ABSTRACT
Aim To identify the serotonin(5-HT)subtype receptor mediated 5-HT-induced depolarization in guinea pig celiac ganglion(CG) neurons.Methods Intracellular recordings were made from the isolated guinea pig CG neurons.Results Cyproheptadine(5-HT_(1/2)antagonist) and BRL 24924(5-HT_(1P) receptor antagonist) reversibly inhibited 5-HT-induced slow depolarization.Whereas,spiperone(5-HT_(1A)receptor antagonist) and mianserin(5-HT_2 receptor antagonist) could not inhibit 5-HT-induced slow depolarization.MDL 72222(5-HT_3 receptor antagonist) could not inhibit 5-HT-induced slow depolarization,but it could reversibly inhibit 5-HT-induced fast depolarization.Pressure ejection of MCPP(5-HT_(1P) receptor agonist) on 5-HT sensitive neurons could induce a slow depolarization which could be inhibited by BRL 24924.Conclusion 5-HT-induced fast and slow depolarization is mediated by 5-HT_3 and 5-HT_(1P) receptor,respectively.
ABSTRACT
The work was carried out to investigate the effects of clonidine on Ach quantal release of presynaptic nerve terminals in guinea pig celiac ganglia in vitro by means of intracellular recording technique. After perfusion of celiac ganglia with clonidine ( 10?mol/L ) for 7 ~10 min, the frequency of spontaneous miniature excitatory postsynaptic potentials ( mEPSP ) which was increased by high K+ (15 mmol/L ) , diminished about 35% with little change in amplitude. Under condition of low Ca2+( 0.5mmol/L )/high Mg2+( 5.5mmol/L ) presynaptic nerve was repetitively stimulated by 200 pulses ( 1 Hz), the failure number of EPSP increased from 82 to 145 in 200 stimuli and the quantal content ( m ) decreased about 62% with little change in quantal size ( q ) under clonidine ( 10?mol/L ) action. It is indicated that clonidine can decrease Ach auantal release from presynaptic nerve terminals without effecting Ach content in vesicles, and is one of the mechanisms for depressant effect of clonidine on synaptic transmission of the sympathetic ganglia.
ABSTRACT
AIM To investigate the effects of several 5-hydroxytryptamine(5-HT) subtype receptor antagonists on late slow excitatory postsynaptic potential(LS-EPSP) of the neurons of guinea pig inferior mesenteric ganglion(IMG). METHODS Intracellular recordings were made from neurons of the isolated guinea pig IMG. RESULTS Cyproheptadine and BRL 24924 suppressed LS-EPSP of 5-HT sensitive neurons reversibly, while mianserin, MDL 72222 and spiperone showed no significant effect. Continuous superfusion of IMG with MCPP suppressed LS-EPSP of 5-HT sensitive neurons by 5-HT 1P receptor desensitizated. CONCLUSION LS-EPSP of 5-HT sensitive neuron is mediated by 5-HT 1P subtype receptor.
