Studies on the effects of smoking on cerebral perfusion and metabolism: basic studies with in vivo tracer methods

In order to examine the effects of smoking on the central nervous system, we applied the radionuclide method to study the in vivo behavior of nicotine and the effects of nicotine on cerebral perfusion and metabolism. Biodistribution studies with optical isomers of carbon-11 labeled nicotine showed greater uptake and prolonged retention of (S)-nicotine in the brain with competitive inhibition by cold nicotine, suggesting the possibility of functional assessment and imaging of nicotinic receptors in human brain. Senescence accelerated model mouse, which was reported to show age related deterioration of memory, demonstrated decreased accumulation of nicotine in the brain. Intravenous injection of nicotine revealed markedly increased cerebral glucose metabolism with regional differences, while it slightly reduced cerebral blood flow. These results suggest that in vivo studies with radiolabeled tracers will play a significant role not only in clarifying the effects of smoking or nicotine but also in understanding the mechanism of interaction between neuronal function and cerebral perfusion and metabolism.