Abstract
The negative chronotropic effect of acetylcholine (ACh) on the sinoatrial node fades in the continuous presence of ACh as a result of desensitization. We have investigated the mechanism underlying desensitization in single rabbit sinoatrial node cells using the whole cell patch clamp technique. The negative chronotropic effect resulting from the injection of a constant hyperpolarizing current faded. ACh activated an inwardly rectifying potassium current (iK,ACh), which faded in the continuous presence of ACh. ACh had no effect on "basal" L-type calcium current (iCa), but ACh decreased iCa, which had been potentiated by isoprenaline. This effect did not fade during a 2-min exposure to ACh. ACh decreased the hyperpolarization-activated current (i(f)). This effect again did not fade. These results suggest that desensitization of the negative chronotropic response to ACh is, in part, the result of the membrane hyperpolarization and, in part, the result of the fade of iK,ACh. These results also suggest that, whereas the activation of potassium current by ACh rapidly fades, the effects resulting from the inhibition of adenylate cyclase do not.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
