Ultrastructural localization of neuropeptide Y Y1 receptors in the rat medial nucleus tractus solitarius: relationships with neuropeptide Y or catecholamine neurons.
Neuropeptide Y (NPY) Y1 receptor (Y1-R) agonists influence cardiovascular regulation. These actions may involve NPY- and catecholamine-containing neurons in the medial nucleus of the solitary tract (mNTS), at the level of the area postrema. The cellular sites through which Y1-R agonists may interact with NPY and catecholamines in the mNTS, however, are not known. To determine potential sites of action for Y1-R agonists, and their relationship to NPY or catecholamines in the mNTS, we used electron microscopic immunocytochemistry for the detection of sequence-specific antipeptide antisera against Y1-R alone or in combination with antisera against NPY or the catecholamine-synthesizing enzyme tyrosine hydroxylase (TH). Analyses were conducted in the rat mNTS, at the level of the area postrema. Y1-R was found mainly in small unmyelinated axons and axon terminals but also in some somata and dendrites as well as a small number of glia. Within axon terminals, labeling for Y1-R was often present on dense core vesicles and small synaptic vesicles as well as extrasynaptic areas of the plasmalemma. Some Y1-R-labeled terminals also contained NPY or TH, suggesting that agonists of Y1-R may influence the release of NPY or catecholamines in the mNTS. In addition, Y1-R was found in dendrites that received asymmetric excitatory-type synapses from unlabeled axon terminals. Some of these dendrites contained NPY or TH, which indicates that Y1-R may be targeted for functional activation within NPY- or catecholamine-expressing neurons in the mNTS. These results demonstrate that Y1-R is a presynaptic receptor in NPY- or catecholamine-containing axon terminals within the mNTS as well as a postsynaptic receptor on NPY- or catecholamine-containing neurons that are contacted by axon terminals that likely contain excitatory amino acid transmitters. Agonists of Y1-R in the mNTS may thus affect cardiovascular regulation by modulating NPY, catecholamine, and excitatory amino acid transmission.
Glass
Michael J
MJ
Department of Neurology and Neuroscience, Division of Neurobiology, Weill Medical College of Cornell University, New York, New York 10021, USA. mjg2003@mail.med.cornell.edu
Chan
June
J
Pickel
Virginia M
VM
D000818:Animals; D001341:Autonomic Nervous System / Q000737:chemistry / Q000166:cytology; D001794:Blood Pressure / Q000502:physiology; D002395:Catecholamines / Q000096:biosynthesis*; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D003712:Dendrites / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D006339:Heart Rate / Q000502:physiology; D008297:Male; D016253:Microscopy, Immunoelectron; D009457:Neuroglia / Q000737:chemistry / Q000648:ultrastructure; D009478:Neuropeptide Y / Q000032:analysis*; D017729:Presynaptic Terminals / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D017476:Receptors, Neuropeptide Y / Q000032:analysis*; D017552:Solitary Nucleus / Q000737:chemistry* / Q000166:cytology; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis / Q000378:metabolism
D002395:Catecholamines; D009478:Neuropeptide Y; D017476:Receptors, Neuropeptide Y; C097212:neuropeptide Y-Y1 receptor; D014446:Tyrosine 3-Monooxygenase