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Fırat Üniversitesi Sağlık Bilimleri Tıp Dergisi
1999, Cilt 13, Sayı 1, Sayfa(lar) 007-012
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The Effects Of Pertussis Toxin-Sensitive G-proteins on Actions of Caffeine on Intracellular Calcium Stores in Cultured Rat Dorsal Root Ganglion Neurones
Ahmet AYAR1, Kadir SERVİ2
1Fırat Üniversitesi, Tıp Fakültesi, Elazığ / TÜRKİYE
2Fırat Üniversitesi, Veteriner Fakültesi, Elazığ / TÜRKİYE
Keywords: : Caffeine, pertussis toxin, ryanodine, sensory neuron, patch clamp

We have investigated the effects of pertussis toxin (PTX) pre-treatment on the effects of caffeine on intracellular Ca2+ stores in cultured rat dorsal root ganglion (DRG) neurones by whole-cell patch-clamp technique. Voltage-activated Ca2+ currents and Ca2+-activated chloride and non-selective cation currents were isolated pharmacologically. The Ca2+-activated chloride and non-selective cation currents were used as indicators of raised free intracellular Ca2+ close to the cell membrane. When DRG cells were voltage clamped at –90 mV, extracellular application of caffeine (1 mM) activated inward currents in 34 out of 37 cells studied, with a mean peak amplitude and mean delay of –1.33±0.12 nA and 278±12 s (n=8), respectively. The caffeine-induced responses were persisted when Ca2+ was removed from extracellular recording medium, and the mean peak amplitude was –1.27±0.11 nA (n=7) and the mean delay from application of caffeine to the activation of first response was 298±9s (n=7). The caffeine response was abolished by ryanodine (10 mM, n=5), applied intracellularly, but not by its inactive analogue, anhydroryanodine (100 mM, n=7). Intracellular application of Ca2+ chelator 1,2-bis-(O-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl ester (BAPTA-AM) also diminished the caffeine-induced inward currents (n=5). But, pre-treating the cultures with PTX for 3-8 hours did not effect the responses to caffeine (n=12). These observations strongly suggest that caffeine causes release of intracellular Ca2+ in cultured DRG neurones from neonatal rats by a mechanism independent of PTX-sensitive guanine nucleotide binding protein.

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