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Opposite modulation effects of substance P on GABA-- and 5--HT--activated currents in the same sensory neurons

Hu Wangping, Li Zhiwang, Ru Liqiang, Fan Youzhen

Department of Neurobiology, Tongji Medical College, Huazhong University of Science and Technology.Wuhan 430030,Hubei

Abstract

The modulation by substance P of #gamma#-aminobutyric acid (GABA)- and 5-hydroxytryptamine(5-HT)-activated currents (I_(GABA) and I_(5-HT)) was studied using patch-clamp technique in rat trigeminal ganglion neurons. The majority of neurons examined responded to GABA and 5-HT with inward cuerrents(63.8%,30/47) in the same cell. In 22 out of 30 neurons sensitive both to GABA and to 5-HT,pretreatment with substance P (SP 0.01 #mu#mol) suppressed I_(GABA) by (35.7±6.1)% and enhanced I_(5-HT) by (65.2±8.7)%. GR 82334, a potent and specific antagonist of NK1 tachykinin receptor- reversibly blocked the modulatory effects of SP. The SP modulatory effect on I_(GABA) and I_(5-HT) was also almost abolished by intracellular dialysis of GDP-#beta#-S, a non-hydrolyzable GDP analog, or GF 109203X, a selective protein kinase C inhibitor. The results suggested that SP could exert opposite modulation of GABA_(A) receptor and 5-HT_(3) receptor activity in the same primary sensory neuron via the same intracellular signal transduction pathway.

Key words: substance P;#gamma#-aminobutyric acid;GABA_(A) receptor;5-hydroxytryptamine;5-HT_(3) receptor;modulation;intracellular dialysis

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Citing This Article：

Hu Wangping, Li Zhiwang, Ru Liqiang, Fan Youzhen. Opposite modulation effects of substance P on GABA-- and 5--HT--activated currents in the same sensory neurons. Acta Physiol Sin 2004; 56 (6): (in Chinese with English abstract).