Relaxation Effect of Patchouli Alcohol in Rat Corpus Cavernous and Its Underlying Mechanisms

Abstract

In this study, we investigated the relaxation effect and mechanisms of patchouli alcohol (PA) on rat corpus cavernosum. Corpus cavernosum strips were used in organ baths for isometric tension studies. The results showed that PA demonstrated concentration-dependent relaxation effect on rat corpus cavernosum. The relaxant response to PA was not influenced by tetrodotoxin and atropine while it was significantly inhibited by removal of endothelium. L-N^G-nitroarginine methyl ester (L-NAME, a nitric oxide synthase inhibitor) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor) significantly inhibited relaxation response to PA, whereas indomethacin (COX inhibitor) had no effect on PA-induced relaxation. The treatment of endothelium-deprived corpus cavernosum with several potassium channel blockers including tetraethylammonium (TEA), 4-aminopyridine (4-AP), and glibenclamide had no effect on PA-induced relaxation. Endothelium-deprived corpus cavernosal contractions induced by cumulative addition of Ca²⁺ to high KCl solution without CaCl₂ were significantly inhibited by PA. Also, PA improved relaxant capacity of sildenafil in rat corpus cavernosum. In addition, the perfusion with PA significantly increased the levels of cGMP and expression of mRNA and protein of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, intracavernous injection of PA enhanced the rise in intracavernous pressure in rats during cavernosal nerve electric stimulation. In conclusion, PA relaxed the rat corpus cavernosum attributed to both endothelium-dependent and -independent properties. While the former component was mostly involved in nitric oxide signaling pathway, the endothelium-independent mechanism involved in PA-induced relaxation was probably linked to calcium antagonism.

Figure 1

Structure of patchouli alcohol.

Figure 2

(a) Representative tracing showing relaxation of corpus cavernosum induced by PA (1–100 μM) in rat corpus cavernosum after precontraction with phenylephrine. (b) Relaxation effects of PA on endothelium-intact corpus cavernosum precontracted with phenylephrine, the control treated with 0.1% DMSO. (n = 6; ^∗∗P < 0.01, unpaired t-test).

Figure 3

Relaxation effects of PA on endothelium-intact corpus cavernosum precontracted with phenylephrine in the absence and presence of (a) tetrodotoxin (1 μM) and (b) atropine (30 μM) (n = 10–11, P > 0.05 by paired t-test).

Figure 4

(a) Comparison of relaxation responses to PA in endothelium-intact (E+) and endothelium-deprived (E−) rat corpus cavernosum (n = 8, ^∗P < 0.05, ^∗∗P < 0.01, unpaired t-test). (b) Relaxation effects of PA on endothelium-intact corpus cavernosum precontracted with phenylephrine in the absence and presence of L-NAME (100 μM), ODQ (10 μM), or indomethacin (30 μM) (n = 8–10; ^∗P < 0.05 and ^∗∗P < 0.01 compared with the PA group, paired t-test).

Figure 5

(a) Relaxation effects of PA against phenylephrine- and 60 mM KCl-evoked contraction in endothelium-deprived corpus cavernosum. Relaxation effects of PA on endothelium-deprived rat corpus cavernosum precontracted with phenylephrine in the absence and presence of (b) TEA (10 μM), (c) 4-AP (300 μM), or (d) glibenclamide (10 μM) (n = 8–10, P > 0.05 by paired t-test).

Figure 6

(a) Effect of PA (100 μM) on endothelium-deprived corpus cavernosum contraction induced by cumulative addition CaCl₂ in Ca²⁺-free high KCl (80 mM) solution. (b) Effect of PA (100 μM) on endothelium-deprived corpus cavernosum contraction induced by phenylephrine in calcium-free solution (n = 8–10, ^∗∗P < 0.01, paired t-test).

Figure 7

Effect of PA (20 μM) incubation on rat corpus cavernosum concentration-dependent relaxation responses to sildenafil (0.01–10 μM) (n = 8, ^∗∗P < 0.01, paired t-test).

Figure 8

The levels of (a) cAMP and (b) cGMP in the rat corpus cavernosum after treatment with PA (20, 40, and 80 μM) (n = 8 in each group, ^∗∗P < 0.01 as compared with the control, one-way ANOVA).

Figure 9

Expressions of nNOS (a) and eNOS (b) mRNA in rat corpus cavernosum after treatment with PA (20, 40, and 80 μM) (n = 8; ^∗∗P < 0.01 as compared with the control, one-way ANOVA).

Figure 10

(a) Representative bands of protein. Expressions of nNOS (b) and eNOS (c) in rat corpus cavernosum after treatment with PA (20, 40, and 80 μM) (n = 4; ^∗P < 0.05, ^∗∗P < 0.01 as compared with the control, one-way ANOVA).

Figure 11

Original traces depicting MAP and ICP (a–d) of the control and PA groups (intracavernous injection with 0.1, 0.2, and 0.4 mg/kg PA) before and after electrical stimulation of the cavernous nerve. (e) Statistical chart of ICP/MAP ratio in each group during electrical stimulation (n = 6 in each group, ^∗∗P < 0.01 as compared with the control, one-way ANOVA).