Effects of smoking on acoustic startle and prepulse inhibition in humans

Rationale: Prepulse inhibition of the acoustic startle response (PPI) is a paradigm in which a startle response to an auditory stimulus is reduced whe n that stimulus is preceded by a lower intensity, non-startling stimulus (p repulse). PPI is used as an operational measure of sensorimotor gating in b oth humans and other mammals. Acute administration of nicotine enhances PPI in rats, an effect that has been recently demonstrated in humans. Objectiv es: We compared PPI in 12 male smokers and 14 male non-smokers tested in fo ur repeat startle sessions across 2 test days in order to examine further t he effects of smoking and smoking withdrawal on acoustic startle and PPI. M ethods: In a crossover design, the smokers smoked ad lib or abstained from smoking overnight prior to 9 a.m. testing. These 2 test days were in random ized order. On both days, smokers were immediately retested after smoking t hree cigarettes. Non-smokers were tested twice on each of 2 separate days. Results: Across sessions, the smokers had reduced startle to pulse alone st imuli in the first block of each session when compared to the non-smokers. The nonsmokers had no change in gating across their four test sessions. For the smokers, the abstinence condition produced a non-significant reduction in PPI compared to that of the ad lib smoking day. During the smoking abst inence session, smokers had comparable gating to nonsmokers. Smoking immedi ately after washout produced a significant improvement in PPI such that gat ing in the smokers exceeded that of the non-smokers. Conclusion: Smoking af ter overnight washout from cigarettes enhanced sensorimotor gating compared to pre-smoking values and compared to gating in non-smokers.