Abstract
Activation of nicotinic acetylcholine receptors is thought to enhance activity-dependent synaptic plasticity processes. The purpose of this study was to assess the effect of systemic administration of nicotine on higher brain function and other physiological system in conscious rats. At least 3 days before study, Wistar male rats (n=12) were chronically implanted with a probe to measure brain blood flow, and catheters to measure systemic arterial pressure and to intravenously infuse nicotine. In addition, electrodes were also placed for measurements of electroencephalogram (EEG), renal and lumbar sympathetic nerve activities (RSNA and LSNA), trapezius electromyogram (EMG) and electrocardiogram (ECG). The EEG was analyzed by Fast Fourier Transform in 10-s epochs. Either 50 or 25 µg of nicotine was administrated through venous catheter after an hour observation, in which rats kept quiet. The response of brain blood flow after nicotine injection was characterized by a rapid elevation and followed by a gradual decrease. The power spectrum of EEG was broadly inhibited after the nicotine injection. Similarly the RSNA, LSNA, EMG and heart rate were rapidly increased, and then steeply decreased. These variables were inhibited more than an hour, while the response of mean arterial pressure was increased and decreased but remained elevated. These data shows that intravenous administration of nicotine causes biphasic responses, such as a rapid elevation and followed by suppression, in both central and sympathetic nervous system. [J Physiol Sci. 2007;57 Suppl:S193]
