rho₁ GABA_C receptors are expressed in fibrous and cartilaginous layers of chick sclera and located on sclera fibroblasts and chondrocytes

Abstract

rho 1 GABA C receptor antagonists inhibit myopia in chick but the site of this effect is not known. The sclera ultimately determines the shape and size of the globe and thus an untested possibility is that GABA agents have a scleral mechanism. Whether rho 1 GABA C receptors are expressed and located in chick sclera is unknown. Real-time PCR, western blot and immunohistochemistry were used to determine whether rho1 GABA C receptors are expressed and located in chick fibrous and cartilaginous sclera. Both layers of the chick sclera were positive for rho1 GABA C receptor mRNA (PCR) and protein (western blot) expression and labeling was observed in both fibroblasts and chondrocytes of the fibrous and cartilaginous layers (immunohistochemistry). These investigations clearly show that chick sclera possesses rho 1 GABA C receptors. The sclera is thus a potential previously unrecognized site for activity of rho 1 GABA C agents.

Identification of GABA receptors in chick retinal pigment epithelium

“…Animals and tissue were prepared as previously described [15]. Twenty-five 12-day-old White Leghorn cockerels ( Gallus gallus ) were obtained from Jinan Spafury Poultry Farms (Jinan, China).…”

“…GABA A [6-8], GABA B [9-11], and GABA C [12] receptors have been reported in the retina. We have recently shown that rho 1 GABA C receptors are present in chick sclera [15]. A small number of cultured human corneal stem cells have been shown to exhibit GABA A receptor immunoreactivity [5].…”

“…The fact that human corneal stem cells express GABA A receptors [5], that there are reports of some GABA actions in the cornea of animal species [16,17], that GABA receptors are present in a range of non-neuronal tissues [21-36], and that the chick sclera possess GABA C receptors [15], lead to the hypothesis that GABA receptors may be present in chick cornea. The aim of this study was to determine if GABA A , GABA B , and/or GABA C receptors are located in the chick cornea.…”

The dynamic sclera: Extracellular matrix remodeling in normal ocular growth and myopia development

“…It has been shown that GABA receptors are located in chick ocular tissues, including the cornea, RPE, and cartilaginous and fibrous sclera, suggesting a potential role for GABA in mediating scleral remodeling (Cheng et al, 2011; Cheng et al, 2012; Cheng et al, 2013). Treatment of cultured chick scleral fibroblasts with GABA agonists resulted in scleral cell proliferation (as evidenced by increased DNA content in cell cultures), as well as a decrease in scleral GAG synthesis (Christian et al, 2014).…”

Gene Expression and Pathways Underlying Form Deprivation Myopia in the Guinea Pig Sclera

“…39 Earlier studies have shown antagonists to GABA receptors (GABA A , GABA A0r , and GABA B ) to inhibit myopia development whereas agonists increased myopia susceptibility in chicks. 40,41 In guinea pigs, the selective GABAc inhibitor, TPMPA, inhibits ocular growth and myopia (McFadden SA, et al IOVS 2011;52:ARVO E-Abstract 6306).…”