Neuropeptides in the sympathetic system: presence, plasticity, modulation, and implications.
Neuropeptides are ubiquitous in the sympathetic system and modulate transmission at the levels of the intermediolateral cell column, sympathetic ganglia, and neuroeffector junctions. Several neuropeptide-containing pathways from the hypothalamus and medulla modulate excitability of preganglionic neurons. Neuropeptides coexist with norepinephrine or acetylcholine in subpopulations of chemically coded, target-specific sympathetic ganglion neurons. Neuropeptide Y is colocalized in adrenergic vasoconstrictor neurons, whereas vasoactive intestinal polypeptide is colocalized in cholinergic sudomotor neurons. Neuropeptide expression is plastic; during development, neurons that switch from a noradrenergic to a cholinergic phenotype increase expression of vasoactive intestinal polypeptide, somatostatin, and substance P. Preganglionic inputs increase neuropeptide Y and inhibit substance P expression. Sympathetic denervation produces sprouting of sensory fibers containing substance P and calcitonin gene-related peptide in target tissues. Neuropeptides from preganglionic fibers (e.g., enkephalin) and primary afferents (e.g., substance P, vasoactive intestinal polypeptide) modulate transmission in sympathetic ganglia. Neuropeptide Y produces vasoconstriction, prejunctional inhibition of norepinephrine release, and postjunctional potentiation of norepinephrine effects. Plasma neuropeptide Y increases during intense sympathoexcitation, hypertension, and pheochromocytoma. Dystrophic neurites containing neuropeptide Y occur in human sympathetic ganglia during aging, diabetes, and dysautonomia. Sympathetic neuropeptides may thus have important clinical implications.
Benarroch
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EE
Department of Neurology, Mayo Clinic, Rochester, MN 55905.
D000375:Aging / Q000502:physiology; D000818:Animals; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology; D002415:Cats; D003929:Diabetic Neuropathies / Q000503:physiopathology; D005728:Ganglia, Sympathetic / Q000737:chemistry / Q000502:physiology; D006801:Humans; D007031:Hypothalamus / Q000502:physiology; D008526:Medulla Oblongata / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009473:Neuronal Plasticity; D009478:Neuropeptide Y / Q000502:physiology; D009479:Neuropeptides / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology
D009478:Neuropeptide Y; D009479:Neuropeptides