title: VIP and PACAP effects on mouse major pelvic ganglia neurons.
abstract: Major pelvic ganglia (MPG) neurons innervate urogenital organs and components of the lower bowel. Immunoreactivity for vasoactive intestinal polypeptide (VIP) has previously been observed in the MPG, and VIP knockout animals have impaired micturition reflexes suggesting a role for this neuropeptide in urogenital function. Here, we investigate the presence and action of VIP and a related neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP), in the pelvic ganglia of male mice. An abundance of VIP-immunoreactive (IR) neurons and nerve fibers were observed in the ganglion, whereas PACAP immunoreactivity was not seen. Extracts from acutely isolated MPG contained transcripts for the VPAC1, VPAC2, and PAC1 receptors. Local application of VIP, PACAP, or maxadilan to isolated pelvic ganglion neurons shortened the duration of the afterhyperpolarization (AHP) of action potentials elicited by brief intracellular depolarization. All three peptides also increased neuronal excitability within a subpopulation of the sampled neurons. Bath application of apamin, a peptide antagonist of SK channels, shortened the duration of the AHP indicating that AHP duration in pelvic neurons is determined principally by SK-channel activity. The results suggest that VIP has a role in the neural control of pelvic organ function and activation of VPAC and/or PAC1 receptors can modulate the activity of the autonomic neurons innervating pelvic organs.
authors.affiliation: Departments of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington, VT 05405, USA. John.Tompkins@uvm.edu
authors.forename: John D
authors.initials: JD
authors.lastname: Tompkins
authors.forename: Beatrice M
authors.initials: BM
authors.lastname: Girard
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Vizzard
authors.forename: Rodney L
authors.initials: RL
authors.lastname: Parsons
mesh_terms: D000818:Animals; D001030:Apamin / Q000494:pharmacology; D004594:Electrophysiology; D005728:Ganglia, Sympathetic / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D019476:Insect Proteins / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010388:Pelvis / Q000294:innervation*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / Q000235:genetics / Q000378:metabolism; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000235:genetics / Q000378:metabolism; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000235:genetics / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D019476:Insect Proteins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D014665:Vasodilator Agents; C069147:maxadilan protein, insect; D001030:Apamin; D014660:Vasoactive Intestinal Peptide