Many nociceptive neurons in the spinal cord of rats project directly to the hypothalamus. The axons of these neurons cross into the contralateral spinal cord and ascend through the posterior thalamus before entering the contralateral hypothalamus. The majority of these axons decussate again in the posterior optic chiasm, enter the ipsilateral hypothalamus, turn posteriorly and descend into the ipsilateral thalamus, midbrain, and in some cases, pens and even medulla before terminating. A smaller number of spinal neurons project directly to several telencephalic areas including the amygdala, nucleus accumbens, septal nuclei and the frontal cortex. Each of these direct projections to the hypothalamus and telencephalon may contribute to nociception.
- Limbic system
- Spinal cord