Biophysical Journal 56: 1267-1272 (1989)
© 1989 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Marchetti, C Articles by Robello, M Search for Related Content PubMed PubMed Citation Articles by Marchetti, C Articles by Robello, M

Guanosine-5'-O-(3-thiotriphosphate) modifies kinetics of voltage-dependent calcium current in chick sensory neurons.

Istituto di Cibernetica e Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy.

ABSTRACT

Internal perfusion with the G-protein activator guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma S) mimics the effect of noradrenaline and dopamine on the voltage-dependent calcium current in chick dorsal root ganglion (DRG) cells. With 100 microM GTP-gamma S in the pipette, the current at +10 mV was depressed by approximately 50%, with a 10-fold increase of its time to peak. The activation time course of the control calcium current could be approximated with a single exponential curve, whereas with GTP-gamma S the activation time course was double exponential, with time constants tau 1 and tau 2. 2 mM Mg-ATP in the pipette prevented the GTP-gamma S-induced current decrease in 70% of the cells, but the time course of the current was always double exponential. From -50 mV, the current at +10 mV was best fitted with tau 1 = 1.7 +/- 0.5 and tau 2 = 25.6 +/- 5.5 in seven cells. Both time constants decreased with increasing depolarizations. In the first 2 min of recording, the current changed with time. However, both tau 1 and tau 2 were constant, whereas the relative contribution of the slow component increased from 10 to 70%. In addition, the effect was independent of the holding potential in the range from -100 to -30 mV. These results suggest that the activation of a G-protein causes a fraction of the high-threshold calcium channels to switch to a new closed state, with slower opening kinetics.

This article has been cited by other articles:

				A. J. Morris and C. C. Malbon Physiological Regulation of G Protein-Linked Signaling Physiol Rev, October 1, 1999; 79(4): 1373 - 1430. [Abstract] [Full Text] [PDF]

				A. Delcour and R. Tsien Altered prevalence of gating modes in neurotransmitter inhibition of N-type calcium channels Science, February 12, 1993; 259(5097): 980 - 984. [Abstract]