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Modulation of calcium currents by G‐proteins and adenosine receptors in myenteric neurones cultured from adult guinea‐pig small intestine
Author(s) -
Baidan Lessia V.,
Zholos Alexander V.,
Wood Jackie D.
Publication year - 1995
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1995.tb16677.x
Subject(s) - adenosine , patch clamp , pipette , biophysics , calcium , guinea pig , gtp' , receptor , voltage clamp , chemistry , electrophysiology , forskolin , voltage dependent calcium channel , calcium in biology , extracellular , medicine , endocrinology , biology , biochemistry , membrane potential , neuroscience , enzyme
1 Whole‐cell patch clamp methods were used to analyse voltage‐dependent calcium currents in cultured myenteric neurones enzymatically isolated from adult guinea‐pig small intestine 2 Activation of G‐proteins by intracellular administration of GTP‐γ‐S (100–200 μ m in pipette) decreased the amplitude of high voltage activated Ca 2+ current ( I Ca ) by more than 50%. Residual I Ca was activated more slowly and was non‐inactivating during 500 ms test pulses when GTP‐γ‐S was included in the pipette solution 3 Inclusion of 500 μ m GDP‐β‐S in the patch pipettes increased the amplitude of I Ca by over 30% without altering the voltage‐dependency 4 Extracellular application of 2‐chloroadenosine suppressed I Ca dose‐dependently by reducing both transient and sustained components of the current 5 Pretreatment of the neurones with cholera toxin or forskolin did not alter the actions of GTP‐γ‐S or GDP‐β‐S or 2‐chloroadenosine 6 The results suggest that high threshold calcium channels in myenteric neurones are influenced by G‐proteins and that the inhibitory action of 2‐chloroadenosine on I Ca involves G‐protein coupling of the adenosine receptors to the Ca 2+ channel.