Developmental changes in GABAA tonic inhibition are compromised by multiple mechanisms in preadolescent dentate gyrus granule cells

The sustained tonic currents (I(tonic)) generated by γ-aminobutyric acid A receptors (GABA(A)Rs) are implicated in diverse age-dependent brain functions. While various mechanisms regulating I(tonic) in the hippocampus are known, their combined role in I(tonic) regulation is not well understood in different age groups. In this study, we demonstrated that a developmental increase in GABA transporter (GAT) expression, combined with gradual decrease in GABA(A)R α₅ subunit, resulted in various I(tonic) in the dentate gyrus granule cells (DGGCs) of preadolescent rats. Both GAT-1 and GAT-3 expression gradually increased at infantile (P₆₋₈ and P₁₃₋₁₅) and juvenile (P₂₀₋₂₂ and P₂₇₋₂₉) stages, with stabilization observed thereafter in adolescents (P₃₄₋₃₆) and young adults (P₄₁₋₄₃). I(tonic) facilitation of a selective GAT-1 blocker (NO-711) was significantly less at P₆₋₈ than after P₁₃₋₁₅. The facilitation of I(tonic) by SNAP-5114, a GAT-3 inhibitor, was negligible in the absence of exogenous GABA at all tested ages. In contrast, I(tonic) in the presence of a nonselective GAT blocker (nipecotic acid, NPA) gradually decreased with age during the preadolescent period, which was mimicked by I(tonic) changes in the presence of exogenous GABA. I(tonic) sensitivity to L-655,708, a GABA(A)R α₅ subunit inverse agonist, gradually decreased during the preadolescent period in the presence of NPA or exogenous GABA. Finally, Western blot analysis showed that the expression of the GABA(A)R α₅ subunit in the dentate gyrus gradually decreased with age. Collectively, our results suggested that the I(tonic) regulation of altered GATs is under the final tune of GABA(A)R α₅ subunit activation in DGGCs at different ages.

Expression of GABA and glutamate vesicular transporter in depressed mice / 重庆医学

Objective To study the expression of vesicular GABA transporter and vesicular glutamate transporter 1 in de‐pression .Methods Mice was divided into control group and defeat group stochastically .By social defeat model and social avoidance , the defeat group was divided into two groups:susceptible group and unsusceptible group .Synaptic proteins were extracted respec‐tively from the 3 groups .We detected the expression abundance of VGAT and VGLUT1 by Western blot .Results Compared with the control group ,in susceptible group ,the residence time in the contact area was significantly reduced ,and the residence time in the corner area was significantly increased ,with statistical difference(P0 .05) .In the striatum ,although the expression levels of VGAT and VGLUT1 were increased in susceptible group ,but in unsusceptible group ,the expression of these proteins also increased significantly .Conclusion The prefrontal cortex and hippo‐campus excitability and inhibitory vesicle transport were changed in depression ,which may relate to the transcription disorder .

GABA and glutamate transporters: new events and function in the vertebrate retina

The neural retina is a highly complex tissue composed of excitatory and inhibitory neurons and glial cells. Glutamate, the main excitatory neurotransmitter, mediates information transfer from photoreceptors, bipolar cells, and ganglion cells, whereas interneurons, mainly amacrine and horizontal cells, use γ-aminobutyric acid (GABA), the main inhibitory neurotransmitter. In this review we place an emphasis on glutamate and GABA transporters as highly regulated molecules that play fundamental roles in neurotransmitter clearance, neurotransmitter release, and oxidative stress. We pharmacologically characterized glutamate transporters in chicken retina cells and identified two glutamate transporters: one Na+-dependent transporter and one Na+-independent transporter. The Na+-dependent uptake system presented characteristics related to the high-affinity xAG- system (EAAT1), and the Na+-independent uptake system presented characteristics related to the xCG- system, which highly contributes to glutamate transport in the retina. Glutamate shares the xCG- system with another amino acid, L-cysteine, suggesting the possible involvement of glutathione. Both transporter proteins are present mainly in Müller glial cells. GABA transporters (GATs) mediate high-affinity GABA uptake from the extracellular space and terminate the synaptic action of GABA in the central nervous system. GABA transporters can be modulated by molecules that act on specific sites to promote transporter phosphorylation and dephosphorylation. In addition to a role in the clearance of GABA, GATs may also release GABA through a reverse transport mechanism. In the chicken retina, a GAT-1 blocker, but not GAT2/3 blocker, was shown to inhibit GABA uptake, suggesting that GABA release from retina cells is mainly mediated by a GAT-1-like transporter.

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.

Immunocytochemical Localization of GABA Transporter-3 in the Guinea Pig Retina / 대한해부학회지

The cellular localization of the GABA transporter-3 (GAT-3) was examined in the guinea pig retina by immunocytochemistry, using antisera against GAT-3. GAT-3 immunoreactivity was localized to cell bodies in the inner nuclear layer, and labeled processes were densely distributed in the inner plexiform layer (IPL) close to the ganglion cell layer. All GAT-3 labeled cells exhibited GAD65 immunoreactivity. In addition, 67% of GAT-3 labeled amacrine cells showed carbohydrate epitope CD15 immunoreactivity. These results indicate that GAT-3 is involved in modulating the rod pathway in the IPL of the guinea pig retina via presumptive A17 amacrine cells.

Expression of GABA Transporters in the Rat's Olfactory Bulb during Development

Developmental changes in the expression of two GABA (gamma-aminobutyric acid) transporter proteins, GAT-1 and GAT-3, in the olfactory bulb of embryonic and postnatal rats were examined with immunocytochemistry using antisera against GAT-1 and GAT-3. The expression and localization of GAT-1 and GAT-3 showed distinct temporal patterns during olfactory bulb development. GAT-1 immunoreactivity appeared weakly in most likely growing axons of the presumptive glomerular layer from embryonic day 18 and increased during the first postnatal week. In contrast, GAT-3 immunoreactivity, first detected at E16, was found in radial glial cell fascicles and was replaced by what were likely astroglial cells postnatally. At P7, GAT-1 and GAT-3 immunoreactivities reached the adult pattern i.e., GAT-1 immunoreactivity was observed in the labeled punctate structures in all layers of the olfactory bulb except the nerve fiber layer, while GAT-3 immunoreactivity was observed in the astroglial processes of all layers of the olfactory bulb. Our results suggest that GABA transporters, especially GAT-3, play important roles in regulating the GABA levels of developing olfactory bulbs.

Effects of kainic Acid-induced seizures on GABA and GABA transporter in the cerebellum of the rat / 대한해부학회지

The effects of kainic acid-induced seizures on GABA and GABA transporter in the rat cerebellum were examined by means of immunohistochemical and Western blot methods. Immunocytochemical analysis showed that kainic acid-induced seizures led to a decreased immunoreactivity for GABA to 3 weeks after seizures with an slight increase in the immunoreactivity of cerebellum 24 h after treatment. Immunoreactivities of GABA transporters, GAT-1 and GAT-3 which are localized neurons and astrocytes, were increased at 24 and 48h and after that weak immunoreactivites for GABA transporters were shown in the cerebellar tissues. Our results indicate that kainic acid-induced seizures exerts specific effects on GABA contents and the GABA transporters in the cerebellum and a decrease of GABA contents might not always associated with the decrease in the number of GABA transporters in the rat cerebellum.

Dynamic change on GABA transporter mRNA in the hippocampus of rats following PTZ-kindled / 临床神经病学杂志

Objective To study the role of GABA (? aminobutyric acid) transporters in kindled.Methods The rat's GABA model following PTZ kindled was made.The expression of GABA transporter subtype in the hippocampus(GAT 1 mRNA) was measured after PTZ (pentylenetetrazol) kindled seizures by using semiquantitative technique,reverse transcription polymerase chain reaction (RT PCR).Results GAT 1 mRNA was significantly increased in the hippocampus at 0 hour,48 hours,and 1 week after PTZ kindled seizures. Up regulation of expression of GAT 1 mRNA returned to the control levels after 1 month. No changes in the expression of GAT 1 mRNA were observed after 60 days of PTZ kindled seizures.Conclusion The expression of GAT 1 mRNA with up regulation may be associated with the epilepsy susceptibility.