Effect of acute subcutaneous nicotine on prepulse inhibition of the acoustic startle reflex in healthy male non-smokers

In a double-blind placebo-controlled trial, the effects of two doses (6 mu g/kg, 12 mu g/kg) of acute SC nicotine were investigated on prepulse inhibition (PPI) of the acoustic startle reflex in healthy non-smoker male volunteers. Each subject received three injections [placebo (saline), 6 mu g/kg nicotine, 12 mu g/kg nicotine] on separate occasions, 2 weeks apart. No influence of either 6 mu g/kg or 12 mu g/kg nicotine was observed for the amplitude and habituation of the startle response over pulse-alone stimuli, relative to the saline-treated condition. Percent of PPI (expressed as percent reduction of non-prepulse trials) was significantly greater, but PPI as measured by absolute difference scores was not significantly different, when subjects were given the 12 mu g/kg dose of nicotine than saline. There was an increase in percent of PPI from saline through low to high doses of nicotine, but PPI observed under the low dose did not differ significantly from either the high dose or placebo. These results provide some support for previous findings showing an enhancement in PPI by cigarette smoking in overnight smoking-deprived smokers and by acutely administered nicotine in experimental animals. The findings indicate that previously observed effects of smoking on percent of PPI in smoking-deprived subjects were not attributable to the restoration of a deficit induced by smoking withdrawal, but represent a direct pharmacological action of nicotine.