Calcium-activated chloride current in cultured myenteric neurons from murine proximal colon

Whole cell patch clamp recordings were made from cultured myenteric neurons taken from murine proximal colon. The micropipette contained Cs to remove K currents. Depolarization elicited a slowly activating time-dependent outward current (Itdo), whereas, repolarization was followed by a slowly deactivating tail current (Itail). Itdo and Itail were present in about 70% of neurons. We identified these currents as Cl currents (ICl), because changing the transmembrane Cl gradient altered the measured reversal potential (Erev) of both Itdo and Itail with that for Itail shifted close to the calculated ECl. ICl are calcium-activated Cl current (ICl(Ca)) because they were Ca dependent. ECl , which was measured from the reversal potential of ICl(Ca) using a gramicidin perforated patch, was 33mV. This value is more positive than the resting membrane potential (-56.3 ± 2.7mV), suggesting myenteric neurons accumulate intracellular Cl ions. ω-Conotoxin GIVA (0.3μM), [N-type Ca channel blocker] and niflumic acid (10μM), [known ICl(Ca) blocker], decreased the ICl(Ca). In conclusion, these neurons have Ca-activated Cl currents, which are activated by calcium entry through N-type calcium channels. These currents likely regulate post spike frequency adaptation.