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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 17:47 |
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Conference: Bucharest University Faculty of Physics 2009 Meeting
Section: Biophysics; Medical Physics
Title:
Capsaicin-activated currents in cultured primary sensory neurons – desensitization properties and effects of acute NGF application
Authors:
T. Selescu, A. Vasile, B. Amuzescu, M. Flonta
Affiliation:
Dept. Biophysics & Physiology, Faculty of Biology, University of Bucharest
E-mail
bogdan@biologie.kappa.ro
Keywords:
transient receptor potential (TRP), vanilloid receptor (TRPV1), capsaicin, desensitization, nerve growth factor (NGF)
Abstract:
Prolonged in vitro exposure to nerve growth factor (NGF) exerts different effects on cultured primary sensory neurons: a trophic action at low concentrations (10-11 M) via specific binding followed by activation of tyrosine kinase receptors (TrkA, B, and C), and a proapoptotic action at higher doses (10-9 M) by unspecific binding to p75 neurotrophin receptors. The aim of our study was to set a standardized protocol for TRPV1 activation by acute exposure to NGF, as a starting point in the assessment of direct and indirect effects of certain polyunsaturated fatty acids on native vanilloid receptors. Primary sensory neurons were obtained from collagenase-dissociated adult rat dorsal root ganglia, cultured for 24 hours in controlled conditions, and approached by whole-cell patch-clamp. After triggering action potentials by current injection (0-500 pA for 10 ms) and applying three voltage protocols to classify neurons using an “electrical fingerprint” method defined by Petruska JC et al. (2000) J. Neurophysiol. 84(5):2365-79, capsaicin-elicited currents were recorded at –80 mV in various conditions (1 mM or 0.3 mM capsaicin applications repeated at 30 min or 10 min, 2 mM or 0.1 mM extracellular Ca2+, 10 mM Na+ or 5 mM Na2ATP + 0.1 mM LiGTP in the pipette solution). Peak current amplitudes at first capsaicin application showed strong positive correlations with membrane capacitance at 2 mM but not at 0.1 mM Ca2+, and they were not significantly correlated with the access resistance. In the presence of ATP in the intracellular solution, there were differences in the amplitude of the second capsaicin-evoked current relative to the first one in experiments where NGF 100 ng/ml was applied during the 10 min interval between the two stimuli (0.5580 ± 0.2077, mean ± SEM, n = 4) compared to control experiments (0.2916 ± 0.1148, n = 4), although they were not statistically significant (p = 0.178, one-tailed unpaired t test).
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