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Immunohistochemical Examination of Developmental Brain Defects *
Author(s) -
FUNAHASHI Atsushi
Publication year - 1992
Publication title -
congenital anomalies
Language(s) - English
Resource type - Journals
eISSN - 1741-4520
pISSN - 0914-3505
DOI - 10.1111/j.1741-4520.1992.tb00258.x
Subject(s) - neuroscience , hippocampus , vasoactive intestinal peptide , cerebral cortex , offspring , biology , cortex (anatomy) , serotonin , neurotransmitter , endocrinology , psychology , medicine , central nervous system , receptor , neuropeptide , pregnancy , genetics
Recent advances in immunohistochemistry have revealed the precise distribution of various neurotransmitter systems, their projections and ultrastructure in the brain. Based on these data, the structure and function of specific neurons or a group of neurons in the brain can be understood in terms of the dynamics of the neurotransmitters they utilize. This strategy of neuroscience may be utilized to explore higher brain functions such as learning, memory, cognition and sleep. Prenatal exposure of pregnant rats to methylazoxymethanol acetate (MAM) on day 15 of gestation produces offspring with severe microcephaly (MAM‐rats). These MAM‐rats show various behavioral abnormalities in learning, memory and cognition as well as hyperactivity and reduction of paradoxical sleep. Developmental abnormalities of serotonin (5HT) fibers in the cerebral cortex and 5HT neurons in raphe nuclei are examined. The cell deficits of cortical target neurons and irregularly arranged cortical layers were observed. Developmental abnormalities of 5HT neurons are discussed in terms of target dependent secondary degeneration. Vasoactive intestinal polypeptide (VIP) has an important role in behavioral modification. VIP is suggested to have a functional correlation with 5HT in the brain. The reduction of VIP neurons and hypo‐aggregation of their axonal boutons were observed in the cerebral cortex and hippocampus of infant MAM‐rats. However, in adult MAM‐rats, VIP axonal boutons showed layer‐dependent hyper‐ or hypo‐aggregation compared with the age‐matched control. The difference in the number of VIP neurons became small between the controls and MAM‐rats. These immunohistochemical observations of brain defects have an important implication for understanding the abnormal behavior of MAM‐rats.