Activation of the nucleus accumbens excites taste/ethanol – responsive cells in the nucleus of the solitary tract

The nucleus of the solitary tract (NST) and the parabrachial nuclei (PbN) are the first and second taste relays in the rodent taste pathway, respectively. From the PbN, taste information is further carried to the forebrain taste areas, including the nucleus accumbens (NAcc), and cortex. It is known that the NAcc plays an important role in the rewarding and subsequent addictive properties of drugs of abuse and alcohol in particular. Here, we investigated whether taste/alcohol‐responsive neurons in the NST are subject to the descending influence of the NAcc. Single‐unit activity was recorded from the urethane anaesthetized hamster NST. Taste/ethanol responses were confirmed by delivery of taste solutions/ethanol to the anterior tongue. After confirming the responsiveness of a NST neuron to taste/ethanol stimulation, the NAcc was stimulated (0.5 ms, ≤ 100 μA, 1/3 Hz) electrically. We recorded a total of 44 taste/ethanol‐responsive cells in the NST; 14 being NaCl‐best, 8 being sucrose‐best, 10‐being citric acid‐best, and 12 being quinine hydrochloride (QHCl)‐best neurons. Except for one cell, all sucrose‐best neurons also responded to ethanol stimulation whereas ethanol stimulation did not elicit responses of other best‐stimulus cell categories. Twenty‐eight neurons (64%) including all 7 sucrose‐best/ethanol‐responding cells were orthodromically activated following the NAcc stimulation; 25 cells after the ipsilateral NAcc stimulation, 3 cells following the contralateral NAcc stimulation. All NAcc‐elicited responses of the NST cells were exclusively excitatory. These results suggest that sucrose‐best cells in the NST preferentially co‐respond to alcohol, and that the NAcc exerts intensive centrifugal influence to taste‐responsive cells in the NST and sucrose/ethanol‐responding cells in particular. (Supported by NIDCD006623 to C.‐S. Li)