HTR5A and sudden infant death syndrome: Thus, to test the hypothesis that our previously identified 5-HT pathway abnormalities in cardiorespiratory and arousal circuits of the brain in SIDS10,11 reflect a more global defect in the 5-HT pathway, in the present study we examined whether platelet 5-HT pathway and/or platelet 14–3–3 pathway biomarkers are also dysregulated in SIDS.