Abstract

Nicotine dependence is the major cause of cigarette smoking. The dependence occurred in the brain mesolimbic system and the amygdala has an important role in its initiation. Nicotine can activate dopaminergic neurons within the amygdaloid complex However, there is no evidence about complete inhibition of amygdala on nicotine dependence, thus in the present study we used conditioned-place preference (CPP) method to study the effect of transient inhibition of left and/or right side of the amygdala by lidocaine on nicotine reward properties in male Wistar rats (W: 250-280 g). One week after two side cannulation and recovery the rats were conditioned to nicotine. Lidocaine hydrochloride (2%) was injected in amygdaloid complex, five min before each nicotine intraperitoneal (IP) injection for transient inhibition. On the test day, the animals were placed in the apparatus and their behaviors were recorded by a camera for 600 seconds. Then the records were analysis off line for sniffing, rearing, locomotion and compartment crossing. Three-way analysis of variance (ANOVA) was performed for statistical analysis. Our results showed that intra-peritoneal injection of nicotine (1 and 1.5 mg/kg) induced place preference. Transient inhibition of left and/or right or both sides of the amygdaloid complex reduces nicotine place conditioning. In addition, rearing and compartment crossing also were reduced. However, when left sides of the nucleus were inhibited, sniffing was increased, but when the right or left side was inhibited the sniffing was decreased. In conclusion, these results confirmed the involvement of both left and right sides of the amygdaloid complex in nicotine place conditioning.

Key words: Amygdaloid Complex; Compartment crossing; Lidocaine; Nicotine; Rearing; Sniffing