Acute effects of nicotine injection into the nucleus accumbens on locomotor activity in nicotine-naive and nicotine-tolerant rats.
To assess the role of nicotine receptors in the nucleus accumbens on locomotor activity we bilaterally implanted guide cannulae for later injection of (-)-nicotine into the nucleus accumbens of Wistar rats. Motor activity was tested in a complex tunnel maze equipped with photocells for automatic recording. This system of dark tunnels elicits spontaneous exploration even after repeated exposure. Half of the rats were made nicotine-tolerant by daily systemic injections of (-)-nicotine for 15 days (nicotine pretreatment); the other half remained nicotine-naive (saline pretreatment). Whereas (-)-nicotine (40 nmol/0.3 microliter) bilaterally injected into the nucleus accumbens of nicotine-naive animals suppressed locomotor activity, the same amount injected into the nucleus accumbens of nicotine-tolerant rats had no effect on locomotor activity. Systemic injections of nicotine (0.4 mg/kg) induced a depression and stimulation of locomotor activity in saline-pretreated and nicotine-pretreated rats, respectively. Our results support a dual role for nicotine in locomotor activity with the initial depressant effect in nicotine-naive animals due to stimulation of the nucleus accumbens and perhaps other structures.
Welzl
H
H
Federal Technical Institute, Laboratory of Behavioral Biology, Zürich, Switzerland.
Bättig
K
K
Berz
S
S
D000818:Animals; D004361:Drug Tolerance; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000033:anatomy & histology; D051381:Rats; D011919:Rats, Inbred Strains
D009538:Nicotine