Prolactin Immunoreactive Neurons of the Rat Lateral Hypothalamus: Immunocytochemical and Ultrastructural Studies

A population of neurons immunoreactive to an antiserum (AS) raised against ovine prolactin (LHPLI neurons) was previously described in the rat perifornical areas and lateral hypothalamus. In the present paper, we demonstrate by complementary immunocytochemical studies using AS to various biologically active peptides or neurotransmitters that these neurons are also detected by AS to bradykinin and to dynorphin B. Electron microscope examination shows that the LHPLI neurons are peptidergic neurons synthesizing apparently only one type of secretory granules. Numerous synapses on their perikarya and processes reflect the complexity of their relationships with other neuron populations, which have yet to be mapped and elucidated.