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.