[Modulation of norepinephrinergic control of hypothalamus preoptic areas on hibernation bouts in ground squirrels (Citellus dauricus)].

In our previous work, it was shown that hibernation could be enhanced by injection of 6-hydroxydopamine (6-OHDA, 200 micrograms) into the lateral cerebral ventricle of ground squirrels by destructing norepinephrine (NE) nerve terminals in brain areas including hypothalamus, cerebral cortex, hippocampus and periaqueductal gray matter of middle brain. In order to identify the specific area contributing for the modulation of NE system on hibernation, small doses of 6-OHDA (4 micrograms) were microinjected bilaterally into medial preoptic hypothalamus (MPA), lateral preoptic hypothalamus (LPA) and ventromedial hypothalamic nucleus (VMH). The results showed: (1) Depletion of NE on MPA may facilitate hibernation. (2) Little effect was seen by microinjection of 6-OHDA into LPA. (3) The effect of 6-OHDA on VMH was similar to that on MPA, through the mechanism remains to be investigated.