Effects of tobacco smoking on the Hoffmann reflex.

Ten normal adult tobacco smoking volunteers 21 to 32 years of age were the subjects of this study. They were asked not to smoke for 12 hours prior to testing. The Hoffmann (H) reflex and its recovery cycle were measured before and just after smoking (on different days) one nonfiltered, zero, low (0.27 mg), or high (2.16 mg) nicotine tobacco cigarette. After smoking the nicotine-containing cigarettes, the subjects showed a reduction of the H reflex recovery cycle. Individual differences were marked. Nevertheless, the data obtained are consistent with evidence in animals that nicotine and tobacco smoke stimulate Renshaw inhibitory neurons in the spinal cord, either directly or indirectly. This technique provides another objective measure of the effects of tobacco smoking in human volunteers.