Responses of the hypothalamic paraventricular neurons to light stimulation with different wavelengths in the rat

During exposure to light with different spectral compositions, the non-visual neural system in the brain gives rise to altered various physiological aspects that are not caused by the well-known primary visual pathway. This study has been designed to investigate non-visual information processing that affects the biological rhythms in humans by studying the properties of paraventricular neurons in Sprague-Dawley rats under urethane anesthesia. The responses of paraventricular nucleus neurons by stimulation with different wavelengths of light were recorded. It turned out that neural responses were most sensitive to 550 nm wavelength light. This result suggests that a non-visual system in the hypothalamus including the paraventricular nucleus responds to light stimuli to control biological rhythms or autonomic functions.