title: Acute nicotine-induced tachyphylaxis is differentially manifest in the limbic system.
abstract: Rapid tolerance develops to many of nicotine's behavioral and autonomic effects. A better understanding of the spatiotemporal patterns in neuronal activity as a consequence of acute nicotine tolerance (tachyphylaxis) may help explain its commonly found inverted 'U'-shaped biphasic dose-effect relationship on various behaviors. To this end, we employed high-resolution functional magnetic resonance imaging and relative cerebral blood volume (rCBV) as a marker of neuronal activity, to characterize the regional development of acute tolerance as a function of nicotine dose in naïve, anesthetized rats. A single intravenous nicotine injection at 0.1 and 0.3, but not 0.03 mg/kg, significantly increased neuronal activity in many neocortical areas. In contrast, dose-dependent increases in rCBV were most pronounced in limbic regions, such that responses seen at 0.1 mg/kg nicotine in accumbens, hippocampus, amygdala, and several other limbic areas were not seen following 0.3 mg/kg nicotine. Finally, whereas profound tolerance was observed in many cortical regions after the second of two paired nicotine injections at either 0.1 or 0.3 mg/kg, subcortical limbic structures showed only a weak trend for tolerance. Lack of rCBV changes in animals receiving nicotine methiodide, a quaternary nicotine analog that does not cross the blood-brain barrier, supports a direct neuronal effect of nicotine rather than an action on the vasculature. These data provide pharmacodynamic insight into the regional heterogeneity of nicotine tachyphylaxis development, which may be relevant to behavioral and neurobiological mechanisms associated with repeated tobacco consumption.
authors.affiliation: Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, Baltimore, MD 21224, USA.
authors.forename: Yantao
authors.initials: Y
authors.lastname: Zuo
authors.forename: Hanbing
authors.initials: H
authors.lastname: Lu
authors.forename: D Bruce
authors.initials: DB
authors.lastname: Vaupel
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Svetlana I
authors.initials: SI
authors.lastname: Chefer
authors.forename: William R
authors.initials: WR
authors.lastname: Rea
authors.forename: Anna V
authors.initials: AV
authors.lastname: Moore
authors.forename: Yihong
authors.initials: Y
authors.lastname: Yang
authors.forename: Elliot A
authors.initials: EA
authors.lastname: Stein
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D008032:Limbic System / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D009538:Nicotine / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013618:Tachyphylaxis / Q000502:physiology*
chemical_list: D009538:Nicotine