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Biomedical subjects

A Niijima

Publications and source records attributed to A Niijima.

At least 73 records · Page 4Linked to original sources
PubMed1991

Noxious and innocuous mechanical cutaneous stimulation increase the sympathetic efferent nerve activity innervating the interscapular brown adipose tissue in anesthetized rats.

Effects of pinching and brushing of the various segmental skin areas (face, ear, neck, forelimb, chest, abdomen, hindlimb) on the activities of the sympathetic efferent nerve innervating the interscapular brown adipose tissue (IBAT) and contributing to its thermogenesis were examined in anesthetized rats. Pinching the face, ear, neck, or forelimb produced significant reflex increases in the efferent nerve activities, whereas pinching the chest, abdomen, or hindlimb did not produce any significant responses. In the case of brushing stimulation, only the stimulation of the ear produced significant increases. These results demonstrated that cutaneous mechanical stimulations at cranial, cervical, and upper thoracic segments were effective in producing reflex increases in the activities of the IBAT sympathetic nerve and that noxious stimulation was more dominant for eliciting the reflex responses.

Adipose Tissue, Brown↗
PubMed1991

Effects of stress and hypophysectomy on distribution of [3H]leucine in the mouse adrenal medulla.

Effect of stress and hypophysectomy on the distribution of [3H]leucine in the adrenal medulla of mice was examined by autoradiography. [3H]Leucine-derived radioactivity in adrenaline-storing (A) cells of the medulla was remarkably increased by immobilization with water immersion stress. The increase was prevented by adrenal denervation. Adrenal denervation itself reduced [3H]leucine incorporation by A cells. Hypophysectomy also reduced the amount of [3H]leucine in A cells. Although changes in noradrenaline-storing (NA) cells were not statistically significant, they were in the same direction as the changes observed in A cells. Present results showed that neural activity exerts trophic influence on leucine incorporation by adrenal chromaffin cells. Basal pituitary adrenocortical activity seems to be necessary for leucine incorporation in chromaffin cells.

Adrenal Glands↗
PubMed1991

Effects of taste stimulation on the efferent activity of the pancreatic vagus nerve in the rat.

The effect of taste stimulation on the efferent discharges in the pancreatic branch of the vagus nerve was studied in anesthetized rats. An increase in discharge rate following taste stimulation with 10% sucrose over the tongue for 5 or 3 min, and a decrease of it following an application of 5% NaCl for the same duration were observed in normal as well as in decerebrated rats. It was further observed that local anesthesia of the surface of the tongue blocked the reflex response originated by taste stimulation. The results indicate the existence of gustatory vago-pancreatic reflex which plays an important role for cephalic phase secretion.

Animals↗
PubMed1991

Effects of taste stimulation on the efferent activity of the autonomic nerves in the rat.

Effects of taste stimulation on the efferent discharges in the pancreatic and hepatic branch of the vagus nerve, and those in the adrenal, pancreatic and hepatic branch of the splanchnic nerve, and the sympathetic nerve innervating interscapular brown adipose tissue, were observed in the anesthetized rat. Sweet taste stimulation with 5% glucose or 10% sucrose caused an increase in activity of pancreatic and hepatic branch of the vagus nerve and brown adipose tissue nerve, and a decrease in discharge rate of the adrenal, pancreatic and hepatic branch of the splanchnic nerve. Salty taste stimulation with 5% NaCl resulted in opposite effects in these nerves. Results suggest preabsorptive reflex control of visceral functions due to taste stimulation.

Adipose Tissue, Brown↗
PubMed1990

Cephalic-phase insulin release induced by taste stimulus of monosodium glutamate (umami taste).

In order to confirm the effect of umami taste stimulation on visceral functions, blood insulin and glucose assays and an electrophysiological study were performed on the rat. Blood insulin and glucose assays were carried out in conscious and free-moving rats. When the oral cavity was infused by MSG solution, a transient increase in blood insulin level was recognized at 3 min after this oral stimulation. The electrophysiological study revealed that applications of monosodium glutamate (MSG) glucose to the tongue in the anesthetized rat caused an increase in efferent activity of the pancreatic branch of the vagus nerve. These observations support the conclusion that taste stimulation of MSG induces cephalic-phase insulin secretion.

Animals↗
PubMed1990

Amino acid sensors sensitive to alanine and leucine exist in the hepato-portal system in the rat.

We reported the existence of vagal arginine sensors in the liver which modulate arginine-induced pancreatic hormone secretion. The present study was carried out to examine the possible existence of other amino acid sensors such as L-alanine and L-leucine in the hepato-portal system in rats using an electrophysiological approach. Afferent discharges were recorded from fine filaments dissected from the peripheral cut end of the hepatic branch of the vagus nerve. Administration of 0.1, 1, and 10 mM L-alanine and L-leucine solution (0.1 ml) into the portal vein caused an increase in the discharge rate of hepatic vagal afferents in a dose-dependent manner. The results suggest the existence of vagal amino acid sensors which are sensitive to alanine and leucine in the hepato-portal system.

Alanine↗
PubMed1989

Uptake of [3H]dopamine in the mouse adrenal medulla during dark and light period.

Uptake of exogenous [3H]dopamine in adrenal chromaffin cells of the mouse was studied by autoradiography under a 12-h light, 12-h dark cycle. The uptake of [3H]dopamine in adrenal chromaffin cells was markedly decreased in the dark period. The decrease was prevented by adrenal denervation. It is postulated that there is a neurally mediated suppression of [3H]dopamine uptake by adrenal chromaffin cells in the dark period. Adrenaline-storing (A) cells are more sensitive to the decreased sympathetic activity than noradrenaline-storing (NA) cells while increased sympathetic activity non-selectively affects both types of adrenal chromaffin cells.

Adrenal Medulla↗
PubMed1989

Nervous regulation of metabolism.

As described previously, the regulatory roles played by the autonomic nervous system on blood glucose homeostasis is well documented in comparison with those on fat and protein metabolism. It can be summarized as follows: It was shown that an increase in blood glucose concentration produced an increase in the activity of the pancreatic branch of the vagus nerve whereas it induced a decrease in the activity of the pancreatic branch of the splanchnic nerve and adrenal nerve. It was also shown that a decrease in blood glucose concentration activated the sympatho-adrenal system and suppressed vago-pancreatic system. It seems rational that these responses are involved in the maintenance of blood glucose level. Studies on the innervation of the liver led us to a conclusion that sympathetic innervation of the liver plays a role in eliciting a prompt hyperglycemic response through liberation of norepinephrine from the nerve terminals, and that the vagal innervation synergically worked with the humoral factor (insulin) for glycogen synthesis in the hyperglycemic condition. The glucose-sensitive afferents from the liver seem to initiate a reflex control of blood glucose level. The gustatory information on early insulin response (EIR), reported by Steffens (1976), is supported by the electrophysiological observations. Mei's reports (1981) also indicated the importance of information from the intestinal glucoreceptors in the reflex control of insulin secretion via the vagus, which has been proved electrophysiologically. The role of integrative function of the hypothalamus and brainstem through neuronal networks on neural control of blood glucose homeostasis is evident. On the neural control of fat metabolism, it is evident that the sympathetic outflows to the brown adipose tissue as well as white adipose tissue predominantly play important roles. However, there is still little information on the central mechanism played by the hypothalamus on the fat metabolism and the neural pathways from the hypothalamus to the sympathetic motoneurons innervating adipose tissues. The reports on the neural control of protein metabolism are very few. Only several studies were reported on the liver function in relation to the protein metabolism. Further extensive studies should be expected.

Adipose Tissue↗
PubMed1989

Neural mechanisms in the control of blood glucose concentration.

Recent studies of sensory signals from the visceral areas have enhanced our understanding of mechanisms that control blood glucose levels. The activity of efferent fibers to the pancreas, liver, and adrenal medulla is modulated by both central glucose-responsive neurons and peripheral (gustatory, intestinal and hepatic) glucose sensors. It is well known that induction of hyperglycemia facilitates efferent activity of the pancreatic and hepatic branches of the vagus nerve. This in turn increases insulin secretion from the pancreas and glycogen synthesis in the liver. Hypoglycemia activates efferent activity of the pancreatic, hepatic and adrenal branches of the splanchnic nerve, and this results in increased glucagon secretion from the pancreas, release of glucose from the liver and secretion of catecholamines from the adrenal medulla. Glucose-responsive neurons in the hypothalamus and medulla oblongata may be involved in the modulation of this autonomic efferent activity.

Adrenal Medulla↗
PubMed1989

The effect of rANP on the efferent activity of the autonomic nerves.

It is well known that the Atrial Natriuretic Peptide (ANP) plays a major role in vasorelaxation and in lowering systolic blood pressure. However, little information is available concerning its effect on the autonomic outflows. The present study deals with the effect of rat ANP (rANP) on the efferent activity of the sympathetic and vagal outflows. Under anesthesia (urethane 700 mg/kg and chrolarose 50 mg/kg, intraperitoneal), the effect of intravenous administration of rANP was observed in rats. A suppression of the efferent activity was recognized after administration of rANP in adrenal, renal and splenic sympathetic nerve fibers, and also in vagal gastric, pancreatic and hepatic nerve fibers. The smallest effective dose was 100 pg. In decerebrated preparations no change in efferent activity after administration of rANP was recognizable. The results indicate that rANP released from the atrium to systemic circulation modulates autonomic outflows through the hypothalamic neurons surrounded by an insufficient blood brain barrier.

Adrenal Glands↗
PubMed1989

[Nervous mechanisms in the regulation of blood sugar].

The aim of this paper is to precise the involvement of the nervous system in blood glucose regulation. The relevant mechanisms, triggered by blood glucose changes (increase or decrease of glycemia), intervene through the control of pancreatic and surrenal hormone release on the one hand, and hepatic glucose synthesis on the other hand. The part of various efferents and afferents, sensory endings and central "glucosensitive" neurons was analyzed in different situations. 1) Hyperglycemia increases the activation of the pancreatic parasympathetic fibres and decreases that of the surrenal sympathetic fibres. Hypoglycemia elicits reverse effects in the two types of efferents. 2) Hyperglycemia produces an activation in hepatic efferent vagal fibres and thus an acceleration of glycogen synthesis. Reversely, hypoglycemia stimulates both the hepatic sympathetic efferents and the glucose release by the liver. 3) The gustative receptors and the gastro-intestinal glucoreceptors are stimulated by glucose, which produces an insulin release. 4) The various kinds of afferents modify the efferent control of blood glucose level, through the "glucosensitive" central neurons located in hypothalamic and medullary regions.

Animals↗
PubMed1988

The effect of endogenous sugar acids on the afferent discharge rate of the hepatic branch of the vagus nerve in the rat.

The effects of intraportal administration of endogenous sugar acids such as 2DTA, 3DPA and 2B40 on afferent activity of the hepatic branch of the vagus nerve were investigated in the rat. A decrease in afferent discharge rate was observed after administration of 2DTA (0.1 mM approximately 10 mM, 0.1 ml) and 2B4O (100 nM approximately 2 microM, 0.1 approximately 0.2 ml), whereas 3DPA (0.1 mM approximately 10 mM, 0.1 ml) increased the afferent activity. These observations suggest that 2DTA and 2B4O suppress, and 3DPA enhances food intake behavior and may be important in the regulation of blood glucose homeostasis through glucose-sensitive vagal hepatic afferent fibers.

4-Butyrolactone↗
PubMed1988

Effects of stimulation of the hypothalamic paraventricular nucleus on blood pressure and renal sympathetic nerve activity.

Effects of electrical and chemical stimulation of the paraventricular nucleus (PVN) of the hypothalamus on blood pressure were examined in rats anesthetized with urethane-chloralose. Focal electrical stimulation (10-25 microA, 50 Hz, 0.5 msec) within the PVN consistently decreased blood pressure. Microinjection of L-glutamate (0.5 M, 80 n1) into the PVN led to a decrease in blood pressure, while the same amount of saline injection had no effect. The depressor response was not affected by cervical vagotomy. In order to obtain direct evidence for involvement of sympathetic nerve activity in the PVN-induced depressor response, effects of PVN stimulation on renal sympathetic nerve activity were examined. Low intensity electrical stimulation of the PVN inhibited renal sympathetic nerve activity, whereas the high intensity stimulation evoked a transient excitation followed by long lasting inhibition in renal sympathetic nerve activity. Latencies of the inhibitory and the excitatory responses were about 200 msec and 50-100 msec, respectively, judged by peristimulus time histograms. The result suggests that activation of PVN neurons produces a decrease in blood pressure due to inhibition of sympathetic outflows.

Adrenergic Fibers↗
PubMed1988

Neural control of blood glucose homeostasis; effect of microinjection of glucose into hypothalamic nuclei on efferent activity of pancreatic branch of vagus nerve in the rat.

Efferent discharges were recorded from the nerve filament dissected from the central cut end of the pancreatic branch of the vagus nerve in the rat. Microinjections of 5% glucose solution (100-200 nl) into the LHA caused an increase in efferent activity, however, those into VMH caused no change in discharge rate. The results of experiments indicate that activation of vagal pancreatic efferents in hyperglycemic situation is originated in LHA and transmitted to the vagal pancreatic motoneurons. The role played by the neural network on blood glucose homeostasis was also discussed.

Action Potentials↗
PubMed1988

Lateral and ventromedial hypothalamic influences on hepatic autonomic nerve activity in the rat.

Effects of hypothalamic stimulation and lesion on hepatic autonomic nerve activity were investigated in anesthetized rats. Stimulation of the lateral hypothalamic area increased activity of the hepatic vagal nerve and decreased activity of the splanchnic nerve. Lesion of this area produced a rapid and strong reduction of vagal nerve activity and induced either an increase or a decrease of splanchnic nerve activity. In contrast, stimulation of the ventromedial hypothalamic nucleus produced a strong inhibition of vagal nerve activity and facilitation of splanchnic nerve activity. However, lesion of this nucleus facilitated or inhibited activities in both nerve branches. The functional significance of the relationship between the hypothalamus and the hepatic autonomic nerve in regulation of glucose metabolism in the liver are discussed.

Animals↗
PubMed1987

Effect of copper sulphate on the rate of afferent discharge in the gastric branch of the vagus nerve in the rat.

The afferent nerve activity was recorded from a nerve filament isolated from the peripheral cut end of the gastric branch of the vagus nerve. The gastric perfusion of 4 ml of two different concentrations (0.04% and 0.08%) of CuSO4 solution provoked an increase in afferent activity. The stimulating effect of the 0.08% solution was stronger than that of the 0.04% solution, and lasted for a longer period of time. The observations suggest a possible mechanism by which CuSO4 elicits emesis.

Animals↗