Development and localisation of GABAA receptor α1, α2, β2 and γ2 subunit mRNA in the chick optic tectum

Abstract

An in situ hybridisation technique was used to analyse the spatial and temporal pattern of expression of the mRNA encoding the four gamma-aminobutyric acid A (GABA(A)) receptor subunits (alpha1, alpha2, beta2, and gamma2) in the developing chick optic tectum. As a rule, layer i, layer h, and transient cell compartment 3 (TCC3) show the highest levels of expression, especially of alpha1, alpha2 and beta2, which undergo striking changes as a function of time. Apart from these common features, the global pattern is highly complex and dynamic. Such complexity derives from the fact that each subunit exhibits a characteristically distinct pattern of expression and the temporal evolution of each differs in the different layers of the tectum. The influence of several developmental cell behaviours such as proliferation, neuronal migration, programmed cell death, and differentiation must be taken into account to understand pattern complexity and dynamics. Our results suggest that differences in the rate of subunit expression, particularly of alpha1, alpha2, and beta2, could have significant consequences on GABA(A) receptor complex subunit composition along development and on the functional properties of the GABA neurotransmitter system.

Localization of CB1 cannabinoid receptor mRNA in the brain of the chick (Gallus domesticus)

“…While it cannot be known for certain that the CB1 localization observed in the 10-to-20-day-old chick is the same as would be observed in the adult, developmental analyses of a variety of neurotransmitter systems suggest that adult-like patterns are typically established by late embryonic or early posthatch ages. This includes studies of GABA (Burger et al, 2005; Fan et al, 1997; Rodriguez Gil et al, 2005), NMDA (Tang and Carr, 2004), bombesin, (Maekawa et al, 2004), acetylcholine (Kaneko et al, 1998), dopamine (Soares et al, 2000) and serotonin (Wallace, 1985) receptors. With this caveat in mind, the following discussion will summarize the labeling patterns observed in the chick and compare these findings to those reported for other species.…”

Neuronal maturation and laminar formation in the chicken optic tectum are accompanied by the transition of phosphorylated cofilin from cytoplasm to nucleus

“…1I). According to the previous study (Rodriguez Gil et al, 2005), we segregated all layers into seven laminae -SAC, SGC, SGFSi, j, h, TCC3 (including the most superficial layers a, c, e and g) and SO. To avoid the space-dependent differences along the spatial axis, the recording of MOD was collected at homologous regions in all cases.…”

“…By E10, not all subdivisions of SGFS are readily identifiable. According to previous study (Rodriguez Gil et al, 2005), tectums can be divided into SAC, SGC, SGFS-j, i, h, TCC3 (the transient cell compartment 3) and SO from E10 to P0. In mature tectums, TCC3 can segregate into SGFS-a, c, e and g.…”

Acute hypoxia differentially affects the γ‐aminobutyric acid type A receptor α1, α2, β2, and γ2 subunit mRNA levels in the developing chick optic tectum: Stage‐dependent sensitivity

“…In this case, the pattern of subunit mRNA levels should remain unchanged under the hypoxic condition. The first argument is supported by previous findings demonstrating that the level of mRNA expression of the α 1 , α 2 , β 2 , and γ 2 subunits significantly changes in several tectal layers as a function of the developmental stage (Rodríguez Gil et al, 2005). The second and third points require experimental support.…”

“…Layer “i” of the chick embryo OT was selected for this analysis because it is the most prominent GABAergic layer in the adult OT (Dietl et al, 1988; Granda and Crossland, 1989). Layer i displays the maximal level of expression of the mRNAs encoding the four subunits (α 1 , α 2 , β 2 , and γ 2 ) of the GABA A receptor during development and undergoes the most drastic changes between embryonic day (ED) 10 and hatching (Rodríguez Gil et al, 2005). The present work aims at 1) determining whether the mRNA level of the α 1 , α 2 , β 2 , and γ 2 subunits are sensitive to acute hypoxia during development, 2) elucidating whether such sensitivity changes as a function of the embryonic age, and 3) finding out whether mRNA levels of all the subunits are equally sensitive to an acute hypoxic state.…”