The Journal of Neurophysiology Vol. 77 No. 5 May 1997, pp. 2515-2524
Copyright ©1997 The American Physiological Society

Serotonin Modulates Voltage-Dependent Calcium Current in Necturus Taste Cells

Rona J. Delay¹, Sue C. Kinnamon^{2, 3}, and Stephen D. Roper^{3, 4}

¹ Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543; ² Department of Anatomy and Neurobiology, Colorado State University, Fort Collins, 80523; ³ Rocky Mountain Taste and Smell Center, University of Colorado Heath Science Center, Denver, Colorado 80262; and ⁴ Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, Florida 33101

Delay, Rona J., Sue C. Kinnamon, and Stephen D. Roper. Serotonin modulates voltage-dependent calcium current in Necturus taste cells. J. Neurophysiol. 77: 2515-2524, 1997. Necturus taste buds contain two primary cell types: taste receptor cells and basal cells. Merkel-like basal cells are a subset of basal cells that form chemical synapses with taste receptor cells and with innervating nerve fibers. Although Merkel-like basal cells cannot interact directly with taste stimuli, recent studies have shown that Merkel-like basal cells contain serotonin (5-HT), which may be released onto taste receptor cells in response to taste stimulation. With the use of whole cell voltage clamp, we examined whether focal applications of 5-HT to isolated taste receptor cells affected voltage-activated calcium current (I_Ca). Two different effects were observed. 5-HT at 100 µM increased I_Ca in 33% of taste receptor cells, whereas it decreased I_Ca in 67%. Both responses used a 5-HT receptor subtype with a pharmacological profile similar to that of the 5-HT_1A receptor, but the potentiation and inhibition of I_Ca by 5-HT were mediated by two different second-messenger cascades. The results indicate that functional subtypes of taste receptor cells, earlier defined only by their sensitivity to taste stimuli, may also be defined by their response to the neurotransmitter 5-HT and suggest that 5-HT released by Merkel-like basal cells could modulate taste receptor function.

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