Glutaminergic neurons expressing c-Fos in the brainstem and amygdala participate in signal transmission and integration of sweet taste / 南方医科大学学报

<p><b>OBJECTIVE</b>To examine the role of glutaminergic neurons in the transmission and integration of the sweat taste information in the brain stem and the amygdala.</p><p><b>METHODS</b>Conscious Sprague-Dawley rats were subjected to oral sweet taste or water (control) stimulations. The activated neurons were identified by detecting c-Fos expression in taste-related brain areas, and the glutaminergic neurons by detecting vesicular glutamate transpoter-3 (VGLUT3).</p><p><b>RESULTS</b>Compared with control group, the rats with oral sucrose solution stimulation exhibited significantly increased c-Fos-expressing and double-labeled neurons in the nucleus of the solitary tract (NST), the parabrachial nucleus (PBN) and the amygdala.</p><p><b>CONCLUSION</b>Neurons in the NST, PBN and amygdala are activated after oral sweet taste stimulation. The sweet taste perception at different levels in the CNS is partly mediated by glutamate.</p>

Inhibitory responses of parabrachial neurons evoked by taste stimuli in rat / 生理学报

In the present study, the responses of inhibitory gustatory neurons in the parabrachial nucleus (PBN) to four basic taste stimuli NaCl, HCl, quinine HCl (QHCl) and sucrose were examined using single-unit recording technique in anesthetized rats. A total of 18 inhibitory taste neurons in the PBN were obtained. Spontaneous firing rates of these inhibitory neurons were 0.2-5.5 Hz with mean firing rate of (2.15+/-0.31) Hz. Most of the neurons responded to more than one of the basic taste qualities. The inhibitory responses to taste occurred quickly and lasted 5-80 s in different PBN neurons. According to the responsive characteristics to the four basic taste stimuli, the neurons could be classified as NaCl-best (n=8), HCl-best (n=3), QHCl-best (n=3), and sucrose-best (n=4). The breadth of tuning of NaCl-best neurons was the highest (0.945). Inhibitory responsive neurons had feeble discrimination among sapid stimuli or aversive stimuli. These results suggest that there exist inhibitory taste neurons in the PBN. These neurons may play some useful roles in precise transmission of taste information and the taste coding for hedonic and aversive tastes.

Study of mechanism and the effect of intracerebroventricular microinjection of serotonin on gastric motility in rabbit / 中国应用生理学杂志

<p><b>AIM</b>To explore the effect of central serotonin (5-hydroxytryptamine, 5-HT) on gastric motility in rabbit and to analysis its mechanism.</p><p><b>METHODS</b>Intracerebroventricular (icv) microinjection of drugs were used. The frequency and the amplitude of contractions of gastric motility were recorded.</p><p><b>RESULTS</b>(1) Injection (icv) of 25 microg 5-HT increased the amplitude of contractions and decreased the frequency of gastric motility. (2) The effects of 5-HT were inhibited by injection (icv) of atropine, but intravenous(iv) injection of atropine could only block the increase effect of 5-HT on intragastric pressure. After injection (icv or iv) of phentolamine or propranolol, the effects of 5-HT on gastric motility were not changed markedly. (3) Microinjection (icv) of naloxone or diphenhydramine inhibited the inhibitory effect of 5-HT on the frequency of gastric contractions, and the diphenhydramine reversed the increase effect of 5-HT on intragastric pressure. (4) Vagotomy abolished the effects of 5-HT completely.</p><p><b>CONCLUSION</b>There may be different nerve mechanisms in regulation of central 5-HT on the frequency and amplitude of contractions of gastric motility. The increase effect of 5-HT on intragastric pressure is medicated by the cholinergic system in brain, and histamine may be one of the important element on the effect of 5-HT. The cholinergic fibers in vagus nerve transmit the effect. The inhibitory effect of 5-HT on the frequency of contractions is also medicated by activating the cholinergic system in brain, enkephalin and histamine are also involved, and it is transmitted via noncholinergic and nonadrenergic fibers in vagus nerve.</p>