Mouse Corpus Cavernosum Smooth Muscle Cells

Evidence of an Excitatory Purinergic Innervation in Mouse Corpus Cavernosum Smooth Muscle

Corpus cavernosum smooth muscle (CCSM) cells are known to express P2X receptors, but their functional role in excitatory innervation is unclear. Here, Lim et al. isolated mouse CCSM myocytes and studied them using patch clamp techniques and measured isometric tension in response to electrical field stimulation (EFS).

In isolated mouse CCSM myocytes held at -60 mV, ATP (1 μm) evoked large inward currents that didn't significantly reduce in amplitude over ≥8-minute intervals (Fig. 1A). Summary data showed no significant difference between the first and second ATP applications (Fig. 1B). Next, α,β-methylene ATP (10 μm), which activates P2X1 or P2X3 receptors, was tested. It evoked a large, rapidly declining inward current. After an 8-minute washout, a second ATP application was ineffective, but a third application after another washout evoked a large current again (Fig. 1C). Summary data from six experiments confirmed that α,β-methylene ATP reversibly reduced ATP-evoked responses (Fig. 1D). NF449, a selective P2X1 receptor blocker, was then tested. ATP initially evoked a large inward current, but a second ATP application in NF449 was ineffective. After an 8-minute washout, ATP again evoked a large current. NF449 reversibly inhibited ATP-evoked currents in six experiments, confirming P2X1 receptor mediation (Fig. 1E and 1F). After the large inward currents evoked by ATP or α,β-methylene ATP declined, smaller currents resembling spontaneous transient inward currents (STICs) often appeared. Ani9 (1 μm), a TMEM16A Ca²⁺-activated Cl^- channel blocker, completely inhibited these STICs, confirming their mediation by TMEM16A.