Abstract
1. Membrane responses were recorded using a standard patch pipette technique in isolated cells freshly dispersed from the rat anococcygeus muscle. Using the whole-cell mode of recording, the ionophoretic application of noradrenaline evoked depolarization (current clamp) and inward current (voltage clamp) at membrane potentials of -50 to -60 mV. 2. The inward current to noradrenaline was reversibly blocked by low concentrations of phentolamine indicating that the response is mediated by alpha-adrenoceptors. The inward current was associated with a conductance increase. 3. The ionic mechanism of the inward current was investigated in potassium-free solutions. Alteration of the chloride equilibrium potential produced similar changes in the reversal potential of the noradrenaline-induced current and it is concluded that noradrenaline opens chloride-selective channels. 4. The noradrenaline-activated chord conductance was increased by depolarization. From a holding potential of -50 mV depolarizing voltage steps in the presence of noradrenaline produced relaxations and the time constants of these relaxations at -50 and +30 mV were respectively 89 and 166 ms. 5. The calcium ionophore A23187 and caffeine applied in the bathing solution also induced an increase in chloride conductance. 6. It is concluded that in isolated cells of the rat anococcygeus muscle the depolarization to noradrenaline is mediated by an increase in membrane chloride conductance.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Aickin C. C., Brading A. F. Measurement of intracellular chloride in guinea-pig vas deferens by ion analysis, 36chloride efflux and micro-electrodes. J Physiol. 1982 May;326:139–154. doi: 10.1113/jphysiol.1982.sp014182. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bamford O. S., Dawes G. S., Ward R. A. Effects of apomorphine and haloperidol in fetal lambs. J Physiol. 1986 Aug;377:37–47. doi: 10.1113/jphysiol.1986.sp016175. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Benham C. D., Bolton T. B. Spontaneous transient outward currents in single visceral and vascular smooth muscle cells of the rabbit. J Physiol. 1986 Dec;381:385–406. doi: 10.1113/jphysiol.1986.sp016333. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Byrne N. G., Large W. A. Comparison of the biphasic excitatory junction potential with membrane responses to adenosine triphosphate and noradrenaline in the rat anococcygeus muscle. Br J Pharmacol. 1984 Nov;83(3):751–758. doi: 10.1111/j.1476-5381.1984.tb16229.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Byrne N. G., Large W. A. Evidence for two mechanisms of depolarization associated with alpha 1-adrenoceptor activation in the rat anococcygeus muscle. Br J Pharmacol. 1985 Nov;86(3):711–721. doi: 10.1111/j.1476-5381.1985.tb08950.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Creed K. E., Gillespie J. S., Muir T. C. The electrical basis of excitation and inhibition in the rat anoccygeus muscle. J Physiol. 1975 Feb;245(1):33–47. doi: 10.1113/jphysiol.1975.sp010833. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gillespie J. S. The rat anococcygeus muscle and its response to nerve stimulation and to some drugs. Br J Pharmacol. 1972 Jul;45(3):404–416. doi: 10.1111/j.1476-5381.1972.tb08097.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
- Large W. A. The effect of chloride removal on the responses of the isolated rat anococcygeus muscle to alpha 1-adrenoceptor stimulation. J Physiol. 1984 Jul;352:17–29. doi: 10.1113/jphysiol.1984.sp015275. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Marty A., Tan Y. P., Trautmann A. Three types of calcium-dependent channel in rat lacrimal glands. J Physiol. 1984 Dec;357:293–325. doi: 10.1113/jphysiol.1984.sp015501. [DOI] [PMC free article] [PubMed] [Google Scholar]