nucleus, and the dorsal part of the supraoptic nucleus, demonstrate d OT-receptor immunoreactivity. However, no immunoreactivity was detec ted in two areas of the brain known to contain dense OT-binding sites by receptor autoradiography studies: the ventral hippocampus and the c entral nucleus of the amygdala. In the pituitary, both the anterior an d posterior lobes were positive for OT receptor immunoreactivity, wher eas the intermediate lobe was negative. These results demonstrate that the same receptor type is expressed in both peripheral OT target tiss ues and the brain, and also suggest the possibility that a different O T receptor subtype may be present in some areas of the brain.