Age-dependent changes in the susceptibility to thiopental anesthesia in mice: Analysis of the relationship to the functional expression of GABA transporter

• Published in: Pharmacology, biochemistry and behavior Vol. 103; no. 2; pp. 267 - 272
• Main Authors: Sogawa, Norio, Hazehara, Yuri, Kunitomo, Muneyoshi, Morita, Yuya, Yoo, Bupsang, Ohyama, Kazumi, Sogawa, Chiharu, Kitayama, Shigeo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-12-2012
• Subjects: Aging - physiology; Anesthesia; Anesthetics, Intravenous - pharmacology; Animals; Base Sequence; DNA Primers; GABA; GABA Plasma Membrane Transport Proteins - drug effects; GABA Plasma Membrane Transport Proteins - genetics; GABA Plasma Membrane Transport Proteins - metabolism; Male; Mice; Mice, Inbred ICR; Nipecotic Acids - pharmacology; Oximes - pharmacology; Polymerase Chain Reaction; RNA, Messenger - genetics; Thiopental; Thiopental - administration & dosage; Thiopental - pharmacology; Transporter; Tritium; Uptake inhibitor; GABA; Anesthesia; Uptake inhibitor; Transporter; Thiopental
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/j.pbb.2012.08.027

The potency of anesthetics changes during development, probably due not only to pharmacokinetic factors such as differential distribution and/or metabolism, but also to pharmacodynamic factors such as changes to the GABAergic system in the brain. To explore the latter mechanism, we focused on the GABA transporter (GAT), the uptake system for GABA, which participates in the synaptic clearance of GABA. Thiopental-induced anesthesia, as assessed by the onset and duration of loss of the righting reflex, was more pronounced in 3-week-old mice than in 7-week-old mice. Both NO-711 and SKF89976A, selective GAT-1 inhibitors, significantly enhanced the anesthesia in the 7-week-old but not in the 3-week-old mice. In synaptosomes prepared from the cerebral cortex, the kinetics of GABA transport was similar between the two age groups, as assessed by [3H]GABA uptake assay. In addition, expression of GAT mRNA was similar between the two age groups, as assessed by quantitative RT-PCR. Thiopental reduced [3H]GABA uptake only at high concentrations in a similar manner at both ages. Conversely, the ability of SKF89976A to inhibit [3H]GABA uptake was greater in the 7-week-old mice than in the 3-week-old mice. Based on these results, GAT seems unlikely to contribute to the greater susceptibility to thiopental anesthesia in 3-week-old mice, while the increased ability of GABA uptake inhibitors to enhance thiopental-induced anesthesia in 7-week-old mice is at least partly due to higher sensitivity of GAT to the inhibitors.
► Thiopental-induced anesthesia is more pronounced in younger mice. ► We examine the contribution of GABA transporter (GAT) to thiopental anesthesia. ► GAT inhibitors enhanced thiopental anesthesia in mice age-dependently. ► The ability of GAT inhibitor to inhibit GABA uptake increased developmentally. ► The mechanism explains the age-dependent contribution of GAT.