Muscarinic Receptor Stimulation Does Not Inhibit Voltage-dependent Ca < sup > 2+ < /sup > Channels in Rat Adrenal Medullary Chromaffin Cells

Acta Histochem Cytochem. 2023 Aug 30;56(4):67-75. doi: 10.1267/ahc.23-00042. Epub 2023 Aug 23.ABSTRACTAdrenal medullary chromaffin (AMC) and sympathetic ganglion cells are derived from the neural crest and show a similar developmental path. Thus, these two cell types have many common properties in membrane excitability and signaling. However, AMC cells function as endocrine cells while sympathetic ganglion cells are neurons. In rat sympathetic ganglion cells, muscarinic M1 and M4 receptors mediate excitation and inhibition via suppression of M-type K+ channels and suppression of voltage-dependent Ca2+ channels, respectively. On the other hand, M1 receptor stimulation in rat AMC cells also produces excitation by suppressing TWIK-related acid sensitive K+ (TASK) channels. However, whether M4 receptors are coupled with voltage-dependent Ca2+ channel suppression is unclear. We explore this issue electrophysiologically and biochemically. Electrical stimulation of nerve fibers in rat adrenal glands trans-synaptically increased the Ca2+ signal in AMC cells. This electrically evoked increased Ca2+ signal was not altered during muscarine-induced increase in Ca2+ signal, whereas it decreased significantly during a GABA-induced increase, due to a shunt effect of increased Cl- conductance. The whole-cell current recordings revealed that voltage-dependent Ca2+ currents in AMC cells were suppressed by adenosine triphosphate, but not by muscarinic agonists. The fractionation analysis and im...
Source: Acta Histochemica - Category: Biochemistry Authors: Source Type: research