Effect of 5-hydroxytrptamine on Spontaneous Firing Activities of STN Neurons

Objective To research the effects of 5-hydroxytrptamine(5-HT)on the neuronal firing activities of the sub- thalamic nucleus(STN)in rats and to explore the relationship between the raphe dorsal nucleus(DRN)and STN.Methods U- sing extracellular recording to investigate the direct effects of iontophoretic applications of 5-HT,cyproheptadine and fluoxetine on the spontanenous firing activities in STN.Results The averaged firing rate of 60.34%(35/58)STN neurons was decreased by 5-HT (P0.01),which was intensity-dependent.Majority of STN neurons were not responded to cyproheptadine,and cyproheptadine, while the spontaneous firing rate in 35.71%(10/28)of neurons was increased.During 5-HT ejection,cyproheptadine increased the spontaneous firing rate in majority(58.06%)of STN neurons.In addition,The averaged firing rate of 56.25%(9/16)STN neurons was decreased by fluoxetine(P0.01).Conclusions STN neurons were inhibited by 5-HT,cyproheptadine applied iontophoretical- ly suppressed the inhibitory effects of 5-HT,STN neurons were inhibited by fluoxetine as well as the effect of 5-HT.