Endothelin B receptor-like immunoreactivity is associated with LHRH-immunoreactive fibers in the rat hypothalamus

Antisera were raised against amino-acid residues 425–439 of the rat endothelin B (ET_B) receptor. Massive ET_B receptor immunoreactive fibers were observed in the median eminence and organum vasculosum lamina terminalis of rats. Double labeling studies with anti-luteinizing hormone-releasing hormone (LHRH) antiserum revealed that ET_B receptor-like immunoreactivity associated with LHRH-immunoreactive fibers in these areas. However, ET_B receptor-like immunoreactivity was not detected in LHRH-immunoreactive somata. This result suggests that endothelin affects the LHRH neuronal systems via ET_B receptors on the axon at the terminal field.