Daily exercise normalizes the number of diaphorase (NOS) positive neurons in the hypothalamus of hypertensive rats.

It is well known that nitric oxide (NO), within the paraventricular nucleus (PVN) of the hypothalamus, mediates sympatho-inhibition via an inhibitory GABA-ergic mechanism. Furthermore, the inhibitory GABA-ergic mechanism is impaired in the spontaneously hypertensive rat (SHR). These data suggest that the NO system, within the PVN, may also be impaired in the SHR. In addition, previous studies have documented that daily exercise attenuates the development of tachycardia, hypertension and blood pressure related cardiovascular disease risk factors in SHR. These data suggest that daily exercise enhances the inhibitory GABA-ergic and/or NO systems. Therefore, this study was designed to test the hypothesis that hypertension, in the SHR, is associated with a lower number of NADPH-diaphorase (a commonly used marker for neuronal NOS activity) positive neurons within the PVN and that daily exercise increases the number of NOS positive neurons. Using a standard histochemical protocol, NOS positive neurons were measured in the PVN, supraoptic nucleus, median preoptic area, lateral hypothalamus, nucleus of the tractus solitarius and rostral ventrolateral medulla. Results document that SHR have significantly fewer NOS-positive neurons in the PVN than their genetic control, the Wistar-Kyoto (WKY) rats (110+/-11 versus 139+/-17). Furthermore, daily exercise increased the number of NOS positive neurons in the SHR to levels seen in the WKY rats. These data demonstrate that hypertension, in the SHR, is associated with a lower number of NOS positive neurons within the PVN and that daily exercise increases the number of NOS positive neurons within the PVN.

Cytoarchitecture of the tectum opticum in the Japanese quail.

The cytoarchitecture of the optic tectum of the Japanese quail, Coturnix coturnix japonica, was studied using the Golgi-Kopsch method, parvalbumin, calbindin and GABA immunohistochemistry and nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry. Our results reveal a large number of different types of interneurons in the quail tectum opticum, only part of which are described in the chick or pigeon. Application of parvalbumin and calbindin immunohistochemistry and nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry reveals the following lamination pattern: The stratum opticum, stratum griseum centrale and stratum album centrale remain unstained, while the laminae of the stratum griseum et fibrosum superficiale exhibit a roughly complementary staining pattern of calbindin (laminae c, d, e, f, g, i) and parvalbumin (laminae a, h, i). Nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry yields a dense band in lamina i. The Golgi material reveals the following cell types in the stratum griseum et fibrosum superficiale: marginal cells in the stratum opticum and in lamina h and i, horizontal cells in laminae a and c, large and small radial cells in laminae b, d, h and i, multiform cells in lamina b, bitufted cells in lamina d and e, large pear-shaped cells in lamina g, wide-field cells in lamina j, and stellate cells in lamina j and in the stratum griseum centrale. We consider horizontal cells, bitufted cells, multiform cells and small radial cells to be GABAergic interneurons of the stratum griseum et fibrosum superficiale which seem to be more numerous than in the pigeon tectum opticum. Golgi impregnation and injection of Phaseolus vulgaris leucoagglutinin into the pretectal nucleus lentiformis yielded regularly distributed clusters of telodendra of pretectal axons in lamina d of the stratum griseum et fibrosum superficiale, which are identical in shape and position with axon plexus revealed by Golgi staining.

Nitric oxide synthase in the adult and developing thalamus: histochemical and immunohistochemical study in the rat.

The distribution of neuronal elements that express nitric oxide synthase (NOS), the synthetic enzyme of the free radical nitric oxide, was investigated in the adult and developing rat thalamus by means of NADPH-diaphorase (NADPH-d) histochemistry, which is a marker of NOS. Immunocytochemistry was also used to confirm the equivalence between the histochemical pattern of staining and the distribution of the expression of the neuronal NOS isoform. In the adult thalamus, NADPH-d-positive and NOS-immunoreactive perikarya were selectively concentrated along the midline (in the paraventricular, rhomboid, and central medial nuclei) and in the dorsal and ventral lateral geniculate nuclei. Isolated clusters of stained neurons were also observed in the lateral posterior nucleus, in the dorsal part of the medial geniculate nucleus, and in the ventromedial nucleus. Positive perikarya were either absent or very sparse in the other thalamic nuclei. Many thalamic domains were, however, characterized by distinct patterns of NADPH-d-positive fibers, preterminal and terminal-like elements. The highest density of stained neuropil was observed in the anteroventral and anteromedial nuclei, in several of the midline nuclei, in the anterior intralaminar nuclei, and in the lateral and medial geniculate nuclei. Although histochemical reactivity was observed in the thalamus at birth, the intensity and the pattern of distribution of staining observed in adulthood was not achieved until the end of the third postnatal week. The NADPH-d histochemical positivity followed discrete developmental schedules in various thalamic domains, and different areas reached a mature pattern at different ages. In addition, populations of transiently stained neuronal cell bodies were observed in the medial thalamus during the first two postnatal weeks. These results show discrete patterns of expression of NOS in the adult and developing thalamus and suggest that nitric oxide may be involved in selected physiological and developmental roles in different thalamic domains.

Properties of "possibly" cholinergic neurons ascending from the rat ponto-mesencephalic area: comparison with noradrenergic and serotonergic neurons.

In urethane-anesthetized rats single neuronal activity was recorded in the laterodorsal tegmental nucleus, which has a dense complement of cholinergic neurons. In many experiments neuronal activity was recorded also in the dorsal raphe and locus coeruleus for comparison. In each experiment two to five active sites were marked with pontamine sky blue, deposited from the recording electrode ionophoretically and located histologically. Most neurons of the laterodorsal tegmental nucleus responded antidromically to stimulation of either one or more of the following sites: medial frontal cortex, medial septal nucleus, lateral geniculate nucleus or superior colliculus. Conduction velocities of their axons, estimated from latencies of antidromic responses, were within the range of unmyelinated fibers. Most of them gave rise to broad spikes (positive stroke, greater than 1.0 msec; negative stroke, greater than 3.0 msec), resembling monoaminergic neurons. Others generated brief spikes (positive and negative strokes, less than 0.8 and less than 2.2 msec). The former are probably cholinergic. Some neurons in the laterodorsal tegmental nucleus had rather regular spontaneous firing at a low rate (0.2-5 Hz), while others were not spontaneously active. Their response to noxious stimulation (tail pinch) was different from neuron to neuron, but that most frequently encountered was limited to phasic excitation, in contrast to locus coeruleus neurons which showed phasic excitation followed by mild tonic excitation; and to dorsal raphe neurons likely to be suppressed. Upon repetition of tail pinch the response of laterodorsal tegmental nucleus neurons tended to become weak or disappear while a desynchronized pattern continued to appear in the EEG in each occasion. Thus, putative cholinergic neurons, which constitute a major group in the laterodorsal tegmental nucleus, have properties similar to those of monoaminergic neurons, except for the phasic and decrementing nature of their response to tail pinch. The cholinergic, noradrenergic, and serotonergic ascending projections seem likely to subserve different roles in regulating activity of the forebrain.

Comparative mapping of acetylcholinesterase and reduced nicotinamide adenine dinucleotide diaphorase in the rabbit dorsal thalamus.

The distribution of acetylcholinesterase and reduced nicotinamide adenine dinucleotide (NADH) diaphorase enzymatic activities was mapped histochemically in the dorsal thalamus of the rabbit. A comparison of the resulting patterns helped in the histochemical delimitation of a number of nuclei, as well as in the detection of some subdivisions, that showed differential expression of these enzymes. It was observed that AChE and NADH diaphorase tend to appear in a complementary fashion in many dorsal thalamic neuropiles, so that intense activity of the one was accompanied by low activity of the other. However, coincident expression of both enzymes was also obtained in a small number of areas. The correlation of these patterns with other chemo-architectonic and hodologic data does not yet disclose an explanation of these regularities, which however suggest some functional significance.

Excess dietary methionine decreases indices of copper status in the rat.

Two groups (n = 5) of male weanling Wistar rats were housed individually and fed copper (Cu)-deficient (0.5 mg Cu/kg) diets either with or without methionine supplementation (18 g/kg) for 49 days. Plasma caeruloplasmin (EC 1.16.3.1) and erythrocyte superoxide dismutase (EC 1.15.1.1, CuSOD) activities were measured in blood. Tissue Cu levels and the activities of cytochrome c oxidase (EC 1.9.3.1, CCO) and CuSOD were measured in the heart and liver. Hepatic activities of the sulfhydryl-sensitive enzymes, creatine kinase (EC 2.7.3.2), fumarase (EC 4.2.1.2) glutathione S-transferase (EC 2.5.1.18) and lipoamide dehydrogenase (EC 1.6.4.3) were also measured. Apart from cardiac CCO activity all of the measured indices of Cu status were found to be significantly (p less than 0.05) decreased in the methionine supplemented rats. Although fumarase activity was significantly (p less than 0.05) decreased in the methionine-supplemented animals compared with controls, the activities of the other sulfhydryl-sensitive enzymes were not significantly decreased. These results suggest that some of the toxic effects of excess dietary methionine may be mediated through interference with copper metabolism rather than through the previously postulated inhibition of sulfhydryl-sensitive enzymes by metabolites of methionine.