Direct evidence for histamine H3 receptor-mediated inhibition of norepinephrine release from sympathetic terminals of guinea pig myocardium
Luo, X.X.; Wen, A.D.; Guo, Z.A.; Tan, Y.H.
Zhongguo Yao Li Xue Bao 17(5): 425-428
1996
ISSN/ISBN: 0253-9756 PMID: 9863165 Document Number: 466555
AIM: To study the histamine H-3 receptors mediated inhibition of norepinephrine (NE) release from cardiac sympathetic terminals of guinea pig isolated atria. METHODS: Release of NE induced by electric field stimulation (50 mA, 5 ms) in the bath solution was measured by HPLC-ECD. RESULTS: The release of NE caused by field stimulation was attenuated by (R)-alpha-methylhistamine (alpha-MeHA, 0.1 nmol cntdot L-1 - 10 mu-mol cntdot L-1 ) in a concentration-dependent manner. Thioperamide concentration-dependently antagonized the inhibition of alpha-MeHA. Blockade of H-1, H-2, alpha-2, beta-2-receptors failed to prevent the inhibitory effect of alpha-MeHA. Thioperamide (1 nmol cntdot L-1 - 10 mu-mol cntdot L-1), when used alone, concentration-dependently facilitated the release of NE evoked by field stimulation. CONCLUSION: The presynaptic histamine H-3-receptors inhibited the NE release from cardiac sympathetic terminals.