Precipitated withdrawal from nicotine reduces reinforcing effects of a visual stimulus for rats.
BACKGROUND
Research has identified at least two positive reinforcement-related effects of nicotine: (a) primary reinforcement and (b) enhancement of reinforcement from concurrently available stimuli. Prior examples of the reinforcement-enhancing effects with rats showed that repeated, intermittent nicotine exposure increased responding for non-nicotine reinforcers, and this effect remained robust over several weeks. However, the effects of continuous nicotine exposure on responding for a non-nicotine reinforcer are unknown, as are the effects of abruptly withdrawing continuous nicotine on behavior maintained by the same reinforcer.


METHODS
Lever pressing for a visual reinforcer under a fixed ratio schedule was assessed while rats were maintained on a chronic, continuous infusion of nicotine (3.16 mg/kg/day; osmotic minipump). The effects of precipitated withdrawal on responding, following 16 days of continuous nicotine exposure, were assessed by pre-session subcutaneous injections of mecamylamine (1.0 mg/kg).


RESULTS
Continuous nicotine initially increased active responding for the visual reinforcer; however, continued exposure resulted in an attenuation of this effect. Precipitated withdrawal from nicotine resulted in a significant decline in active responding.


CONCLUSIONS
The initial increase in responding for the visual reinforcer with chronic nicotine exposure is consistent with prior research showing that intermittent exposure to nicotine acts as a reinforcement enhancer. However, the attenuation of this enhancement following prolonged nicotine exposure is in contrast with the persistent effects previously reported. Finally, the decrease in visual reinforcers below control levels (nicotine-naive animals) following nicotine withdrawal highlights a potential for affective withdrawal, which may serve as a motive for continued nicotine use.
Department of Psychology, School of Arts and Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA. mtw31@pitt.edu
Matthew T
MT
Weaver
Maggie
M
Sweitzer
Sarah
S
Coddington
Jaimee
J
Sheppard
Nicole
N
Verdecchia
Anthony R
AR
Caggiula
Alan F
AF
Sved
Eric C
EC
Donny
D000818:Animals; D003216:Conditioning, Operant; D007279:Injections, Subcutaneous; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009538:Nicotine / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018733:Nicotinic Antagonists / Q000494:pharmacology; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D013375:Substance Withdrawal Syndrome / Q000523:psychology*; D013997:Time Factors
D018733:Nicotinic Antagonists; D008464:Mecamylamine; D009538:Nicotine