Muller J F, Marc R E
Department of Physiology, University of Utah School of Medicine, Salt Lake City 84108.
J Comp Neurol. 1990 Jan 8;291(2):281-304. doi: 10.1002/cne.902910210.
GABA-ergic and glycinergic circuitry in the inner plexiform layer of the goldfish retina was evaluated by electron microscopic autoradiography of 3H-GABA and 3H-glycine uptake, combined with retrograde horseradish peroxidase (HRP) labeling of ganglion cells. GABA-ergic and glycinergic synapses were found on labeled ganglion cells throughout the inner plexiform layer. This reinforces the idea that physiological evidence of GABA-ergic and glycinergic influence on a variety of ganglion cells in goldfish and carp often reflects direct inputs. Double-labeled synapses are presented as evidence of direct type Ab amacrine cell input to on-center ganglion cells. At least one population of type Aa sustained-off GABA-ergic amacrine cell is proposed, on the basis of profuse GABA-ergic inputs onto bipolar cells in sublamina a. Similar GABA-labeled profiles are shown to synapse onto HRP-labeled probable off-center ganglion cells. Thus GABA-ergic amacrine cells not only provide the predominant feedback to depolarizing (on-center) and hyperpolarizing (off-center) bipolar cells but also provide feed-forward inputs to on- and off-center ganglion cells. Large-caliber GABA-ergic dendrites present in both sublaminae a and b resemble those expected of a previously described bistratified, transient amacrine cell. These processes synapse onto HRP-labeled ganglion cell profiles in both sublaminae. Two morphologies of glycinergic amacrine cell are proposed on the basis of light microscopic autoradiography, 1) the previously described small pyriform cell and 2) a multipolar cell. The differential connectivity of the glycinergic neurons described, however, remains indistinguishable. Whereas abundant glycinergic inputs to ganglion cells occur throughout the inner plexiform layer, contacts between glycinergic profiles and bipolar cells are extremely rare. Therefore, interpreting the meaning of glycinergic input to ganglion cells will require further study of amacrine cell circuitry.
通过对³H - GABA和³H - 甘氨酸摄取进行电子显微镜放射自显影，并结合对神经节细胞的逆行辣根过氧化物酶（HRP）标记，评估了金鱼视网膜内网状层中的GABA能和甘氨酸能神经回路。在整个内网状层中，在标记的神经节细胞上发现了GABA能和甘氨酸能突触。这强化了这样一种观点，即金鱼和鲤鱼中GABA能和甘氨酸能对多种神经节细胞影响的生理学证据通常反映了直接输入。双标记突触被作为直接的A b型无长突细胞输入到中心型神经节细胞的证据。基于a层中双极细胞上大量的GABA能输入，提出了至少一群Aa型持续关闭的GABA能无长突细胞。类似的GABA标记轮廓显示与HRP标记的可能的离中心神经节细胞形成突触。因此，GABA能无长突细胞不仅为去极化（中心型）和超极化（离中心型）双极细胞提供主要反馈，还为中心型和离中心型神经节细胞提供前馈输入。a层和b层中都存在的大口径GABA能树突类似于先前描述的双分层、瞬态无长突细胞的树突。这些突起在两层中都与HRP标记的神经节细胞轮廓形成突触。基于光学显微镜放射自显影，提出了两种甘氨酸能无长突细胞形态，1）先前描述的小梨形细胞和2）多极细胞。然而，所描述的甘氨酸能神经元的不同连接性仍然难以区分。虽然在整个内网状层中都有大量的甘氨酸能输入到神经节细胞，但甘氨酸能轮廓与双极细胞之间的接触极其罕见。因此，解释甘氨酸能输入到神经节细胞的意义需要对无长突细胞回路进行进一步研究。
