Multi-drug therapies are common in cardiovascular disease intervention; however, io channel/pump coordination has not been tested electrophysiologically. Apparently, inward currents were not elicited by Yoda1/10 nM or Dobutamine/100 nM alone in Ah-type baroreceptor neurons, but were by their combination. To verify this, electroneurography and the whole-cell patch-clamp technique were performed. The results showed that Ah- and C-volley were dramatically increased by the combination at 0.5 V and 5 V, in contrast to A-volley, as consistent with repetitive discharge elicited by step and ramp with markedly reduced current injection/stimulus intensity. Notably, a frequency-dependent action potential (AP) duration was increased with Iberiotoxin-sensitive K+ component. Furthermore, an increased peak in AP measured in phase plots suggested enhanced Na+ influx, cytoplasmic Ca2+ accumulation through reverse mode of Na+/Ca2+ exchanger, and, consequently, functional KCa1.1 up-regulation. Strikingly, the Yoda1- or Dbtm-mediated small/transient Na+/K+-pump currents were robustly increased by their combination, implying a quick ion equilibration that may also be synchronized by hyperpolarization-induced voltage-sag, enabling faster repetitive firing. These novel findings demonstrate multi-channel/pump collaboration together to integrate neurotransmission at the cellular level for baroreflex, providing an afferent explanation in sexual dimorphic blood pressure regulation, and raising the caution regarding the individual drug concentration in multi-drug therapies to optimize efficacy and minimize toxicity.
Keywords: action potential; aortic depressor nerve; baroreceptor neurons; compound action potential; ion channels/ion pumps.