Localization of neuropeptide Y1 receptor immunoreactivity in the rat retina and the synaptic connectivity of Y1 immunoreactive cells

Abstract

Neuropeptide Y (NPY), an inhibitory neuropeptide expressed by a moderately dense population of wide-field amacrine cells in the rat retina, acts through multiple (Y1-y6) G-protein-coupled receptors. This study determined the cellular localization of Y1 receptors and the synaptic connectivity of Y1 processes in the inner plexiform layer (IPL) of the rat retina. Specific Y1 immunoreactivity was localized to horizontal cell bodies in the distal inner nuclear layer and their processes in the outer plexiform layer. Immunoreactivity was also prominent in cell processes located in strata 2 and 4, and puncta in strata 4 and 5 of the IPL. Double-label immunohistochemical experiments with calbindin, a horizontal cell marker, confirmed Y1 immunostaining in all horizontal cells. Double-label immunohistochemical experiments, using antibodies to choline acetyltransferase and vesicular acetylcholine transporter to label cholinergic amacrine cell processes, demonstrated that Y1 immunoreactivity in strata 2 and 4 of the IPL was localized to cholinergic amacrine cell processes. Electron microscopic studies of the inner retina showed that Y1-immunostained amacrine cell processes and puncta received synaptic inputs from unlabeled amacrine cell processes (65.2%) and bipolar cell axon terminals (34.8%). Y1-immunoreactive amacrine cell processes most frequently formed synaptic outputs onto unlabeled amacrine cell processes (34.0%) and ganglion cell dendrites (54.1%). NPY immunoreactivity in the rat retina is distributed primarily to strata 1 and 5 of the IPL, and the present findings, thus, suggest that NPY acts in a paracrine manner on Y1 receptors to influence both horizontal and amacrine cells. Indexing termsamacrine cells; choline acetyltransferase; calcium binding protein; horizontal cells; neuropeptides Neuropeptide Y (NPY) has multiple physiologic actions in both the central and peripheral nervous system, including effects on blood flow, memory retention, food intake, epilepsy, and pain (Lundberg et al., 1996;Munglani et al., 1996;Balasubramaniam, 1997;Blomqvist and Herzog, 1997;Thorsell et al., 2000;Furtinger et al., 2001;Naveilhan et al., 2001). These NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript effects are mediated by means of at least five G-protein-coupled receptors, designated as Y1, Y2, Y4, Y5, and y6, which are coupled to pertussis toxin-sensitive inhibitory Gproteins (Lundberg et al., 1996;Munglani et al., 1996;Balasubramaniam, 1997;Blomqvist and Herzog, 1997;Michel et al., 1998). Y-receptors have been localized to specific regions of the central and peripheral nervous system by receptor binding autoradiography, immunohistochemistry, and in situ hybridization (Zhang et al., 1994;Bao et al., 1997;Jacques et al., 1997;Dumont et al., 1998;Hökfelt et al., 1998;Gackenheimer et al., 2001). Y1 receptor is the most studied Y-receptor and it plays key roles in many of the central and peripheral effects of NPY (Lundberg et al., 1996;Munglani et al., 1996;Balasubramaniam, 1997;Blomqvist and H...

Activation of Neuropeptide Y Receptors Modulates Retinal Ganglion Cell Physiology and Exerts Neuroprotective Actions In Vitro

“…Y 1 receptor-ir was detected in cell bodies in the distal and proximal INL ( Figure 1 (cb)), arrows). A previous study has identified these cells as horizontal and amacrine cells ( D’Angelo et al., 2002 ). In accordance, we also detected Y 1 -ir processes ramifying in strata 2 and 4 of IPL.…”

Glutamate release by neurons evokes a purinergic inhibitory mechanism of osmotic glial cell swelling in the rat retina: Activation by neuropeptide Y

“…In the sensory retina of the rat, Y1‐like immunoreactivity is expressed by neurons but not by glial cells (D'Angelo et al, 2002). We used tetrodotoxin to discriminate whether the swelling‐relevant Y1 receptors are expressed by neuronal or glial cells.…”

Emerging novel roles of neuropeptide Y in the retina: From neuromodulation to neuroprotection

“…In rat retina, we and others have detected the presence of mRNAs for NPY Y 1 , Y 2 , Y 4 and Y 5 receptors (Alvaro et al, 2007;D'Angelo and Brecha, 2004). The NPY Y 1 receptor-IR was found to be localized in horizontal and amacrine cell bodies and processes (D'Angelo et al, 2002).…”

“…On the other hand, when applied exogenously, NPY stimulates the release of (Bruun and Ehinger, 1993). These results and the presence of NPY in amacrine cells (in the INL) and displaced amacrine cells (in the GCL), which may connect with other amacrine cell subtypes and ganglion cells that are not immunoreactive for NPY, suggest that NPY may also play a role as a neuromodulator in the inner retinal layers (D'Angelo et al, 2002;Oh et al, 2002)".…”

“…bipolar cells Wetzel and Eldred, 1997) Birds Chicken cell bodies of amacrine cells in the middle and innermost INL and processes in the IPL (Bruun et al, 1986) Pigeon cell bodies of amacrine cells in INL and processes in the IPL (Bruun et al, 1986;Verstappen et al, 1986) A c c e p t e d M a n u s c r i p t Mouse mRNA expression in room air reared mouse retina. (Yoon et al, 2002) Rat Immunoreactivity in horizontal cell bodies in INL and processes in OPL, in cholinergic amacrine cell processes in IPL and in all calbindin horizontal cells in rat retina; (D'Angelo et al, 2002) mRNA in rat retinas and cultured rat retinal cells; (Alvaro et al, 2008;Alvaro et al, 2009;Alvaro et al, 2007) Immunoreactivity in photoreceptors, bipolar, horizontal, amacrine and ganglion cells as well as in macroglial and microglial cells of rat retinal cells in culture. (Santos-Carvalho et al, 2012) Guinea Pig NPY Y 1 receptor in cultured Müller cells.…”