Mammalian cerebral cortical tissue responds to low-intensity visible light.

Abstract

Low levels of visible light directed onto slices of rat cerebral cortical tissue enhanced net potassium-induced release of the neurotransmjtter y-aminobutyric acid (GABA) from these brain slices. At higher light intensity, net potassiuminduced release was suppressed. These effects were apparently not from increased temperature. The amount of light enhancing this neurotransmitter release is approximately equal to the amount of light that can penetrate the head and reach the brain at the intensities of sunlight; this was determined by measuring the light entering the rat head through fur, scalp, skull, and dura mater and considering several natural lighting conditions. These results suggest that ambient light may be sufficient to alter the release of transmitters from mammalian cerebral cortex in vivo.

Laser stimulation of the auditory nerve

“…In the latter study, action potentials were measured and Fork demonstrated an increased rate of action potentials upon irradiation. Another group used a tungsten lamp to irradiate cortical brain slices [14]. They measured a significant increase in neurotransmitter release as compared to the non-irradiated condition.…”

Evolution of Mammalian Opn5 as a Specialized UV-absorbing Pigment by a Single Amino Acid Mutation

“…Direct binding of all-trans-retinal causes the formation of the active state and elevates the G protein activation ability without light irradiation, which lowers the signal to noise ratio in light-dependent signaling. Light can penetrate the skull in several mammalian species, including humans (26), and mammalian cerebral cortical tissues were reported to respond to low intensity light to regulate neurotransmitter release (32). In birds, the measurement of the light transmit- tance into the deep brain revealed that the hypothalamus can receive light enough to trigger opsin-mediated signal transduction (33) because of the high quantum yield of opsins (34).…”

Extraocular Phototransduction and Circadian Timing Systems in Vertebrates

“…Exposure of rat cortical tissue to light alters GABA transmission (113). Such results suggest that the investigation of the location, identification, and functioning of extraocular photoreceptors may be far from complete.…”