Cerebral Cortical Vasodilation via Nicotinic Receptors by Heated Tobacco Product Aerosol Extract in Rats

Abstract

Introduction: Smoking increases the risk of lung cancer due to a number of components of smoke. The use of novel heated tobacco products (HTPs), alternative to conventional combustion cigarettes, has increased in recent years. However, the in vivo biological effects of HTPs are poorly understood. This study aimed to clarify the acute effects of injecting aerosol extract prepared from an HTP on regional cerebral blood flow (rCBF) in rat cortex by comparing them to the effects of injecting smoke extract prepared from conventional combustible cigarettes. Methods: In urethane anesthetized rats, rCBF was measured using laser speckle contrast imaging simultaneously with arterial pressure. Results: Both cigarette smoke extract and HTP aerosol extract, at a dose equivalent to 30 μg nicotine/kg, injected intravenously, increased cortical rCBF without changing arterial pressure. The magnitude and time course of the increased rCBF response to both extracts were similar throughout the cortical area, and the rCBF increases were all abolished by dihydro-β-erythroidine, an α4β2-preferring nicotinic acetylcholine receptor (nAChR) antagonist. Conclusion: In conclusion, our study demonstrated that the effect of injecting aerosol extract prepared from an HTP, an acute increase in cortical rCBF, is mediated via activation of α4β2-like neuronal nAChRs in the brain.