Choline Acetyltransferase Positive Neurons in the Laboratory Shrew (Suncus murinus) Brain: Coexistence of ChAT/5-HT (Raphe dorsalis) and ChAT/TH (Locus ceruleus)

Abstract

We determined the distribution pattern of cholinergic neurons in laboratory shrews (Suncus murinus) based on comparative morphology by an immunohistochemical method using an anticholine acetyltransferase (ChAT) antibody. ChAT-positive neurons were observed in the striatum, magnocellular nucleus and basal nucleus, pontine tegmentum and cranial nerve motor nuclei (IV, V, VII, X and XII). Specific findings were as follows: many ChAT-positive neurons were observed in the locus ceruleus (LC) and raphe dorsalis (RD), and the colocalization of ChAT-positive neurons and tyrosine hydroxylase in the LC and that of ChAT-positive neurons and serotonin in the RD were clarified. On the other hand, in the rat brain, ChAT-positive neurons were present in the central amygdaloid nucleus; however, this was not observed in the brains of laboratory shrews. Laboratory shrews are among the most primitive mammalian species and have a different distribution pattern of aminergic neurons, other than cholinergic neurons, from that in rats. A unique distribution pattern of ChAT-positive neurons in the laboratory shrew brain was thus noted.