Immunohistochemical analysis of neuropeptide Y in the Bullfrog Retina / 第三军医大学学报

Objective To investigate the distribution and synaptic connectivity of neuropeptide Y (NPY)-like immunoreactivity (IR) in Bullfrog retina, Rana Calesbeiana, especially in the inner plexiform layer. Methods Light microscopy immunofluorescence and post-embedding colloidal gold labeling electron microscopy techniques were employed in this study. Results NPY immunoreactivity was associated with a small population of amacrine cell bodies in the inner nuclear layer and cell processes, ramified with 3 distinct bands, in the inner plexiform layer. As for ultrastructure, quantitative analysis showed that NPY-IR amacrine cell processes were most often presynaptic to NPY negative amacrine cell processes (49.7%) and ganglion cell dendrites (49.3%). NPY-IR amacrine cells predominantly received synaptic input from bipolar cell axon terminals (86%), while a few input from other amacrine cell processes (14%). Conclusion NPY-IR in Bullfrog retina is mainly distributed in the inner part and predominately receives excitatory glutamate modulation from bipolar cells.

Distribution and synaptic organization of nitric oxide synthase immunoreactive neurons in the rat olfactory / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Nitric oxide (NO) has been reported to play important roles in the regulation of olfactory information in the mammarian olfactory bulb. Although the distribution of nitric oxide synthase (NOS)-immunoreactive neurons in the olfactory bulb in the rat and other animals have been investigated by light microscopy, ultrastructures of the synaptic organization between NOS-immunoreactive neurons have not been studied yet. This study was conducted in order to identify NOS- immunoreactive neurons in the rat olfactory bulb and to define their synaptic organizations under the electron microscope using the preembedding immunocytochemical method which utilizes anti-NOS antiserum. MATERIALS AND METHODS: The olfactory bulbs of the rats were cut into 50 micromiter thick vertical sections and immunostained using the ABS method. Stained sections were observed under the light microscope. Some of the stained sections, additionally stained with uranyl acetate and dehydrated, were embedded in Epon 812 and prepared into 80 nm thick sections to be observed under the electron microscope. RESULT: NOS-immunoreactive neurons of the rat olfactory bulb made up 25.0% of periglomerular cells and 18.9% of granule cells. NOS-immunoreactive periglomerular cells received synaptic input from unlabeled axon terminals of the olfactory nerve and unlabeled periglomerular cells within the glomeruli. The output targets of NOS immunoreactive periglomerular cells were unlabeled axon terminals of the olfactory nerve and unlabeled periglomerular cells. NOS-immunoreactive granule cells received synaptic input from unlabeled processes of granule cells and axon terminals of mitral cells, and made output synapses onto the unlabeled axon terminals of mitral cells. CONCLUSION: NOS-immunoreactive neurons are periglomerular cells and granule cells, and NO liberated from NOS cells may play important roles in the modulation of olfactory transmission.

Distribution Pattern and Synaptic Circuitry of Cholinergic Neurons in the Rat Retina / 대한해부학회지

The role of acetylcholine as an excitatory neurotransmitter is well established, and cholinergic neurons appear to play an important role in the mammalian retinae. Though it has been reported that certain conventional and displaced amacrine cells are consistently labeled with anti-choline acetyltransferase antiserum in the mammalian retinae, little has been studied on the synaptic circuitry of cholinergic neurons to clarify mechanism of its action in the visual processing of the mammalian retinae. This study was conducted to localize cholinergic neurons and to define their synaptic circuitry in the rat retina by immunocytochemical method using anti-choline acetyltransferase antiserum. The results were as follows: 1. Cholinergic neurons of the rat retina were conventional amacrine cells located in the inner nuclear layer and displaced amacrine cells in the ganglion cell layer. 2. Cholinergic amacrine cells were branched in the middle of the sublamina a of the inner plexiform layer, and cholinergic displaced amacrine cells branched in the sublamina b, forming one prominent band, respectively. 3. Presynaptic processes to cholinergic amacrine cell processes were axon terminals of invaginating and flat cone bipolar cells, and unlabelled amacrine cell processes in the inner plexiform layer. Postsynaptic dyads at the ribbon synapses of axon terminals of cone bipolar cells were cholinergic amacrine cell process and dendrite of ganglion cell, cholinergic amacrine cell process and unlabelled amacrine cell process and cholinergic amacrine cell process and cholinergic amacrine cell process. In addition, cholinergic amacrine cell process formed postsynaptic monoad at the ribbon synapse. 4. Cholinergic amacrine cell processes made output conventional chemical synapses onto the dendrites of ganglion cells, unlabelled amacrine cell processes and cholinergic amacrine cell processes in the inner plexiform layer. These results demonstrate that (1) cholinergic neurons are conventional amacrine cells and displaced amacrine cells of which somata are located in the inner nuclear layer and ganglion cell layer, respectively, (2) cholinergic conventional amacrine cells are involved in OFF pathway, and cholinergic displaced amacrine cells play an important role in ON pathway in visual processing of lightness, and (3) acetylcholine released from cholinergic neurons by light excites directly ON and OFF ganglion cells or indirectly ON and OFF ganglion cells via non-cholinergic amacrine cells.