In a double-blind placebo-controlled trial, the effects of two doses (6 micrograms/kg, 12 micrograms/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 micrograms/kg nicotine, 12 micrograms/kg nicotine] on separate occasions, 2 weeks apart. No influence of either 6 micrograms/kg or 12 micrograms/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 micrograms/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.

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One method of increasing the value of aquacultured product is to produce fillets that are fortified with minerals that are beneficial to human health -that is enhance the functionality of an already healthy product. A good candidate mineral in this regard is selenium (Se) which is of vital importance to normal metabolism in humans. In order to evaluate the dose response and tissue accumulation of supplemental dietary Se, a study was undertaken with hybrid striped bass (HSB). Animals were fed diets supplemented with either organic (0-3.2 mg kg )1 as SelPlex Ò ) or inorganic (0.2 and 0.4 mg kg )1 as sodium selenite) Se for 6 weeks. Because basal fishmeal-based diets contained 1.22 mg Se kg )1 , doses of Se delivered equated to 1.22-4.42 mg kg )1 . At trial end, greatest weight gain was observed in fish receiving 0.2 mg Se kg )1 , irrespective of form (organic/inorganic). Se accumulation in HSB liver and fillet revealed a classical dose-response once a threshold level of 0.2 mg Se kg )1 was surpassed. Greatest tissue accumulation of Se was observed in fish fed the 3.2 mg Se kg )1 level (P > 0.0001). A 100 g portion of Se-enhanced HSB fillet would contain between 33 and 109 lg Se, amounting to a dietary intake of between 25 and 80 lg Se; a level that would satisfy present daily intake recommendations. Comparison of tissue Se levels indicated that the muscle provides a more conspicuous gauge of dietary Se dose-response than does liver. Dietary treatments of between 0.4 and 1.6 mg organic Se kg )1 reduced (P < 0.024) plasma glutathione peroxidase (GSH-Px) activity. No differences were observed in ceruloplasmin, lysozyme or GSH-Px activities between organic and inorganic Se when delivered at the 0.2 mg Se kg )1 level. Ceruloplasmin, lysozyme and GSH-Px levels were elevated (P ‡ 0.025) in fish fed the diet containing 0.4 mg inorganic Se kg )1 . KEY WORDS

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The present study investigated in healthy human volunteers whether clonidine reduced the amplitude of the acoustic startle reflex and whether this effect, if found, was due to an accelerated rate of habituation. Subjects were presented with startle-eliciting noise-bursts after intravenous (iv) infusion of clonidine (1.5 microgram/kg) and saline on separate days. Clonidine significantly reduced the amplitude of the acoustic startle reflex (as indexed by the eyeblink component) relative to the saline treated condition. This effect was neither due to an accelerated rate of habituation of the startle reflex nor to the sedative effect of clonidine. These findings complement an earlier report (Morgan et al. 1993) that yohimbine augments the amplitude of the startle reflex in man. Taken together, the two reports indicate a new model for the clinical investigation of central alpha2 adrenoceptor function in humans.