Ultrastructural localization of neuropeptide Y Y1 receptors in the rat medial nucleus tractus solitarius: Relationships with neuropeptide Y or catecholamine neurons

Mar 14, 2002Journal of neuroscience research

Precise locations of neuropeptide Y Y1 receptors in the rat brain area controlling bodily functions and their relation to neuropeptide Y and stress-related neurons

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Abstract

Y1 receptors are primarily located in small unmyelinated axons and axon terminals in the medial nucleus of the solitary tract.

Y1 receptors are found in axon terminals, dendrites, and some glial cells within the medial nucleus of the solitary tract.
Labeling for Y1 receptors is often associated with dense core vesicles and small synaptic vesicles in axon terminals.
Some axon terminals labeled for Y1 receptors also contain neuropeptide Y or the enzyme responsible for catecholamine synthesis.
Y1 receptors are present on dendrites that receive excitatory synapses from axon terminals, indicating a potential role in signal modulation.
Agonists of Y1 receptors may influence cardiovascular regulation by altering the release of neuropeptide Y, catecholamines, and excitatory amino acids.

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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.

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Ultrastructural localization of neuropeptide Y Y1 receptors in the rat medial nucleus tractus solitarius: Relationships with neuropeptide Y or catecholamine neurons

Abstract

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