2D). WT mice entered the open and closed arms a similar number of times, but the KO mice showed a strong preference for the closed arms. Avoidance of the open arms and decreased entries are symptomatic of increased anxiety. Together, these behavioral tests suggest that the α4 subunit-deficient mice exhibit increased anxiety-like behavior in the absence of major changes in motor function. Levels of other buy PD0325901 extrasynaptic GABAA receptor subunit mRNAs in the pons are altered in α4 KO mice Previous Inhibitors,research,lifescience,medical studies found that subunit loss can lead to compensatory changes in the expression of other subunits in a region-specific
manner (Ogris et al. 2006; Liang et al. 2008). To further examine the selectivity of the α4 subunit in regulating respiratory function, subunit expression was examined in WT and KO mice in the pons, a brainstem region involved in respiratory Inhibitors,research,lifescience,medical control. In WT mice, extrasynaptic GABAA receptor subunit expression was age dependent. The α6 subunit mRNA was undetectable at P30, but was found at relatively low levels Inhibitors,research,lifescience,medical at
P65 (Fig. 3A). Similarly, the δ subunit mRNA was absent at P30, and low levels were found by P65. In contrast to WT mice, extrasynaptic subunit expression in α4 subunit KO mice was not age dependent. Both the α6 and δ subunit mRNAs were barely detectable at all ages examined (Fig. 3A). Despite this lack of the of the most prominent extrasynaptic subunits, compensatory increases in the expression of mRNAs encoding α5 and ε, two other less abundant extrasynaptic subunits, were not observed (not shown). Figure 3 Loss of γ-aminobutyric acid (GABAA) receptor α4 subunit affects the expression of other GABAA receptor subunits. (A) Quantitative real-time polymerase chain reaction (q-PCR) analysis of abundant synaptic Inhibitors,research,lifescience,medical and extrasynaptic subunit mRNAs … In contrast Inhibitors,research,lifescience,medical to the impact of α4 subunit loss on other extrasynaptic subunits, synaptic subunit expression was only modestly affected. The levels of the mRNAs encoding the most abundant synaptic subunits, α1, β2, and γ2, were similar in
WT and KO mice at postnatal days P30 and P65 (Fig. 3A) as well as P90 (not shown). In contrast, the level of a sparse synaptic subunit, α2, was differentially affected in Fossariinae the WT and KO mice (Fig. 3B). While all mice expressed the subunit in the pons, the loss of α4 led to a three- to fivefold increase in its expression. In addition, although α2 subunit expression increased with age in all mice, the change was greater in KO animals. A similar age-dependent increase of α2 subunit expression was found in other brain regions (not shown). Thus, loss of α4 leads to genotype-, age-, and tissue-dependent changes in the expression of both synaptic and extrasynaptic GABAA receptors subunits. It is likely that these differences in subunit expression in WT and KO mice affect GABAA receptor composition and alter the balance of synaptic and extrasynaptic receptors (Hsieh et al.