V. VLACHOVÁ, A. LYFENKO, L. VYKLICKÝ, †R.K. ORKAND¹

Institute of Physiology, Academy of Sciences of the Czech Republic, Czech Republic and ^IInstitute of Neurobiology, University of Puerto Rico, San Juan, USA

†Deceased, January 12, 2002

Received May 12, 2001
Accepted August 7, 2001

Summary
The effect of suramin, an inhibitor of G protein regulated signalling, was studied on the membrane currents induced by noxious heat and by capsaicin in cultured dorsal root ganglia neurones isolated from neonatal rats. Whole-cell responses induced by a heat ramp (24-52 °C) were little affected by suramin. The noxious heat-activated currents were synergistically facilitated in the presence of 0.3 µM capsaicin 13.2-fold and 6.3-fold at 40 °C and 50 °C, respectively. In 65% of neurones, the capsaicin-induced facilitation was inhibited by 10 µM suramin to 35±6 % and 53±6 % of control at 40 °C and 50 °C (S.E.M., n=15). Suramin 30 µM caused a significant increase in the membrane current produced by a nearly maximal dose (1 µM) of capsaicin over the whole recorded temperature range (2.4-fold at 25 °C and 1.2-fold at 48 °C). The results demonstrate that suramin differentially affects the interaction between capsaicin and noxious heat in DRG neurones and thus suggest that distinct transduction pathways may participate in vanilloid receptor activation mechanisms.

Key words
Dorsal root ganglia neurones · Vanilloid receptor · Capsaicin · Noxious heat · Whole-cell

Reprint requests
RNDr. Viktorie Vlachová, DSc., Institute of Physiology, AS CR, Vídenská 1083, 142 20 Prague 4, Czech Republic. Tel.: 420-2-4106 2711, Fax.: 420-2-4106 2488, E-mail address: vlachova@biomed.cas.cz

ISSN 0862 - 8408