Terumi Takeuchi

Transient tyrosine hydroxylase-immunoreactive neurons in the region of the anterior olfactory nucleus of pre- and postnatal mice do not contain dopamine

The transient appearance of tyrosine hydroxylase (TH)-immunoreactive (IR) neurons in the anterior olfactory nuclear region of mice was investigated using TH-immunocytochemistry. In this region, a new cell group composed of a small number of neurons immunoreactive to TH was demonstrated for the first time from the embryonic stages of E16-E18. These cells were not shown using antisera against aromatic L-amino acid decarboxylase, dopamine-beta-hydroxylase, phenylethanolamine-N-methyl-transferase, dopamine or serotonin. TH-IR cells progressively increased in number until birth. After birth the numbers reached maximum at postnatal days 9-12 and decreased until 4 weeks old, and then mostly disappeared at 6 weeks. Only single TH-IR cells were occasionally observed in this brain area of adult mice. Ultrastructurally some of these TH-IR neurons had immature Golgi apparatus, only a few mitochondria and deformed nuclei along with thin cytoplasma. Some other TH-IR cells, however, had mature Golgi apparatus, many mitochondria and a round nucleus more closely resembling mature cells. These neurons do not belong to the dopaminergic neuron system, because they lack dopamine production, and may be tentatively involved in early limbic circuits.

Immunohistochemical colocalization of GTP cyclohydrolase I in the nigrostriatal system with tyrosine hydroxylase

Immunohistochemical colocalization of GTP cyclohydrolase I (GCH) in the mouse nigrostriatal system with tyrosine hydroxylase or aromatic L-amino acid decarboxylase in the somata and terminals of GCH-positive catecholaminergic neurons are proved for the first time by a double-labeling immunofluorescence method with a confocal laser-scanning microscope. GCH-immunoreactive somata in the mouse substantia nigra have synaptic contacts with monoaminergic and non-monoaminergic terminals.

Expression in brain sensory neurons of the transgene in transgenic mice carrying human tyrosine hydroxylase gene

We have recently reported the production of transgenic (Tg) mice carrying the human tyrosine hydroxylase (TH) gene, and have described tissue-specific expression of the transgene in catecholaminergic (CAergic) neurons and adrenal glands. This paper describes the transgene expression in non-catecholaminergic (nCAergic) neurons in the brain of Tg mice by immunocytochemistry and in situ hybridization. In adult Tg mice, human TH was atypically expressed in the olfactory (typically, the anterior olfactory nucleus and pyriform cortex) and visual (typically, n. suprachiasmaticus and n. parabigeminalis) systems, in addition to typical CAergic neuron-rich nuclei in the brain. These results suggest the possibility that TH plays some novel roles in sensory systems.

Phenylethanolamine-N-methyltransferase – immunoreactive nerve terminals afferent to the mouse substantia nigra

In the substantia nigra pars compacta, many phenylethanolamine-N-methyltransferase immunoreactive (PNMT-ir) terminals as well as serotonin-ir terminals were observed for the first time to be very closely situated to the tyrosine hydroxylase (TH)-ir, aromatic L-amino acid decarboxylase-ir, and GTP cyclohydrolase I (GCH)-ir dopaminergic cells [Nagatsu, I., Arai, R., Sakai, M., Yamawaki, Y., Takeuchi, T., Karasawa, N. and Nagatsu, T., Neurosci. Lett., 224 (1997) 185-188]. Immunohistochemical colocalization of TH with GCH or PNMT in the somata and dendrites of TH-positive neurons in the rostral ventrolateral reticular formation of the medulla oblongata (C1 region, [Hokfelt, T., Fuxe, K., Goldstein, M. and Johansson, O., Brain Res., 66 (1974) 235-251]) was proved by a double-labeling immunofluorescence method with a confocal laser-scanning microscope, indicating that the neurons are adrenergic. These results suggest that dopaminergic neurons in the substantia nigra receive PNMT-ir, adrenergic afferents from the C1 region of the medulla oblongata.

Transient appearance of tyrosine hydroxylase-immunoreactive non-catecholaminergic neurons in the medial geniculate nucleus of postnatal mice☆

Tyrosine hydroxylase-immunoreactive (TH-ir) cells were found to appear transiently in the medial geniculate nuclear region of mice at postnatal day 7 (P7) by use of an avidin-biotin peroxidase complex (ABC) method for the first time. The numbers of TH-ir cells reached maximum between P14 and P21 and decreased until P29. These cells were GTP cyclohydrolase I-negative, aromatic L-amino acid decarboxylase-negative, and dopamine-negative. Thus, they do not belong to the catecholaminergic neuron system, because they lack dopamine production. The results suggest that TH in the cells in the medial geniculate nuclear region of mice has some new functions besides catecholamine biosynthesis.

Expression of human tyrosine hydroxylase-chloramphenicol acetyltransferase (CAT) fusion gene in the brains of transgenic mice as examined by CAT immunocytochemistry.

We have produced transgenic (Tg) mice carrying 5.0-kb fragment from the 5′-flanking region of the human tyrosine hydroxylase (hTH) gene fused to a reporter gene, chloramphenicol acetyltransferase (CAT) [Sasaoka et al. (1992) Mol Brain Res 16: 274–286]. In the brain of the Tg mice, CAT expression has been observed in catecholaminergic (CAnergic) neurons and also in non-CAnergic neurons. The aim of the present study is to examine in detail the cell-type specific expression of the hTH-CAT fusion gene in the brain of the Tg mice, by use of immunohistochemistry for CAT, TH, and aromatic L-amino acid decarboxylase (AADC). CAT-immunoreactive cells were found in CAnergic brain regions which contained TH-positive cells, and also in non-CAnergic brain regions which contained no TH-labeled cells. The non-CAnergic brain regions that represented CAT-stained cells were further divided into two groups: (i) regions containing AADC-labeled cells, for example, bed nucleus of the stria terminalis, nucleus suprachiasmaticus, mammillary body, nucleus raphe dorsalis, inferior colliculus, and nucleus parabrachialis, and (ii) regions containing no AADC-positive cells, for example, main olfactory bulb (except A16), accessory olfactory bulb, nucleus olfactorius anterior, caudoputamen, septum, nucleus accumbens, hippocampus, medial nucleus of the amygdala, entorhinal cortex, nucleus supraopticus, and parasubiculum. The results indicate that the 5.0-kb DNA fragment flanking the 5′ end of the hTH gene may contain the element(s) specific for neuron-specific TH expression but which may be insufficient to attenuate ectopic expression.

CATECHOLAMINE SYNTHETIC ENZYMES OF SPONTANEOUSLY HYPERTENSIVE RATS AND MICROBIAL HYPOTENSIVE PRODUCTS

Summary1.Oudenone, an inhibitor of tyrosine hydroxylase, and fasaric acid, an inhibitor of dopamine-β-hydroxylase, both newly described inhibitors of microbial origin showed more pronounced hypotensive effects on spontaneously hypertensive rats than on normotensive Wistar rats.2.Spontaneously hypertensive rats had about 2-fold highe tyrosine hydroxylase and dopamine-β-hydroxylase activities in adrenal glands, and lower tyrosine hydroxylase activity in mesenteric artery. After adrenalectomy, blood pressure of spontaneously hypertensive rats decreased, and the lower tyrosine hydroxylase activity in mesenteric artery increased to the enzyme level of normotensive Wistar rats.

Tyrosine hydroxylase (TH)-only-immunoreactive non-catecholaminergic neurons in the brain of wild mice or the human TH transgenic mice do not contain GTP cyclohydrolase I

We previously reported the presence of transiently tyrosine hydroxylase (TH)-only-immunoreactive (ir), non-catecholaminergic (non-CAnergic) neurons in some brain regions of postnatal mice; anterior olfactory nucleus, medial geniculate nucleus, and spinal trigeminal nucleus, where CAnergic terminals but not cell bodies are present in the adult wild mouse. These transiently TH-ir brain regions of the postnatal wild mouse showed stable TH-immunoreactivity in the adult brain of the human TH transgenic (hTHTg) mice. TH expression was also observed in the nucleus parabigeminalis of the hTHTg mice. Using the antiserum against GTP cyclohydrolase I (GCH), first rate-limiting enzyme of the biosynthesis of tetrahydrobiopterin (BH4), the cofactor for TH, we proved that these TH-only-ir neurons in the wild mice and in the hTHTg mice were not stained with the antiserum against GCH. The results indicate that these TH-only-ir neurons which do not synthesize the BH4 cofactor do not produce dihydroxyphenylalanine, suggesting a new unknown function of TH in these neurons.

Transient appearance of GTP cyclohydrolase I--positive non-monoaminergic neurons in the ventral lateral geniculate nucleus of postnatal mice.

The transient appearance of GTP cyclohydrolase I (GCH)-immunoreactive (ir) cells in the ventral lateral geniculate nuclear region of mice was detected by use of an avidin-biotin peroxidase complex method with an antibody specific for an oligopeptide of rat GCH (residues from 12 to 23, GFPERELPRPGA). In this brain region, we found for the first time novel GCH-ir cells already at postnatal day 1 (P1). The numbers reached maximum at P14 and decreased until P29, and they had mostly disappeared by P56. These cells were tyrosine hydroxylase negative and aromatic L-amino acid decarboxylase negative, indicating a lack of dopamine or serotonin production, and thus do not belong to the monoaminergic neuron system.

Enhanced expression of human tyrosine hydroxylase in the lower brainstem of transgenic mice

We have previously reported the distribution of human tyrosine hydroxylase (TH) transgene expression in dopaminergic neurons (ventral tegmental area and substantia nigra), adrenal gland, and non-catecholaminergic neurons in the forebrain of transgenic (Tg) mice. In this paper, we analysed the transgene expression in catecholaminergic (CAergic) neurons in the lower brainstem of Tg mice, by in situ hybridization and immunocytochemistry at the light and electron microscopic levels. High-level hybridization signals of the human TH mRNA were observed in the locus ceruleus and nucleus tractus solitarii of the Tg brain. Intense TH immunoreactivity was expressed specifically in the Tg brainstem, as was observed in non-Tg mice. These results reveal that the human TH transgene contains the regulatory elements responsible for the expression in three kinds of CAergic (dopaminergic, noradrenergic and adrenergic) neurons of the mouse brain.