Regional Blood Flow in Canine Brain During Nicotine Infusion: Pentobarbital vs. Chloralose Anesthesia*

We compared vasoactive effects of intravenous nicotine (36 μg/kg/min) in regional cerebral circulations under pentobarbital and chloralose anesthesia. Experiments were conducted in three groups of dogs: Group I, pentobarbital anesthesia with fixed ventilation; Group II, chloralose anesthesia with fixed ventilation; Group III, chloralose anesthesia with free breathing. Values for regional cerebral blood flow measured with 15 /u. radioactive microspheres were used to compute regional cerebral vascular resistance (rCBR). In Group I, nicotine had no effect on rCVR in cerebral cortex, and it increased significantly rCVR in cerebellum (+17%), pons (+13%), medulla (+ 23%), and spinal cord (+19%). Using chloralose instead of pentobarbital in dogs with fixed ventilation (Group II), caused a significant reduction in rCVR in the cerebral cortex during nicotine, although it did not alter significantly nicotine-induced changes in rCVR in other regions of the brain. Hypocapnic alkalosis during nicotine-induced hyperventilation (Group III) resulted in significant increases in rCVR in all regions of the brain; however, the increases in rCVR in non- cortical regions more than doubled those in the cerebral cortex. The present results indicate: 1) Nicotine- induced vasodilation in cerebral cortex was blunted by pentobarbital anesthesia. 2) Nicotine-induced vasodilation in cerebral cortex under chloralose anesthesia was sufficient to nullify in part the potent vasoconstrictor effect of hypocapnic alkalosis. Stroke Vol 15, No 4, 1984