The effects of nucleus raphe magnus lesions on an ascending thermal pathway in the rat.

Publisher Website
Google Scholar
Abstract
In the thalamus and hypothalamus of rats, anesthetized with urethane, single unit recordings were made from cells which respond to small innocuous changes in scrotal skin temperature applied with a water-perfused brass thermode. Once a scrotal temperature-sensitive neuron was isolated the brain stem was electrolytically lesioned through implanted tungsten electrodes to determine whether the input from the scrotal skin temperature sensors ascends through the brain stem lemniscal pathways or the mid-line raphe nuclei. All recording sites and lesions were identified histologically. Neurons (36) were studied of which half were located in the ventrobasal thalamus, 6 were located in the anterior thalamic nuclei and the remainder were in the medial hypothalamus. The nucleus raphe magnus was lesioned on 18 separate occasions; in each case the temperature-responsive activity of the thalamic or hypothalamic neuron was abolished. Extensive brain-stem lesions which spared only the mid-line nucleus raphe magnus had no discernible effect on the responses of the thalamic or hypothalamic neurons to scrotal skin temperature. The ascending pathway from the thermal sensors of the rat scrotal skin must pass through, or relay in, the nucleus raphe magnus.