Isolation of rod early receptor potential from frog retina

Receptor targets of amacrine cells

Amacrine cells are a morphologically and functionally diverse group of inhibitory interneurons. Morphologically, they have been divided into approximately 30 types. Although this diversity is probably important to the fine structure and function of the retinal circuit, the amacrine cells have been more generally divided into two subclasses. Glycinergic narrow-field amacrine cells have dendrites that ramify close to their somas, cross the sublaminae of the inner plexiform layer, and create cross talk between its parallel ON and OFF pathways. GABAergic wide-field amacrine cells have dendrites that stretch long distances from their soma but ramify narrowly within an inner plexiform layer sublamina. These wide-field cells are thought to mediate inhibition within a sublamina and thus within the ON or OFF pathway. The postsynaptic targets of all amacrine cell types include bipolar, ganglion, and other amacrine cells. Almost all amacrine cells use GABA or glycine as their primary neurotransmitter, and their postsynaptic receptor targets include the most common GABA(A), GABA(C), and glycine subunit receptor configurations. This review addresses the diversity of amacrine cells, the postsynaptic receptors on their target cells in the inner plexiform layer of the retina, and some of the inhibitory mechanisms that arise as a result. When possible, the effects of GABAergic and glycinergic inputs on the visually evoked responses of their postsynaptic targets are discussed.

Filtering effect of cone oil droplets detected in the P-III response spectra of Japanese quail

While absorption spectra of bird cone visual pigments have been well studied, physiological study of bird cone cells has been less advanced owing to their small sizes. We measured the P-III components of electroretinograms (ERG) from isolated retinas of Japanese quail. We recorded responses to monochromatic flashes of equal photon numbers, and found that the shape of the response spectrum is dependent on the incident direction of the flashes. The spectrum obtained with the flashes from the cornea side had a steeper peak around 500 nm than that with flashes from the receptor side. This is clear electrophysiological evidence of the filtering effect of the oil droplets in the cone cells, which has long been suspected. We analyzed these spectra with respect to the absorption spectra of cone pigments and transmittance spectra of oil droplets.