Fig. 1. Blocking e-ATP signaling in vivo increases the density of retinal cholinergic neurons in neonatal rats. (A) A sample of a control array of cholinergic (ChAT immunoreactive) neurons in the ganglion cell layer (GCL) of a P2 neonatal rat. (B) The density of cholinergic cells is increased 24 hours after in vivo treatment with oATP. Scale bar: 50 µm. (C,D) The density of cholinergic neurons in both the GCL (C) and the INL (D) is increased in vivo 24 hours after intraocular injection of oATP (an irreversible blocker of the P2X receptors), suramine (a blocker of the purinergic receptors), or apyrase (an eATP-degrading enzyme). Eight retinas were sampled per treatment. Data are displayed as means ± standard deviation. In all cases the increase in cholinergic cell density was statistically significant (P<0.0001, t-test). ctrl, normal control; sham, vehicle injected; oATP, oxidized-ATP injected; sura, suramine injected; apy, apyrase injected.