Dysregulation of kappa-opioid receptor systems by chronic nicotine modulate the nicotine withdrawal syndrome in an age-dependent manner.
BACKGROUND
Mechanisms that mediate age differences during nicotine withdrawal are unclear.


OBJECTIVE
This study compared kappa-opioid receptor (KOR) activation in naïve and nicotine-treated adolescent and adult rats using behavioral and neurochemical approaches to study withdrawal.


METHODS
The behavioral models used to assess withdrawal included conditioned place and elevated plus maze procedures. Deficits in dopamine transmission in the nucleus accumbens (NAcc) were examined using microdialysis procedures. Lastly, the effects of KOR stimulation and blockade on physical signs produced upon removal of nicotine were examined in adults.


RESULTS
Nicotine-treated adults displayed a robust aversion to an environment paired with a KOR agonist versus naïve adults. Neither of the adolescent groups displayed a place aversion. KOR activation produced an increase in anxiety-like behavior that was highest in nicotine-treated adults versus all other groups. KOR activation produced a decrease in NAcc dopamine that was largest in nicotine-treated adults versus all other groups. Lastly, KOR activation facilitated physical signs of withdrawal upon removal of nicotine and KOR blockade reduced this effect.


CONCLUSIONS
Chronic nicotine enhanced the affective, anxiogenic, and neurochemical effects produced by KOR activation in adult rats. Our data suggest that chronic nicotine elicits an increase in KOR function, and this may contribute to nicotine withdrawal since KOR activation facilitated and KOR blockade prevented withdrawal signs upon removal of nicotine. Given that chronic nicotine facilitated the neurochemical effects of KOR agonists in adults but not in adolescents, it is suggested that KOR regulation of mesolimbic dopamine may contribute to age differences in nicotine withdrawal.
Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA.
Hugo A
HA
Tejeda
Luis A
LA
Natividad
James E
JE
Orfila
Oscar V
OV
Torres
Laura E
LE
O'Dell
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000008:administration & dosage / Q000494:pharmacology*; D000375:Aging; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008297:Male; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017473:Receptors, Opioid, kappa / Q000819:agonists* / Q000037:antagonists & inhibitors*; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy; D014029:Tobacco Use Disorder / Q000188:drug therapy*
D017473:Receptors, Opioid, kappa; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009538:Nicotine; D004298:Dopamine