Activating mGluR8 Attenuates Visceral Hypersensitivity in Neonatal Maternally Separated Rats / 胃肠病学

ABSTRACT

Activating metabolite glutamate receptor 8 (mGluR8) has anti-hyperpathia effect in central nervous system, however, studies of effects in gastrointestinal tract are rare. Visceral hypersensitivity is one of the pathogenesis factors of irritable bowel syndrome (IBS). Aims: To investigate the effect and potential mechanism of activating mGluR8 on visceral hypersensitivity in neonatal maternally separated (NMS) rats. Methods: Twenty-four male newborn SD rats were randomly divided into normal control (NC) group, NMS group and mGluR8 agonist (S)-3, 4-DCPG group (3, 10 mg/kg). Newborn rats were subjected to 3 hours daily maternal separation on postnatal day 2-14 to establish the NMS model; in (S)-3, 4-DCPG group, (S)-3, 4-DCPG (3 or 10 mg/kg) were administered 1 hour prior to the visceral sensitivity test in NMS rats. Abdominal withdrawal reflex (AWR) score and abdominal electromyography (EMG) activity were used to measure visceral sensitivity. mGluR8 mRNA and protein expressions in colon mucosa were measured by RT-PCR and Western blotting, respectively; TNF-α, IL-1β and IL-6 mRNA expressions in colon mucosa were measured by RT-PCR. The protein expression of myeloperoxidase (MPO) was measured by immunohistochemistry. Results: AWR score and EMG activity in NMS group were significantly higher than those in NC group under different colorectal distension (CRD) pressure. AWR score and EMG activity were significantly decreased in (S)-3, 4-DCPG group. mGluR8 mRNA and protein expressions in NMS group were significantly higher than those in NC group (P<0.05). Compared with NMS group, TNF-α mRNA expression was significantly decreased in 3 mg/kg (S)-3, 4-DCPG group (P<0.05), and MPO protein expression was significantly decreased in 10 mg/kg (S)-3, 4-DCPG group (P<0.05). Conclusions: Activating mGluR8 attenuates visceral hypersensitivity in NMS rats, the mechanism may be related to decrease of pro-inflammatory cytokine TNF-α.