Developmental Expression and Distribution of GABA_A Receptor α₁-, α₃- and β₂-Subunits in Pig Brain

Abstract

The principal function of the γ-aminobutyric acid (GABA) system in the adult brain is inhibition; however, in the neonatal brain, GABA provides much of the excitatory drive. As the brain develops, transmembrane chloride gradients change and the inhibitory role of GABA is initiated and continues throughout juvenile and adult life. Previous studies have shown that GABA_A receptor subunit expression is developmentally regulated, and it is thought that the change in GABA function from excitation to inhibition corresponds to the changeover in expression of ‘immature’ to ‘mature’ subunit isoforms. We examined the protein expression pattern and distribution of GABA type A (GABA_A) receptor α₁-, α₃- and β₂-subunits in the parietal cortex and hippocampus of the developing piglet brain. Four perinatal ages were studied; 14 days preterm (P–14), 10 days preterm (P–10), day of birth (P0) and at postnatal day 7 (P7). Animals were obtained by either caesarean section or spontaneous birth. Protein expression levels and subunit localization were analysed by Western blotting and immunohistochemistry, respectively. In the cortex and hippocampus, GABA_A receptor α₁-subunit showed greatest expression at P7 when compared to all other age groups (p < 0.05). In contrast, α₃ expression in the cortex was elevated in preterm brain, peaking at P0, followed by a significant reduction by P7 (p < 0.05); a similar trend was observed in the hippocampus. GABA_A receptor β₂-subunit protein expression appeared relatively constant across all time points studied in both the cortex and hippocampus. Immunolabelling of the α₁-, α₃- and β₂-subunits was observed throughout all cortical layers at every age. GABA_A receptor α₃-subunit appeared to show specific localization to layers V and VI whilst labelling for the β₂-subunit was observed in layer IV. In the hippocampus of all animals, the α₁- and β₂-subunits were shown to immunolabel various cells and processes in the dentate gyrus (DG), CA1 and CA3; the α₃-subunit was barely observed except at the stratum moleculare of the DG. We report for the first time the ontogenesis of GABA_A receptor subunits α₁, α₃ and β₂ in the perinatal pig brain.

GABAA receptor expression and white matter disruption in intrauterine growth restricted piglets

“…Term (P0–normally grown (NG) n = 10; IUGR n = 9) and week‐old piglets (P7–NG n = 10; IUGR n = 10) were born spontaneously. Caesarean sections were performed on pregnant sows at 100 days of gestation (NG, n = 7; IUGR, n = 6) and at 104 days of gestation (NG, n = 7; IUGR, n = 6) (Kalanjati et al, 2011). Both spontaneously born and c‐section delivered animals were collected randomly across several litters.…”

“…Early prenatal neuronal synaptic responses to GABA are initially excitatory however during the early postnatal period in the rat, GABA A receptor responses switch to inhibitory (Ben‐Ari, 2002; Plotkin et al, 1997). We have previously demonstrated the change in GABA A receptor α 3 –α 1 subunit expression at birth in the normal developing piglet brain (Kalanjati et al, 2011) coinciding with the excitatory/inhibitory switch. The timing of the switch in GABA A receptor function in humans however has not been firmly established and may not be complete until 3–4 months of age (Herlenius and Lagercrantz, 2001; Murphy et al, 2005).…”

Pengaruh Ekstrak Bayam Merah (Amaranthus gangeticus) terhadap Morfologi Stratum Hipokampus Model Anak Mencit Pascasapih Induk yang Terpapar Timbal Selama Masa Kehamilan

“…[6][7][8] Dapat dimungkinkan terjadi proses pembentukan sel neuroglia menggantikan neuron dan interneuron yang rusak akibat paparan timbal, sehingga lebar stratum granulare pada girus dentatus kelompok M1 lebih tinggi dibandingkan dengan M0.…”

“…[9][10][11] Selain itu, vitamin B6 dalam bayam merah dapat meningkatkan level enzim antioksidan pada jaringan. [5][6][7][8][9][10] Perbaikan susunan dan tebal strata pada berbagai bagian hipokampus mencit yang diberi timbal asetat pada penelitian ini kemungkinan dapat terjadi oleh karena efek antioksidan bayam merah yang memutus rantai …”

Examining the GABA_A receptor alpha-subunits in the neonatal pig brain: changes across development and the effect of seizures after hypoxic-ischaemic brain injury

“…Large animal models are becoming increasingly popular in the study of human physiology, development, and disease pathology. Pigs are frequently used as a model for the study of brain and cardiovascular system across development [9,10], and in pathological disease states such as neonatal hypoxic-ischaemic HI encephalopathy [11] due to the similarity of brain development when compared with humans [12,13].…”