VIP and PACAP potentiation of nicotinic ACh-evoked currents in rat parasympathetic neurons is mediated by G-protein activation.
The effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP27 and PACAP38) on isolated parasympathetic neurons of rat intracardiac and submandibular ganglia were examined under voltage clamp using whole-cell patch-clamp recording techniques. VIP and PACAP (</= 10 nM) selectively and reversibly increased the affinity of nicotinic acetylcholine receptor channels (nAChRs) for their agonists resulting in a potentiation of acetylcholine (ACh)-evoked whole-cell currents at low agonist concentrations. VIP-induced potentiation was observed with either ACh or nicotine as the cholinergic agonist. The VIP- but not the PACAP-induced potentiation of ACh-evoked currents was inhibited by [Ac-Tyr1, D-Phe2]-GRF 1-29, amide (100 nM), a selective antagonist of VPAC1 and VPAC2 receptors; whereas the PACAP38- but not the VIP-induced potentiation was inhibited by 100 nM PACAP6-38, a PAC1 and VPAC2 receptor antagonist. The signal transduction pathway mediating VIP- and PACAP-induced potentiation of nicotinic ACh-evoked currents involves a pertussis toxin (PTX)-sensitive G-protein. Intracellular application of 200 microM GTPgammaS or GDPbetaS inhibited VIP-induced potentiation of ACh-evoked whole-cell currents. GTPgammaS alone potentiated ACh- and nicotine-evoked currents and the magnitude of these currents was not further increased by VIP or PACAP. The G-protein subtype modulating the neuronal nAChRs was examined by intracellular dialysis with antibodies directed against alphao, alphai-1,2, alphai-3 or beta G-protein subunits. Only the anti-Galphao and anti-Gbeta antibodies significantly inhibited the effect of VIP and PACAP on ACh-evoked currents. The potentiation of ACh-evoked currents by VIP and PACAP may be mediated by a membrane-delimited signal transduction cascade involving the PTX-sensitive Go protein.
Liu
D M
DM
Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia.
Cuevas
J
J
Adams
D J
DJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D004357:Drug Synergism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D005726:Ganglia, Parasympathetic / Q000166:cytology / Q000187:drug effects*; D005731:Ganglionic Stimulants / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006321:Heart / Q000294:innervation; D020962:Heterotrimeric GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D006727:Hormone Antagonists / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D009479:Neuropeptides / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009538:Nicotine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051381:Rats; D011978:Receptors, Nicotinic / Q000502:physiology*; D017337:Sermorelin / Q000031:analogs & derivatives / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013363:Submandibular Gland / Q000294:innervation; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
C495403:Adcyap1 protein, rat; D000906:Antibodies; D005731:Ganglionic Stimulants; D006727:Hormone Antagonists; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011978:Receptors, Nicotinic; D014665:Vasodilator Agents; D014660:Vasoactive Intestinal Peptide; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009538:Nicotine; D017337:Sermorelin; C045616:somatotropin releasing hormone (1-29)-amide, N-Ac-Tyr(1)-Phe(2)-; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins; D000109:Acetylcholine