Journal of Neurophysiology, Vol 73, Issue 4 1374-1382, Copyright © 1995 by APS

ARTICLES

Neuropeptide galanin inhibits omega-conotoxin GVIA-sensitive calcium channels in parasympathetic neurons

L. A. Merriam and R. L. Parsons
Department of Anatomy and Neurobiology, University of Vermont, College of Medicine, Burlington 05405, USA.

1. We determined the effect of the neuropeptide galanin on barium currents (IBa) flowing through voltage-gated calcium channels. We voltage clamped parasympathetic neurons dissociated from mudpuppy cardiac ganglia using both the standard whole cell and the perforated-patch variations of the patch-clamp technique. 2. Galanin produced a concentration-dependent inhibition of IBa. The maximal inhibition was 50-60% and the concentration that produced half-maximal inhibition (IC50) was 0.42 nM. In mud-puppy parasympathetic neurons, omega-conotoxin-GVIA (CTX)-sensitive channels are the predominant type of calcium channels, and only a small portion of IBa is contributed by dihydropyridine-sensitive channels. Galanin preferentially inhibited a portion of the CTX-sensitive current. 3. In currents recorded with the standard whole cell technique, activation of IBa was slowed in the presence of galanin. In contrast, in the majority of neurons studied with the perforated-patch technique, galanin decreased IBa without altering the kinetics of current activation. With both recording methods, the decrease in IBa was greatest with voltage steps to 0 mV and persisted with steps to +50 mV. For control currents, large depolarizing voltage steps (+70 to +120 mV) did not markedly facilitate IBa when either recording technique was used. However, the degree of facilitation in galanin was significantly greater with the standard whole cell recording technique. 4. IBa exhibited inactivation under the conditions of these experiments. Inactivation of IBa recorded during a 900-ms depolarizing voltage step was fitted to a double exponential. Galanin decreased the amplitude of IBa but did not alter the time constants of inactivation.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				J. C. HARDWICK, J. D. TOMPKINS, S. A. LOCKNAR, L. A. MERRIAM, B. A. YOUNG, and R. L. PARSONS Calcium Influx through Channels Other than Voltage-Dependent Calcium Channels Is Critical to the Pituitary Adenylate Cyclase-Activating Polypeptide-Induced Increase in Excitability in Guinea Pig Cardiac Neurons Ann. N.Y. Acad. Sci., July 1, 2006; 1070(1): 317 - 321. [Abstract] [Full Text] [PDF]

				J. D. Tompkins, J. C. Hardwick, S. A. Locknar, L. A. Merriam, and R. L. Parsons Ca2+ Influx, But Not Ca2+ Release From Internal Stores, Is Required for the PACAP-Induced Increase in Excitability in Guinea Pig Intracardiac Neurons J Neurophysiol, April 1, 2006; 95(4): 2134 - 2142. [Abstract] [Full Text] [PDF]

				R. L. Parsons, K. L. Barstow, and F. S. Scornik Spontaneous Miniature Hyperpolarizations Affect Threshold for Action Potential Generation in Mudpuppy Cardiac Neurons J Neurophysiol, September 1, 2002; 88(3): 1119 - 1127. [Abstract] [Full Text] [PDF]

				F. S. Scornik, L. A. Merriam, and R. L. Parsons Number of KCa Channels Underlying Spontaneous Miniature Outward Currents (SMOCs) in Mudpuppy Cardiac Neurons J Neurophysiol, January 1, 2001; 85(1): 54 - 60. [Abstract] [Full Text] [PDF]

				L. A. Merriam, F. S. Scornik, and R. L. Parsons Ca2+-Induced Ca2+ Release Activates Spontaneous Miniature Outward Currents (SMOCs) in Parasympathetic Cardiac Neurons J Neurophysiol, August 1, 1999; 82(2): 540 - 550. [Abstract] [Full Text] [PDF]

				R. L. PARSONS, J. M. MULVANEY, and L. A. MERRIAM Galanin Activates an Inwardly Rectifying Potassium Conductance and Inhibits a Voltage-Dependent Calcium Conductance in Mudpuppy Parasympathetic Neurons Ann. N.Y. Acad. Sci., December 21, 1998; 863(1): 156 - 169. [Abstract] [Full Text] [PDF]

				A. C. Myers Ca2+ and K+ currents regulate accommodation and firing frequency in guinea pig bronchial ganglion neurons Am J Physiol Lung Cell Mol Physiol, August 1, 1998; 275(2): L357 - L364. [Abstract] [Full Text] [PDF]

				G. A. Kinney, P. J. Emmerson, and R. J. Miller Galanin Receptor-Mediated Inhibition of Glutamate Release in the Arcuate Nucleus of the Hypothalamus J. Neurosci., May 15, 1998; 18(10): 3489 - 3500. [Abstract] [Full Text] [PDF]

				S.-W. Jeong and R. D. Wurster Calcium Channel Currents in Acutely Dissociated Intracardiac Neurons From Adult Rats J Neurophysiol, April 1, 1997; 77(4): 1769 - 1778. [Abstract] [Full Text] [PDF]