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This Article Full Text Full Text (PDF) All Versions of this Article: 575/2/573    most recent jphysiol.2006.110130v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Brock, J. Articles by Belmonte, C. Search for Related Content PubMed PubMed Citation Articles by Brock, J. Articles by Belmonte, C. Related Collections Neuroscience

¹ Prince of Wales Medical Research Institute, University of New South Wales, Randwick, NSW 2031, Australia
² Instituto de Neurociencias de Alicante, Universidad Miguel Hernandez-CSIC, Sant Joan d'Alacant, Spain

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 Ba²⁺ 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 Ba²⁺ prolonged the duration of the negative component. As the shape of the NTI is determined by the first derivative (dV/dt) 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. Ba²⁺ 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 Ba²⁺ 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.

(Received 21 March 2006; accepted after revision 19 June 2006; first published online 22 June 2006)
Corresponding author J. Brock: Prince of Wales Medical Research Institute, Barker St, Randwick, NSW 2031, Australia. Email: j.brock{at}unsw.edu.au