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Barium ions inhibit the dynamic response of guinea‐pig corneal cold receptors to heating but not to cooling
Author(s) -
Brock James,
Acosta M. Carmen,
Al Abed Amr,
Pianova Svetlana,
Belmonte Carlos
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.110130
Subject(s) - receptor , chemistry , tetraethylammonium , biophysics , medicine , membrane potential , endocrinology , repolarization , guinea pig , 4 aminopyridine , electrophysiology , potassium channel , biochemistry , biology , potassium , organic chemistry
An in vitro preparation of the guinea‐pig cornea was used to study the effects of the K + channel blockers 4‐aminopyridine (4‐AP), tetraethylammonium (TEA) and Ba 2+ on nerve terminal impulses (NTIs) recorded extracellularly from cold sensory receptors. These receptors have an ongoing discharge of NTIs that is increased by cooling and decreased by heating. The K + channel blocker 4‐AP reduced the negative amplitude of the diphasic (positive–negative) NTIs, whereas TEA and Ba 2+ prolonged the duration of the negative component. As the shape of the NTI is determined by the first derivative (d V /d t ) of the membrane voltage change, these changes in the negative component are consistent with the blockade of K + channels that contribute to action potential repolarization. Only TEA changed the basal activity of the receptors, increasing the likelihood of burst discharges. Ba 2+ selectively reduced the response of the receptors to heating, whereas neither 4‐AP nor TEA modified the response to heating or to cooling. The findings indicate that K + channels blocked by 4‐AP, TEA and Ba 2+ contribute to action potential repolarization in corneal cold receptors, and that ionic mechanisms that underlie the reduction in NTI frequency in response to heating differ from those that increase activity in response to cooling.