Dissociating the primary reinforcing and reinforcement-enhancing effects of nicotine using a rat self-administration paradigm with concurrently available drug and environmental reinforcers.
BACKGROUND
Nicotine has two effects on reinforcement in traditional self-administration paradigms. It serves as a primary reinforcer by increasing the probability of behaviors that result in nicotine delivery. However, nicotine also potently enhances behaviors that result in the delivery of nonpharmacological reinforcers.


OBJECTIVE
The present study sought to dissociate these two effects of nicotine on reinforcement.


METHODS
For one group of rats (2 lever), a nonpharmacological reinforcer [visual stimulus (VS)] was available for pressing one lever. Nicotine infusions were available for pressing a different lever. A second group (NIC + VS) received more traditional self-administration training; both the VS and nicotine were delivered for pressing a single active lever. Control groups received either nicotine infusions (NIC only) or VS presentations (VS only) for pressing the active lever.


RESULTS
Nicotine alone was a weak reinforcer; the VS alone was slightly more reinforcing than nicotine. When these two reinforcers were combined (NIC + VS), response rates were synergistically increased. For the 2-lever group, responding on the nicotine lever was weak, matching the response rates of rats receiving nicotine alone. However, responding on the VS lever was potently enhanced in this group; equaling the response rates for rats receiving both reinforcers for making a single response (NIC + VS).


CONCLUSIONS
These data indicate that the reinforcement-enhancing effects of nicotine are very potent even when only moderate quantities of the drug are self-administered. Moreover, they provide the first demonstration that the reinforcement-enhancing and primary reinforcing effects of nicotine can be dissociated behaviorally.
Palmatier
Matthew I
MI
Department of Psychology, University of Pittsburgh, 3137 Sennott Square, 210 S. Bouquet St., Pittsburgh, PA 15260, USA. mip16@pitt.edu
Evans-Martin
F Fay
FF
Hoffman
Alycia
A
Caggiula
Anthony R
AR
Chaudhri
Nadia
N
Donny
Eric C
EC
Liu
Xiu
X
Booth
Sherri
S
Gharib
Maysa
M
Craven
Laure
L
Sved
Alan F
AF
D000818:Animals; D001245:Association Learning; D003463:Cues; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D007262:Infusions, Intravenous; D008297:Male; D009042:Motivation; D011597:Psychomotor Performance; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012646:Self Administration; D012931:Social Environment; D014029:Tobacco Use Disorder / Q000523:psychology*; D014796:Visual Perception