Distribution of Histamine-Containing Neurons in the Laboratory Shrew (Suncus murinus) Brain.

Abstract

The distribution of histamine (HIS)-containing neurons was studied by the avidin-biotin peroxidase complex (ABC) method, and compared with that of the monoaminergic and aromatic L-amino acid decarboxylase-positive neurons (D neurons) in the laboratory shrew (Suncus murinus) brain. In the laboratory shrew brain, HIS-immunoreactive (IR) neurons were strictly confined to the mammillary area. Packed clusters of HIS-IR neurons were localized to four regions: the dorsal and ventral premammillary nucleus, lateral mammillary nucleus and the posterior hypothalamic nucleus. HIS-IR nerve fibers were found mainly in the diencephalon and telencephalon. In particular, dense histaminergic innervation was observed in the preoptic area, bed nucleus of the stria terminalis and suprachiasmatic nucleus. Some HIS-IR nerve fibers were detected in the paraventricular nucleus, anterior hypothalamic nucleus, lateral septal nucleus and cerebral cortex. Few HIS-IR nerve fibers were found in the caudate nucleus, medial septal nucleus, colliculus, hippocampus and locus coeruleus. Comparison of the distribution of HIS-IR neurons with those of monoaminergic neurons and D neurons in the laboratory shrew brain revealed the following findings, which are unique to the laboratory shrew: 1) The distribution of HIS IR neurons was localized to a specific area. 2) Although HIS-IR nerve fibers were densely distributed in the median eminence in the rat brain, only a small number of HIS-IR nerve fibers were observed in this area in the laboratory shrew.