What may be the anatomical basis that secretin can improve the mental functions in autism?

Autism was first described and characterized as a behavioral disorder more than 50 years ago. The major abnormality in the central nervous system is a cerebellar atrophy. The characteristic histological sign is a striking loss or abnormal development in the Purkinje cell count. Abnormalities were also found in the limbic system, in the parietal and frontal cortex, and in the brain stem. The relation between secretin and autism was observed 3 years ago. Clinical observations by Horváth et al. [J. Assoc. Acad. Minor. Physicians 9 (1998) 9] supposed a defect in the role of secretin and its receptors in autism. The aim of the present work was to study the precise localization of secretin immunoreactivity in the nervous system using an immunohistochemical approach. No secretin immunoreactivity was observed in the forebrain structures. In the brain stem, secretin immunoreactivity was observed in the mesencephalic nucleus of the trigeminal nerve, in the superior olivary nucleus, and in scattered cells of the reticular formation. The most intensive secretin immunoreactivity was observed in the Purkinje cells of the whole cerebellum and in some of the neurons of the central cerebellar nuclei. Secretin immunoreactivity was also observed in a subpopulation of neurons in the primary sensory ganglia. This work is the first immunohistochemical demonstration of secretin-immunoreactive elements in the brain stem and in primary sensory ganglia.