Premium
Effects of gadolinium and tetrodotoxin on the response of slowly adapting type I mechanoreceptors to mechanical stimulation in frog dorsal skin
Author(s) -
Takeda Mamoru,
Nishikawa Toshimi,
Sato Sumie,
Aiyama Shigeo,
Matsumoto Shigeji
Publication year - 2003
Publication title -
journal of the peripheral nervous system
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 67
eISSN - 1529-8027
pISSN - 1085-9489
DOI - 10.1111/j.1085-9489.2003.03032.x
Subject(s) - stimulation , tetrodotoxin , receptive field , merkel cell , excitatory postsynaptic potential , mechanoreceptor , electrophysiology , neuroscience , chemistry , sodium channel blocker , biophysics , anatomy , channel blocker , nociceptor , sodium channel , nociception , medicine , biology , inhibitory postsynaptic potential , receptor , sodium , biochemistry , calcium , merkel cell carcinoma , organic chemistry , carcinoma
To elucidate the excitatory mechanism of mechanoreceptors innervating the frog skin, we examined the effects of gadolinium (Gd 3+ ) and tetrodotoxin (TTX) on the response of single‐unit activity of slowly adapting type I mechanoreceptors to mechanical stimulation topically applied to the receptive field (RF). Recordings were made from 46 fibers responding to mechanical stimulation with von Frey hairs, which caused an irregular firing pattern with slow adaptation. Application of a mechanically gated channel blocker, Gd 3+ (30 µM), and a Na + channel blocker, TTX (3 µM), caused the suppression of discharge rates, which was characterized by the conversion of a slowly adapting to a rapidly adapting discharge pattern. The administration of a high‐voltage‐activated (HVA) Ca 2+ channel blocker, Cd 2+ (100 µ m ), inhibited the unit discharge and caused the conversion of a slowly adapting to a rapidly adapting discharge pattern. Tonic discharges evoked by anodal electrical stimulation were inhibited by the application of Gd 3+ or TTX. Electron microscopic examination showed that the cytoplasm of Merkel cells seen in the RF contained numerous Merkel granules. These results suggest that the excitatory mechanism of frog cutaneous mechanoreceptors may be mediated by the activation of Gd 3+ ‐sensitive stretch‐activated channels in the Merkel cell–neurite complex, which are related to the Na + influx via voltage‐gated Na + channels and/or the Ca 2+ influx through HVA Ca 2+ channels.