Evidence for glutamate receptor mediated transmission at mechanoreceptors in the skin.
The functional role of Merkel cells in the mechanosensitivity of the slowly adapting type I responses has been a controversial issue for many years. Here we show, for the first time, that glutamate receptor-mediated transmission is largely responsible for the static component of the slowly adapting type I response. An isolated sinus hair preparation was used to study the two types (I and II) of slowly adapting units. A broad spectrum ionotropic glutamate receptor antagonist kynurenate (1-10 mM) caused reliable and dose-dependent reductions in the static component of type I unit responses to mechanical stimulation. In addition, an amino acid transmitter candidate aspartate applied to the preparation selectively increased responses in type I units but not responses in type II units. This evidence establishes that the Merkel cell is a mechano-electric transducer, and challenges prevailing views that the Merkel cell acts merely as a support or target cell in the epidermis.
Fagan
B M
BM
Department of Psychology, University of Stirling, UK.
Cahusac
P M
PM
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007736:Kynurenic Acid / Q000494:pharmacology; D018862:Merkel Cells / Q000737:chemistry / Q000502:physiology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000502:physiology*; D012867:Skin / Q000294:innervation*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation
D018691:Excitatory Amino Acid Antagonists; D010726:Phosphodiesterase Inhibitors; D017470:Receptors, Glutamate; D002110:Caffeine; D007736:Kynurenic Acid