Effect of clonidine on the human acoustic startle reflex

V Kumari, P Cotter, P J Corr, J A Gray, S A Checkley

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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.
Original languageEnglish
Pages (from-to)353-360
Number of pages8
Issue number4
Publication statusPublished - Feb 1996


  • Acoustic Stimulation
  • Adrenergic alpha-2 Receptor Agonists
  • Adrenergic alpha-Agonists
  • Adult
  • Affect
  • Attention
  • Blood Pressure
  • Clonidine
  • Cross-Over Studies
  • Double-Blind Method
  • Female
  • Habituation, Psychophysiologic
  • Humans
  • Infusions, Intravenous
  • Male
  • Startle Reaction

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