BACKGROUND: We investigated the effects of pre-emptive administration of ketamine and norBNI on pain behavior and the expression of DREAM, c-Fos, and prodynorphin proteins on the ipsilateral side of the rat spinal cord at 2 and 4 hours after formalin injection. METHODS: Eighty-four male Sprague Dawley rats were divided into 4 major groups consisting of control rats (C) (n = 12), rats given only formalin injections (F) (n = 24), and rats treated with pre-emptive administration of either ketamine (K+F) (n = 24) or norBNI (N+F) (n = 24). The non-control groups were further divided into subgroups consisting of rats that were sacrificed at 2 and 4 hours (n = 12 for each group) after formalin injection. Pain behavior was recorded for 1 hour. After 2 and 4 hours, the rats were sacrificed and the spinal cords (L4-L5 sections) were removed for immunohistochemistry and Western blot analysis. RESULTS: The pain behavior response was reduced in the K+F group compared to the other groups during the second phase of the formalin pain response. We detected an increase in the nuclear DREAM protein level in the K+F group at 2 and 4 hours and a transient decrease in the N+F group at 2 hours; however, it increased at 4 hours after injection. Fos-like immunoreactivity (FLI) and Prodynorphin-like immunoreactivity (PLI) neurons decreased in the K+F group but increased in the N+F group at 2 hours after injection. While FLI decreased, PLI increased in all groups at 4 hours after injection. CONCLUSIONS: We suggest that NMDA and kappa opioid receptors can modulate DREAM protein expression, which can affect pain behavior and protein transcriptional processes at 2 hours and bring about either harmful or protective effects at 4 hours after formalin injection.
Animals ; Blotting, Western ; Enkephalins ; Formaldehyde ; Humans ; Immunohistochemistry ; Ketamine ; Male ; N-Methylaspartate ; Neurons ; Pain Measurement ; Protein Precursors ; Proteins ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, kappa ; Spinal Cord

BACKGROUND: This study investigated the role of NR2B in a modulated pain process in the painful diabetic neuropathy (PDN) rat using various pain stimuli. METHODS: Thirty-two Sprague-Dawley male rats were randomly allocated into four groups (n=8): control, diabetes mellitus (DM) rats and diabetic rats treated with ifenprodil at a lower dose (0.5 µg/day) (I 0.5) or higher dose (1.0 µg/day) (I 1.0). DM was induced by a single injection of streptozotocin at 60 mg/kg on day 0 of experimentation. Diabetic status was assessed on day 3 of the experimentation. The responses on both tactile and thermal stimuli were assessed on day 0 (baseline), day 14 (pre-intervention), and day 22 (post-intervention). Ifenprodil was given intrathecally for 7 days from day 15 until day 21. On day 23, 5% formalin was injected into the rats' hind paw and the nociceptive responses were recorded for 1 hour. The rats were sacrificed 72 hours post-formalin injection and an analysis of the spinal NR2B expression was performed. RESULTS: DM rats showed a significant reduction in pain threshold in response to the tactile and thermal stimuli and higher nociceptive response during the formalin test accompanied by the higher expression of phosphorylated spinal NR2B in both sides of the spinal cord. Ifenprodil treatment for both doses showed anti-allodynic and anti-nociceptive effects with lower expression of phosphorylated and total spinal NR2B. CONCLUSION: We suggest that the pain process in the streptozotocin-induced diabetic rat that has been modulated is associated with the higher phosphorylation of the spinal NR2B expression in the development of PDN, which is similar to other models of neuropathic rats.
Animals ; Diabetes Mellitus ; Diabetic Neuropathies ; Formaldehyde ; Humans ; Hyperalgesia ; Male ; N-Methylaspartate ; Pain Measurement ; Pain Threshold ; Phosphorylation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; Spinal Cord ; Streptozocin

Introduction: Minocycline has been demonstrated to have potent effects on neurologic structures and functions in several animal models. However, its neuroprotective properties following a single injection of lipopolysaccharide (LPS) in an adult rat model have not been clearly elucidated. This study investigated minocycline’s neuroprotective effects in the LPS-induced neuroinflammation rat model. Methods: Fifty adult male Sprague Dawley rats were split into five groups at random: (i) control, (ii) distilled water-treated LPS, (iii) 25 mg/kg minocycline-treated LPS, (iv) 50 mg/kg minocycline-treated LPS, and (v) 10 mg/kg memantine-treated LPS. On day 5, LPS (5 mg/kg) was given intraperitoneally once, whereas minocycline and memantine were given once daily for 14 days. Results: LPS was found to significantly induce β-amyloid peptide deposition and neuronal damage, and impair recognition memory, while administration of minocycline dose-dependently reversed these effects. These data suggest that LPS-induced recognition memory impairment by inducing β-amyloid peptide deposition and neuronal damage in the cortical and hippocampal areas. Furthermore, we compared minocycline with memantine administration, and these data suggested better effects in minocycline (50 mg/kg) and comparable effects between minocycline (25 mg/kg) and memantine (10 mg/kg) treatments in reducing β-amyloid peptide deposition, neuronal damage and recognition memory impairment induced by LPS. Conclusion: Minocycline may be a strong contender as an effective preventive-therapeutic drug for neuroinflammatory diseases such as Alzheimer’s disease (AD) based on these findings.

OBJECTIVE: This study was done to determine whether Tualang honey could prevent the altered nociceptive behaviour, with its associated changes of oxidative stress markers and morphology of the spinal cord, among the offspring of prenatally stressed rats. METHODS: Pregnant rats were divided into three groups: control, stress, and stress treated with Tualang honey. The stress and stress treated with Tualang honey groups were subjected to restraint stress from day 11 of pregnancy until delivery. Ten week old male offspring (n = 9 from each group) were given formalin injection and their nociceptive behaviours were recorded. After 2 h, the rats were sacrificed, and their spinal cords were removed to assess oxidative stress activity and morphology. Nociceptive behaviour was analysed using repeated measures analysis of variance (ANOVA), while the levels of oxidative stress parameters and number of Nissl-stained neurons were analysed using a one-way ANOVA. RESULTS: This study demonstrated that prenatal stress was associated with increased nociceptive behaviour, changes in the oxidative stress parameters and morphology of the spinal cord of offspring exposed to prenatal stress; administration of Tualang honey reduced the alteration of these parameters. CONCLUSION This study provides a preliminary understanding of the beneficial effects of Tualang honey against the changes in oxidative stress and neuronal damage in the spinal cord of the offspring of prenatally stressed rats.

Introduction: Increased nociceptive responses were shown in the offspring of prenatally stressed rats. Reports have demonstrated the anti-nociceptive effects of Tualang honey in the rat offspring. The present study was done to determine whether the modulation of nociceptive behaviour by Tualang honey was mediated by modulating changes in the histology, oxidative stress parameters and N-methyl-D-aspartate (NMDA) receptors in the thalamus of the rat offspring. Methods: Eighteen Sprague Dawley pregnant rats were randomly assigned to control (C), stress (S) and stress-treated with Tualang honey (SH) groups. Stress was given in a form of restraint stress.Tualang honey was given to SH group from first day of pregnancy until delivery. Thirty-three adult male offspring were subjected to formalin test before they were sacrificed. Nociceptive behaviour score, number of neurons, level of oxidative stress parameters and NMDA receptors in the thalamus were analysed by using one-way ANOVA. Results: The study demonstrated a significant decrease in mean nociceptive behaviour score (p<0.05) with lower malondialdehyde (MDA, p<0.05) and higher superoxide dismutase SOD and catalase levels in the thalamus of SH group compared to S group (p<0.05). There was also increased Nissl positive neurons in the thalamus of SH group compared to S group. There was no significant difference in NMDA receptor level between S and SH groups. Conclusion: The modulation of nociceptive responses in the prenatally stressed rat offspring by Tualang honey was associated with improvement in oxidative stress parameters and histology of the thalamus in the rat offspring exposed to prenatal stress.