Cerebrovascular and cerebral metabolic responses of aged rats to changes in arterial PCO2.

Cerebrovascular and cerebral metabolic responses to changes in arterial PCO2 were tested in young (4 month) and aged (24 month) Sprague-Dawley rats. Rats were anesthetized with 70% nitrous oxide and 30% oxygen, paralyzed with tubocurare and artificially ventilated. Cerebral blood flow (CBF) was measured with radioactive microspheres and cerebral oxygen metabolism (CMRO2) was analyzed from arterial and sagittal sinus oxygen content differences. CBF increased in both young and aged rats with increasing arterial PCO2. Aged rats had significantly depressed cerebrovascular reactivity to changes in CO2 compared to young rats (p less than 0.05). CMRO2 was not significantly different between young and aged rats and did not significantly change with changes in arterial PCO2.