Developmental alterations in locomotor and anxiety-like behavior as a function of D1 and D2 mRNA expression.
The majority of smokers start smoking in adolescence, beginning a potentially lifelong struggle with nicotine use and abuse. In rodent models of the effects of nicotine, the drug has been shown to elicit both locomotor and anxiety-like behavioral effects. Research suggests that these behavioral effects may be due in part to dopamine (DA) receptors D1 and D2 in the mesolimbic system, specifically the nucleus accumbens (NAc). We examined early adolescent (P28), late adolescent (P45), and adult (P80) male Long-Evans rats in the elevated plus maze (EPM) under normal conditions and the open field (OF) post-nicotine in order to test locomotor and anxiety-like behavior. These behavioral findings were then correlated with expression of DA D1 and D2 mRNA levels as determined via in situ hybridization. Nicotine-induced locomotor behavior was found to be significantly different between age groups. After a single injection of nicotine, early adolescents exhibited increases in locomotor behavior, whereas both late adolescents and adults responded with decreases in locomotor behavior. In addition, it was found that among, early adolescents, open arm and center time in the EPM were negatively correlated with D2 mRNA expression. In contrast, among adults, distance traveled in the center and center time in the OF were negatively correlated with D2 mRNA expression. This study suggests that DA D2 receptors play a role in anxiety-like behavior and that the relationship between observed anxiety-like behaviors and D2 receptor expression changes through the lifespan.
Department of Psychology, George Mason University, United States. Electronic address: afalco2@unl.edu.
A M
AM
Falco
Department of Psychology, George Mason University, MSN 3F5, Fairfax, VA 22030, United States. Electronic address: cmcdona3@gmu.edu.
C G
CG
McDonald
Department of Psychology, George Mason University, MSN 3F5, Fairfax, VA 22030, United States. Electronic address: sbachus@gmu.edu.
S E
SE
Bachus
Department of Psychology, George Mason University, MSN 3F5, Fairfax, VA 22030, United States. Electronic address: bsmith@gmu.edu.
R F
RF
Smith
D000375:Aging / Q000378:metabolism; D000818:Animals; D001007:Anxiety / Q000139:chemically induced* / Q000188:drug therapy / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017403:In Situ Hybridization; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D009483:Neuropsychological Tests; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D017447:Receptors, Dopamine D1 / Q000235:genetics / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D013647:Task Performance and Analysis
D018722:Nicotinic Agonists; D012333:RNA, Messenger; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D009538:Nicotine
Adolescence; Anxiety; Dopamine; In situ hybridization; Locomotion; Nicotine