Inhibition of intestinal cholesterol absorption might explain cholesterol-lowering effect of telmisartan.

WHAT IS KNOWN AND OBJECTIVE: Telmisartan, an angiotensin II type 1 receptor blocker (ARB), acts as a partial agonist for peroxisome proliferator-activated receptor-γ, and thus improves abnormalities of glucose metabolism and hypertriglyceridaemia in addition to its documented blood pressure-lowering effects. Recently, it has been demonstrated that telmisartan also lowers the levels of total cholesterol and low-density lipoprotein (LDL) cholesterol levels. This study was designed to investigate the mechanism of cholesterol reduction. METHODS: We measured serum levels of cholestanol, a cholesterol absorption marker, and lathosterol, a cholesterol synthesis marker, in 20 patients with both hypercholesterolaemia and hypertension. Ten patients were treated with telmisartan and the remaining 10 with fluvastatin. RESULTS: After 3 months of treatment, total and LDL cholesterol levels decreased in the telmisartan group (P<0.01 for both total and LDL cholesterol levels) and the fluvastatin group (P<0.001 for both total and LDL cholesterol levels). The change in cholestanol level after 3 months of treatment was positively correlated with the levels of total (R=0.72, P<0.05) and LDL cholesterol (R=0.81, P<0.01) in the telmisartan group. The change in lathosterol level was positively correlated with the levels of total (R=0.88, P=0.001) and LDL cholesterol (R=0.89, P=0.001) in the fluvastatin group. WHAT IS NEW AND CONCLUSIONS: Our results suggest that the cholesterol-lowering effect of telmisartan might be caused by inhibition of cholesterol absorption, whereas that of statins is by inhibition of cholesterol synthesis. If confirmed, co-treatment with the two agents may be useful for synergistically lowering cholesterol in hypertensive patients.

Possible emergence of drug-resistant variants of Babesia gibsoni in clinical cases treated with atovaquone and azithromycin.

BACKGROUND: There is no well-established treatment strategy for Babesia gibsoni infection. A new therapeutic protocol using atovaquone (ATV) and azithromycin (AZM) has been proposed, but there is concern about the possible induction of relapse and the emergence of ATV-resistant variants after treatment. OBJECTIVE: To evaluate the clinical use of combination therapy with ATV and AZM as a first-line treatment of clinical B. gibsoni infection in dogs, and to investigate the emergence of ATV-resistant variants. ANIMALS: Eight B. gibsoni naturally infected dogs showing signs of acute onset of disease. METHODS: Retrospective case study. Eight clinical cases received combination therapy with ATV and AZM at Kagoshima University Veterinary Teaching Hospital during 2007-2008, and their clinical courses and clinicopathological parameters were evaluated. In addition, alterations in the cytochrome b (CYTb) gene of B. gibsoni were analyzed by polymerase chain reaction and DNA sequencing techniques. RESULTS: All of the dogs responded well to the treatment, with rapid improvement in their clinical condition and hematological parameters. However, 5 of the 8 dogs relapsed after treatment. Analysis of the CYTb gene strongly suggested the emergence of ATV-resistant variants after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: The combination of ATV and AZM can be used as a first-line treatment for dogs with babesiosis, but relapses occur. Attention should be paid to the possible in vivo selection of drug-resistant variants.

Low response rate of second-line chemotherapy for recurrent or refractory clear cell carcinoma of the ovary: a retrospective Japan Clear Cell Carcinoma Study.

Clear cell carcinoma (CCC) of the ovary has been recognized to show resistance to anticancer agents in the first-line chemotherapy. Our aim was to evaluate the effect of second-line chemotherapy in a retrospective study. A total of 75 patients diagnosed with CCC and treated between 1992 and 2002 in collaborating hospitals were reviewed. Criteria for the patients' enrollment were 1) diagnosis of pure-type CCC at the initial operation, 2) treatment after one systemic postoperative chemotherapy, 3) measurable recurrent or refractory tumor, 4) at least two cycles of second-line chemotherapy and assessable for the response, and 5) adequate clinical information. Regimens of first-line chemotherapy were conventional platinum-based therapy in 33 cases, paclitaxel plus platinum in 24 cases, irinotecan plus platinum in 9 cases, and irinotecan plus mitomycin C in 7 cases. Treatment-free periods were more than 6 months in 24 cases (group A) and less than 6 months in 51 cases (group B). In group A, response was observed in two cases (8%): one with conventional platinum therapy and another with irinotecan plus platinum. In group B, three cases (6%) responded: two with platinum plus etoposide and one case with irinotecan plus platinum. Median overall survival was 16 months in group A and 7 months in group B (P = 0.04). These findings suggest recurrent or resistant CCC is extremely chemoresistant, and there is only small benefit of long treatment-free period in CCC patients. Another strategy including molecular-targeting therapy is warranted for the treatment of recurrent or refractory CCC.

Leptin resistance conferred by a combination of single nucleotide polymorphism and the adoption of a Western lifestyle in urban areas of Thailand.

OBJECTIVES: An increasing number of lifestyle disorders have emerged in response to the rapid urbanization that has occurred in Thailand. Recently, leptin resistance has been nominated as a possible marker for the onset of metabolic disorders in Asian countries. The research aimed to assess the relationship between leptin-resistance and environmental and/or genetic factors by comparing urban and rural inhabitants in Thailand. METHODS: A total of 212 age- and sex-matched subjects from an urban area (Bangkok) and from rural areas (Sai Noi) participated in the study. Anthropometric measurements, blood biochemistry, single nucleotide polymorphism analyses, and interviews concerning lifestyles and dietary habits were conducted individually. Backward elimination multiple regression analyses and least trimmed sum of square methods were used to estimate the effects of possible factors. RESULTS: A transition of staple food from rice to bread (decreased rice intake; p < 0.01 and increased bread intake; p < 0.05) was significant in urban areas. Leptin levels were higher in urban groups, with a significant difference in women (p < 0.001 in women and p = 0.06 in men), but not in men. Predictors selected for leptin-resistance in women were genotypes of UCP2, PPARg2, bread intake, living area, and smoking habit (r = 0.510); in men, genotypes of UCP2 and UCP3p, smoking habit, and rice intake (r = 0.315). CONCLUSIONS: Urban women with del/del type of UCP2 exhibited significant leptin resistance. A combination of urbanization and UCP2 genotype were considered to be responsible.

Induction of peroxisomal beta-oxidation enzymes by dehydroepiandrosterone and its sulfate in primary cultures of rat hepatocytes.

Treatment of cultured rat-hepatocytes with 50 microM dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) for up to 5 days resulted in a progressive increase in peroxisomal beta-oxidation and carnitine acetyltransferase activity. After 5 days, the increases in activity were 2.6- and 4.8-fold for peroxisomal beta-oxidation and 11.7- and 17.1-fold for carnitine acetyltransferase over the initial activity, in DHEA- and DHEAS-treated cells, respectively. The stimulation of the activity of these enzymes by the respective agents was dose-related; it was maximum with 50 to 100 microM DHEA and 50 to 250 microM DHEAS, although DHEAS was more effective for stimulation than DHEA. Western blot analyses revealed the induction of acyl-CoA oxidase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme and carnitine acetyltransferase in the treated cells. Moreover, induction of fatty acid omega-hydroxylase proteins (P-450IVAS) was also revealed. These results indicate that DHEA and DHEAS act directly on hepatocytes. The induction of hepatic peroxisomal beta-oxidation enzymes and several other enzymes in rats administered with DHEA could be accounted for, at least in part, by the direct action of DHEA and its sulfate-conjugate (DHEAS) on liver cells.

Induction of peroxisomal beta-oxidation by structural analogues of dehydroepiandrosterone in cultured rat hepatocytes: structure-activity relationships.

The structural requirements of dehydroepiandrosterone (DHEA) for the induction of peroxisomal beta-oxidation were studied in cultured rat hepatocytes. The hepatocytes were incubated for 5 days with various steroids, including 3- and 17-substituted analogues and 5-hydrogenated analogues of DHEA, and the activities of peroxisomal beta-oxidation and carnitine acetyltransferase were measured. Among the steroids examined, DHEA, DHEA sulfate (DHEAS), dehydroandrosterone sulfate, androstenediol 3-sulfate, epiandrosterone sulfate and androsterone sulfate significantly induced the enzymes; 4.6- to 14.2-fold for beta-oxidation and 5.1- to 10.9-fold for carnitine acetyltransferase at 50 microM. All of the sulfated steroids were more effective than the corresponding unsulfated forms. DHEAS was the most potent inducer. The 3-sulfuric group was required for the marked induction of peroxisomal beta-oxidation, and the 17-carbonyl group was also important. Furthermore, the relatively planar conformation of the steroidal hydrophobic backbone was crucial for inducing the enzyme. The configuration of the 3-sulfuric group (beta-configuration) and the presence of a double bond at position C5 were not primary determinants for the action of DHEAS. On the other hand, the introduction of bulky substituents to position C17 or aromatization of ring A led to a loss of inducing activity. Thus, there are strict structural requirements for the DHEA induction of peroxisomal beta-oxidation, suggesting the presence of a certain specific recognition site in the cell for DHEAS, which mediates the peroxisome proliferator action of DHEA.

Specific binding of dehydroepiandrosterone sulfate to rat liver cytosol: a possible association with peroxisomal enzyme induction.

Incubation of [3H]dehydroepiandrosterone sulfate (DHEAS) with rat liver cytosol demonstrated its specific binding with a dissociation constant of 72 +/- 14 nM and a maximal binding capacity of 312 +/- 105 fmol/mg cytosol protein. The binding correlated with the amount of cytosol protein, and depended on time, temperature and pH, with equilibrium being reached after 6 h at 0 degrees C and pH 7.5. Boiling or treatment of the cytosol with proteases or sulfhydryl-blocking reagents affected the binding. The apparent molecular mass of the binding entity was estimated to be 160-230 kDa by HPLC gel filtration. In competitive binding studies, free steroids, including dehydroepiandrosterone (DHEA), sulfatase substrates and ligands of organic anion binders such as ligandin and fatty acid binding protein, had no effect on the [3H]DHEAS binding. Peroxisome proliferators also had no effect, except Wy-14,643. Competition with various steroids related to DHEAS revealed strict structural requirements for DHEAS binding, in which epiandrosterone sulfate was almost as effective as unlabeled DHEAS in inhibiting [3H]DHEAS binding. These findings indicated the presence of a binding protein highly specific to DHEAS in rat liver cytosol. The DHEAS binding in liver cytosol was 2-fold higher in male than in female rats. The cytosolic DHEAS binding was highest in the liver, followed by the kidney and heart. The possibility of association between the DHEAS binding and DHEA induction of peroxisomal beta-oxidation is discussed.

Characteristics of dehydroepiandrosterone as a peroxisome proliferator.

Treatment of rats with dehydroepiandrosterone (300 mg/kg body weight, per os, 14 days) caused a remarkable increase in the number of peroxisomes and peroxisomal beta-oxidation activity in the liver. The activities of carnitine acetyltransferase, microsomal laurate 12-hydroxylation, cytosolic palmitoyl-CoA hydrolase, malic enzyme and some other enzymes were also increased. The increases in these enzyme activities were all greater in male rats than in female rats. Immunoblot analysis revealed remarkable induction of acyl-CoA oxidase and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme in the liver and to a smaller extent in the kidney, whereas no significant induction of these enzymes was found in the heart. The increase in the hepatic peroxisomal beta-oxidation activity reached a maximal level at day 5 of the treatment of dehydroepiandrosterone and the increased activity rapidly returned to the normal level on discontinuation of the treatment. The increase in the activity was also dose-dependent, which was saturable at a dose of more than 200 mg/kg body weight. All these features in enzyme induction caused by dehydroepiandrosterone correlate well with those observed in the treatment of clofibric acid, a peroxisome proliferator. Co-treatment of dehydroepiandrosterone and clofibric acid showed no synergism in the enhancement of peroxisomal beta-oxidation activity, suggesting the involvement of a common process in the mechanism by which these compounds induce the enzymes. These results indicate that dehydroepiandrosterone is a typical peroxisome proliferator. Since dehydroepiandrosterone is a naturally occurring C19 steroid in mammals, the structure of which is novel compared with those of peroxisome proliferators known so far, this compound could provide particular information in the understanding of the mechanisms underlying the induction of peroxisome proliferation.

Abnormalities in plasma lipoprotein in familial partial lecithin:cholesterol acyltransferase deficiency.

Abnormalities in plasma lipoproteins from patients with familial partial lecithin:cholesterol acyltransferase deficiency were studied. In these patients the plasma cholesterol ester ratio was about 40% and plasma apolipoprotein B level remained within the normal range. The content of large-sized low-density-lipoproteins (LDL) was low. Apolipoprotein B-100 and B-48 were detected in very-low-density lipoproteins (VLDL) and LDL in patients' plasma. In patients' LDL, apolipoprotein B-48 was primarily present in large-sized particles. Apolipoprotein E and A-I were mainly detected in intermediate-sized LDL. High-density lipoproteins (HDL) were separated into three fractions by gel permeation chromatography. Large-sized HDL particles (150-200 A) including discoidal particles contained apolipoproteins, E, A-IV and A-I. The content of discoidal HDL was low and, on electron micrograph, rouleau-formed particles were rarely seen. Normal-sized HDL (80-100 A) contained apolipoproteins A-I and A-II and small-sized HDL (about 60 A) contained only apolipoprotein A-I. Although several lipoprotein abnormalities were similar to those in classical familial lecithin:cholesterol acyltransferase deficiency, remaining lecithin:cholesterol acyltransferase activity may, however, cause a lack of reduction of apolipoprotein B level, a low level of large-sized LDL and also a low level of discoidal HDL.

Ambulatory blood pressure of adults in Ohasama, Japan.

We performed a cross-sectional study in a small town in northern Japan to evaluate the distribution, reference values, and daily variation in ambulatory blood pressure. A total of 705 subjects (229 men aged 61.3 +/- 13.4 years [mean +/- SD] and 476 women aged 57.5 +/- 13.3 years; 41.1% of the regional adult population, n = 1716), including those treated with antihypertensive drugs (n = 231, 66.5 +/- 9.5 years) as well as untreated subjects (n = 474, 55.0 +/- 13.5 years), participated in the study. Both ambulatory and screening blood pressures were measured in 659 subjects. Ambulatory blood pressure was measured with an automatic device (Colin ABPM-630). The 24-hour ambulatory blood pressure in the total population was 121.7 +/- 13.0/71.1 +/- 7.6 mm Hg (95th percentile value [95%] = 146/85 mm Hg). The corresponding value in the untreated subjects was 119.4 +/- 12.5/70.1 +/- 7.4 mm Hg (95% = 144/83 mm Hg). The 24-hour average ambulatory blood pressure was 118.0 +/- 11.1/69.4 +/- 6.8 mm Hg (95% = 139/81 mm Hg) in subjects identified as normotensive by their screening blood pressure (n = 448, 57.2 +/- 13.1 years) and 133.6 +/- 14.2/78.9 +/- 8.8 mm Hg in those identified as hypertensive by their screening blood pressure (n = 73, 63.1 +/- 10.6 years). Based on the mean+SD of the 24-hour ambulatory blood pressure in the normotensive subjects by their screening blood pressure (129/76 mm Hg), the 24-hour ambulatory blood pressures in 25 (34.2%) of these 73 hypertensive subjects by screening blood pressure were below this level. Nine (2%) of 448 normotensive subjects by screening blood pressure were above the mean+2 SDs (140/83 mm Hg) of the 24-hour ambulatory blood pressure in the normotensive group by screening blood pressure. Ambulatory and screening blood pressures increased with age. The age-dependent increase in ambulatory blood pressure was less apparent in men. The 24-hour average pulse rate decreased with age. The daily variation in ambulatory blood pressure (standard deviation) increased with age, whereas that of pulse rate decreased with age. Increases in blood pressure variation were observed in nighttime and daytime blood pressure values. The differences between day versus night ambulatory blood pressures decreased with age in men but not in women.(ABSTRACT TRUNCATED AT 400 WORDS)

Manipulation of blood serotonin and platelets in the rat.

Dietary administration of L-tryptophan to rats failed to increase blood platelets. Instead platelet counts were decreased after feeding either a tryptophan-deficient or tryptophan-enriched (10%) diet, but were unchanged in animals on a 1% tryptophan diet. Platelet median volumes were not affected by any of these dietary regimens. As expected these dietary manipulations altered both brain and blood serotonin levels in the direction expected for a substrate dependence of serotonin biosynthesis.

A prospective follow-up study of brain morphology and cognition in first-episode schizophrenic patients: preliminary findings.

Brain morphological abnormalities have been reported in several independent investigations of chronic schizophrenic patients. The present study is a prospective 4-year follow-up of first-episode schizophrenic patients to determine whether some of these abnormalities may be a consequence of regional brain structural change over time after the onset of a first psychotic episode. Whole hemisphere, temporal lobes, superior temporal gyrus, hippocampus, caudate, corpus callosum, and lateral ventricles were measured in a series of MRI scans taken over a 4-year period in 20 patients and five controls. Total volume reduction was noted in both hemispheres to a greater degree in patients than controls. When adjusted for total brain size, left ventricular enlargement occurred in patients, but not controls, over time. These preliminary data suggest that subtle cortical atrophy may be occurring over time after the onset of illness.

Lack of association between duration of untreated illness and severity of cognitive and structural brain deficits at the first episode of schizophrenia.

OBJECTIVE: The purpose of the study was to determine whether the duration of illness before antipsychotic drug treatment for schizophrenia was associated with the severity of cognitive deficits and volumetric brain structure anomalies observed in some patients with a first episode of schizophrenia. METHOD: Duration of psychotic symptoms and of other symptoms marking a behavioral change was estimated from structured interviews with 50 patients who had a first episode of schizophrenia and their family members. Interviews were conducted within a month of the patients' hospitalization. Duration of untreated psychotic symptoms and of behavioral change was correlated with neuropsychological summary scores from a comprehensive cognitive battery and with measurements of lateral ventricular, temporal lobe, and cerebral hemispheric volumes. RESULTS: No significant correlations were observed between measures of untreated illness and the severity of either cognitive or structural brain deficits at baseline. CONCLUSIONS: The duration of untreated symptoms of schizophrenia, for which an association with an uncontrolled toxic brain process has been proposed, is unlikely to explain why first-episode patients with schizophrenia have widespread deficits in cognitive functioning and have detectable ventricular enlargement and some loss of cortical mass.

Longitudinal neuropsychological follow-up study of patients with first-episode schizophrenia.

OBJECTIVE: The primary purpose of this article was to determine if cognitive abilities decline, remain unchanged, or modestly improve throughout the course of schizophrenic illness. METHOD: Forty-two patients with a first hospitalization for schizophrenia or schizophreniform disorder and 16 normal comparison subjects had a battery of neuropsychological tests and a magnetic resonance imaging (MRI) brain scan at approximate yearly intervals for the first 2 to 5 years of illness. Summary rating scales for language, executive, memory, processing speed, and sensory-perceptual functions were constructed. RESULTS: Patients with schizophrenia scored 1 to 2 standard deviations below normal comparison subjects on neuropsychological test measures during the course of the study. Patients exhibited less improvement than comparison subjects on measures of verbal memory. In general, improvement in positive symptoms over the time interval was associated with improvement in cognition. No changes in regional brain measurements were correlated with cognitive change in the patient group. CONCLUSIONS: Patients with schizophrenia have considerable cognitive dysfunction in the first 4 to 5 years of illness, which is stable at a level of 1 to 2 standard deviations below that of comparison subjects. There is little evidence for deterioration of cognitive abilities over the first few years of illness, with the exception of verbal memory, which shows significantly less improvement in patients over time relative to that of comparison subjects.

Sex differences in neuropsychological functioning of first-episode and chronically ill schizophrenic patients.

OBJECTIVE: The purpose of this study was to determine whether men and women with schizophrenia demonstrate differences in cognitive abilities. METHOD: Two cohorts of patients with schizophrenia, an acute first-episode and a chronically hospitalized group, were evaluated with a neuropsychological battery and compared with a normal group of subjects. RESULTS: After adjustment for age, age at onset, and premorbid IQ, male chronic patients performed worse than female chronic patients on measures of visual memory. These differences were eliminated after control for symptom severity. No other differences were found in cognitive function between men and women in either cohort. CONCLUSIONS: Sex differences in cognitive function in schizophrenic patients are not robust findings.

Characteristics of a community-based distribution of home blood pressure in Ohasama in northern Japan.

OBJECTIVE: To evaluate the distribution, reference values and day-to-day variation of blood pressure of untreated subjects measured at home. DESIGN: Cross-sectional study of a cohort. SETTING: General community in northern Japan. SUBJECTS: Blood pressure was measured in 871 subjects (mean +/- SD age 46.0 +/- 19.5 years, range 7-98, constituting 38.7% of the local population of Uchikawama region, Ohasama) who were not receiving antihypertensive medication. METHODS: Subjects measured their own blood pressure at home at least three times (mean +/- SD 19.7 +/- 8.4) each morning using a semi-automatic oscillometric blood pressure measuring device. Screening blood pressure was measured once. MAIN OUTCOME MEASURES: Distribution of home blood pressure in the study population as a whole and with respect to age and sex, and the distribution of day-to-day variation of home blood pressure were determined. RESULTS: Mean home blood pressure was 117.3 +/- 13.4/69.3 +/- 9.7 mmHg (95% confidence interval 116.4-118.2/68.7-70.0). The 95th centile value was 143/85 mmHg, mean+SD 131/79 mmHg and mean + 2SD 144/89 mmHg. Mean screening blood pressure was 126.2 +/- 18.9/72.1 +/- 11.7 mmHg (95th centile 159/92 mmHg). Age- and sex-specific 95th centile values as well as mean +/- SD were obtained. Mean+SD, mean + 2SD and the 95th centile values obtained as reference upper limits of home blood pressure from subjects identified as normotensive by screening blood pressure (n = 707) were 125/77, 137/86 and 134/83 mmHg, respectively. Home blood pressure increased gradually with increasing age in both men and women, although blood pressure was significantly higher in men until 50 years of age. Day-to-day variation of home systolic blood pressure also increased with age. CONCLUSION: Since the distribution of home blood pressure values was affected by age and sex, age- and sex-matched reference values for home blood pressure should be established. Home blood pressure values in elderly subjects should be evaluated carefully, since these exhibit greater day-to-day variation.

Prediction of mortality by ambulatory blood pressure monitoring versus screening blood pressure measurements: a pilot study in Ohasama.

OBJECTIVE: To compare the prediction of mortality by ambulatory blood pressure monitoring and screening blood pressure measurements in a general population. DESIGN: A prospective cohort study. PATIENTS AND METHODS: We obtained blood pressure data for 1542 subjects (565 men and 977 women) aged > or = 40 years who were followed up for up to 8.1 years (mean 5.1 years). Subjects were subdivided into five groups according to their ambulatory and screening blood pressure levels. The prognostic significance of blood pressure for mortality was examined by the Cox proportional hazards regression model. RESULTS: The association between blood pressure level and mortality was more distinctive for the ambulatory blood pressure than it was for the screening blood pressure. The risk of cardiovascular mortality increased significantly for the highest quintiles of 24 h ambulatory blood pressure, whereas there was no significant association between the screening blood pressure and the cardiovascular mortality. When both 24 h and screening blood pressure values were included in the Cox model, only the systolic ambulatory blood pressure was related significantly to the increased risk of cardiovascular mortality. CONCLUSIONS: The ambulatory blood pressure had a stronger predictive power for mortality than did the screening blood pressure. This appears to have been the first study of the prognostic significance of ambulatory blood pressure monitoring versus screening blood pressure measurements in a general population.

Cutaneous nerve-evoked cholinergic inhibition of monosynaptic reflex in the neonatal rat spinal cord: involvement on M2 receptors and tachykininergic primary afferents.

The mechanisms of a cutaneous nerve-evoked inhibition of monosynaptic reflex were investigated in an isolated spinal cord-peripheral nerve preparation of the neonatal rat. Conditioning stimulation of the saphenous nerve, with five pulses at 50 Hz and a strength sufficient to activate C fibers, evoked an inhibition lasting about 20 s of the monosynaptic reflex that was elicited by stimulation of the nerve branch to quadriceps femoris muscle and recorded from the L3 ventral root. This inhibition of monosynaptic reflex was potentiated by an anticholinesterase, edrophonium, and mostly blocked by atropine. Application of acetylcholine, muscarine, bethanechol, carbachol, arecoline and oxotremorine induced an inhibition of monosynaptic reflex. From the effects of muscarinic antagonists, pirenzepine, AF-DX 116, and 4-diphenylacetoxy-N-methylpiperidine on the agonist-evoked and primary afferent-evoked inhibition of monosynaptic reflex it was concluded that the muscarinic receptors involved in the cutaneous nerve-evoked inhibition of monosynaptic reflex are of M2 type. When monosynaptic reflexes were evoked by two successive stimuli with intervals of 15 ms to 1 s, the second response was smaller than the first. This depression of monosynaptic reflex became less pronounced when the reflex was reduced by application of oxotremorine or arecoline or by conditioning stimulation of primary afferents, suggesting that the inhibition of monosynaptic reflex is presynaptic in nature. The late phase of the cutaneous nerve-evoked inhibition of monosynaptic reflex (5-20 s after conditioning stimulation) was markedly depressed by a tachykinin antagonist, spantide. Perfusion of the spinal cord with capsaicin (1 microM) for 1 h also abolished the late phase of the inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P-evoked release of GABA from isolated spinal cord of the newborn rat.

Isolated spinal cords of newborn rats were perfused with artificial cerebrospinal fluid and the effects of substance P and its analogs on the release of endogenous GABA were examined. Application of substance P evoked a dose-dependent release of GABA from spinal cords. The threshold concentration of substance P for induction of a significant increase in the GABA release was 3 microM. The substance P-evoked GABA release was neither blocked by removal of Ca2+ from perfusion medium nor by tetrodotoxin. In contrast, the GABA release evoked by high K+ (90 mM) was abolished in Ca(2+)-free medium, and the GABA release evoked by veratridine (5 microM) was suppressed by tetrodotoxin (1 microM). A GABA uptake inhibitor, cis-4-hydroxynipecotic acid, markedly augmented the GABA release induced by high K+, but not that induced by substance P or veratridine. These results suggest the possibility that a carrier-mediated mechanism might be involved in the GABA release induced by substance P, as well as by veratridine, in the newborn rat spinal cord. Two N-terminal fragments of substance P, substance P free acid and substance P1-10 amide, as well as [D-Arg1,D-Trp7,9,Leu11]substance P (spantide), evoked an increase in the GABA release, whereas substance P1-6, and a C-terminal fragment, substance P5-11 were inactive. Somatostatin and compound 48/80 also evoked a GABA release, which was independent of external Ca2+ and resistant to tetrodotoxin. [D-Pro4,D-Trp7,9,10]substance P4-11 (10-15 microM) inhibited the GABA release evoked by substance P, somatostatin and compound 48/80.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P-evoked release of acetylcholine from isolated spinal cord of the newborn rat.

Isolated spinal cords of newborn rats were perfused with artificial cerebrospinal fluid and the release of endogenous acetylcholine was measured using high-performance liquid chromatography with an electrochemical detection system. Application of high-K+ (90 mM) medium evoked about an eight-fold increase in the acetylcholine release, and the K(+)-evoked release was Ca2+ dependent. Veratridine (20 microM) also evoked about a four-fold increase in the acetylcholine release, and this increase was suppressed by 0.2 microM tetrodotoxin. Application of substance P at 0.3-3 microM evoked a concentration-dependent release of acetylcholine. The substance P-evoked acetylcholine release was Ca2+ dependent and abolished by tetrodotoxin. Neurokinin A, neurokinin B, acetyl-Arg6-septide and senktide (3 microM each) also evoked a release of acetylcholine. Electrophysiological experiments using isolated spinal cords of newborn rats showed that bath application of substance P induced a depolarization of motoneurons, which was enhanced by edrophonium. This enhancement of substance P-induced depolarization by edrophonium disappeared in a low-Ca2+ medium or in the presence of atropine and dihydro-beta-erythroidine. In the presence of edrophonium and dihydro-beta-erythroidine, substance P induced an inhibition of monosynaptic reflex, and this inhibition was abolished by atropine. These results suggest that substance P and other tachykinins induce a release of acetylcholine from the newborn rat spinal cord by exciting cholinergic neurons.