Chronic Ketamine Administration Modulates Midbrain Dopamine System in Mice

Ketamine is an anesthetic and a popular abusive drug. As an anesthetic, effects of ketamine on glutamate and GABA transmission have been well documented but little is known about its long-term effects on the dopamine system. In the present study, the effects of ketamine on dopamine were studied in vitro and in vivo. In pheochromocytoma (PC 12) cells and NGF differentiated-PC 12 cells, ketamine decreased the cell viability while increasing dopamine (DA) concentrations in a dose-related manner. However, ketamine did not affect the expression of genes involved in DA synthesis. In the long-term (3 months) ketamine treated mice, significant increases of DA contents were found in the midbrain. Increased DA concentrations were further supported by up-regulation of tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. Activation of midbrain dopaminergic neurons could be related to ketamine modulated cortical-subcortical glutamate connections. Using western blotting, significant increases in BDNF protein levels were found in the midbrain, suggesting that perhaps BDNF pathways in the cortical-subcortical connections might contribute to the long-term ketamine induced TH upregulation. These data suggest that long-term ketamine abuse caused a delayed and persistent upregulation of subcortical DA systems, which may contribute to the altered mental status in ketamine abusers

Protective effects and potential mechanisms of Pien Tze Huang on cerebral chronic ischemia and hypertensive stroke

<p>Abstract</p> <p>Background</p> <p>Stroke caused by brain ischemia is the third leading cause of adult disability. Active prevention and early treatment of stroke targeting the causes and risk factors may decrease its incidence, mortality and subsequent disability. Pien Tze Huang (PZH), a Chinese medicine formula, was found to have anti-edema, anti-inflammatory and anti-thrombotic effects that can prevent brain damage. This study aims to investigate the potential mechanisms of the preventive effects of Pien Tze Huang on brain damage caused by chronic ischemia and hypertensive stroke in rats.</p> <p>Methods</p> <p>The effects of Pien Tze Huang on brain protein expression in spontaneously hypertensive rat (SHR) and stroke prone SHR (SHRsp) were studied with 2-D gel electrophoresis and mass spectrometric analysis with a matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)/TOF tandem mass spectrometer and on brain cell death with enzyme link immunosorbent assay (ELISA) and immunostaining.</p> <p>Results</p> <p>Pien Tze Huang decreased cell death in hippocampus and cerebellum caused by chronic ischemia and hypertensive stroke. Immunostaining of caspase-3 results indicated that Pien Tze Huang prevents brain cells from apoptosis caused by ischemia. Brain protein expression results suggested that Pien Tze Huang downregulated QCR₂in the electron transfer chain of mitochondria preventing reactive oxygen species (ROS) damage and possibly subsequent cell death (caspase 3 assay) as caused by chronic ischemia or hypertensive stroke to hippocampus and cerebellum.</p> <p>Conclusion</p> <p>Pien Tze Huang showed preventive effects on limiting the damage or injury caused by chronic ischemia and hypertensive stroke in rats. The effect of Pien Tze Huang was possibly related to prevention of cell death from apoptosis or ROS/oxidative damage in mitochondria.</p

Increase in Brain-derived neurotrophic factor (BDNF) protein expression in mouse brain following 3-month ketamine administration.

<p>Sal, saline group; Ket, ketamine group; A) Representative immunoblots of BDNF and Actin. B) Quantification of the increase in BDNF in ketamine treated mice brain. Data are mean ± SEM (n = 6). *P<0.05 as compared with control group.</p

Different dopamine concentrations in mouse brain following 3 months ketamine treatment.

<p>Ketamine (30 mg/kg) were given to the mice for 3 months. Dopamine contents were measured by ELISA. Significant dopamine level change was found in the midbrain. PFC, prefrontal cortex. Sal, saline group; Ket, ketamine group; Data were presented as Mean± SEM (n = 6). * <i>p</i><0.05 as compared with control.</p

Cell viability of pheochromocytoma 12 (PC12) and differentiated PC12 cells following 24 hours ketamine treatment.

<p>A) Phase contrast image of undifferentiated PC12 cells. B) Phase contrast image of PC12 cells differentiated with nerve growth factor (NGF) (50 ng/ml) for 6 days. C) Dosage effects of ketamine on cell viability in undifferentiated PC12 cells. D) Dosage effects of ketamine on cell viability in differentiated PC12 cells. Data are presented as Mean± S.E.M. * <i>p</i><0.05 as compared with control; **<i>p</i><0.005 as compared with control.</p

Dosage effects of ketamine on dopamine in pheochromocytoma 12 (PC12) cells and differentiated PC12 cells (d-PC12).

<p>PC12 cells and d-PC12 cells were exposed to ketamine from 10 to 500 µg/ml for 24 hours. After the treatment, dopamine concentrations were measured using ELISA. Data were presented as Mean± SEM (n = 3). * <i>p</i><0.05 as compared with control; **<i>p</i><0.005 as compared with control.</p

Effects of ketamine on dopamine-related genes <i>in vitro</i> and <i>in vivo</i>.

<p>A) Changes in dopamine-related genes in pheochromocytoma 12 (PC12) and differentiated PC12 (d-PC12) cells. Cells were exposed to ketamine (100 µg/ml) for 24 hours. mRNA levels were measured by real-time PCR and fold changes were calculated using mRNA levels in ketamine group over saline group. B) Changes in dopamine-related genes in mouse brain following 3 months ketamine treatment. DBH, dopamine beta-hydroxylase; DDC, dopa decarboxylase; SNAP25, synaptosomal-associated protein 25; TH, Tyrosine hydroxylase; VMAT2, vesicular monoamine transporter 2; PFC, prefrontal cortex. Significant gene expression changes were found for SNAP25 in PFC and TH in midbrain. Data were presented as Mean± SEM (n = 4). * <i>p</i><0.05 as compared with control.</p