<b>Physiological impacts of neurochemical regulation by vision in rats</b>

Abstract

The neurochemical pathways play a crucial role in the central nervous system, transmitting signals and regulating motor, sensory, and visual processes, thereby facilitating receptor function in the human body. However, the impact of neurochemicals, such as glycine, glutamate and serotonin on neuro-receptive actions on vision remains unclear. Thus, this study evaluated the effects of light patterns on neurochemicals. Adult male rats were randomly assigned to 4 groups (n = 6) and exposed for 8 weeks. Group 1 received no exposure (control). Group 2 – total darkness, group 3 – tonic light, and group 4 – rhythmic light 24 h per day. Behavioural tests (for short-term memory and motor functions) – the walk-beam, the rotating wheel and the novel object recognition tests were done. Thereafter, the levels of glycine, glutamate and serotonin in the prefrontal cortex and cerebellum were assayed. We found that the tonic light exposure showed a significant (p < 0.05) increase in the levels of prefrontal cortical and cerebellar glycine, leading to increased circadian locomotor activity, recognition memory and enhanced motor coordination compared to control, unlike those associated with total darkness. Tonic light also reduced glutamate and serotonin levels in the prefrontal cortex and cerebellum by 20-30% compared to controls, while total darkness significantly (p < 0.05) increased glutamate and serotonin levels in these brain regions. These changes were modulated by rhythmic light relative to tonic light or total darkness. Our study demonstrates that different light conditions influence neurochemical release in the retina, particularly with tonic light reducing glutamatergic and serotonergic transmission, thus preventing damage to the retina in rats.