Comparison of sucrose and ethanol-induced c-Fos-like immunoreactivity in the parabrachial nuclei and accumbens nucleus

Kim, Yiseul; Cho, Young Kyung

Abstract

Sucrose and alcohol are rewarding and appetitive. They are occasionally over-consumed and cause addiction. The parabrachial nuclei (PbN) are the second taste relay in the central taste pathway. The nucleus accumbens (NAcc) is an important neural substrate in the reward system. Intake of sucrose or alcohol induces dopamine release in the NAcc. Although alcohol is not classified as a taste stimulus, a substantial number of sucrose-responsive neurons in the PbN respond to stimulation by alcohol on the tongue. In the present study, we investigated whether or not application of 0.5 M sucrose, 10% ethanol (EtOH), mixture of sucrose and EtOH, and double-distilled water (DDW) to the tongue induces c-Fos-like immunoreactivity (cFLI) in the PbN and NAcc. We also examined whether or not the number of cFLI following sucrose/EtOH is comparable to the number of cFLIs following sucrose and EtOH, respectively. Male Sprague-Dwaley rat was anesthetized with a mixture of Zoletil and Rompun while stimulation solution was applied to the anterior tongue. The rat was sacrificed by perfusion, and the fixed brain was sectioned and immunostained. Data from a total of 18 animals were analyzed. The number of cFLI following stimulation with sucrose and/or EtOH was greater than that of DDW in the PbN. Numbers of cFLI following sucrose, EtOH, and sucrose/EtOH were not significantly different from each other in the PbN. The number of cFLI in response to stimulation solution was not different from that of DDW in the NAcc. The result of the present study suggests that not only sucrose but also EtOH activates some neurons in the PbN, and that some pontine neurons possibly respond to both sucrose and EtOH.