Reflex control of cardiac sympathetic nerve activity in anesthetized rats.

Reflex control of sympathetic outflow to the heart was evaluated by recording the efferent discharges of the interior cardiac sympathetic nerves in anesthetized rats. The reflex responses of inferior cardiac sympathetic nerve activity (ICNA) to arterial baroreceptor loading by phenylephrine and to arterial/atrial baroreceptor unloading by hemorrhagic hypotension were compared with those of renal sympathetic nerve activity (RNA) and adrenal sympathetic nerve activity (ANA). The reflex decrease in ICNA to the phenylephrine-induced graded increase in arterial blood pressure was smaller than that of RNA or ANA. Thus ICNA is less sensitive to arterial baroreceptor stimulation. Hemorrhage produced a volume-dependent decrease in ICNA. The response was significantly smaller than that in RNA and was directionally opposite to that in ANA. Cervical vagotomy but not sinoaortic denervation abolished the hemorrhage-induced ICNA response, suggesting an important role of vagal pathways. These findings demonstrate that the reflex responses of sympathetic outflow to the heart were quantitively and qualitatively different from those to the kidney and the adrenal gland, indicating the regional control of sympathetic nerve activity in the regulation of cardiovascular functions.

Endoscopic ultrasonographic-guided punctured pancreatic ductography: an initial and successful trial.

A 71-year-old male suffering from an intraductal papillary tumor of the pancreas was admitted to our hospital for further investigation. Diagnostic trials, including endoscopic retrograde pancreatography, did not produce an adequate ductography because of a large amount of mucinous fluid. Therefore, we performed endoscopic ultrasonographic-guided punctured pancreatic ductography (EPPD). This procedure was safely performed without any complications. We report this initial and successful trial of EPPD.

Modulation of norepinephrine release by serotonergic receptors in the rat hippocampus as measured by in vivo microdialysis.

The functional modulation of norepinephrine (NE) release by serotonergic receptors in the hippocampus of freely moving rats was studied by use of in vivo microdialysis. To stimulate NE release from the nerve terminals, a high concentration of potassium (K+, 120 mM) was added through the perfusion system. The K(+)-evoked NE release was inhibited in a concentration-dependent manner when serotonin (5-HT, 0.01-10 microM) was coperfused with K+. A selective 5-HT3 receptor agonist, 2-methyl-5-HT, mimicked the 5-HT response at a concentration of 0.01 to 10 microM. The 5-HT-induced (1 microM) inhibition of NE release was blocked by pretreatment with ondansetron (1 and 10 microM), a 5-HT3 receptor antagonist. On the other hand, K(+)-evoked NE release was also reduced by coperfusion with the 5-HT reuptake inhibitor, fluoxetine (10 microM), which caused increases in the dialysate 5-HT concentration. The fluoxetine-induced (10 microM) decreases in the K(+)-evoked NE release were prevented by serotonergic denervation caused by pretreatment with 5,7-dihydroxytryptamine (200 micrograms/rat i.c.v.). These results indicate that the inhibition on NE release by fluoxetine was due to increased synaptic concentrations of endogenous 5-HT. The fluoxetine-induced inhibitory effect was furthermore abolished by pretreatment with ondansetron (1 and 10 microM). These findings indicate the possibility that both exogenous and endogenous 5-HT inhibit NE release occurs from the rat hippocampus by 5-HT3 receptors. Thus, the present study suggests that the functional modulation of NE release by 5-HT3 receptors exists in vivo.

Acetylcholine measurement of cerebrospinal fluid by in vivo microdialysis in freely moving rats.

Acetylcholine (ACh) and choline (Ch) levels in rat cerebrospinal fluid (CSF) were determined by in vivo microdialysis (CSF microdialysis) in both halothane-anesthetized and freely-moving rats. The Ch/ACh ratio in CSF perfused with Ringer's solution (30 microliters/30 min) containing 10(-5) M physostigmine, a centrally active cholinesterase inhibitor, was significantly lower than that in unprocessed CSF due to significantly higher ACh levels in the former. The successive measurement on the 2nd and 7th day after the guide cannula implantation demonstrated the feasibility of the CSF microdialysis method for repetitive monitoring of CSF ACh and Ch levels in freely moving rats without extensive tissue damage. Intraperitoneal administration of physostigmine caused an increase in CSF ACh levels, whereas administration of neostigmine, which cannot penetrate into the blood brain barrier, did not. Furthermore, a centrally active acetylcholinergic M1-receptor agonist, AF102B, produced an increase in CSF ACh and Ch levels. Thus, the present study demonstrates that CSF microdialysis is a useful method for evaluating overall central cholinergic activity and investigating the pharmacological effects of various drugs that act via the central cholinergic system.

mu-Opioid receptors modulate noradrenaline release from the rat hippocampus as measured by brain microdialysis.

The modulation of noradrenaline (NA) release via presynaptic opioid receptors in the hippocampus of freely moving rats was studied by the use of brain microdialysis. Extracellular levels of NA were estimated by assaying its concentrations in the perfusion fluid using high-performance liquid chromatography (HPLC) with electrochemical detection (ECD). Spontaneous NA levels were reduced by tetrodotoxin (1 microM) co-perfusion and were increased by peripheral administration of desipramine (5 and 10 mg/kg, i.p.). Addition of potassium (K+, 60 and 120 mM) to the perfusion fluid evoked a concentration-dependent release of NA. K+ (120 mM)-evoked NA release was markedly reduced by removal of calcium (Ca2+) from the perfusion fluid. These results indicate that both the spontaneous and the K(+)-evoked NA release measured by the use of brain microdialysis coupled with HPLC-ECD can be used as indices of neuronal release from the noradrenergic nerve terminals. A mu-opioid receptor agonist, morphine (0.01-10 microM), when co-perfused with K+ (120 mM), produced a reduction of K(+)-evoked NA release in a concentration-dependent manner. Neither co-perfusion with a high concentration of [D-Pen2, D-Pen5]-enkephalin (DPDPE) (10 microM), an agonist selective for delta-opioid receptors, nor with U-69593 (10 microM), an agonist selective for kappa-opioid receptors, modified the K+ (120 mM)-evoked release of NA. Morphine-induced (1 microM) inhibition of NA release was blocked by a mu-opioid receptor antagonist, naltrexone (3 and 9 mg/kg, i.p). Naltrexone by itself did not alter the spontaneous NA levels or the K(+)-evoked NA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of clonidine on serotonergic neuronal activity as measured by cerebrospinal fluid serotonin and its metabolite in anesthetized rats.

Clonidine-induced changes in the serotonergic neuronal activity of the central nervous system were estimated by measuring the concentrations of serotonin (5-HT) and its major metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), in the cerebrospinal fluid (CSF) of anesthetized rats. Clonidine (30 and 300 micrograms/kg, i.v.) led to 74% and 60% reductions in the concentration of 5-HT in the CSF 60 min after administration. CSF 5-HIAA concentrations were also decreased to 77% and 66%, respectively. Clonidine-induced (30 micrograms/kg, i.v.) decreases in CSF 5-HT and 5-HIAA concentrations were attenuated by pretreatment with idazoxan (5 mg/kg, i.p.). Idazoxan by itself did not alter the CSF 5-HT and 5-HIAA concentrations. Decreased CSF 5-HT and 5-HIAA concentrations after i.v. administration of clonidine (30 micrograms/kg) were abolished by noradrenergic denervation after pretreatment with 6-hydroxydopamine (200 micrograms/rat, i.c.v.). These results suggest the possibility that clonidine acts to inhibit the serotonergic neuronal activity, which is mediated via the alpha 2-adrenoceptors. It indicates, moreover, that noradrenergic nervous systems are involved in the clonidine-induced inhibition of serotonergic neuronal activity. Therefore, noradrenergic neurons play a significant role in mediating the actions of clonidine on serotonergic neuronal activity in the rat brain.

[Hepatoblastoma: clinico-radiological study of fifteen cases].

From January 1976 to October 1989, 15 patients with hepatoblastoma who underwent surgery at the National Cancer Center Hospital were evaluated by clinico-radiological techniques. Eight patients were boys and seven were girls; their average age was 3 years and 5 months. Abdominal mass or distention was initially noted in 12 patients. Alpha-fetoprotein level was extremely high (average, 327 micrograms/ml) in all cases but one. Hepatitis B surface antigen was negative in all cases. Tumors occupied mainly the right lobe of the liver in 67% of patients, and the mean tumor diameter was 11.1 cm. Of 15 hepatoblastomas, 10 were grossly classified as massive type and five as multinodular. Histopathological diagnosis was well differentiated (fetal type) hepatoblastoma in 10 patients and poorly differentiated (embryonal type) hepatoblastoma in five. Fibrous capsule was also recognized in eight. The noncancerous liver was normal in all cases. Ultrasonography (US) (n = 7 patients) demonstrated an inhomogeneous internal echo with well demarcated margin in five cases and without such margin in two. Nonenhanced CT (n = 6) showed an isodense or low density mass in all cases. Drip infusion CT (n = 5) revealed isodensity in the early phase. Dynamic CT performed in one patient showed a well enhanced mass that appeared hypervascular on angiography. Preoperative chemotherapy and radiation therapy provoked histological changes such as necrosis, fibrosis and calcifications. These changes were reflected on CT images. Both US and CT demonstrated the characteristic internal structure and gross appearance of hepatoblastoma.

Significant correlation between cerebrospinal fluid and brain levels of norepinephrine, serotonin and acetylcholine in anesthetized rats.

The present study was undertaken to determine cerebrospinal fluid (CSF) and brain levels of norepinephrine (NE), serotonin (5-HT) and their metabolites--3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenylacetic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA)--in rats pretreated with 6-hydroxydopamine (6-OHDA) or 5,7-dihydroxytryptamine (5,7-DHT). In the 6-OHDA pretreated rats, both CSF and brain concentrations of NE, DOPAC and HVA sustained significant decreases as compared with those in non-treated rats. Positive and significant correlations between CSF and brain levels were observed in respect to NE, DOPAC and HVA. In 5,7-DHT pretreated rats, both CSF and brain concentrations of 5-HT and 5-HIAA were significantly decreased. A positive and significant correlation between CSF and brain levels in respect to 5-HT and 5-HIAA was observed. Further studies were carried out to determine ACh levels of both the CSF and the brain in microspheres (MS)-treated rats, which are used as a model of microembolization. The CSF ACh concentrations in MS-treated groups were significantly decreased as compared with those in non-treated rats. The brain ACh contents also tended to decrease in this group. A positive and significant correlation was observed between CSF and brain levels of ACh. These findings suggest that NE, 5-HT and ACh concentrations in the CSF are direct indications of central noradrenergic, serotonergic and cholinergic nerve activity, respectively.

Differential effects of hemorrhage on adrenal and renal nerve activity in anesthetized rats.

Evidence that sympathetic outflow to organs with different functions reacts nonuniformly to various stimuli has accumulated. To clarify the difference in outflow characteristics of adrenal and renal nerves, the neural and neurochemical mechanisms involved in the response to hemorrhage were examined in anesthetized rats. Hemorrhage (2, 5, and 10 ml/kg) increased adrenal nerve activity (ANA) and decreased renal nerve activity (RNA) in a bleeding volume-dependent manner, accompanied with a decrease in mean arterial blood pressure and heart rate. Bilateral vagotomy attenuated the response in ANA and completely abolished the response in RNA. Sinoaortic denervation (SAD) and vagotomy combined with SAD inversely decreased ANA during hemorrhage. However, SAD appears to have no effect on the response in RNA, which was completely abolished by combined denervation. Our results suggest that the differential effects of hemorrhage on ANA and RNA may be due to different contributions via the afferent neural pathways from the baro- and cardiopulmonary receptors. Because naloxone attenuated the dissociated response to hemorrhage, the endogenous opioid system may be involved.

Discrepancy between central sympathoinhibitory action and peripheral hemodynamic effects of pindolol in anesthetized rats.

The present study was carried out to elucidate the relationship between changes in central sympathetic nerve activity and the peripheral hemodynamic effects of pindolol in anesthetized rats. Intravenous pindolol (0.1 mg/kg) produced a decrease in cardiac sympathetic nerve activity without a significant change in heart rate. Renal sympathetic nerve activity was also decreased by pindolol (0.1 and 0.5 mg/kg, i.v.) dose-dependently, but changes in mean arterial pressure were not dose-related. In addition, pindolol (0.1 and 0.5 mg/kg, i.v.) produced a dose-dependent reduction of preganglionic splanchnic nerve activity. These findings suggest that pindolol possesses a central sympathoinhibitory action, but there is a discrepancy between this central effect and peripheral cardiovascular effects of pindolol in rats.

[Effect of ketanserin on blood pressure in rats].

Ketanserin, a selective serotonergic (5-HT2) antagonist, also has affinity for alpha 1-adrenoceptors. It is not clear whether the hypotensive mechanism of ketanserin is due to its antagonistic action to 5-HT2 receptor or to its affinity for alpha 1 adrenoceptors. The hypotensive mechanism of ketanserin was studied in both stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY). Anesthetized rats were used (alpha-chloralose + urethane, i.p.). Up to 3 ml of blood was drawn from each rat for analysis. Plasma norepinephrine (NE) was determined by radioenzymatic assay. Plasma serotonin (5-HT) was determined by HPLC-ECD. Adrenal nerve discharges were counted by a digital pulse counter. Ketanserin (0.5 mg/kg, 5.0 mg/kg, i.v.) produced a dose-dependent reduction of mean arterial pressure (MAP) in both SHRSP and WKY. MAP of SHRSP decreased significantly as compared with WKY. Both plasma NE and 5-HT showed a tendency to increase during ketanserin administration (5.0 mg/kg, i.v.). Ketanserin significantly antagonized the BP response induced by exogenously injected 5-HT (30 micrograms/kg) and NE (10 micrograms/kg). Adrenal nerve activity was reduced in parallel with the decrease in BP and HR. These findings suggest that ketanserin produced a decrease in BP via both peripheral and central action in rats.

[Effects of new antihypertensive agent, 2-[4-(n-butyryl)-homopiperazine-1-ul]-4-amino-6, 7-dimethoxy-quinazoline (E-643), on blood pressure, urinary sodium excretion and urinary norepinephrine excretion rate in stroke-prone, spontaneously hypertensive rats].

Present study was undertaken to elucidate the effects of E-643, on blood pressure, urinary electrolyte (U-Na, U-K) and catecholamines excretion rates in stroke-prone spontaneously hypertensive rats (SHRSP). An attempt was also made to clarify the effects of E-643 on plasma catecholamine concentration and sympathetic efferent nerve discharges including renal and adrenal nerve activity. E-643 (10 mg/kg/day X 4 weeks, p.o.) administered SHRSP (E-643 SHRSP) produced a significant hypotensive effect as compared with sex-age matched nondrug control SHRSP (control SHRSP). Both U-Na and U-K in E-643 SHRSP increased significantly as compared with those of control SHRSP. Urinary norepinephrine content (U-NE) also increased significantly in E-643 SHRSP. Plasma NE concentration tended to increase in E-643 SHRSP. While, plasma epinephrine (E) concentration decreased significantly in E-643 SHRSP. E-643 did not produce any significant effects on both sympathetic renal nerve activity and adrenal nerve activity in SHR. The changes induced by exogenous administered NE (blood pressure rise, tachycardia and the change in sympathetic nerve activity) were antagonized by pretreatment of E-643 in SHR. It was demonstrated that therapeutic doses of E-643 did not seem to produce any significant effect on central nervous system. These findings suggest that E-643 is a peripherally acting alpha 1 antagonist with natriuretic effect.