Reversal and Preventive Pleiotropic Mechanisms Involved in the Antipsychotic-Like Effect of Taurine, an Essential β-Amino Acid in Ketamine-Induced Experimental Schizophrenia in Mice

Schizophrenia is a life disabling, multisystem neuropsychiatric disease mostly derived from complex epigenetic-mediated neurobiological changes causing behavioural deficits. Neurochemical disorganizations, neurotrophic and neuroimmune alterations are some of the challenging neuropathologies proving unabated during psychopharmacology of schizophrenia, further bedeviled by drug-induced metabolic derangements including alteration of amino acids. In first-episode schizophrenia patients, taurine, an essential β-amino acid represses psychotic-symptoms. However, its anti-psychotic-like mechanisms remain incomplete. This study evaluated the ability of taurine to prevent or reverse ketamine-induced experimental psychosis and the underlying neurochemical, neurotrophic and neuroinmune mechanisms involved in taurine's clinical action. The study consisted of three different experiments with Swiss mice (n = 7). In the drug alone, mice received saline (10 mL/kg/p.o./day), taurine (50 and 100 mg/kg/p.o./day) and risperidone (0.5 mg/kg/p.o./day) for 14 days. In the preventive study of separate cohort, mice were concomitantly given ketamine (20 mg/kg/i.p./day) from days 8 to 14. In the reversal study, mice received ketamine for 14 days before taurine or risperidone treatments from days 8 to 14 respectively. Afterwards, stereotypy behaviour, social, non-spatial memory deficits, and body weights were assessed. Neurochemical (dopamine, 5-hydroxytryptamine, glutamic acid decarboxylase, (GAD)), brain derived-neurotrophic factor (BDNF) and pro-inflammatory cytokines [tumor necrosis factor-alpha, (TNF-α), interleukin-6, (IL-6)] were assayed in the striatum, prefrontal-cortex and hippocampal area. Taurine attenuates ketamine-induced schizophrenia-like behaviour without changes in body weight. Taurine reduced ketamine-induced dopamine and 5-hydroxytryptamine changes, and increased GAD and BDNF levels in the striatum, prefrontal-cortex and hippocampus, suggesting increased GABAergic and neurotrophic transmissions. Taurine decreases ketamine-induced increased in TNF-α and IL-6 concentrations in the striatum, prefrontal-cortex and hippocampus. These findings also suggest that taurine protects against schizophrenia through neurochemical modulations, neurotrophic enhancement, and inhibition of neuropathologic cytokine activities.

Pharmacological Evaluation of Central Nervous System Effects of Ethanol Leaf Extract of Olax Subscorpioidea in Experimental Animals

BACKGROUND

Olax subscorpioidea Oliv. (Olacaceae) is a medicinal plant used in folk medicine in the management of pain, mental illness, and convulsion. We evaluated neurosedative and anticonvulsant properties of the ethanol leaf extract of O. subscorpioidea (ELEOS).

METHODS

Effects of ELEOS (3.125, 6.25, 12.5, 25 mg/kg) on novelty-induced behaviors were determined using open field test. Anxiolytic effect of ELEOS (3.125, 6.25, 12.5, 25 mg/kg) was assessed using hole-board and elevated-plus maze paradigms. The effect of O. subscorpioidea on pentobarbitone sleeping time was also investigated. Anticonvulsant property of ELEOS (12.5-50 mg/kg) was evaluated using pentylenetetrazole, picrotoxin and strychnine-induced convulsions assays. The extract was administered once intraperitoneally.

RESULTS

The LD50 of ELEOS was 300 mg/kg. ELEOS (3.125, 6.25, 12.5, 25 mg/kg) significantly reduced rearing (99.8±2.8, 76.2±2.9, 37.4±1.2, 5.8±0.8) and grooming (48.0±3.6, 33.8±2.9, 25.4±1.6, 7.6±0.8) as compared with controls (185.8±5.1; 63.8±4.3). Treatment with ELEOS (3.125, 6.25, 12.5, 25 mg/kg) significantly reduced head-dipping on hole-board (10.6±1.9, 8.8±1.2, 7.2±0.9, 6.0±1.1) as compared with control (27.8±1.5). However, there was no anxiolytic effect on EPM. ELEOS (12.5, 25, 50 mg/kg) significantly prolonged pentobarbitone-induced sleeping time (43.0±1.4, 51.0±1.2, 61.0±1.8) as compared with control (31.0±0.7). At 50 mg/kg, ELEOS significantly prolonged onset of seizure (2.72±2.07) and latency to death (9.20±1.24) as compared with controls (0.54±0.02; 2.00±0.44) in pentylenetetrazole-induced convulsions with no effect on picrotoxin and strychnine-induced convulsions.

CONCLUSION

The ELEOS is sedative and has mild anticonvulsant activity and this study supports pharmacological basis for its use in the management of mental illness and convulsion.

In vitro binding and utilization of lipoproteins by luteal cells from ferrets treated with dopaminergic drugs during pseudopregnancy

The effects of administration of dopaminergic drugs in vivo on the binding and utilization of lipoproteins for progesterone synthesis in vitro by ferret luteal cells were investigated. Pimozide, a dopamine antagonist, and bromoergocriptine (CB-154), a dopamine agonist, were administered to pseudopregnant ferrets to alter prolactin (PRL) concentrations daily beginning the day after ovulation. The control group received the vehicle solution only. Corpora lutea taken on Day 13 after ovulation were dissociated and the cells were incubated with canine lipoproteins, cyclic adenosine monophosphate (cAMP), and 5-cholesten-3 beta-25-diol (25-OH-cholesterol). Canine high-density lipoprotein (HDL) and low-density lipoprotein (LDL) stimulated progesterone accumulation by luteal cells from pimozide-treated animals but not from CB-154-treated ferrets. However, when 25-OH-cholesterol, which bypasses the LDL receptor, was provided as the substrate, steroidogenesis was stimulated in all groups. Together these observations suggest that dopaminergic alteration of PRL levels preferentially affects the utilization of lipoproteins. The uptake of canine HDL and LDL by luteal cells was saturable, and a high degree of cross-reactivity was observed. Heparin released surface-bound HDL and LDL, suggesting that HDL was binding to the LDL receptor. The quantity of LDL which could be released from luteal cells by heparin treatment was greater in animals treated with pimozide and decreased by treatment with CB-154, relative to luteal cells from control animals. It was concluded that the chronic administration of pimozide or CB-154 alters serum PRL levels in vivo, and influences the subsequent binding and utilization of lipoproteins by luteal cells in vitro. PRL may increase the number of LDL binding sites in luteal cells, thereby enhancing lipoprotein uptake for progesterone synthesis.

Evidence for dopaminergic regulation of prolactin and a luteotropic complex in the ferret

The role of dopaminergic agents in prolactin (Prl) release and the luteotrophic role of Prl and luteinizing hormone (LH) were investigated in pseudopregnant female ferrets. A single injection of the dopamine antagonist pimozide (0.63 mg/kg) resulted in a tenfold elevation of plasma Prl in anestrous females. Subcutaneous injection of pimozide on alternate days from Day 2 through Day 16 of pseudopregnancy elevated both Prl and progesterone levels. Daily treatment with the dopamine agonist 2 alpha-bromoergocryptine (bromocriptine, 4 mg/kg), from Day 2 through Day 16 of pseudopregnancy lowered levels of both plasma Prl and progesterone. Neither pimozide nor bromocriptine had a direct effect on progesterone secretion by luteal cells in vitro. Daily intraperitoneal administration of a monoclonal antibody against gonadotropin-releasing hormone from Day 2 through Day 10 of pseudopregnancy lowered both plasma LH and progesterone, but had no effect on plasma Prl concentrations. Daily administration of equine antisera against bovine LH or 100 IU of human chorionic gonadotrophin to pseudopregnant ferrets lowered progesterone levels. It is concluded that Prl release is influenced by dopaminergic compounds, and both Prl and LH are required for luteal maintenance in the ferret.