[Different effect of L-glutamate microinjection into medial or lateral habenular nucleu on pain threshold]

The habenulae (Hb) are related to modulation of pain sensation, but the results from different laboratories are inconsistant. The aim of the present investigation is to clarify the discrepancy. L-Glutamic acid (L-Glu) was microinjected into medial (MHb) and lateral habenular nucleus (LHb) on light anesthetized or conscious rats, and pain threshold was then determined on the different models of animal. The results showed that the activation of MHb increased TFL, whereas activation of LHb decreased TFL.