Decay in prepulse facilitation of calcium channel currents by Gi/o-protein attenuation in hamster submandibular ganglion neurons, but not Gq/11.
The calcium ion influx through voltage-dependent calcium channels (VDCCs) has a vital role in the control of neurotransmitter release and membrane excitability. Prepulse facilitation is a phenomenon in which a strong depolarizing pulse induces a form of the VDCCs that exhibits an increased opening probability in response to a given test potential; this persists for several seconds after repolarization. It has been reported that prepulse facilitation occurs via dissociation of the guanosine triphosphate (GTP)-binding proteins (G-proteins) from the VDCCs and that recovery from facilitation involves rebinding of the G-proteins. The heterotrimeric G-proteins act as switches that regulate information processing circuits connecting cell surface G-protein-coupled-receptors to a variety of effectors. In this study, we have studied the characterization of G-protein subtypes in prepulse facilitation of VDCCs currents (Ica) in hamster submandibular ganglion (SMG) neurons, using whole-cell patch clamp recordings. Under control conditions, with GTP (0.1 mM) in the recording pipette, the rate of prepulse facilitation was 19.0 +/- 1.9% (n = 13). Intracellular dialysis with GDP-beta-S (0.1 mM), G-protein blocker, and pretreatment of neurons with N-ethylmaleimide (NEM) (100 microM for 2 min), Gi/o blocker, attenuated the rate of prepulse facilitation. Intracellular dialysis of anti-Gq/11-antibody did not alter it. These results suggest that prepulse facilitation of VDCCs is due to Gi/o-types of G-protein, but not to the Gq/11-type, in SMG neurons.
Endoh
T
T
Department of Physiology, Tokyo Dental College, 1-2-2, Masago, Mihama-ku, Chiba 261-8502, Japan.
Abe
M
M
Suzuki
T
T
D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D006224:Cricetinae; D004558:Electric Stimulation; D005033:Ethylmaleimide / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D008564:Membrane Potentials; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D013363:Submandibular Gland / Q000294:innervation*
D015220:Calcium Channels; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins; D005033:Ethylmaleimide