In vivo changes in brain catecholamine release from rat hypothalamus following olfactory bulbectomy

The mechanism eliciting mouse-killing behavior (muricide), induced by bilateral olfactory bulbectomy, has been shown to involve the brain noradrenergic system; this is because muricide is specifically inhibited by the drugs which potentiate the activity of catecholaminergic neurons such as tricyclic antidepressants. Our previous reports also demonstrated that the hypothalamic noradrenaline (NA) contents increased in the rats which exhibited muricide. To further examine the hypothalamic noradrenergic function in muricide, a push-pull perfusion technique was applied for direct measurement of NA release from the lateral (LH) and ventromedial (VMH) hypothalamus in freely moving rats. Subsequently, the perfusates, including catecholamines and their metabolites were measured by means of high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Three days after olfactory bulbectomy, 67% of the rats elicited muricide and NA release from LH tended to decrease. Moreover, 7 days after olfactory bulbectomy, most of the rats elicited muricide and NA release from LH was significantly decreased, but not from VMH. On the other hand, dopamine (DA) release from VMH without LH conversely increased on the 7th day after olfactory bulbectomy. These results suggest that the dysfunction of the noradrenergic system caused by the decrease in NA release from LH played an important role for the incidence of muricide.