AIM OF STUDY: To investigate the effect of mitragynine after chronic morphine treatment on cyclic AMP (cAMP) level and mRNA expression of mu-opioid receptor (MOR) in human neuroblastoma SK-N-SH cell.
METHOD AND MATERIALS: Mitragynine was isolated from the Mitragyna speciosa plant using the acid-base extraction method. The cAMP level upon forskolin stimulation in the cells was determined using the Calbiochem(®) Direct Immunoassay Kit. The mRNA expression of the MOR was carried out using quantitative RT-PCR.
RESULT: Cotreatment and pretreatment of morphine and mitragynine significantly reduced the production of cAMP level at a lower concentration of mitragynine while the higher concentration of this compound could lead to the development of tolerance and dependence as shown by the increase of the cAMP level production in foskolin stimulation. In MOR mRNA expression study, cotreatment of morphine with mitragynine significantly reduced the down-regulation of MOR mRNA expression as compared to morphine treatment only.
CONCLUSION: These finding suggest that mitragynine could possibly avoid the tolerance and dependence on chronic morphine treatment by reducing the up-regulation of cAMP level as well as reducing the down-regulation of MOR at a lower concentration of mitragynine.
OBJECTIVE: This study aims to determine the effect of age on the function of rostral C1 (rC1) neurons in mediating feeding response.
METHOD: Male Sprague Dawley rats at 3-months (n = 22) and 24-months (n = 22) old were used and further divided into two subgroups; 1) treatment group with 2-deoxy-d-glucose (2DG) and 2) vehicle group. Feeding hormones such as cholecystokinin (CCK), ghrelin and leptin were analysed using enzyme-linked immunosorbent assay (ELISA). Rat brain was carefully dissected to obtain the brainstem RVLM region. Further analysis was carried out to determine the level of proteins and genes in RVLM that were associated with feeding pathway. Protein expression of tyrosine hydroxylase (TH), phosphorylated TH at Serine40 (pSer40TH), AMP-activated protein kinase (AMPK), phosphorylated AMPK (phospho AMPK) and neuropeptide Y Y5 receptor (NPY5R) were determined by western blot. Expression of TH, AMPK and NPY genes were determined by real-time PCR.
RESULTS: This study showed that blood glucose level was elevated in young and old rats following 2DG administration. Plasma CCK-8 concentration was higher in the aged rats at basal and increased with 2DG administration in young rats, but the leptin and ghrelin showed no changes. Old rats showed higher TH and lower AMPK mRNA levels. Glucoprivation decreased AMPK mRNA level in young rats and decreased TH mRNA in old rats. Aged rC1 neurons showed higher NPY5R protein level. Following glucoprivation, rC1 neurons produced distinct molecular changes across age in which, in young rats, AMPK phosphorylation level was increased and in old rats, TH phosphorylation level was increased.
CONCLUSION: These findings suggest that glucose-counterregulatory responses by rC1 neurons at least, contribute to the ability of young and old rats in coping glucoprivation. Age-induced molecular changes within rC1 neurons may attenuate the glucoprivic responses. This situation may explain the impairment of feeding response in the elderly.
METHODS: Orchidectomized adult male Sprague-Dawley (SD) rats received seven days subcutaneous testosterone treatment (125 μg/kg/day or 250 μg/kg/day), with or without flutamide or finasteride. Following completion of treatment, MAP was determined in rats under anaesthesia via carotid artery cannulation. In another cohort of rats, kidneys were removed following sacrifice and AQP-1, 2, 3, 4, 6 and 7 protein and mRNA levels were determined by Western blotting and Real-time PCR respectively. Distribution of AQP subunits' protein in the nephrons were visualized by immunofluorescence.
RESULTS: Testosterone caused MAP, AQP-1, 2, 4, 6 and 7 protein and mRNA levels in kidneys to increase while AQP-3 protein and mRNA levels in kidneys to decrease (p