Increased expression of gamma-aminobutyric acid transporter-1 in the forebrain of infant rats with corticotropin-releasing hormone-induced seizures but not in those with hyperthermia-induced seizures

High affinity, gamma-aminobutyric acid (GABA) plasma membrane transporters (GATs) influence the availability of GABA, the main inhibitory neurotransmi tter in the brain. Recent studies suggest a crucial role for GATs in mainta ining levels of synaptic GABA in normal as well as abnormal (i.e., epilepti c) adult brain. However, the role of GATs during development and specifical ly changes in their expression in response to developmental seizures are un known. The present study examined GAT-1-immunolabeling in infant. rats with two types of developmental seizures, one induced by corticotropin-releasin g hormone (CRH) lasting about 2 h and the other by hyperthermia (a model of febrile seizures) lasting only 20 min. The number of GAT-1-immunoreactive (ir) neurons was increased in several forebrain regions 24 h after inductio n of seizures by CRH as compared to the control group. Increased numbers of detectable GAT-1-ir cell bodies were found in the hippocampal formation in cluding the dentate gyrus and CA1, and in the neocortex, piriform cortex an d amygdala. In contrast, hyperthermia-induced seizures did not cause signif icant changes in the number of detectable GAT-1-ir somata. The increase in GAT-1-ir somata in the CRH model and not in the hyperthermia model may refl ect the difference in the duration of seizures. The brain regions where thi s increase occurs correlate with the occurrence of argyrophyllic neurons in the CRH model. (C) 2000 Elsevier Science B.V. All rights reserved.