[Effects and possible mechanism of cocaine on the neurons of lateral habenular nucleus].

AIM

To investigate the effects and the possible mechanism of cocaine on the neurons of lateral habenular nucleus (LHb).

METHODS

We observed the effects on c-Fos protein expression in lateral habenular nucleus and medial habenular nucleus after injecting cocaine into a belly cavity and spontaneous and evoked discharge of pain-correlative unit through iontophoresis of cocaine into LHb. The delayed rectifier K+ current was recorded in the acute isolated LHb neuron in whole-cell mode.

RESULTS

(1) The c-Fos protein expression was increased by cocaine treatment in LHb, but little effect in MHb. (2) Iontophoresis of cocaine into LHb increased the discharges of pain excitation unit and enhanced excitation response to noxious stimulation, but it decreased the discharges of pain inhibition unit and its responses to noxious stimulation in LHb. Cocaine inhibited the delayed rectifier K+ current.

CONCLUSION

Cocaine can excite the LHb and increase its sensitivity. The probable mechanism is that cocaine inhibits the delayed rectifier K+ channels.