Morphological organization of catecholamine terminals in the diencephalon of the rhesus monkey

The hypothalamus and thalamus of the rhesus monkey were investigated using the fluorescence histochemical method of Falck and Hillarp. The hypothalamus was found to be richly supplied with catecholamine fluorescent nerve terminals with many thick and a few varicosities, whereas nerve terminals with fine varicosities were found to be distributed over the thalamus except for the midline and medial nuclei which were innervated by nerve terminals with thicker and more intense fluorescent varicosities. The morphological characteristics and distribution pattern of catecholamine terminals were similar between the rhesus monkey and the rat. However, some species differences were noted in the suprachiasmatic nucleus, arcuate nucleus and internal layer of infundibulum in the hypothalamus. The pulvinar, which was nonexistent in the rat, had fine terminals.

[Distribution of catecholamine containing nerve endings in the hypothalamus of the rhesus monkey]

Using the Falck-Hillarp method, the distribution of catecholamine nerve terminals in the rhesus monkey hypothalamus was studied. The distribution pattern was fundamentally similar to that in the rat, cat and human fetus; abundunt catecholamine varicosities (presumed noradrenaline nerve terminals) were observed in the dorsomedial nucleus, supraoptic nucleus, paraventricular nucleus, medial forebrain bundle, periventricular layer and internal layer of the infundibulum, while little were in the mamillary nucleus, ventromedial nucleus and anterior hypothalamic area. A band of diffuse green fluorescence (dopamine nerve terminals) was observed around the capillary loops in the external layer of the infundibulum. the discrepancy with the rat was noted in the abundunt noradrenaline nerve terminals in the suprachiasmatic nucleus and denser innervation of them in the arcuate nucleus and internal layer of the infundibulum. In addition to the noradrenaline nerve fibers from the peripheral sympathetic NA nerve, the noradrenaline nerve terminals of central origin closely approximated to the small intracerebral vessels.

[Synthesis of norepinephrine from 3,4-dihydroxyphenylserine by L-aromatic amino acid decarboxylase of the rat brain and kidneys]

The enzymic decarboxylation of stereoisomers of DOPS was examined using rat brain and kidney decarboxylase. Optimal assay conditions for racemic threo- and racemic erythro-DOPS decarboxylation were determined by the experiments concerning 1) time course, linear for 20 min, 2) optimal pH, pH 8.2, 3) optimal temperature, 37 degrees C except racemic L-threo-DOPS decarboxylation by kidney enzyme and 4) protein concentration, 1 to 5 mg in incubation medium. Under the optimal assay condition, Km of brain enzyme for L-threo-DOPS was 1.43 X 10(-3)M and Vmax, 2.22 nmoles NE/mg/15min, and Km for racemic erythro-DOPS was 10(-3)M and Vmas, 4.3 nmoles NE/mg/15min. Km of kidney enzyme for L-threo-DOPS was 1.37 X 10(-3)M and Vmax 21 nmoles NE/mg/15min, and Km for racemic erythro-DOPS was 8.7 X 10(-4)M and Vmax, 16.7 nmoles NE/mg/15min. On the other hand, D-threo and D-erythro-DOPS were scarcely decarboxylated. Decarboxylation of L-threo-DOPS in kidney enzyme was markedly inhibited by D-threo-DOPS. Kinetic analysis revealed that the type of inhibition was non-competitive. In helically-cut strips of isolated rabbit aorta, the contractile response to NE (10(-8)g/ml) formed from L-threo-DOPS was 95% that of 1-NE (10(-8)g/ml) while the response to NE (10(-8)g/ml) formed from racemic erythro-DOPS was not detectable. These results suggest that L-threo-DOPS is a more effective precursor of natural 1-NE than racemic threo-DOPS.

Histochemical mapping of dopamine neurons and fiber pathways in dog mesencephalon

A topographic mapping of dopamine (DA)-containing neurons and fibers was done mainly in the mesencephalon of the dog using the fluorescent histochemical technique of Falck and Hillarp. The extensive DA neuron system was found to be located in the ventral and medial regions of the mesencephalon; the pars compacta of the substantia nigra, the area almost corresponding to the ventral tegmental area of Tsai (which consists of three groups, a caudal, the nucleus parabrachialis pigmentosus, a ventral, the nucleus paranigralis and a rostral, the caudal part of the nucleus tegmentalis ventralis of Tsai), the nucleus linearis of the raphe, and the mesencephalic reticular formation. The nigro-neostriatal projection can be traced in the non-treated or nialamide plus L-dopa treated puppies without the lesion-degeneration technique. Most fibers arising from these DA cell groups assemble at the prerubral area and ascend just dorsal to the medial forebrain bundle. Most fibers turn laterally at the lateral hypothalamus and enter the neostriatum via the dorsal part of the subthalamic nucleus, the zona incerta and the capsula interna. These findings show that the distribution of DA neurons and the nigro-neostriatal pathway are fundamentally similar to those in other mammals. In this study, the processes of the nigral and paranigral DA neurons have been demonstrated to project into the pars reticulata in the dog.

Echocardiographic measurement of aortic root diameter

One hundred and thirty patients with various heart diseases who underwent angiocardiography were studied to assess the clinical usefulness of echocardiographic aortic root diameter. The echocardiographic aortic root diameter was measured from the anterior surface of the anterior wall to the anterior surface of the posterior wall at end-diastole. A significant correlation was found between aortic root diameters measured by angiocardiograms and those by echocardiograms (r = 0.944, p less than 0.001). The aortic root diameter in normal subjects was 15 to 40 mm with a mean value of 29.0 mm. The corrected aortic root diameter by body surface area in normal subjects ranged from 10.1 to 29.5 mm/M2 with a mean value of 19.18 mm/M2. There appeared to be direct relationship between corrected aortic root diameter and the age. Echocardiography is a simple, safe, and reliable noninvasive method for estimating aortic root diameter.

[Inhibition of harmaline induced tremor by L-threo-3, 4-dihydroxyphenylserine, an L-norepinephrine precursor]

Effect of 3, 4-dihydroxyphenylserine (DOPS), a norepinephrine precurosr, on harmaline tremor was investigated in mice to elucidate the role of norepinephrine in the genesis of tremor. 1) Spontaneous motor activity was inhibited by L-threo-DOPS (200 mg/kg i.p.). 2) Tremor induced by harmaline (5 and 7 mg/kg i.p.) was enhanced by alpha-methyl-p-tyrosone (200 mg/kg i.p.). 3) The development and duration of tremor induced by harmaline (10 mg/kg i.p.) were inhibited significantly in a dose dependent manner by L-threo-DOPS (50, 70, 100, 150 and 200 mg/kg i.p.), but neither by D-threo-DOPS (200 mg/kg i.p.) nor DL-erythro-DOPS (200 mg/kg i.p.). 4) L-threo-DOPS (200 mg/kg i.-.) had no effect on the development of tremor induced by tremorine (5 and 10 mg/kg i.p.), while lacrimation and diarrhea caused by tremorine was markedly inhibited. 5) Administration of harmaline (10 mg/kg i.p.) produced an increase in brain 5-hydroxytryptamine content but not in that of norepinephrine. Administration of L-threo-DOPS (100 mg/kg i.p.) increased the norepinephrine content but not the 5-hydroxytryptamine content in the brain. Inhibition of harmaline tremor induced by L-threo-DOPS is attributed to the L-norepinephrine converted from L-threo-DOPS and the involvement of a noradrenergic mechanism in harmaline tremor has to be considered.

Histochemical mapping of catecholamine neurons and fiber pathways in the pontine tegmentum of the dog

The distribution of catecholamine-containing neurons and fiber pathways were studied in the dog's pontine tegmentum by the Falck-Hillarp method. There are fundamental similarities between the dog and other mammals. Most catecholamine fluorescent cell bodies in the dog are located within the nucleus locus coeruleus and subcoeruleus in the pontine tegmentum. They are more diffuse and extensive than in the rat, monkey and human, and rather similar to those of the cat. In this study, catecholamine fiber pathways were clearly traced without using the lesion-degeneration technique. The dorsal pathway from the locus coeruleus consists of more compact bundles of non-varicose fibers than the rat, cat and monkey. It runs parallel to the mesencephalic tract of the trigeminal nerve in pons and midbrain. The ventral pathway courses as loosely arranged varicose fibers in the midreticular formation of the pons and sends axon collaterals to the caudal midbrain to form a dense network of varicose fibers. There are fluorescent plexi of fine varicose fibers at the ventromedial and dorsolateral aspect of the superior cerebellar peduncle. Cells of the medial and lateral parabrachial nucleus, in addition to those of locus coeruleus, send fluorescent fibers to this peduncle. No fluorescent fibers are found in other peduncles.