Y1 RECEPTORS IN THE NUCLEUS-ACCUMBENS - ULTRASTRUCTURAL-LOCALIZATION AND ASSOCIATION WITH NEUROPEPTIDE-Y

Neuropeptide Y (NPY) is present in aspiny neurons in the nucleus accum bens (NAc), which also contains moderate levels of ligand binding and mRNA or the Y1 receptor, To determine the potential functional sites f or receptor activation, we examined the electron microscopic immunocyt ochemical localization of antipeptide antisera against the Y1 receptor in the kat NAc, We also combined immunogold and immunoperoxidase labe ling to show that, in this region, Y1 receptors are present in certain somatodendritic and axonal profiles that contain NPY or that appose N PY containing neurons, The Y1-like immunoreactivity (Y1-LI) was seen o ccasionally along: plasma membranes but was associated more commonly w ith smooth endoplasmic reticulum (SER) and tubulovesicular organelles iu somata and dendrites of spiny: and aspiny neurons, The mean density of immunoreactive dendrites and spines per unit volume was greater in the ''motor-associated'' sore than ha the shell of the NAc., Y1-LI wa s also seen in morphologically heterogenous axon terminals, including those forming asymmetric excitatory-type synapses, and ha selective as trocytic processes near this type of junction. We conclude that Y1 rec eptors play a role in autoregulation of NPY-containing neurons but are also likely to be internalized along with endogenous NPY in NAc. Our results also implicate Y1 receptors in the NAc in post- and presynapti c effects of NPY and in glial functions involving excitatory neurotran smission. In addition, they suggest involvement of Y1 receptors in det ermining the output of a select population of neurons associated with motor control in the NAc core. (C) 1998 Wiley-Liss, Inc.