Serotonergic neurons as carbon dioxide sensors that maintain pH homeostasis

Serotonergic neurons in the medulla have recently been shown to be sensors of carbon dioxide and pH. There is compelling evidence that the co-release of serotonin, substance P and thyrotropin-releasing hormone from these neurons stimulates the neural network that controls breathing at numerous sites using many different mechanisms. Serotonergic neurons in the midbrain are also chemosensitive, and might mediate non-respiratory responses to increased carbon dioxide, such as arousal. This role in control of pH homeostasis could provide a neurobiological explanation for the link between changes in the serotonin system and sudden infant death syndrome (SIDS).