EFFECTS OF SURGICAL ANESTHESIA ON THE VIABILITY OF NIGRAL GRAFTS IN THE RAT STRIATUM

Only a small proportion of dopamine neurons in nigral grafts typically survive transplantation into the adult striatum, Since many anaesthet ics reduce blood flow and disturb a variety of brain metabolites, surg ical anaesthesia may be one of the factors that compromise graft survi val. Conversely, the lowered core body temperature induced by some ana esthetics might promote the survival of grafted cells by slowing their metabolism. In an initial screen, the widely-used surgical anaestheti c, equithesin, was found to reduce core temperature, mean arterial blo od pressure, and to increase the partial pressure of oxygen in arteria l blood without producing any significant alteration in arterial pH or the partial pressure of carbon dioxide. In the main experiment, rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal bundle received dopamine-rich embryonic nigral grafts injected into the deaff erented neostriatum via previously implanted guide cannulae, which all owed comparison to be made of graft survival after transplantation int o awake and in re-anaesthetised animals. There were no significant dif ferences between groups in either the functional effects of the grafts to compensate amphetamine-induced rotation, or in the survival and gr owth of the grafts as measured in post mortem histology, We therefore conclude that anaesthesia per se is not a major contributory factor in the relatively poor survival of dopamine neurons following transplant ation into the rat striatum.