EFFECT OF ACUTE SUBCUTANEOUS NICOTINE ON PREPULSE INHIBITION OF THE ACOUSTIC STARTLE REFLEX IN HEALTHY MALE NONSMOKERS

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 prepu lse inhibition (PPI) of the acoustic startle reflex in healthy non-smo ker male volunteers. Each subject received three injections [placebo ( saline), 6 mu g/kg nicotine, 12 mu g/kg nicotine] on separate occasion s, 2 weeks apart. No influence of either 6 mu g/kg or 12 mu g/kg nicot ine was observed for the amplitude and habituation of the startle resp onse over pulse-alone stimuli, relative to the saline-treated conditio n. Percent of PPI (expressed as percent reduction of non-prepulse tria ls) was significantly greater, but PPI as measured by absolute differe nce scores was not significantly different, when subjects were given t he 12 mu g/kg dose of nicotine than saline. There was an increase in p ercent of PPI from saline through low to high doses of nicotine, but P PI observed under the low dose did not differ significantly from eithe r the high dose or placebo. These results provide some support for pre vious findings showing an enhancement in PPI by cigarette smoking in o vernight smoking-deprived smokers and by acutely administered nicotine in experimental animals. The findings indicate that previously observ ed effects of smoking on percent of PPI in smoking-deprived subjects w ere not attributable to the restoration of a deficit induced by smokin g withdrawal, but represent a direct pharmacological action of nicotin e.