Multiple effects of gymnopilin on circulatory system of the rat.

Gymnopilin is one of the substances produced by the hallucinogenic mushroom, Gymnopilus junonius. In this study, we examined effects of gymnopilins purified from wild fruiting bodies of G. junonius on contractile activity of aorta preparations and blood pressure in rats. Gymnopilins at lower concentrations than 5 mg/mL did not evoke contraction of helical strips of the thoracic aorta. In contrast, gymnopilins (5 mg/mL) applied to the aorta strips pre-contracted by norepinephrine (100 nM) caused relaxation. This relaxing action did not depend on the activity of the endothelium cells. The relaxing effect of 5-mg/mL gymnopilins was observed in aorta strips contracted by angiotensin II (10 nM) and the high K+ solution (60 mM). Moreover, the adenylyl cyclase inhibitor, SQ-22536, significantly inhibited the relaxing effect of gymnopilins at 1 mg/mL on the norepinephrine-contracted strips. These results suggested that gymnopilins acted directly on smooth muscle cells of the aorta and activated the cAMP-dependent cascade to cause the vasodilation. Paradoxically, gymnopilins injection into the jugular vein transiently increased blood pressure without affecting the heart rate. This result suggests that gymnopilins increase cardiac output and/or tension of the artery through the excitation of the vasomotor nerve that overcame the direct relaxing effect on the vascular smooth muscle.