title: Galanin-induced hyperpolarization and decreased membrane excitability of neurones in mudpuppy cardiac ganglia.
abstract: 1. Membrane hyperpolarization and decreased excitability produced by galanin were investigated in vitro on parasympathetic postganglionic neurones in the cardiac ganglion of the mudpuppy, Necturus maculosus. 2. Galanin produced a slowly developing hyperpolarization which, in 2.5 mM-KCl, reversed at -105.4 +/- 2.7 mV. The reversal potential was shifted by 38.7 +/- 4.9 mV following a fourfold elevation of the extracellular potassium concentration. 3. Galanin inhibited action potential firing in spontaneously active neurones and decreased the number of spikes in a train produced by long (500-680 ms) depolarizing current pulses. Both effects were independent of the galanin-induced hyperpolarization. 4. Galanin increased the threshold for spike generation, prolonged the spike hyperpolarizing after-potential and decreased the maximum rate of rise, amplitude and maximum rate of fall of the sodium spike. These effects occurred independently of the galanin-induced hyperpolarization. 5. Galanin decreased the amplitude and duration of TTX-insensitive spikes initiated in cells maintained in a solution containing 9 mM-calcium, 20 mM-TEA and 1.5 microM-TTX. 6. These results suggest that a galanin-like peptide may act as an inhibitory transmitter in the mudpuppy cardiac ganglion.
authors: Department of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington 05405.
authors: L M
authors: LM
authors: Konopka
authors: T W
authors: TW
authors: McKeon
authors: R L
authors: RL
authors: Parsons
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D019004:Galanin; D005726:Ganglia, Parasympathetic / Q000502:physiology*; D006321:Heart / Q000294:innervation; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009337:Necturus; D009474:Neurons / Q000502:physiology; D009479:Neuropeptides / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D009479:Neuropeptides; D010455:Peptides; D013779:Tetrodotoxin; D019004:Galanin; D011188:Potassium