Overexpression of ORX or MCH Protects Neurological Function Against Ischemic Stroke

In recent years, orexin (ORX) and melanin-concentrating hormone (MCH) have been demonstrated to exert neuroprotective roles in cerebral ischemia. Hence, this study investigated the regulatory function of ORX and MCH in neurological function following ischemic stroke and explored the molecular mechanism underlying these functions. A rat model of ischemic stroke was developed by middle cerebral artery occlusion (MCAO), and Longa scoring was employed to evaluate the degree of neurological function deficit. The expression patterns of ORX and MCH were examined by real-time polymerase chain reaction in the brain tissues of rats with ischemic stroke induced by middle cerebral artery occlusion (MCAO). Moreover, electroencephalography (EEG) analysis and high-performance liquid chromatography (HPLC) were respectively performed to detect rapid-eye movement (REM) sleep, the glutamate (Glu) uptake, and the expression of γ-aminobutyric acid B receptor (GABA_B). Immunoblotting was performed to test the levels of autophagic markers LC3, BECLIN-1, and p62. Immunohistochemistry (IHC) staining and TUNEL assays were respectively used to assess the autophagy and neuronal apoptosis. Results demonstrated that ORX and MCH were lowly expressed in brain of rats with ischemic stroke. ORX or MCH overexpression decreased neuronal apoptosis and autophagy, and improved the sleep architecture of post-stroke rats, while rescuing Glu uptake and GABA expression. ORX or MCH upregulation exerted protective effects on neurological function. Taken together, ORX and/or MCH protect against ischemic stroke in a rat model, highlighting their value as targets for the clinical treatment of ischemic stroke.

Pharmacological modulation of colorectal distension evoked potentials in conscious rats

BACKGROUND

Cerebral evoked potentials (CEP) induced by colorectal distension (CRD) in conscious rats provides a novel method in studies of visceral sensitivity. The aim of this study was to explore the pharmacological effect on CEP of compounds known to reduce the visceromotor response to CRD.

METHODS

Epidural electrodes were chronically implanted in eight female Sprague-Dawley rats. Evoked potentials were elicited by colorectal rapid balloon distensions (100 ms, 80 mmHg) and the effect of WIN55 (cannabinoid CB receptor agonist), clonidine (adrenergic α₂ receptor agonist), MPEP (mGluR5 receptor antagonist), pregabalin (ligand of α₂δ subunits in voltage-gated calcium channels) and baclofen (GABA-B receptor agonist) on amplitudes and latency of CEP were determined.

RESULTS

WIN55 (0.1 μmol kg^-1), clonidine (0.05 μmol kg^-1), MPEP (10 μmol kg^-1) and pregabalin (200 μmol kg^-1) caused a significant, p < 0.05, reduction of the N2 to P2 peak-to-peak amplitude by 23 ± 8%, 25 ± 8%, 39 ± 5%, and 47 ± 6% respectively. Baclofen (9 μmol kg^-1) induced a prolongation of the N2 peak latency of 18 ± 4% but had no significant effect on the amplitudes.

CONCLUSION

The obtained results suggest that MPEP, WIN55, clonidine, and pregabalin reduce visceral nociceptive input to the brain, whereas the lack of effect of baclofen on CRD evoked CEP amplitudes suggest that the effect on VMR is not due to a direct analgesic effect. Brain responses to colorectal distension provide a useful tool to evaluate pharmacological effects in rats and may serve as a valuable preclinical model for understanding pharmacological mechanisms related to visceral sensitivity.

The Role of Spinal GABAB Receptors in Cancer-Induced Bone Pain in Rats

Cancer-induced bone pain (CIBP) remains a major challenge in advanced cancer patients because of our lack of understanding of its mechanisms. Previous studies have shown the vital role of γ-aminobutyric acid B receptors (GABABRs) in regulating nociception and various neuropathic pain models have shown diminished activity of GABABRs. However, the role of spinal GABABRs in CIBP remains largely unknown. In this study, we investigated the specific cellular mechanisms of GABABRs in the development and maintenance of CIBP in rats. Our behavioral results show that acute as well as chronic intrathecal treatment with baclofen, a GABABR agonist, significantly attenuated CIBP-induced mechanical allodynia and ambulatory pain. The expression levels of GABABRs were significantly decreased in a time-dependent manner and colocalized mostly with neurons and a minority with astrocytes and microglia. Chronic treatment with baclofen restored the expression of GABABRs and markedly inhibited the activation of cyclic adenosine monophosphate (cAMP)-dependent protein kinase and the cAMP-response element-binding protein signaling pathway.

PERSPECTIVE

Our findings provide, to our knowledge, the first evidence that downregulation of GABABRs contribute to the development and maintenance of CIBP and restored diminished GABABRs attenuate CIBP-induced pain behaviors at least partially by inhibiting the protein kinase/cAMP-response element-binding protein signaling pathway. Therefore, spinal GABABR may become a potential therapeutic target for the management of CIBP.

Expression of truncated γ-aminobutyric acid B receptor in liver fibrosis in rats

AIM: To investigate the expression of truncated γ-aminobutyric acid B receptor 1 (GABBR1) in liver fibrosis in rats.

METHODS: Sprague-Dawley rats were divided into three groups: a normal control group, a model group and a treatment group. Liver fibrosis was induced with carbon tetrachloride (CCl₄) in rats of the model group and treatment group, and the normal control group was given olive oil. The treatment group was additionally given GABA. Western blot analysis and PCR were performed to detect the expression of GABBR1 protein and mRNA.

RESULTS: Both Western blot and PCR analyses indicated the presence of a truncated GABBR1 in rats of the three groups. DNA sequencing and NCBI blast sequence analysis confirmed that the protein is GABBR1e. PCR results showed that the mRNA expression level of GABBR1e in the model group was higher than those in the GABA group and the control group. However, there was no significant difference in the protein expression level of GABBR1e among the three groups.

CONCLUSION: Our findings suggest the expression of GABBR1e in liver tissue. The role of GABBR1e in liver fibrosis and its biological significance still need further research.

Expression of γ-aminobutyric acid B receptor in carbon tetrachloride-induced liver fibrosis in rats

AIM: To investigate the expression of γ-aminobutyric acid (GABA) B receptor in carbon tetrachloride-induced liver fibrosis in rats.

METHODS: Male Sprague-Dawley rats were intraperitoneally injected with 50% carbon tetrachloride to induce liver fibrosis. Six weeks after induction, liver tissue samples were taken once a week. Each sample was divided into two parts: one was used for hematoxylin and eosin and Masson's trichrome staining to assess the degree of liver fibrosis and immunohistochemistry to determine the level of α-smooth muscle actin (α-SMA), the other was used for real-time reverse transcription-polymerase chain reaction to detect the expression of GABA B receptor, α-SMA, transforming growth factor-β (TGF-β), collagen I and collagen III mRNAs.

RESULTS: The expression levels of α-SMA, TGF-β, collagen I, collagen III and GABA(B) receptor mRNAs in liver fibrosis at week 7 increased 19.2, 2.1, 37.5, 183.5 and 116.2 times as much as those at week 6, respectively. At week 6, the expression level of GABA(B) receptor in the liver in rats with liver fibrosis was reduced by two times when compared with that in normal control rats. At week 12 when pseudolobule formed, the expression levels of α-SMA and collagen I mRNAs increased 21.6 and 20.6 times as much as those at week 6, respectively, while those of TGF-β and collagen III mRNAs showed no obvious changes. The expression levels of these genes at other time points were almost unchanged when compared with those at week 6.

CONCLUSION: GABA(B) receptor may be involved in the progression of liver fibrosis. In advanced liver fibrosis, the extracellular matrix synthesized is mainly collagen I. The expression of α-SMA is positively correlated with the degree of liver fibrosis.