Catecholamine synthesizing enzyme activity in brainstem areas from victims of sudden infant death syndrome

In order to investigate whether central catecholaminergic neurons are altered in sudden infant death syndrome (SIDS), the activities of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) were determined in nine brainstem areas from 19 victims of totally unexplained SIDS (tSIDS), 9 victims of partially unexplained SIDS (pSIDS) and 8 control infants. The distinction between tSIDS and pSIDS was made according to the results of the autopsy. They were totally negative for the tSIDS victims, while minor pathological alterations were found in pSIDS victims. In both tSIDS and pSIDS victims, the PNMT activity was significantly decreased in the medullary C2m and C21 areas and in the nucleus medullae oblongatae centralis. In the C21 area only DBH activity was decreased. Further, in the nucleus ambiguus PNMT activity was decreased in tSIDS, while DBH was lowered in pSIDS victims. No significant modifications were found in the areas from the dorso-lateral pons (locus coeruleus, Kolliker Fuse and parabrachialis nuclei). Thus, in the two groups of SIDS victims the capacity to synthesize adrenaline was decreased in some medullary areas. It is considered that these biochemical alterations are related to the abnormal central respiratory and arousal control, which is thought to be present in SIDS.