Local changes in cerebral 2-deoxyglucose uptake during alphaxalone anaesthesia with special reference to the habenulo-interpeduncular system.

The effects of the steroid anaesthetic Althesin (alphaxalone plus alphadolone acetate) on regional cerebral metabolism was studied in female rats. [14C]2-Deoxyglucose (2-DG) uptake was measured in 19 discrete anatomical areas by quantitative autoradiography. Under Althesin anaesthesia metabolic activity, relative to the corpus callosum ( rma ), was significantly (24-46%) increased in the locus coeruleus, medial (but not lateral) habenula (Hb) and interpeduncular nucleus (IPN). The Hb-IPN tract, not discernible in autoradiograms from conscious rats, became readily apparent in films from anaesthetized rats. However, the increased metabolic activity of this pathway was not associated with a significant change in the tissue concentrations of substance P in either the Hb or IPN. In sensorimotor and visual cortex, caudate nucleus, thalamic nuclei and the medial geniculate body rma was significantly (26-38%) depressed. Metabolic activity in the other 8 areas measured was unaffected by Althesin. Destruction of the stria medullaris input to the habenulae prevented the Althesin-induced increase in 2-DG uptake by the MHb and LHb.