The corpus cavernosum restricts blood flow through the penis to maintain penile detumescence until an erectile stimulus causes it to relax. The detumescent state is partly maintained by a myogenic mechanism resident in the smooth muscle bundles lining the corporal sinuses (1). A previous study found that isolated rabbit corpus cavernosum myocytes fire spontaneous transient inward currents (STICs) mediated by Ca2+ -activated Cl- channels (2). Recently, we have shown that these cells also fire regular intracellular Ca2+ waves mediated by Ca2+-release from intracellular stores (3). The aim of the present study was to determine if there was any contribution of voltage-dependent Ca2+ channels to the Ca2+ waves in these cells. Male New Zealand white rabbits were humanely killed and cells were freshly dispersed from the corpus cavernosum as described previously (2). Cells were loaded with Fluo-4 am for study of cytosolic Ca2+ signals using a spinning disk confocal microscope at acquisition rates of 5-50 frames s-1 (3). Under unstimulated conditions cells developed regular Ca2+ waves at a frequency of 14 ± 4.53 min-1 (mean ± s.e.m) and amplitude of 1.20 ± 0.27 ΔF/F0, which were abolished in Ca2+-free bath solution (n = 5, p < 0.05, paired t test). Similarly, in 6 cells, nifedipine (1 μM) reduced frequency from 13.83 ± 2.12 to 2.17 ± 1.37 min-1 (p < 0.05) and amplitude from 0.99 ± 0.15 to 0.44 ± 0.23 ΔF/F0 (p < 0.05). At acquisition rates of 50 frames s-1 it was possible to also discriminate Ca2+ sparks, occurring during the periods between waves. Interestingly, sparks were more resistant to nifedipine treatment than waves. In contrast to the effect of nifedipine, the L-type Ca2+ channel agonist, FPL-64176 (300 nM), induced a rapid rise in intracellular Ca2+, followed by a series of Ca2+ oscillations in 4 of 5 cells, while in the 5th cell a sustained rise in Ca2+ was observed. The Ca2+-activated Cl- channel blockers anthracene-9-carboxylic acid (9-AC) and niflumic acid both reduced the amplitudes of Ca2+ waves (9-AC 1mM: from 0.58 ± 0.14 to 0.19 ± 0.05 ΔF/F0, n=5, p <0.05; niflumic acid 100 μM: from 1.92 ± 0.61 to 0.16 ± 0.10 ΔF/F0, n=5, p <0.05). In conclusion, spontaneous Ca2+ waves in rabbit corpus cavernosum myocytes appear to depend not only on store-released Ca2+, but on Ca2+ influx via L-type Ca2+ channels. We propose that release of Ca2+ from stores activates plasmalemmal Ca2+-activated Cl- channels, which then cause membrane depolarisation that results in Ca2+ influx via L-type Ca2+ channels. This mechanism is likely to contribute to the spontaneous detumescent tone widely reported in corpus cavernosum smooth muscle.