Nikotinerger Einfluss auf die durch gepaarte assoziative Stimulation ausgelöste fokale inhibitorische Neuroplastizität bei Rauchern und Nichtrauchern

Abstract

Nicotine is considered to be the component in cigarette smoke responsible for its addictive properties. Furthermore nicotine has an impact on the induction of long-lasting cortical excitability alterations, also referred to as neuroplasticity, which is the neurophysiological basis for learning and memory processes. The cognitive abilities in smokers under nicotine withdrawal are reduced and are restituted by nicotine consumption. Non-smokers also show improved cognitive performances under the influence of nicotine. In this study we explored the impact of nicotinergic acetylcholine receptors on induction of inhibitory cortical excitability alterations in human brain by using nicotine, the specific ligand on these receptors. The impact of nicotine on inhibitory cortical excitability alterations in smokers and non-smokers was explored by using fast invading nicotine in form of nasal spray and a continuous high nicotine level in form of a nicotine patch. The focal inhibitory excitability alterations were induced by Paired associative stimulation (PAS). Changes in amplitudes of motor evoked potentials (MEP) in Musculus abductor digiti minimi, elicited by transcranial magnetic stimulation (TMS), were recorded to measure changes in cortical excitability. Without nicotine, both smokers and non-smokers showed inhibitory cortical excitability alterations, however this has been found to be less pronounced in smokers under nicotine withdrawal than in non-smokers. In non-smokers nicotine abolished or reduced the inhibitory after-effects of PAS, whereas these effects in smokers under nicotine initially last shorter, but then reappear delayed. Our results show that nicotine plays an important role in the induction of inhibitory cortical excitability alterations. As neuroplasticity is seen to be the neurophysiological correlate for learning and memory processes, an impact of nicotine addiction and nicotine withdrawal on cognition is presumed. Furthermore, nicotine has an impact on effects elicited by cerebral stimulation protocols like Paired associative stimulation.