The objectives of this research proposal are two fold: (1) to explore the nature of the dendritic tree of neurosecretory neurons both in the adult and during ontogenesis and (2) to determine the biochemical and regional nature of the synaptic input to the LHRH neurons(s). The type and extent of the dendritic arbor will be determined both qualitatively and quantitatively using both Golgi impregnated and immunocytochemically stained material for arcuate and supraoptic nuclei neurons and LHRH neurons. Once the adult parameters are known, the time course of dendritogenesis for these neuronal types will be studied and we shall explore the possibility that dendritic form or time course of outgrowth are influenced by the gonadal steroid environment. Additional electron microscopic observations will be carried out to explore the possibility that the neurosecretory dendrites are presynaptic elements and hence that the neurons can serve both as projection neurons and as local circuit neurons. Two aspects of synaptic input to LHRH neurons will be studied. We shall determine if the monoamines, serotonin and norepinephrine, synapse on LHRH neurons and we shall determine what regions (i.e., amygdala, subiculum) are afferents to the LHRH neurons. These studies will be carried out at both the light and electron microscopic levels by combining radioautography (for 3H-NE or 5-HT or 3H-proline) with immunocytochemistry for LHRH. In both kinds of experiments we will determine where on the neuron the synapses occur, the type of synapse made, etc. Once these parameters are known for the adult we shall follow the ontogeny of the synaptic input and relate this to ongoing reproductive events. The studies will be made in rats and guinea pigs of both sexes to investigate possible species or sex differences.