Involvement of somatostatin in breathing control before and after birth, and in perinatal and infant sudden unexplained death.

The distribution of the somatostatin was studied by immunohistochemistry on serial sections of the 56 brain stems from subjects aged from 30 gestational weeks to 12 postnatal months, dying of both known and unknown causes. The unexplained deaths included 13 sudden intrauterine deaths, 4 sudden neonatal deaths and 24 sudden infant deaths. We observed intense somatostatin positivity in the cell bodies and fibres of many brainstem nuclei prevalently involved in the respiratory activity (parabrachial/Kölliker-Fuse complex, locus coeruleus, hypoglossus nucleus, dorsal vagus motor nucleus, tractus solitarii nucleus, ambiguus nucleus, and reticular formation) in stillbirths. Only in 8 foetuses with unexplained death the hypoglossus nucleus was somatostatin-negative. In the postnatal deaths, the immunopositivity was prevalently limited to the ventrolateral and ventral subnuclei of the tractus solitarii nucleus. In 13 sudden infant death victims and in one case of death due to pneumonia, somatostatin-positivity was also present in the hypoglossus nucleus. We concluded that: 1) the somatostatin is an important foetal breathing-inhibitor, but it becomes important for the physiological control of respiration immediately after delivery; 2) functional alterations of the hypoglossal nucleus can occur in both sudden perinatal and infant deaths and contribute to the induction of both fatal breathing movements in foetuses and abnormal ventilatory control in infants leading to irreversible apneic phenomena.