Proteomic Analysis of Proteins changed by Bilateral Orchiectomy in the Male Rabbit Bladder

PURPOSE: The aim of this study was to investigate the effects of testosterone deprivation on urinary bladder in male rabbits by proteomic analysis. MATERIALS AND METHODS: New Zealand white male rabbits (2.5-3 kg) were divided into 2 group; control group with 5 rabbits and bilateral orchiectomized group, bilateral orchiectomized group was divided into post-operative 4 weeks group (group 1), and 8 weeks group (group 2) with 5 rabbits respectively. Bladder wall was excised partly at 4 or 8 weeks from the beginning of the experiment. Conventional proteomics was performed with high resolution 2-D gel electrophoresis followed by computational image analysis and protein identification using mass spectrometry. We decided to consider 'significant' if protein had 50% decreasing or 200% increasing expression rate. RESULTS: Six proteins were significantly changed in orchiectomy group, compared to control group; serum albumin precursor, GABA transaminase, dimethylarginine dimethylaminohydrolase 2, serum/glucocorticoid regulated kinase and LOC304923 protein were over-expressed in both group 1 and group 2. Annexin A1 was significantly over-expressed in the group 2 only. CONCLUSION: An overexpression of Annexin A1 and GABA transaminase mean a processing of neuronal reactions to injury in orchiectomized rabbit bladder. Also an overexpression of dimethylarginine dimethylaminohydrolase 2 would increase NO synthesis and thereby promote re-endothelialization in the rabbit bladder after orchiectomy. Serum/glucocorticoid regulated kinase would relate to Na+ transport. Albumin precursor and LOC304923 protein are remained to further research. These data suggested that bilateral orchiectomy would make the urinary bladder unstable. However more information is needed in human bladder tissue.

The Changes in the Expression of gamma-Aminobutyric Acid Related Enzymes in the Mouse Hippocampus Following Ketogenic Diet / 대한해부학회지

The ketogenic diet (KD) has been used to treat intractable childhood epilepsy. However, its mechanism of action remains unknown. In the present study, we examined the effects of KD on the expression of multiple constituents of the GABAergic system in the hippocampus through immunohistochemistry and northern blot analysis. From the results, we have shown that KD increased expression of GABA and decreased GABA transporter1 (GABATp) and GABA transaminase (GABA-T) mRNA levels in the hippocampus. These results suggest that the neuroinhibitory effect of KD may be mediated, at least in part, by the increment of GABAergic activity in the hippocampus. KD may increase the GABA levels in the synaptic space by limiting GABA reuptake and in the presynaptic nerve terminal by inhibiting GABA degradation.

The Effects of Repeated Stress on the GABAergic Neurotransmission in Rats / 신경정신의학

OBJECTIVES: Changes of GABAergic neurotransmission in response to the application of different types of environmental stress have been the subject of research for over two decades. However, the nature of the changes induced by stress appear to show a dependent phenomena on the type and duration of stressor agent employed. METHODS: For this reason, this study was performed to observe the effects of repeated stress on the radioligands binding to GABA A/benzodiazepine receptors of discrete brain regions. The author also examined the activity of GABA transaminase and the concentration of endogenous GABA. Male Sprague-Dawley rats, weighing 150-200g were forced to suffer an immobilization stress for 2 hours during 14 consecutive days. RESULTS: Repeated immobilization stress decreased the binding of [3H]flunitrazepam on the benzodiazepine receptor in the cortex, hippocampus and hypothalamus. Saturation experiments followed by scatchard analyses of the results showed decreased density of benzodiazepine receptor and the affinity remained unchanged. Repeated immobilization stress did not affect the binding of [3H]muscimol on the GABAA receptor, the activity of GABA transaminase, and the concentration of endogenous GABA in the brain regions. CONCLUSIONS: From these results, it can be concluded that repeated immobilization stress modulated GABAergic neurotransmission via downregulation of the benzodiazepine receptor in the brain.

Mechanisms of Antiepileptic Drugs / 대한간질학회지

Established antiepileptic drugs (AEDs) decrease membrane excitability by interacting with neurotransmitter receptors or ion channels. AEDs developed prior to 1980 appear to act on sodium channels, gamma-amino butyric acid type A (GABA(A)) receptors or calcium channels. Benzodiazepines and barbiturates enhance GABA(A) receptormediated inhibition. Barbiturates increase the duration of chloride channel opening and at higher doses, they block voltage-dependent calcium channels presynaptically, decreasing excitatory amino acid (EAAs) transmission. Benzodiazepines also interact with the GABA(A) receptor complex and increase the frequency of chloride channel opening. Phenytoin, carbamazepine and possibly sodium valproate decrease high frequency repetitive firing of action potentials by enhancing sodium channel inactivation. At higher doses, PHT may block sodium channels presynaptically and decrease EAAs release. In addition to the action on sodium channel, CBZ interacts with adenosine receptor and decrease C-AMP, and block reuptake of norepinephrine. VPA shows diverse mechanisms including sodium channel blocking. It increases synaptosomal GABA by increasing production and decreasing break-down and interacts with T-type calcium channels preventing thalamocortical interaction necessary for absence. Ethosuximide and sodium valproate reduce a low threshold (T-type) calcium channel current. The mechanisms of action of newly developed AEDs are not fully established. Felbamate is broad-spectrum, and probably has multiple actions on sodium channels, interaction with GABA(A) receptors, and interaction with NM.D.A receptors. Gabapentin binds to a high affinity site on neuronal membranes in a restricted regional distribution of the CNS. This binding site may be related to a possible active transport process of gabapentin into neurons. However this has not proven and the mechanism of action of gabapentin remains uncertain. It is structurally related to GABA and its action of antiepileptic activity is suspected due to change of neuronal amino acids (interfere glutamate synthesis, block GABA uptake, and enhance GABA release). Lamotrigine, initially developed as an antifolate drug, decreases sustained high frequency repetitive firing of voltage-dependent sodium action potentials that may result in a preferential decreased release of presynaptic glutamate. It may also interact with GABA receptors but its primary antiepileptic action is on the sodium channel similar to the PHT and CBZ. Because of such a diverse mechanism of action, LTG is one of the wide spectrum AEDs. Oxcarbazepine's mechanism of action is not known ; however, its similarity in structure and clinical efficacy to that of carbamazepine suggests that its mechanism of action may involve inhibition of sustained high frequency repetitive firing of voltage-dependent sodium action potentials. Vigabatrin is a "designer" drug as is developed rationally, and it reversibly inhibits GABA transaminase, the enzyme that degrades GABA, thereby producing greater available pools of presynaptic GABA for release in central synapses. Increased activity of GABA at postsynaptic receptors may underlie the clinical efficacy of VGB. Tiagabine is a potent blocker of GABA re-uptake by glia and neuron.

GABAergic agents modify imipramine analgesia.

The influence of GABA agonists and antagonists on analgesic activity of imipramine (IMA, 20 mg/kg, ip) was studied using the hotplate method. Administration of GABAA receptor agonist muscimol (1 mg/kg, ip), GABAB receptor agonist baclofen (3 mg/kg, ip) or GABA-T inhibitor aminooxyacetic acid (25 mg/kg, ip) increased the analgesic effect of IMA. On the other hand pretreatment of GABAA receptor antagonist bicucukline (2 mg/kg ip), GABAB receptor antagonist delta-amino-n-valeric acid (50 mg/kg, ip) or GABA synthesis inhibitor thiosemicarbazide (50 mg/kg, ip) attenuated the IMA analgesia. These results suggest that the analgesic action of IMA may be mediated by functional alteration of a central GABAergic mechanism and/or subsequent stimulation of GABA receptors.

Vigabatrin como droga agregada en 20 niños con epilepsia de difícil control: evaluación a los 3 y 6 meses de tratamiento / Add-on vigabatrin therapy in 20 children with intractable epilepsy

Con el propósito de demostrar la eficacia y tolerabilidad del vigabatrin en pacientes pediátricos, hemos utilizado esta droga en 20 niños con síndromes epilépticos refractarios al tratamiento tradicional, como droga agregada y sin modificar el esquema terapéutico anterior. El 47 por ciento de los pacientes demostró una muy buena respuesta clínica (reducción del número de crisis>75 por ciento ), y el 16 por ciento una buena respuesta (reducción del 50 al 74 por ciento ). No se observaron cambios significativos en el 21 por ciento y el 16 por ciento restante evidenció un incremento en el número de crisis. El vigabatrin mostró mayor eficacia en los pacientes con epilepsias parciales criptogénicas y sintomáticas. Los resultados presentados en este estudio permiten considerar al vigabatrin como una alternativa útil en el tratamiento de los síndromes epilépticos refractarios en la infancia

Methyl parathion induced alterations in GABAergic system during critical stage of central nervous system development in albino rat pups.

Sublethal doses of methyl parathion (o, o-dimethyl-o-nitrophenyl thiophosphate) injected intraperitoneally to 7th day old developing albino rat pups induced alterations in the inhibitory GABAergic system of CNS. A substantial simulation of the inhibitory system was noticed. A profound increase was found in the level of the inhibitory transmitter, GABA on methyl parathion injection. An increase in the activity levels of the enzymes glutamic acid decarboxylase and 4-aminobutyrate-2-oxoglutarate-amino transferase in the cortex, brain stem and spinal cord of the CNS was found. It is observed that methyl parathion causes potentiation of the inhibitory transmission (GABAergic system) in the wake of inducing suppression of cholinergic system in CNS of developing rat pups.

The antimyoclonic action of clonazepam through a GABA--independent mechanism.

The present study investigates whether clonazepam exerts its antimyoclonic action through a GABA independent mechanism. We have studied the antimyoclonic effect of clonazepam and compared it with that of aminooxyacetic acid (AOAA), a GABA transaminase inhibitor, against myoclonus induced by picrotoxin, a GABA receptor antagonist and allylglycine, a drug which inhibits synthesis and release of GABA. We have also investigated the effect of clonazepam against picrotoxin-induced myoclonus in rats pretreated with either AOAA or submyoclonic dose of allylgylycine. Clonazepam pretreatment inhibited both picrotoxin and allylglycine-induced myoelonus whereas AOAA was effective in inhibiting only picrotoxin-induced myoclonus. The protective effect of clonazepam against picrotoxin-induced myoclonus was potentiated by AOAA pretreatment. Moreover, clonazepam afforded protection against picrotoxin-induced myoclonus in rats pretreated with a submyoclonic GABA reducing dose of allylglycine. These findings indicate that a GABA independent mechanism may also be involved in the antimyoclonic action of clonazepam.

Luteinizing hormone release induced by noradrenaline after administration of drugs that increase hypothalamic GABA levels

Recientes evidencias señalan al GABA como un compuesto que inhibe la liberación de LH en ratas, no conociéndose aún su mecanismo de acción. En el presente trabajo se examina la liberación de LH que produce la noradrenalina (NA), una de las sustancias neuroactivas que regulan a las neuronas LHRH, en ratas que recibieron un pretratamiento con drogas que aumentan los niveles de GABA endógeno. Gamma-acetil y gamma-vinil-GABA, así como la NA se inyectaron en el 3er ventrículo cerebral en ratas ovariectomizadas tratadas con estradiol y progesterona. En esas condiciones, los animales presentaron una marcada descarga de LH luego de la inyección de la NA, como se observó en ratas que recibieron como pretratamiento solución salina. Se concluye que las neuronas LHRH retienen la capacidad de respuesta a la NA en presencia de elevados niveles de GABA en el hipotálamo