Reduction in choline acetyltransferase immunoreactivity but not muscarinic-M2 receptor immunoreactivity in the brainstem of SIDS infants

The cholinergic neurotransmitter system is vital for several brainstem func tions including cardiorespiratory control and central chemosensitivity. Thi s study has examined aspects of the cholinergic neurotransmitter system in the brainstem of sudden infant death syndrome (SIDS) and control infants. T he cellular localisation and the optical density of the immunoreactivity of the cholinergic enzyme choline acetyltransferase (CHAT-TR) and the muscari nic acetylcholine receptor m2 (m2-IR) in the medulla was described in 14 SI DS and 9 control cases. There was a reduction in the number of CHAT-IR neur ons in the hypoglossal nucleus (control: 71.2 +/- 8.3% vs SIDS: 46.1 +/- 5. 3%) and the dorsal motor nucleus of the vagus (DMV) (control: 77.2 +/- 5.0% vs SIDS: 52.5 +/- 7.4%) and reduced optical density of CHAT-IR in the hypo glossal nucleus (control: 0.20 +/- 0.01 vs SIDS; 0.14 +/- 0.02) in SIDS inf ants. Tn contrast there were no changes in the optical density of m2-IR in the hypoglossal nucleus, the DMV, or the arcuate nucleus. Hypoplasia of the arcuate nucleus was observed in one SIDS infant. These results suggest tha t there is a specific defect in some cholinergic motor neurons in the medul la of SIDS infants. This could lead to abnormal control of cardiovascular a nd respiratory function and airway patency and may be one of the contributi ng factors in the etiology of SIDS.