Descending projections from the nucleus accumbens shell suppress activity of taste-responsive neurons in the hamster parabrachial nuclei

Abstract

The parabrachial nuclei (PbN), the second central relay for the gustatory pathway, transfers taste information to various forebrain gustatory nuclei and to the gustatory cortex. The nucleus accumbens is one of the critical neural substrates of the reward system, and the nucleus accumbens shell region (NAcSh) is associated with feeding behavior. Taste-evoked neuronal responses of PbN neurons are modulated by descending projections from the gustatory nuclei in the forebrain. In the present study, we investigated whether taste-responsive neurons in the PbN project to the NAcSh and whether pontine gustatory neurons are subject to modulatory influence from the NAcSh in urethane-anesthetized hamsters. Extracellular single-unit activity was recorded in the PbN, and taste responses were confirmed by the delivery of 32 mM sucrose, NaCl, quinine hydrochloride, and 3.2 mM citric acid to the anterior tongue. The NAcSh was then stimulated (0.5 ms, ≤100 μA) bilaterally using concentric bipolar stimulating electrodes. A total of 98 taste neurons were recorded from the PbN. Eighteen neurons were antidromically invaded from the NAcSh, mostly the ipsilateral NAcSh (n = 16). Stimulation of the ipsilateral and contralateral NAcSh suppressed the neuronal activity of 88 and 55 neurons, respectively; 52 cells were affected bilaterally. In a subset of pontine neurons tested, electrical stimulation of the NAcSh during taste stimulation also suppressed taste-evoked neuronal firing. These results demonstrated that taste-responsive neurons in the PbN not only project to the NAcSh but also are under substantial descending inhibitory influence from the bilateral NAcSh.

Descending projections from the nucleus accumbens shell excite activity of taste-responsive neurons in the nucleus of the solitary tract in the hamster

“…2. Overall, the distribution of NAcSh stimulating sites was similar to those described in our previous report (Li et al 2012).…”

“…Young adult male Syrian golden hamsters (Mesocricetus auratus, n ϭ 36) weighing between 138 and 176 g were used in this study. The animal preparation and insertion of stimulating electrodes were previously described (Li et al 2012). Briefly, each animal was deeply anesthetized with urethane (1.7 g/kg ip) and tracheotomized.…”

“…A considerable volume of evidence suggests that the NAcSh plays a significant role in mediating the hedonic value of orosensory stimuli and motivated behavior (Di Chiara 2002;Loriaux et al 2011;Norgren et al 2006). Recently, we reported that electrical stimulation of the NAcSh inhibits the spontaneous and taste-evoked neuronal activities of hamster pontine cells (Li et al 2012). In addition to inhibitory modulation of pontine gustatory cells following NAcSh activation, one-fifth of all gustatory neurons recorded in the PbN projected to the NAcSh (Li et al 2012).…”

“…Recently, we reported that electrical stimulation of the NAcSh inhibits the spontaneous and taste-evoked neuronal activities of hamster pontine cells (Li et al 2012). In addition to inhibitory modulation of pontine gustatory cells following NAcSh activation, one-fifth of all gustatory neurons recorded in the PbN projected to the NAcSh (Li et al 2012).…”

D1 and D2 antagonists reverse the effects of appetite suppressants on weight loss, food intake, locomotion, and rebalance spiking inhibition in the rat NAc shell

“…To relate the behavioral studies to neural activity, we recorded the responses to DEP20 in the NAc shell, a brain region involved in reward, feeding, and motor activity Kelley et al 2005;Li et al 2012). A total of 154 well-isolated single neurons were recorded and classified into putative medium spiny projection neurons (pSPNs; n ϭ 47), putative fast-spiking interneurons (pFSIs; n ϭ 37), putative choline acetyltransferase interneurons (pChATs; n ϭ 36), and unidentified neurons (U; n ϭ 34) (see Table 1 for data regarding firing rates and waveform shapes for each putative cell type).…”