Abstract:

Objective To investigate the electrophysiological and pharmacological properties of acid-sensing currents in vagal primary afferent neurons innervating murine small intestine, and explore the ion channels inducing acid-sensing currents. Methods Vagal primary afferent neurons were labeled retrogradely through injection of active fluorescent dye (DiI) into the jejunal wall, whole-cell patch clamp technique was employed to record the acid-sensing currents induced by extracellular fluid with different pH, and the relationship between acid-sensing currents and pH was explored. Acid-sensing ion channel (ASIC) antagonists (30 μmol/L benzamil and 100 μmol/L amiloride) and transient receptor potential vanilloid-1 (TRPV1) antagonists (10 μmol/L capsazepine and 10 μmol/L ruthenium red) were added to extracellular fluid with pH 5 (control), and the changes of induced acid-sensing currents were observed. Results Among a total of 52 DiI-labled neurons, inward currents consisting of three distinct types (fast-type current, slow-type current and sustained current) were recorded in 33 neurons. The amplitudes of acid-sensing currents increased with the decrease of pH. The transient component of fast-type current and amplitude of slow-type current significantly decreased by 30 μmol/L benzamil and 100 μmol/L amiloride (P<0.05 and P<0.01), and the amplitude of sustained current significantly decreased by 10 μmol/L capsazepine and 10 μmol/L ruthenium red (P<0.05). Conclusion Vagal primary afferent neurons of the small intestine express at least three types of acid-responsive ion channels, including TRPV1 and two subtypes of ASIC.

Key words: vagal primary afferent neurons, acid-sensing current, whole-cell patch clamp technique, acid-sensing ion channel, transient receptor potential vanilloid-1, antagonist