S66 Purinergic Signalling (2012) 8 (Suppl 1):S61–S79 Fig. 2 Differential expression of P2Y receptors in glial following retinal detachment. Immunohistochemical staining of control retinas and from detached areas of porcine retinas 7 days after surgery was done using anti-P2Y1 receptor (#APR-009), anti-P2Y2 receptor (#APR-010), and anti-P2Y4 receptor (#APR-006) antibodies (red). Immunoreactivities for P2Y1, P2Y2, and P2Y4 receptor proteins (red) coincide with that of intermediate filament constituents vimentin fibroblast to myofibroblasts leads to the expression of discoidin domain receptor 2 and α-smooth muscle actin. Therefore, this cell type can be distinguished in part by the expression of these proteins. Using a panel of Alomone Labs anti-P2Y receptor antibodies, it was demonstrated that P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, and P2Y13 are all expressed by myofibroblasts and that all except for P2Y13 are also functional, as demonstrated by the use of pharmacological agents [20]. Overall, the study shows that the expression of different P2Y receptors which are stimulated by different agonists suggests a complex physiological role for these nucleotide receptors in regulat- ing cardiac myofibroblast function in heart disease. In the blood, integrins play an important role in mediating the interaction between monocytes and epithelial cells [22, 23]. In addition, integrins can also interact with other proteins, leading to the activation of various signaling pathways, many of which have an impact on many cellular events [24]. The αVβ3 integrin influences cell signaling via a plethora of receptors, including P2Y2 [25–27]. However, the biological outcome of the interaction between P2Y2 and αVβ3 integrin is not understood. The activation of P2Y2 receptors which are endogenously expressed in U037 cells (monocytes) caused clustering of αV integrins, thereby activating a signaling cascade involving the ERK1/2 MAPK pathway and cell migration [24]. The downregula- tion of P2Y2 expression via shRNA abolished αV integrin expression and concomitantly downstream signaling, as demonstrated by Western blot analysis which showed that both P2Y2 and αV integrin expression were downregulated following treatment with their respective shRNA, but that (green and yellow for merging signal). Arrows, vimentin-positive fibers in the outer retina that were also stained for P2Y2 protein. GCL ganglion cell layer, INL inner nuclear layer, IPL inner plexiform layer, NFL nerve fiber layer, ONL outer nuclear layer. Scale bars, 20 μm. Adapted from reference 15 with permission of Association for Research in Vision and Ophthalmology αV integrin shRNA had no effect on the expression of P2Y2 expression. The ability of P2Y2 to activate cell motility via integrin activation may have important implications in inflammatory processes and the treatment of inflammation per se [24]. P2Y receptors in the gastrointestinal tract and its surroundings Purinoceptors play an important role in the regulation of the GI tract motility. Reports show that P2 receptors modulate relaxation of the GI tract [28], while others demonstrate that they participate in the contraction [29]. These contradicting results suggest that the contracting/relaxing activities of purinergic receptors may be developmentally regulated. Different approaches were used in order to verify this hypothesis. Alomone Labs anti-P2Y1, P2Y2, P2Y4 receptor antibodies were used to show that mostly P2Y1 and P2Y2 receptors are expressed, and the use of pharmacological tools showed that P2Y1 mediates the relaxant response in the GI tract from the first week after birth, whereas the contractile activities observed shortly after birth decrease. The transition from contraction to relaxation properties of P2Y1 may be related to the cells which express the receptors or to a change in the coupling to G proteins [28]. The nature of purinocetors was studied in the rat distal colon since the neurotransmission input is usually non- adrenergic and non-cholinergic [30]. Using Alomone Labs anti-P2Y receptor antibodies in immunocytochemical studies showed that various P2Y receptors are expressed in different