HTR2A and sudden infant death syndrome: In the youngest SIDS infants, low 5-HT2A/C binding appears frequently in 5-HT source nuclei, with low 5-HT1A binding appearing most often in 2 major motor nuclei: the HG which provides drive to the tongue and a number of upper airway muscles to reduce airway resistance during inspiration, and the DMX which contains neurons that provide parasympathetic control of the viscera.