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This study was conducted to identify the possible effect of recombinant vertebrate ancient long (VAL) opsin as a non-visual "photoreceptor" in the deep brain of goldfish, Carassius auratus. In addition, we investigated the effects of green-wavelength light on the predictable reproductive function of VAL-opsin as a green-sensitive pigment in the deep brain. To determine this, we quantified changes in gonadotropin hormone (GTH) [GTHα, follicle stimulating hormone (FSH) and luteinizing hormone (LH)] and estrogen receptor (ER; ERα and ERβ) mRNA expression levels associated with goldfish reproduction as well as changes in plasma FSH, LH, and 17β-estradiol (E 2 ) activities after injection of recombinant VAL-opsin protein in two concentrations (0.1 or 0.5 μg/g body mass) for 4 weeks (injection once weekly) and examined the possible impact of green-wavelength light (500, 520, and 540 nm) on the function of VAL-opsin. As a result, all parameters associated with reproduction significantly increased with time and light-emitting diode (LED) exposure. Based on these results, we suggested that VAL-opsin in the deep brain is involved in goldfish maturation, and it is possible that green-wavelength light improves the ability of VAL-opsin to promote maturation by increasing VAL-opsin expression.

Background: Widespread opsin expression in the cortex of rats, where transgenic models have not been established, is not practical to achieve with the traditional diffusion-based virus transduction methods (DBD)., New Method: We developed protocols for convection-enhanced delivery (CED) of virus for optogenetic transduction of the rat cortex. Targeting the motor forelimb area as an example, we performed dual-site CED (6μL of virus per site, 3mm pitch between sites) in the rat motor cortex., Results: We identified injection parameters optimized for horizontal spread of infusate in the agarose gel model and then demonstrated in vivo widespread opsin expression over the cortical area (7.4±1.0mm in the AP direction, 4.4±1.1mm in the ML direction, N=13 rats) using CED. The optogenetic transduction was also functionally robust, in which both optical modulation of neuronal activity and elicitation of overt motor responses was reliably observed., Comparison With Existing Method(s): CED led to about 24-fold increase in the volume of opsin expression, compared with the conventional DBD method. The total injection time was also reduced by at least 10 times, if similar extent of expression were to be achieved with the conventional DBD method., Conclusions: CED is a reliable and effective method of virus delivery for optogenetic transduction of planar superficial structures, such as the cortex in rats., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)