Introduction: Nicotine acts through different cholinergic receptors in the peripheral and central vestibular system and may cause nystagmus, postural imbalance, vertigo and nausea. The inter-relationship of these signs and symptoms as well as their dependence on the blood nicotine concentration has not yet been studied. Therefore, the aim of this study was to investigate the correlation between the nicotine (NIC) plasma-concentration and (a) nicotine-induced nystagmus (NIN), (b) imbalance, (c) vertigo and (d) nausea in healthy volunteers. Vertigo and nausea were estimated at rest and during vestibular and optokinetic stimulation.
Methods: A total of 50 healthy volunteers (20 female, 30 male, age 27±6 years, all non-smokers) were included. The subjects were tested before NIC (once) and after NIC (six times) with the following test protocol: First, a blood sample was drawn to determine the NIC-concentration. Next the subject was stimulated first with rollvection (60 s) and then with head-shaking (60 s). Eye movements were then recorded using 2-D-video-oculography (VOG) to detect vertical and horizontal NIN (30 s). Simultaneously with the VOG, the total sway path (tSP) was measured during upright stance with the eyes closed using a Kistler platform (30 s). At each timepoint of the investigation, the subject evaluated nausea and vertigo on a visual analogue scale (0–10). The duration of each cycle was 4.5 minutes, the total duration of all 7 cycles was 31.5 minutes. The subjects were randomized into 5 groups (10 subjects in each): (1) nicotine nasal spray (NIS) 1mg without stimulation, (2) NIS 1mg with stimulation, (3) NIS 2mg without stimulation, (4) NIS 2mg with stimulation, and (5) stimulation only.
Results: Our investigation showed a significant positive correlation between NIC-plasma-concentrations and (a) NIN, (b) imbalance, (c) vertigo and (d) nausea. Subjects, who were stimulated by rollvection and head-shaking complained significantly more about vertigo and nausea.
Conclusion: The significant correlation of occurrence, intensity and time-course of nicotine-concentrations and nicotine-induced nystagmus, body sway, vertigo and nausea can all be explained by a common, transient, nicotine-induced vestibular tone imbalance. Nicotine appears a feasible substance for perturbing the vestibulo-ocular and vestibulo-spinal system.
