Measurement of intracavernous and mean arterial pressure (MAP)

The pentobarbital anaesthesized rats breathed spontaneously and body temperature was monitored continuously and maintained at 37°C by placing them on a heating blanket. A heparinized (100 IE mL⁻¹) polyethylene (PE) catheter (PE 50) connected to a pressure transducer (Disposable BP Transducer, AD Instruments, Oxford, UK) was introduced into the carotid artery to measure MAP. Another pressure transducer connected to a 25-gauge needle attached to a heparinized catheter PE, was inserted into the crus CC, after scrotum incision, to measure the intracavernous pressure (ICP). Continuous direct measurements of MAP and ICP were obtained, registered and analyzed on a computerized data acquisition system (PowerLab, ADInstruments). A stabilizing period of 20–30 min was allowed before registration of basal ICP and MAP.

The cavernous nerve was isolated, after an incision in the abdominal middline, by locating the nerve running on the bladder and prostate area as previously described (Kun et al., 2009). The electrical stimulation was performed with a tip curve bipolar platinum electrode, which was connected to a S48 stimulator (Grass Instrument Co., Boston, MA, USA). NS309, NS4591, or vehicles (DMSO and PEG400) were administered by infusion in the jugular vein. Before the beginning of the experiment, three leads or electrodes, configured in an Einthoven configuration, were positioned to obtain the second lead derivation to access the electrical activity of the heart and the heart rate.