Intragastric gavage with denatonium benzoate acutely induces neuronal activation in the solitary tract nucleus via the vagal afferent pathway

Natural toxic substances have a bitter taste and their ingestion sends signals to the brain leading to aversive oral sensations. In the present study, we investigated chronological changes in c-Fos immunoreactivity in the nucleus tractus solitarius (NTS) to study the bitter taste reaction time of neurons in the NTS. Equal volumes (0.5 mL) of denatonium benzoate (DB), a bitter tastant, or its vehicle (distilled water) were administered to rats intragastrically. The rats were sacrificed at 0, 0.5, 1, 2, 4, 8, or 16 h after treatment. In the vehicle-treated group, the number of c-Fos-positive nuclei started to increase 0.5 h after treatment and peaked 2 h after gavage. In contrast, the number of c-Fos-positive nuclei in the DB-treated group significantly increased 1 h after gavage. Thereafter, the number of c-Fos immunoreactive nuclei decreased over time. The number of c-Fos immunoreactive nuclei in the NTS was also increased in a dose-dependent manner 1 h after gavage. Subdiaphragmatic vagotomy significantly decreased DB-induced neuronal activation in the NTS. These results suggest that intragastric DB increases neuronal c-Fos expression in the NTS 1 h after gavage and this effect is mediated by vagal afferent fibers.

THE EXPRESSION OF THE VANILLOID RECEPTOR SUBTYPE 1 IN AFFERENT FIBERS OF THE RAT ESOPHAGUS / 解剖学报

Objective To study the expression of the capsaicin receptor,vanilloid receptor subtype 1(VR1) immunoreactivity,their morphology and distribution in afferent fibers of rat esophagus. Methods Laser scanning confocal microscope combined with immunohistochemical double labeling methods were used. Results VRl-like immunoreactivity was observed on nerve fibers and terminalis within mucosa,submucosa,muscle layer and surrounding blood vessel throughout esophagus.Their profiles were fine fibers with some spiny,possessing varicose-like swellings along their lengths.About(92.3?3.7)% VR1 positive fibers co-localized with CGRP immunoreactivity,which representing large majority of afferent fibers in the esophagus was extrinsic in origin with cell bodies located in dorsal root ganglia.In dorsal root ganglion,VR1 was expressed in small-and middle-sized cell bodies.About(41.5?4.5)% VRl-immunoreactive neurons co-stained with CGRP and(67.9?3.2)% CGRP positive neurons co-localized with VR1.In nodose ganglion,the expression of VR1 was similar with dorsal root ganglion,but CGRP immunoreactive neurons very few.Only(4.7?1.4)% VR1 positive neurons co-stained with CGRP.Conclusion These results suggest that VR1 is expressed in afferent fibers in the wall of the rat esophagus which is in origin in dorsal root ganglion.

AFFERENT PROJECTIONS FROM THE DIENCEPHALON AND SUBCORTICAL TELENCEPHALON TO THE PREFRONTAL CORTEX IN THE RAT——A WGA-HRP STUDY / 解剖学报

WGA-HRP was injected into the dorsal part of anterior cingulate area,prelim- bic area,and dorsal agranular insular area of the prefrontal cortex in 25 rats to observe the afferent connections from the diencephalon and subcortical telencephalon. The afferent projections from the diencephalon mainly originate from the dorsome- dial nucleus of the thalamus,and some topographic localization may exist.Further- more,the afferent projections to the prefrontal cortex arise from the thalamic intralaminar nuclei(centrolateral nucleus,paracentral nucleus,centromedial nucleus and parafascicular nucleus),the ventral thalamic nuclei(ventrolateral nucleus,ven- tromedial nucleus,ventroanterior nucleus and ventroposterior nucleus),the midline nuclei(rhomboid nucleus,reuniens nucleus,paratenial nucleus,and paraventricular nucleus of the thalamus),the anteromedial nucleus,the lateral habenular nucleus, the posterior nucleus of the thalamus,and the lateral nucleus of the thalamus.The numbers projecting to the prefrontal cortex were different in different thalamic nuclei.The afferent projections from the hypothalamus mainly originate from the lateral hypothalamic area,lateral preoptic area,caudal magnocellular nucleus,and supramamillary nucleus.A few of afferent projections from the posterior hypothala- mic area,dorsomedial and ventromedial nucleus of the hypothalamus and zona inserta were also observed.The afferent projections from the subcortical telence- phalon mainly originate from the globus pallidus,the diagonal band nucleus,the septal nuclei(medial septal nucleus,lateral septal nucleus,septofimbrial nucleus and nucleus triangularis septi),the amygdaloid nuclei(lateral amygdaloid nucleus,lateral and medial part of basal amygdaloid nucleus,medial amygdaloid nucleus and cortical amygdaloid nucleus)and the claustrum.

ULTRASTRUCTURE OF TH, 5-HT, SP AND L-ENK IMMUNOREACTIVE FIBERS AND BOUTONS IN THE LATERAL HORN OF THE RAT SPINAL CORD / 解剖学报

The synaptic organization of monoaminergic and peptidergic fibers in the lateral horn of the rat spinal cord was studied under electron microscopy by immunocytochemistry ABC method. TH, 5-HT, SP and L-ENK immunoreactive fibers in the lateral horn were unmyelinated. In the cell clusters of the lateral horn these fibers appeared in the space between cell bodies and some pressed on the soma, but axosomatic synapses were seldom found. Many immunoreactive fibers ran along the dendrites, especially in the dendritic bundle. Occasionally a small bundle of unmyelinated fibers all contained the same kind of substance. Majority of the immunoreactive boutons formed axodendritic synapses. All the four kinds of neuroactive substancecontaining boutons or varicosities contained almost round clear vesicles or plus a few large granular vesicles. The SP and L-ENK varicosities included more large granular vesicles than the boutons did. Both symmetrical and asymmetical contacts were encountered in TH, 5-HT, SP and L-ENK boutons.