The aim of present work was to study how nucleus raphe magnus(NRM) neurons are modulated by the nucleus lateral habenula(NLH)

that plays a pivotal role in funnelling information from the limbic forebrain to the limbic midbrain area. Neuron discharges of NRM were recorded extracellularly by glass microelectrode in rats. Electrical stimulation of NLH for 5 see

when its intensity over 4V

could excitate NRM neurons

increasing unit discharges during stimulation

and inhibit the neurons

decreasing discharges after stopping stimulation

besides

the bi-directional modulation of immediate-excitation and post-inhibition of NLH on NRM neurons could be enhanced with the increase of stimulation intensity. But the effects of stimulation of nucleus accumbens(NAc) with the same series of intensities on the same neuron were all excitation during and stopping stimulation. Thus the bi-directional modulation of NLH on NRM neuron may be a specificity. After lesion of bilateral NLH

the discharges of NRM neurons were obviously increased (P < 0. 05 )

showing a tonic inhibition on them to be removed. On the background of discharge increase of NRM neurons after NLH lesion

the excitatory responses of NRM neuron to Sin Ⅱ stimulation were reversed to inhibitory responses. The phenomenon of excitatory-inhibitory change may be a regularity.