Xylazine, a type of α₂-adrenoceptors, is a commonly used drug in veterinary medicine. Xylazine-induced changes in the content of amino acid neurotransmitters – glycine (Gly) and aspartic acid (Asp), in different brain regions and neurons were studied. Wistar rats were administered 50 mg/kg or 70 mg/kg of xylazine by intraperitoneal injection. In addition, in vitro experiments were conducted, in which neurons were treated with 15 μg/mL, 25 μg/mL, 35μg/mL, and 45 μg/mL of xylazine. Test methods were based on the enzyme-linked immunosorbent assays (ELISA). During anaesthesia, Asp levels in each brain area were significantly lower compared to the control group. Except for the cerebrum, levels of Gly in other brain areas were significantly increased during the anaesthesia period. In vitro, xylazine-related neuron secretion of Gly increased significantly compared to the control group at 60 min and 90 min. Moreover, xylazine caused a significant decrease in the levels of Asp secreted by neurons at 20 min, but gradually returned to the level of the control group. The data showed that during anaesthesia the overall levels of Asp decreased and overall levels of Gly increased. In addition, the inhibitory effect of xylazine on Asp and the promotion of Gly were dose-dependent. Our data showed that different effects of xylazine on excitatory and inhibitory neurotransmitters provided a theoretical basis for the mechanism of xylazine activity in clinical anaesthesia.

Effect of some neurotransmitters on pituitary in bull-camelThe present in vitro study is an attempt for profound exploration of the influence of some inhibitory (GABA and taurine) and excitatory neurotransmitters (glutamic acid and L-Argnine) on pituitary gland gonadotropic hormones in camels. For this purpose, neurotransmitters were added individually to pituitary cells in vitro. Results of current study revealed that addition of GABA alone has a potent inhibitory influence on gonadotropins release; an action which was dosedependent. In addition, exaggerated high dose of GABA added to culture resulting in depression of GnRH activity. Inhibitory neurotransmitter taurine preserved gonadotropins release within their normal values and maintained the stimulatory potentials of GnRH. On the other side, nitric oxide had a stimulatory action at small dose rates and a depressive effect at higher dose rates. Glutamic acid as the major endogenous excitatory neurotransmitter had a potent dose-dependent excitatory effect upon FSH and LH as well as GnRH stimulatory influence.

The present study has been carried out to investigate the effect of three neurotransmitters (Glutamate, L-Arginine and GABA) on some aspects of the reproductive performance of mature male Albino rats. For this purpose, a total of 100 mature male Albino rats were used. Rats were divided into 4 comparable groups; the first consists of 10 rats, was left as control. The second was administered glutamate 10 mg/ kg, the third group was injected by L- Arginine 20 mg/ kg while the fourth was injected by GABA 1 mg / rat. The results showed that administration of glutamate was concomitant with increase in synthesis and release of pituitary LH causing increase in its serum level as well as decrease serum level of testosterone. On the other hand, prolonged L-Arginine administration led to remarkable elevation in both pituitary and serum LH and significant decrease of serum testosterone. While, GABA administration led to remarkable decrease in pituitary and serum LH with significant decrease in serum testosterone level.

We established an in vitro experimental system using the following procedure. We first introduced tritium-labeled norepinephrine ([³H]-NE) into PC12 cells. The [³H]-NE incorporated into PC12 cells were then stimulated by a high concentration (60 mM) of K+ buffer during 12 minutes. Then, we collected 100 μl supernatant and counted the amount of [³H]-NE release from PC12 cells with a scintillation counter. After screening fungal, Streptomyces spp. or bacterial product using this experimental sytem, we obtained FS11052 from Streptomyces spp. which inhibited [³H]-NE release from PC12 cells.

The concentrations of dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindole-3-acetic acid (5-HIAA) in CSF obtained from the cisterna magna of 21 nonneurologically compromised dogs were determined by high-pressure liquid chromatography and electrochemical detection. A rapid method of sample preparation, which involved single filtration through a deproteinizing membrane, was used. Canine CSF obtained in this manner contained 5.78 +/- 0.78 ng of DOPAC/ml, 72.19 +/- 4.09 ng of HVA/ml, and 29.95 +/- 1.67 ng of 5-HIAA/ml. Linear regression analysis between HVA and 5-HIAA yielded a correlation coefficient of 0.4804. The neurotransmitter index, HVA/5-HIAA, was found to be more indicative of the dopaminergic metabolite HVA than the acid metabolite of serotonin, 5-HIAA (correlation coefficient with HVA = 0.5529 vs a correlation coefficient with 5-HIAA = -0.4462). A poor relationship (correlation coefficient = -0.1715) was found to exist between the 2 dopaminergic metabolites DOPAC and HVA in the CSF.

Objective-To investigate differences in CSF concentrations of excitatory and inhibitory neurotransmitters in dogs with and without T2-weighted (T2W) MRI hyperintense areas in the limbic system. Sample-Archived CSF samples and stored brain MRI images of 5 healthy research dogs (group 1), 8 dogs with idiopathic epilepsy (IE) with no abnormal MRI findings (group 2), and 4 dogs with IE with hyperintense areas in the limbic system detected by means of T2W MRI (group 3). Procedures-Archived CSF samples and stored MRI images obtained from all dogs were evaluated. Dogs in groups 2 and 3 were matched on the basis of age and breed. High-performance liquid chromatography was used to evaluate glutamate and γ-aminobutyric acid (GABA) concentrations in CSF samples. Results-Glutamate concentrations were higher in CSF of both groups of dogs with IE than in healthy dogs. However, glutamate concentrations in CSF were not significantly higher in dogs with IE and with hyperintense areas than in dogs with IE but no abnormal MRI findings. Concentrations of GABA in CSF were higher in group 3 than in group 2 and in group 2 than in group 1. Conclusions and Clinical Relevance-No significant difference was evident between glutamate concentrations in CSF of dogs with IE and with and without hyperintense areas detected by means of T2W MRI. However, glutamate concentrations typically were higher in CSF of dogs with IE and MRI hyperintense areas. Future studies with larger sample sizes should be conducted to confirm this finding and to determine the clinical importance of high glutamate concentrations in CSF of dogs with IE.

Objective: The purpose of this work was to investigate the effect of phosphodiesterase type 5 (PDE-5) inhibitor sildenafil citrate (SC) on the level of brain hippocampal neurophysiological parameters (inhibitory and excitatory neurotransmitters), oxidant/antioxidant status, minerals, and anxiety-like behavior using albino male rats. Materials and methods: A total of 24 albino male rats were allocated to three separate groups (each one had eight rats): control and SC 5 and 10 mg/kg treatments via i.p. infusion every 3 days for 12 injections. For the behavior of anxiety evaluation, the elevated plus maze test was conducted 1 day after the last treatment, and then all the rats were killed. For serum separation, the blood samples were taken, and hippocampus was dissected from the brain and stored frozen until analysis. Results: Both doses of sildenafil significantly improved brain hippocampal neurotransmitter [nor¬epinephrine, serotonin (5-hydroxytryptamine), and gamma-aminobutyric acid] values accompa¬nied by a decreased dopamine level. Interestingly, the SC higher given dose (10 mg/kg) increased the malondialdehyde level with the reduction of the antioxidant parameters [reduced glutathione (GSH) level, catalase (CAT), and superoxide dismutase (SOD) activities] although the lower dose of SC did not cause oxidative stress. Serum and brain hippocampal K, Cu, and Se concentrations were also increased with SC treatments. Moreover, the test of elevated plus maze revealed an anxiolytic impact of sildenafil. Conclusion: It was concluded that SC improved the parameters of some hippocampal neurotrans¬mitters and minerals accompanied by anxiolytic impact with the test of elevated plus maze, with a state of oxidative stress revealed with the higher dose of SC which was not recorded with the lower dose. [J Adv Vet Anim Res 2020; 7(2.000): 281-289]