c-Fos expression in the parabrachial nucleus following intraoral bitter stimulation in the rat with dietary-induced zinc deficiency

Altered peripheral taste function in a mouse model of inflammatory bowel disease

Increased sugar intake and taste dysfunction have been reported in patients with inflammatory bowel disease (IBD), a chronic disorder characterized by diarrhea, pain, weight loss and fatigue. It was previously unknown whether taste function changes in mouse models of IBD. Mice consumed dextran sodium sulfate (DSS) during three 7-day cycles to induce chronic colitis. DSS-treated mice displayed signs of disease, including significant weight loss, diarrhea, loss of colon architecture, and inflammation of the colon. After the last DSS cycle we assessed taste function by recording electrophysiological responses from the chorda tympani (CT) nerve, which transmits activity from lingual taste buds to the brain. DSS treatment significantly reduced neural taste responses to natural and artificial sweeteners. Responses to carbohydrate, salt, sour or bitter tastants were unaffected in mice with colitis, but umami responses were modestly elevated. DSS treatment modulated the expression of receptor subunits that transduce sweet and umami stimuli in oral taste buds as a substrate for functional changes. Dysregulated systemic cytokine responses or dysbiosis that occurs during chronic colitis may be upstream from changes in oral taste buds. We demonstrate for the first time that colitis alters taste input to the brain, which could exacerbate malnutrition in IBD patients.

Altered peripheral taste function in a mouse model of inflammatory bowel disease

Increased sugar intake and taste dysfunction have been reported in patients with inflammatory bowel disease (IBD), a chronic disorder characterized by diarrhea, pain, weight loss and fatigue. It was previously unknown whether taste function changes in mouse models of IBD. Mice consumed dextran sodium sulfate (DSS) during three 7-day cycles to induce chronic colitis. DSS-treated mice displayed signs of disease, including significant weight loss, diarrhea, loss of colon architecture, and inflammation of the colon. After the last DSS cycle we assessed taste function by recording electrophysiological responses from the chorda tympani (CT) nerve, which transmits activity from lingual taste buds to the brain. DSS treatment significantly reduced neural taste responses to natural and artificial sweeteners. Responses to carbohydrate, salt, sour or bitter tastants were unaffected in mice with colitis, but umami responses were modestly elevated. DSS treatment modulated the expression of receptor subunits that transduce sweet and umami stimuli in oral taste buds as a substrate for functional changes. Dysregulated systemic cytokine responses, or dysbiosis that occurs during chronic colitis may be upstream from changes in oral taste buds. We demonstrate for the first time that colitis alters taste input to the brain, which could exacerbate malnutrition in IBD patients.

Taste Impairments in a Parkinson’s Disease Model Featuring Intranasal Rotenone Administration in Mice

Background: Taste impairments are often accompanied by olfactory impairments in the early stage of Parkinson’s disease (PD). The development of animal models is required to elucidate the mechanisms underlying taste impairments in PD. Objective: This study was conducted to clarify whether the intranasal administration of rotenone causes taste impairments prior to motor deficits in mice. Methods: Rotenone was administrated to the right nose of mice once a day for 1 or 4 week(s). In the 1-week group, taste, olfactory, and motor function was assessed before and after a 1-week recovery period following the rotenone administration. Motor function was also continuously examined in the 4-weeks group from 0 to 5 weeks. After a behavioral test, the number of catecholamine neurons (CA-Nos) was counted in the regions responsible for taste, olfactory, and motor function. Results: taste and olfactory impairments were simultaneously observed without locomotor impairments in the 1-week group. The CA-Nos was significantly reduced in the olfactory bulb and nucleus of the solitary tract. In the 4-week group, locomotor impairments were observed from the third week, and a significant reduction in the CA-Nos was observed in the substantia nigra (SN) and ventral tegmental area (VTA) at the fifth week along with the weight loss. Conclusion: The intranasal administration of rotenone caused chemosensory and motor impairments in an administration time-period dependent manner. Since chemosensory impairments were expressed prior to the locomotor impairments followed by SN/VTA CA neurons loss, this rotenone administration model may contribute to the clarification of the prodromal symptoms of PD.

Zinc Plasma Status and Sensory Perception in Nondialysis Chronic Kidney Disease Patients

OBJECTIVE

The aim of this study was to evaluate the association between zinc plasma levels and sensory perception in patients with chronic kidney disease (CKD).

METHODS

A cross-sectional study with 21 nondialysis CKD patients (11 men, 51.1 ± 7.1 years, body mass index 27.9 ± 7.1 kg/m², estimated glomerular filtration rate 32.7 ± 19.9 mL/min) and 22 non-CKD volunteers (10 men, 49.8 ± 8.3 years, body mass index 28.5 ± 5.4 kg/m²) was conducted. Blood samples were collected to obtain plasma for zinc analysis. Anthropometric and biochemical parameters, as well as food intake and salivary flow rate, were also evaluated. Taste sensory perception for sweet, acidic, bitter, and salty flavors was determined by the "three-drop method," with 4 concentrations of the 4 basic tastes.

RESULTS

As expected, zinc plasma levels were significantly lower in CKD patients (70.1 ± 19.2ug/dL) when compared with the control group participants (123.2 ± 24.6 μg dL) (P ˂ .0001). The bitter taste perception was lower in the CKD group (p˂0.0001). Our findings showed that sensitivity to sour (P = .047), salty (P = .03), and bitter tastes was significantly lower in participants with lower zinc plasma levels. Also, bitter taste sensitivity was lower in participants with less zinc intake (P = .038). When grouping control subjects and CKD patients, significant correlations were observed between zinc plasma levels and the number of correct answers for bitter taste (r = 0.49, P = .001), number of correct answers for salty taste (r = 0.30, P = .048), and total score of correct answers (r = 0.30, P = .044).

CONCLUSIONS

Reduced zinc plasma levels in nondialysis CKD patients may be associated with lower perception of bitter, sour, and salty tastes and strategies to restore these levels are crucial due many factors, including food preferences and intake.

Activation of P2X3 receptors in the cerebrospinal fluid-contacting nucleus neurons reduces formalin-induced pain behavior via PAG in a rat model

The cerebrospinal fluid (CSF)-contacting nucleus is implicated in the descending inhibitory pathway in pain processing, whereas the cellular and molecular mechanisms underpinning CSF-contacting nucleus regulating pain signals remains largely elusive. ATP is evidenced to inhibit pain transmission at supraspinal level by the mediation of the receptor P2X, wherein its subtype P2X3 is identified as the most potent. Our present experiment investigated the functionality of P2X3 receptors in CSF-contacting nucleus in the formalin-evoked inflammatory pain. Immunofluorescence and western blot revealed the expression of P2X3 receptors in the CSF-contacting nucleus and their upregulated expression subsequent to administration of formalin in rat model. ATP (a P2X3 receptor agonist, 100nmol/5µl) by intracerebroventricular (i.c.v.) administration ameliorated pain behaviors and enhanced c-Fos immunoreactivity in the neurons of the periaqueductal gray (PAG), both of which were discounted by pre-administration of A-317491 (a selective P2X3 receptor antagonist, 25nmol/5µl). After the CSF-contacting nucleus was ablated by cholera toxin subunit B-saporin, ATP failed to induce analgesia, with the c-Fos immunoreactivity in the PAG neurons remaining intact. Our results validated that P2X3 receptors in the CSF-contacting nucleus are pivotal in inflammatory pain processing via the activation of PAG neurons.