Abstract

THE EFFECTS OF NOISE AND NORDRENERGIC DRUGS ON CHOICE REACTION TIME

*Andrew P. Smith, PhD

.

Abstract

Background: Clonidine, an antihypertensive α2-adrenergic receptor agonist, induces a state similar to sleep deprivation. This leads to impaired sustained attention, slower saccadic eye movements and reduced alertness. The selective antagonist, Idazoxan, reverses the Clonidine-induced reduction in alertness and impairment of sustained attention. Acute exposure to noise, but not longer exposure, also reduces the effects of Clonidine on alertness and attention. The present analyses investigated the effects of Clonidine on choice reaction time and examined whether the effects of Clonidine were modified by noise and blocked by Idazoxan. Method: A double-blind, parallel-group design was used. Seventy-six healthy male participants were given either 200μg Clonidine, 40mg Idazoxan, a combination of 200μg Clonidine plus 40mg Idazoxan, or a placebo. Half of each drug treatment group was exposed to 80dB white noise via headphones. At baseline and on three occasions post-drug administration, participants carried out two choice reaction time tasks, one near the start of the hour-long test session and the other near the end. Results: Clonidine significantly slowed reaction time, and this effect was reversed by Idazoxan and initially noise. Prolonged exposure to noise did not have a significant effect in the clonidine condition. Conclusion: At the start of the test session, Clonidine led to slower reaction times in the quiet group, and this effect was reduced by Idazoxan and noise. At the end of the session, Clonidine led to slower responses and this effect was significantly reduced by Idazoxan but not by noise.

Keywords: Central Noradrenaline; Noise; Clonidine; Idazoxan; Choice Reaction Time.