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Biomedical subjects

A Niijima

Publications and source records attributed to A Niijima.

At least 55 records · Page 3Linked to original sources
PubMed1995

Involvement of cerebral neurotensin in hyperglycemic response caused by 2-deoxy-D-glucose in rats.

Previous studies have indicated that neurons containing a vasoactive intestinal polypeptide (VIP)-like immunoreactive substance (VIP neurons) in the suprachiasmatic nucleus (SCN) are involved in regulating glucose metabolism in rats. In this connection, it has been suggested that in rats, VIP neurons in the SCN have neurotensin (NT) receptors. To clarify the role of NT, we examined the effects of intracranial injection of NT and an NT-antagonist on the hyperglycemic response to intracranial injection of 2-deoxy-D-glucose (2DG) in rats. The hyperglycemic and hyperglucagonemic responses caused by intracerebroventricular injection of 2DG were significantly enhanced by intracerebroventricular co-injection of NT, but suppressed by co-injection of the NT-antagonist. Intraperitoneal injection of the NT-antagonist did not affect the hyperglycemic and hyperglucagonemic responses to 2DG. These results suggest that intracranial NT plays an endogenously enhancive role in the hyperglycemic and hyperglucagonemic responses caused by 2DG.

Animals↗
PubMed1995

The effect of interleukin-1 beta on the efferent activity of the vagus nerve to the thymus.

The effects of intravenous (i.v.) administration of recombinant human interleukin-1 beta (rhIL-1 beta) and human interleukin-1 beta-fraction (hfrIL-1 beta) on the activity of vagal efferent fibers innervating the thymus were observed in urethane-anesthetized rats. An i.v. injection of 10 ng rhIL-1 beta or hfrIL-1 beta caused a similar degree of increase in the efferent activity, which lasted longer than 2 h. The least effective dose was 1 ng and dose-dependent responses were observed after i.v. injection of rhIL-1 beta at doses of 1 ng, 10 ng and 100 ng. The IL-1 beta-induced activation of efferent activity of the vagal branch to the thymus implicates their involvement in the neural modulation of the thymic function.

Animals↗
PubMed1995

An electrophysiological study on amino acid sensors in the hepato-portal system in the rat.

The existence of amino acid sensors sensitive to arginine, alanine, leucine and glycine in the hepato-portal region was previously reported based on recording of the afferent signals from the hepatic branch of the vagus nerve. The present study was carried out to investigate the effects of fifteen different amino acids on the activity of the vagal hepatic afferents. Intraportal administration (10 mM, 0.1 mL) of alanine, arginine, histidine, leucine, lysine, serine, tryptophane and valine increased vagal afferent discharge rate, and that of cysteine, glycine, isoleucine, methionine, phenylalanine, proline and threonine suppressed it. The results indicate the existence of two groups of amino acids sensors which exhibit excitatory or inhibitory effect on the afferent activity of the hepatic branch of the vagus nerve. The change in afferent activity to the hypothalamus may affect reflex regulation of the visceral functions and thereby influence appetite.

Afferent Pathways↗
PubMed1995

An electrophysiological study on the vagal innervation of the thymus in the rat.

Vagal innervation of the thymus was studied by means of electrophysiological technique in the rat. Under urethane anesthesia, evoked action potentials originated from cervical vagus by electrical stimulations were recorded from the central cut end of the thymic branch of the vagus nerve after averaging for 32 times. It was observed that the conduction velocities are distributed in the range of 0.56-6.84 m/s, and the majority of vagal fibers in the thymic branch of the vagus nerve belong to a nonmyelinated C-fiber group. Further, it was confirmed that the right and left lobes of the thymus are innervated by cervical vagi bilaterally. The results suggest that the thymic branch of the vagus nerve plays a role in modulation of thymic function.

Anesthesia, Local↗
PubMed1995

Effects of arginine-lysine mixture, glucose and ATP on the autonomic outflows to the thymus and spleen.

Effect of arginine-lysine mixture, glucose and ATP on the efferent activities of the vagal thymic branch and splenic nerve were studied in urethane anesthetized rat. In male Wistar rats jugular vein was cannulated for drug administration. In one group the thymus was exposed and a nerve filament of the central cut end of vagal thymus was isolated. In another group a filament was isolated from that of the splenic nerve. The nerve filament was placed on electrodes to record efferent activity before and after administration of argininelysine mixture solution, glucose or ATP solution. Enhancement of efferent activity of vagal thymic nerve was observed after i.v. administration of arginine-lysine mixture, glucose and ATP solution. Suppression in efferent activity of splenic nerve was investigated following i.v. administration of arginine-lysine mixture, glucose and ATP solution. These results suggest that i.v. arginine-lysine, glucose and ATP increase thymic lymphocyte release, and that i.v. arginine-lysine, glucose and ATP enhance NK cell activity.

Adenosine Monophosphate↗
PubMed1994

A unique receptor-mediated mechanism in vagal chemoreception of somatostatin in the hepatoportal area.

Our previous results have indicated that the hepatic vagus is receptive to intraportal appearance of somatostatin-14 (SS), a gastroenteropancreatic peptide hormone, in rat. To examine the actual involvement of the SS receptor mechanism in the neural reception, the receptor function was modified with monoclonal antibody against rat neural SS receptor. Our monoclonal antibody of IgG1(kappa) isotype bound to the SS binding site of the receptor in competition with the ligand. Intraportal SS injection at a physiological dose (3.05 pmol) significantly facilitated the afferent firing discharge rate of the hepatic vagus in rats anesthetized with urethane and chloralose. The antibody ascites, but not the control ascites, administered intraportally 5 min prior to the SS injection abolished completely the SS-induced increase in discharge rate. However, when the antibody was administered more than 15 min after the SS injection, the SS-induced increase in discharge rate did appear, implying an unique post-receptor mechanism in reception. The present results indicate that the SS receptor mechanism operates in the neurochemoreception of SS, suggesting the existence of a hepatic vagal, receptor-mediated system for monitoring the hormone secreted from the splanchnic organs.

Afferent Pathways↗
PubMed1994

Circadian rhythms and energy metabolism with special reference to the suprachiasmatic nucleus.

The role of the hypothalamic suprachiasmatic nucleus (SCN) was examined in rats and obtained following results: (a) The time-dependent (light > dark) hyperglycemic response to intracranial injection of 2-deoxy-D-glucose (2DG) disappeared in rats with bilateral lesions of the SCN, in rats on weeks 4-6 after surgical blinding, and in congenitally blind (hereditary microphthalmic) rats; (b) The hyperglycemia induced by electrical stimulation of the SCN was not observed in weeks 4-8 after surgical blinding; (c) Change in the blood glucose concentration after insulin injection into the SCN was eliminated by SCN lesions; (d) Alterations in activity of autonomic efferents to peripheral organs on light exposure disappeared after SCN lesions; (e) SCN lesions decreased the blood glucagon level and increased the blood insulin level; (f) SCN lesions decreased protein intake, and glucagon increased it; (g) Increases in the plasma renin activity and vasopressin concentration after water-deprivation were suppressed in hereditary microphthalmic rats with abnormal SCN. These findings suggest that the SCN is involved in the mechanism of blood glucose and body fluid intake as well as that of circadian rhythm.

Animals↗
PubMed1994

The effects of lithium chloride on the activity of the afferent nerve fibers from the abdominal visceral organs in the rat.

The effect of lithium chloride on the activity of the afferent nerve fibers from the abdominal organs was studied in anesthetized rats. The administration of the lithium chloride solution (0.15 M) over the mesentery increased afferent discharge rate of the splanchnic and vagal gastric nerve. Injection of the same solution into the portal vein caused an increase in afferent activity of the vagal hepatic nerve. Further, infusion of the same solution into the duodenum resulted in facilitation of the afferent activity of the splanchnic as well as vagal celiac nerves. The results may explain the mechanism played by lithium chloride as unconditioned stimulus in the conditioned taste aversion paradigm.

Abdomen↗
PubMed1994

Parenteral nutrients in rat suppresses hepatic vagal afferent signals from portal vein to hypothalamus.

BACKGROUND: Parenteral nutrition (PN) suppresses spontaneous food intake in rats by stimulating dopamine in lateral hypothalamic area (LHA), which is attenuated by vagotomy. Sensors for glucose and for some individual amino acids exist in hepatoportal areas sending signals via hepatic vagal afferents to LHA. Hypothesizing that the decrease in spontaneous food intake occurs because a PN amino acid solution is recognized by portal vein sensors, we measured afferent nerve discharges in hepatic vagus in response to PN. METHODS: Hepatic vagus was divided in 11 rats, and an isolated nerve filament was placed on recording electrodes. Afferent firing rate was recorded before and after injecting during 1 minute a well-balanced crystalline amino acid mixture into either the portal or peripheral vein. Isotonic glucose was used as standard solution. RESULTS: A significant decrease in hepatic vagal afferent discharge rate was recorded after both intraportal and intravenous injection of the PN amino acid mixture. The mean discharge rate was inversely related to the concentration of the solution. Successive injections produced further decreases in discharge rate, and the effect was more sustained. CONCLUSIONS: The observed decrease in discharge rates suggests that the crystalline amino acid PN solution is sensed in hepatoportal areas informing LHA via hepatic afferents. This effect may play a role in regulating food intake during PN.

Afferent Pathways↗
PubMed1993

Glycine sensor in the hepato-portal system and their reflex effects on pancreatic efferents in the rat.

We earlier reported the existence of vagal arginine, alanine, and leucine sensors in the liver which modulate amino acid-induced pancreatic hormone secretion. To determine the possible existence of glycine sensors in the liver and their reflex effects, afferent discharges from the hepatic branch and efferent discharges from the pancreatic branch of the vagus nerve were recorded. Intraportal administration of 0.1, 1, and 10 mM of L-glycine solution (0.1 ml) depressed the afferent discharge rate of the hepatic branch of the nerve in a dose-dependent manner, and increased the efferent discharge rate of the pancreatic vagal branch. The results suggest the existence of glycine sensors in the hepato-portal system that exert reflex regulation on the pancreatic vagus nerve activity.

Animals↗
PubMed1993

Hepatic glucose-sensitive unit regulation of glucose-induced insulin secretion in rats.

Vagal glucose receptors, or glucose-sensitive units which modulate insulin secretion, exist in the liver. This study sought to determine the pathway of portal glucose-sensitive unit-regulated insulin secretion by measuring plasma insulin after intraperitoneal (IP) injection of glucose under unanesthetized and unrestrained conditions (Experiment 1), and by recording electrical discharge after intraportal injection of glucose (Experiment 2) in rats with hepatic and/or celiac vagotomy. In Experiment 1, plasma insulin was significantly reduced and plasma glucose elevated after IP glucose injection (1 g/kg) in the three groups of hepatic-, celiac-, and hepatic- and celiac-vagotomized rats in comparison with a sham-vagotomized group. There were no significant differences among the four groups in plasma insulin or glucose after IV glucose injection (0.5 g/kg). In Experiment 2, intraportal injection of 400 mg/dl of glucose solution, a similar concentration to that produced by 1 g/kg of IP glucose injection, caused a reduction in the discharge rate of hepatic vagal afferents and an increase in that of pancreatic vagal efferents. This increase was blocked by prior sectioning of the hepatic branch of the vagus nerve. These results suggested that hepatic glucose-sensitive units enhanced glucose-induced insulin secretion via the hepatic vagal afferents and the pancreatic vagal efferents mediated by the brain stem center in vivo. The physiological role of these hepatic glucose-sensitive units is assumed to maintain blood glucose homeostasis by enhancing glucose-induced insulin secretion.

Afferent Pathways↗
PubMed1993

Effects of light stimulation on the activity of the autonomic nerves in anesthetized rats.

The existence of the retino-hypothalamic pathway suggests that light stimulation may influence the activity of the autonomic outflows. Efferent activities of the pancreatic, hepatic, and gastric branches of the vagus nerve and those of pancreatic, hepatic, splenic, adrenal, and renal branch of the splanchnic nerve were recorded. Light stimulation with 2000 1x for 10 min to the left eye increased the splanchnic (sympathetic) outflows and suppressed the vagal outflows. The effects lasted for several hours. The minimal effective stimulation was 20 1x for 1 min or 200 1x for 0.1 min. These responses were observed in the light period as well as dark period. However, in the suprachiasmatic nucleus (SCN) lesioned rat, the changes in autonomic outflows following light stimulation were absent. The observations suggest that light stimulation modulates visceral functions through changes in the autonomic nervous system activities via the SCN.

Animals↗
PubMed1993

Effect of Pinellia ternata tuber on the efferent activity of the gastric vagus nerve in the rat.

Effect of intraduodenal infusion with the hot aqueous extract of Pinellia ternata tuber on the efferent discharges in the gastric branch of the vagus nerve was observed in the anesthetized rat. The infusion of the extract in doses of 2-15O mg per animal (c.a. 300 g, b.wt.) resulted in a dose-related increase in efferent activity of the vagal gastric nerve. The enhancement of the nerve activity following administration of 150 mg of this substance lasted longer than 90 min. It was observed that the suppressive effect on vagal gastric activity due to apomorphine and copper sulfate was antagonized by prior administration of the extract. From these observations it is suggested that Pinellia tuber acts as a facilitatory agent on gastric function.

Animals↗
PubMed1992

Light enhances sympathetic and suppresses vagal outflows and lesions including the suprachiasmatic nucleus eliminate these changes in rats.

Neurons in the suprachiasmatic nucleus (SCN) are suggested to be involved in the mechanism of glucose homeostasis. This mechanism was examined by studies on the effect of illumination on the activity of autonomic efferents to the adrenals, pancreas and liver. Exposure of one eye of anesthetized rats to light enhanced the efferent activity of the adrenal nerve and suppressed that of vagal pancreatic and hepatic nerves. No change in efferent activities of these nerves was observed on light-stimulation of rats with lesions that included the bilateral SCN. These findings indicate that light signals modulate visceral functions including metabolic processes through the retinohypothalamic tract probably via the SCN to autonomic efferent pathways innervating visceral organs.

Adrenal Glands↗
PubMed1992

Electrophysiological study on the vagal innervation of the adrenal gland in the rat.

Action potentials evoked by stimulation of the ventral or dorsal subdiaphragmatic vagal nerve trunks were recorded from the adrenal branch of the splanchnic nerve in the urethane-anesthetized rat. Action potentials were clearly demonstrated after averaging over 50 times by a computer. In some experiments action potentials evoked by stimulation of the adrenal branch of the splanchnic nerve were observed in the celiac branch of the vagus nerve. The observations indicate the existence of a nervous pathway from the ventral and dorsal subdiaphragmatic vagus nerve to the adrenal gland, and the conduction velocities (0.32-0.91 m/s) suggest that the majority of the nerve fibers belong to the non-myelinated C-fiber group.

Action Potentials↗
PubMed1991

Effects of oral and intestinal stimulation with umami substance on gastric vagus activity.

Oral or intestinal stimulation with isotonic MSG solution caused an increase in discharge rate of the gastric branch of the vagus nerve. However, stimulation with physiological saline was without effect. The observations indicate that the oral or intestinal administration of MSG stimulates taste receptors in the tongue or amino acid receptors (MSG receptors) in the intestine which results in activation of the gastric branch of the vagus nerve, and explain the mechanism of reflex activation of gastric function originated by the ingestion of umami substance such as MSG.

Administration, Oral↗
PubMed1991

The effects of interleukin-1 beta on the activity of adrenal, splenic and renal sympathetic nerves in the rat.

The effects of intravenous (i.v.) administration of recombinant human interleukin-1 beta (rhIL-1 beta) on the activity of adrenal, splenic and renal sympathetic nerves were observed in urethane-anesthetized rats. An i.v. injection of IL-1 beta in doses of 10 pg-20 ng per animal (300-400 g, b.w.) resulted in a dose-dependent increase in the activity of the adrenal and splenic nerves, which lasted for more than 2-6 h. On the other hand, the activity of renal nerves showed a transient increase which was followed by a long-lasting suppression after injection of rhIL-1 beta (100 pg, i.v.). An i.v. injection of cyclooxygenase inhibitors (6 mg ibuprofen or 20 mg sodium salicylate) suppressed almost completely the rhIL-1 beta (100 pg)-induced activity in adrenal and splenic nerves. Although rhIL-1 beta (100 pg, i.v.) produced a fall in arterial blood pressure, baroreceptor denervation did not affect the excitatory responses of the adrenal and splenic nerves to rhIL-1 beta. The results suggest the regional differentiation of activity in the visceral sympathetic nerves in response to rhIL-1 beta. The rhIL-1 beta-induced activation of splenic sympathetic nerves implicates their involvement in the modulation of immunity by brain.

Adrenal Glands↗