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Neuronal and vascular localization of histamine N‐methyltransferase in the bovine central nervous system
Author(s) -
Nishibori Masahiro,
Tahara Akihito,
Sawada Ken,
Sakiyama Junko,
Nakaya Naoki,
Saeki Kiyomi
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00914.x
Subject(s) - histaminergic , nucleus , spinal trigeminal nucleus , anatomy , dorsal motor nucleus , hypoglossal nucleus , spinal cord , biology , central nervous system , pons , chemistry , histamine , neuroscience , endocrinology , nociception , vagus nerve , receptor , biochemistry , stimulation
Histamine N‐methyltransferase (HMT) (EC 2.1.1.8) plays a crucial role in the inactivation of the neurotransmitter histamine in the CNS. However, the localization of HMT remains to be determined. In the present study, we investigated immunohistochemical localization of HMT in the bovine CNS using a polyclonal antibody against bovine HMT. The HMT‐like immunoreactivity was observed mainly in neurons. Strongly immunoreactive neurons were present in the oculomotor nucleus and ruber nucleus in the midbrain, the facial nucleus in the pons, the dorsal vagal nucleus and hypoglossal nucleus in the medulla oblongata and in the anterior horn as well as intermediolateral zone of the spinal cord. Intermediately immunoreactive neurons were present in the piriform cortex and the inferior olivary nucleus. The grey matter of the forebrain regions was diffusely and faintly stained. In the cerebellum and the striatum, the nerve fibres in the white matter were positive. The tuberomammillary nucleus, where histaminergic neurons are present, were weakly positive. The other immunoreactive structures in the CNS were blood vessels. Almost all of the blood vessel walls, irrespective of whether they were arterial or venous, were variably stained. The glial fibrillary acidic protein‐ (GFAP‐) immunoreactive astrocytes were not stained. These findings indicated that histamine released from histaminergic nerve terminals or varicose fibres is methylated mainly in postsynaptic or extrasynaptic neurons rather than in astrocytes. The localization of HMT in the blood vessel wall may mean that blood‐borne histamine and histamine released from mast cells associated with the blood vessels are catabolized in this structure.