Biomedical subjects

M Domae

Publications and source records attributed to M Domae.

At least 19 recordsLinked to original sources

PubMed1996

Inhibitory effects of putative dopamine D3 receptor agonists, 7-OH-DPAT and quinpirole, on prolactin secretion in rats.

The present experiments were performed to investigate effects of (+/-)-2-(dipropylamino)-7-hydroxy-1,2,3,4-tetrahydronaphthalene (7-OH-DPAT) or quinpirole (LY 171555), putative dopamine (DA) D3 receptor agonists, on serum prolactin levels in male rats. Basal prolactin levels were reduced dose-dependently by SC administration of 7-OH-DPAT or quinpirole at respective doses of 10-100 micrograms/kg and 25-250 micrograms/kg. Daily treatment with estradiol, 35 micrograms/kg/day for 3 days, increased serum prolactin levels to fourfold higher levels than those of nonprimed rats. Intraperitoneal injection of alpha-methyl-p-tyrosine (alpha-MT), 300 mg/kg, also increased serum prolactin levels. 7-OH-DPAT or quinpirole at a dose of 50 micrograms/kg caused a marked reduction in serum prolactin levels in both the estradiol- and alpha-MT-induced hyperprolactinemia. The 7-OH-DPAT- and quinpirole-induced decreases in serum prolactin levels were antagonized by the administration of the DA D2 receptor antagonist, spiperone, at 0.5 mg/kg. The results indicate that 7-OH-DPAT and quinpirole decrease prolactin levels in rats by stimulation of the D2 receptor.

Animals↗

PubMed1996

The new muscarinic M1-receptor agonist YM796 evokes yawning and increases oxytocin secretion from the posterior pituitary gland in rats.

The present experiments were performed to examine the effects of a new muscarinic M1-receptor agonist, (-)-YM796 ((-)-S-2,8-dimethyl-3-methylene-1-oxa-8-azaspiro[4.5]decane L-tartrate monohydrate), on yawning and oxytocin secretion from the posterior pituitary gland in rats YM796, at doses of 2.5-50 mg/kg (SC), elicited yawning. The yawning response was markedly increased by pretreatment with a beta-adrenoceptor antagonist, pindolol (20 mg/kg, IP), which per se did not elicit yawning. The yawning induced by YM796 (10 mg/kg, SC) in combination with pindolol (20 mg/kg, IP) was inhibited by scopolamine (0.5 mg/kg, SC), a muscarinic receptor antagonist, and pirenzcpine (300 micrograms/ rat, ICV) and EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline) (5 mg/kg, IP), muscarinic M1-receptor antagonists, but not by spiperone (0.5 mg/kg, SC), a dopamine D2-receptor antagonist, 4-DAMP (4-diphenylacetoxy-N-methylpiperidine methiodide) (100 micrograms/rat, ICV), a muscarinic M3-receptor antagonist, and [d(CH2)5, Tyr(Mc)2, Orn8]-vasotocin (100 ng/rat, ICV), an oxytocin receptor antagonist. YM796 at 2.5-50 mg/kg (SC) did not exert an action on prolactin levels but increased oxytocin secretion from the posterior pituitary gland in rats. This augmentation of oxytocin secretion by YM796 was inhibited by scopolamine (0.5 mg/kg, SC) and pirenzepine (3 mg/kg, SC), but not by mecamylamine (1 mg/kg, IP), a nicotinic receptor antagonist. The present findings obtained with YM796 suggest that the muscarinic M2-receptor stimulation participates in causing yawning behavior and oxytocin secretion in rats.

Adrenergic beta-Antagonists↗

PubMed1996

Lung cancer cell lines inhibit leukotriene B4 production by human polymorphonuclear leukocytes at the level of phospholipase A2.

We studied cellular interactions between human polymorphonuclear leukocytes (PMN) and lung cancer cell lines by investigating the influence of cancer cells on the production of leukotriene B4 (LTB4) and superoxide anion (O2-) by stimulated PMN. Of the nine cancer cell lines established from human lung cancers that we examined, H23 cells showed the highest LTA4 hydrolase activity. When PMN were stimulated by the calcium ionophore A23187 in the presence of H23 cells, the production of LTB4, 5(S)-hydroxyeicosatetraenoic acid (5-HETE), and 12(S)-hydroxyeicosatetraenoic acid (12-HETE) decreased in a dose-dependent manner. On the contrary, H23 did not inhibit O2- production by PMN. Two other cell lines (N417 and Q9) caused similar inhibition of LTB4 production by PMN. These three cancer cell lines alone did not generate any metabolites of the arachidonic acid (AA) lipoxygenase pathway or any O2- upon stimulation with A23187 alone. The addition of AA dose-dependently reversed the H23-induced inhibition of LTB4, 5-HETE, and 12-HETE production by PMN, suggesting inhibition at the phospholipase A2 (PLA2) level. Furthermore, addition of the cancer cell line Q9 inhibited 14C release from [14C]AA prelabeled PMN in a cell number-dependent manner in the buffer, with and without albumin. The supernatant of H23 cells also inhibited the production of LTB4 by PMN stimulated by A23187, as did the addition of H23 lysate or its 10(4) x g centrifugation supernatant. While neither the 10(5) x g supernatant (cytosol) nor the pellet (microsome) exhibited inhibitory activity, the combination of the separated cytosol and microsomal fractions restored the inhibitory activity. Furthermore, addition of the 10(4) x g supernatant of Q9 lysate to partially purified human cytosolic PLA2 inhibited PLA2 activity in a dose-dependent manner. Our results indicate that the lung cancer cell lines used in our study inhibit LTB4 production by human PMN through inhibition of phospholipase A2 activity, which may contribute to a predisposition to pulmonary infections in patients with lung cancer.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1996

Effects of the novel antipsychotic agent 7-(4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy)-3,4-dihydro -2(1H)-quinolinone (OPC-14597) on prolactin release from the rat anterior pituitary gland.

The effects of a novel antipsychotic agent, 7-(4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy)-3,4-dihydro-2 (1H)-quinolinone (OPC-14597, generic name aripiprazole), on prolactin (PRL) release from isolated rat anterior pituitary slices and on the serum PRL levels were investigated in male rats. In in vitro experiments on the isolated anterior pituitary, the spontaneous PRL release was decreased by talipexole, a dopamine D2 receptor full agonist, in a dose-dependent manner to 36% of the basal release, and the decrease was antagonized by haloperidol, a D2 receptor antagonist. OPC-14597 also decreased the release of PRL at the same concentration range with a maximal decrease to 78%, the potency being weaker than that of talipexole. The decrease in PRL release induced by OPC-14597 was completely antagonized by haloperidol. Moreover, OPC-14597 antagonized the inhibition of PRL release induced by talipexole. In in vivo experiments, haloperidol increased the serum PRL levels to 8 times the basal PRL level, whereas talipexole decreased the levels to 49% of the basal level. OPC-14597 increased the serum PRL levels by 2-fold and also antagonized the talipexole-induced decrease. The hyperprolactinemia induced by estrogen, which was inhibited by talipexole but enhanced by haloperidol, was enhanced by OPC-14597, whereas the hyperprolactinemia induced by reserpine, which was inhibited by talipexole but elevated by haloperidol, was inhibited by OPC-14597. In addition, the OPC-14597-induced inhibition was antagonized by haloperidol. These results suggest that OPC-14597 has a mixed agonist/antagonist profile at D2 receptors on lactotroph cells and thereby exerts either an antagonistic or an agonistic action, depending on the preexisting tone of the dopaminergic neuronal activities.

Animals↗

PubMed1994

Endothelins stimulate cyclic AMP accumulation in the isolated rat anterior pituitary gland: possible involvement of ETA receptor activation and prostaglandin E2 production.

Effects of endothelin-1 (ET-1) and endothelin-3 (ET-3) on cyclic AMP (cAMP) levels were studied in the isolated rat anterior and intermediate-posterior pituitary slices. In the anterior pituitary, ET-1 increased cAMP levels in a concentration-dependent manner (10(-7)-10(-5) M). ET-3 also increased the levels at the same concentration range, but ET-1 was more potent than ET-3 at an approximate ED50, 10(-6) M. The stimulatory effects of ET-1 and ET-3 (10(-6) M) on cAMP levels were antagonized by the ETA receptor antagonist BQ 123, 2 x 10(-6) M, and the ETB receptor agonist IRL 1620 evoked only a weak increase in cAMP levels. Moreover, the effects of ET-1 and ET-3 were completely abolished by the cyclooxygenase inhibitor indomethacin, 2 x 10(-5) M. On the other hand, among prostaglandins, prostaglandin E2 (PGE2) increased cAMP levels in a concentration-dependent manner (10(-7)-10(-5) M), whereas prostaglandin D2 and prostaglandin I2 did not exhibit such effects. PGE2 levels were increased by application of ET-1 (10(-8)-10(-5) M). The ET-1-induced PGE2 accumulation was strongly inhibited by indomethacin and BQ 123, but not by treatment with pertussis toxin (100 ng/ml, 6 hr). Treatment with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine also elevated the cAMP level by approximately 9-fold above the basal cAMP level. After 3-isobutyl-1-methylxanthine, ET-1 failed to increase PGE2 and cAMP levels. In the intermediate-posterior pituitary, ET-1 and ET-3 did not affect cAMP levels. The results suggest that endothelins increase cAMP levels via ETA receptor activation interacting with the pertussis toxin-insensitive G-protein, in which PGE2 production is involved in the rat anterior pituitary, whereas endothelins lack these effects in the intermediate-posterior pituitary.

1-Methyl-3-isobutylxanthine↗

PubMed1992

Inhibitory effects of endothelin-1 and endothelin-3 on prolactin release: possible involvement of endogenous endothelin isopeptides in the rat anterior pituitary.

Spontaneous prolactin release from the isolated rat anterior pituitary was inhibited by endothelin-1 in a dose-dependent manner (10(-8)-10(-6) M). Endothelin-3 also inhibited spontaneous prolactin release with an almost identical dose-response relationship as endothelin-1. These inhibitory effects were unaffected by application of a dopamine D2-receptor antagonist, YM-09151-2 (10(-7) M). Rat anterior and posterior pituitary glands were abundant in both endothelin-1 and endothelin-3, as compared with other regions of the brain. The present results suggest that endogenous endothelin-1 and endothelin-3 in the anterior and posterior pituitary are involved in the inhibitory regulation of prolactin secretion as autocrine or paracrine factors.

Analysis of Variance↗

PubMed1990

Decrease of prolactin secretion via stimulation of pituitary dopamine D-2 receptors after application of talipexole and SND 919.

The present experiments were performed to investigate the effects of talipexole (B-HT 920) and SND 919 on prolactin release from the anterior pituitary glands of rats both in vivo and in vitro. The basal serum prolactin levels were reduced dose dependently by s.c. administration of talipexole or SND 919 at doses of 5-100 micrograms/kg. Daily treatment with estradiol (35 micrograms/kg for 3 days) increased serum prolactin levels in male rats to levels 4-fold higher than those of non-primed rats. This increase was suppressed by administration of talipexole or SND 919. In vitro, the spontaneous prolactin release into perfusates from isolated anterior pituitary was inhibited by talipexole or SND 919 added at concentrations ranging from 10(-9) to 10(-6) M. This inhibitory effect of SND 919 was blocked by concurrent application of a dopamine D-2 receptor antagonist, YM-09151-2. The spontaneous prolactin release from the anterior pituitary isolated from estradiol-primed rats was 2-fold higher than that from non-primed rats. This increased release was also inhibited by application of either drug. The inhibitory effects of these drugs were greater in estradiol-primed rats than in non-primed rats when expressed as percent inhibition of control prolactin release. The results suggest that talipexole and SND 919 have a selective dopamine D-2 receptor agonistic property and are almost completely effective to counteract the enhancement of prolactin release induced by estrogens via stimulation of dopamine D-2 receptors in the anterior pituitary.

Animals↗

PubMed1989

Occurrence of yawning and decrease of prolactin levels via stimulation of dopamine D2-receptors after administration of SND 919 in rats.

SND 919 [S)-2-amino-4,5,6,7-tetrahydro-6-propylamino-benzothiazole) is expected to have a potent and selective dopamine D2-receptor agonistic activity. From this information, the present study was performed to investigate effects of SND 919 on yawning behavior and prolactin secretion in rats. Subcutaneous injections of SND 919 (25-500 micrograms/kg, s.c.) elicited yawning responses. Its dose-response curve was bell-shaped with maximal effects at a dose of 100 micrograms/kg. Yawning behavior was also evoked by the putative dopamine autoreceptor agonists, talipexole (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo [4,5-d]azepine) (B-HT 920) (5-100 micrograms/kg, s.c.) and (+)-3-PPP ((+)-3-(3-hydroxyphenyl)-N-n-propylpiperidine) (5-15 mg/kg, s.c.). The yawning induced by SND 919 (100 micrograms/kg, s.c.) as well as talipexole (25 micrograms/kg, s.c.) was inhibited by pretreatment with dopamine D2-receptor antagonists such as spiperone (0.5 mg/kg, i.p.) and YM-09151-2 (cis-N-(1-benzyl-2-methylpyrrolidin-3-yl)-5-chloro-2-methoxy-4-met hylamino- benzamide) (0.1 mg/kg, i.p.), or the muscarinic receptor antagonist, scopolamine (0.5 mg/kg, i.p.). However, the yawning was not affected by the dopamine D1-receptor antagonist, SCH 23390 (R(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-o l) (0.5 mg/kg, i.p.). Stereotypy such as licking and biting was not observed following the administration of SND 919, talipexole and (+)-3-PPP. Administration of SND 919, talipexole or (+)-3-PPP in respective yawn-inducing doses caused a reduction in both the basal prolactin levels and the alpha-methyl-p-tyrosine-induced hyperprolactinemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Effects of isofloxythepin enantiomers on prolactin secretion and postdecapitation convulsions in rats.

Racemic isofloxythepin and its enantiomers (0.05-1.0 mg/kg) administered subcutaneously increased serum prolactin levels in a dose-dependent manner in rats. The potencies of the drugs were equal for this variable. They (0.05-1.0 mg/kg, SC) also decreased dose-dependently the incidence and duration of postdecapitation convulsions, the convulsions being abolished at 1.0 mg/kg in all groups. Although (-)-enantiomer had slightly stronger effects than those of raceme and (+)-enantiomer, there were no great differences in their inhibitory effects on postdecapitation convulsions. The results indicate that isofloxythepin enantiomers in addition to raceme increase serum prolactin levels and inhibit postdecapitation convulsions and that they seem to have similar potency in blocking of dopamine receptors and alpha 1-adrenoceptors.

Animals↗

PubMed1987

Actions of prostaglandin I2 and thromboxane A2 on vascular smooth muscle tissues.

Actions of prostaglandin I2 (PGI2) and thromboxane A2 (TXA2) on vascular smooth muscles were investigated in relation to the function of the endothelium. In intact vascular smooth muscle tissues of the thoracic aorta, PGI2-Na, used as a substitute substrate of PGI2, relaxed the precontracted tissue, in a dose dependent manner, in intact tissues and also after mechanical ablation of the endothelium. Acetylcholine (ACh) relaxed the tissue precontracted by noradrenaline, in the presence or absence of indomethacin; however, the relaxation required the presence of an intact endothelium. On the other hand, increased amounts of PGI2 with the application of acetylcholine, as estimated from the amount of 6-keto-PGF1 alpha, were markedly attenuated by indomethacin. In smooth muscles of this tissue without the endothelium, ACh synthesized lesser amounts of PGI2, while PGI2-Na increased the amount of cyclic AMP. Thus, PGI2 was synthesized in both the endothelium and smooth muscles. The former produces a larger amount of PGI2 than the latter, but the PGI2 synthesized in smooth muscles may act more potently on the smooth muscle than does that synthesized in the endothelium. In the canine coronary artery, mechanical responses induced by TXA2, as estimated from actions of 9, 11,-epithio-11, 12-methano-thromboxane A2 (STA2) were enhanced after ablation of the endothelium. The minimum concentration of STA2 required to produce the contraction was above 1 nM and the maximum amplitude was evoked with 30 nM. The amplitude of the STA2-induced contraction was reduced in Ca-free solution or with the application of nifedipine. However, prazosin, propranolol or atropine had no effect on the STA2-induced contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Actions of nicorandil on vascular smooth muscles.

The action of nicorandil on vascular smooth muscles has been studied in vitro using the microelectrode, Ca-transient, isometric tension recording methods, and the bioassay methods of cyclic nucleotides and inositol phospholipids. Nicorandil increased Ca-insensitive K conductance and hyperpolarized the membrane and thus prevented the activation of the voltage-dependent Ca channel. The hyperpolarization occurred to a greater extent in venous tissue than in arterial tissue. Nicorandil stimulated the synthesis of cyclic guanosine monophosphate (cGMP) in the polarized and depolarized muscle tissues, as did nitroglycerin. Consequently, nicorandil reduces the concentrations of free Ca in the myoplasm, due to acceleration of the Ca pump at the sarcolemma, and may prevent the phosphorylation of myosin through phosphorylation of myosin light chain kinase. These actions of nicorandil may not contribute to the synthesis of inositol-1,4,5-trisphosphate hydrolyzed from phosphatidylinositol-4,5-bisphosphate. The above actions of nicorandil--hyperpolarization and increase in the cyclic GMP--may cause relaxation of the tissues precontracted by various stimulants.

Action Potentials↗

PubMed1986

Effects of prostaglandin I2 synthesized in the endothelium and in the smooth muscle on mechanical properties of the canine thoracic aorta.

In circular-cut strips prepared from canine thoracic aorta, acetylcholine (ACh) and A23187 relaxed endothelium-intact tissues [E(+) preparations] pre-contracted with noradrenaline or excess concentrations of K. These relaxations were associated with marked increases in the amount of 6-keto PGF1 alpha. After removal of the endothelium [E(-) preparations] the relaxation ceased, and the amounts of 6-keto PGF1 alpha were markedly reduced. In E(+) preparations, application of indomethacin attenuated the increase in 6-keto PGF1 alpha induced by ACh or A23187 in the presence of noradrenaline or high K, but not the endothelium-dependent relaxations. In E(-) preparations, ACh (0.1-10 microM) neither increased the amount of 6-keto PGF1 alpha nor produced a contraction. In dispersed single endothelial cells, A23187 markedly increased but 118 mM K did not modify the amount of 6-keto PGF1 alpha. Both noradrenaline and high K increased the production of 6-keto PGF1 alpha in the E(-) preparations but to a lesser extent than that in the E(+) preparations. This action was attenuated by indomethacin. The amplitude of the noradrenaline- and K-induced contractions was enhanced with indomethacin pretreatment in both E(+) and E(-) tissues. PGI2-Na (10 nM), reduced the amplitude of noradrenaline-induced contractions, concentration dependently and to the same extent in both E(+) and E(-) preparations. These results indicate that synthesis of PGI2 in the endothelium is not causally related to the endothelium dependent relaxation. PGI2 synthesized in the endothelium may not act directly on the muscle tissue, but PGI2 synthesized in the smooth muscle tissue may produce an inhibition of contraction.

6-Ketoprostaglandin F1 alpha↗

PubMed1983

The effect of prostacyclin on increased hydraulic conductivity of pulmonary exchange vessels following microembolization in dogs.

Prostacyclin (PG I2) generated by vascular endothelium is a strong antiaggregating substance. As platelet aggregation and release of humoral factor(s) have been reported to be crucial in the pathogenesis of acute lung injury following pulmonary microembolization, PG I2 could have a protective effect against microembolic lung vascular injury. Following unilateral microembolization, we have observed a large increase in the filtration coefficient in the nonembolized lung with a significant increase in 6-keto PG F1 alpha, the stable metabolite of PG I2, in arterial blood. The pretreatment with indomethacin (10 mg/kg) prevented the increase in 6-keto PG F1 alpha and potentiated the lung injury after microembolization. Exogenously administered PG I2 (20 ng/kg/min) prevented completely the increase in the filtration coefficient without any effects on hemodynamics, although these effects of indomethacin and PG I2 did not relate to their effects on platelet aggregation. Based on these results, we could conclude that prostacyclin could play an important role in preserving cell integrity of the lung and in prevention of increased lung vascular permeability following pulmonary microembolization.

6-Ketoprostaglandin F1 alpha↗

PubMed1983

A pathophysiological role of endogenous prostacyclin in endotoxin induced increase in lung vascular permeability in dogs.

Escherichia coli endotoxin (1 mg/kg) infusion over 30 min into anesthetized artificially ventilated dogs caused a biphasic response: an early phase of pulmonary hypertension and a late phase of increased lung vascular permeability. During an early phase, PG F2 alpha, Tx A2 (as Tx B2) and prostacyclin (as 6-keto-PG F1 alpha) concentrations increased in plasma or right duct lymph of dogs. During a late phase, the concentrations of PG F2 alpha and Tx A2 decreased to near the base-line values, while the concentration of prostacyclin remained elevated. Administrations of PG synthetase inhibitors 45 min prior to endotoxin inhibited the increase in concentration of prostacyclin following the infusion of endotoxin and potentiated the increase in lung vascular permeability at the beginning of the late phase. Continuous infusion of prostacyclin (20 ng/kg/min) starting one hour before endotoxin for 5 hour periods prevented the increase in lung vascular permeability induced by endotoxin. Based on these results, we could conclude that endogenous prostacyclin might play an important role in preserving cell integrity of lungs and counteract the deleterious effects of endotoxin.

Animals↗

PubMed1983

The effect of prostacyclin infusion on increased pulmonary vascular permeability following microembolization in dogs.

Prostacyclin (PG I2) generated by vascular endothelium is a strong antiaggregating substance. As platelet aggregation and release of humoral factor(s) have been reported to be crucial in the pathogenesis of acute lung injury following pulmonary microembolization, prostacyclin could have a protective effect against microembolic lung vascular injury. Following unilateral microembolization, the filtration coefficient in the nonembolized lung increased significantly to 0.14 +/- 0.02 from the base line value of 0.07 +/- 0.01 ml/min/mmHg/100g. Prostacyclin as measured as 6-keto PG F1 alpha in arterial blood increased significantly to 4.15 +/- 1.76 at 30 min from the base line value of 1.90 +/- 0.45 ng/ml and increased further to 5.67 +/- 1.49 ng/ml at 60 min following microembolization. Exogenously administered PG I2 methylester (20 ng/kg/min) prevented completely the increase in the filtration coefficient without any effects on hemodynamics, although the effects of PG I2 methylester did not depend on its action on platelet aggregation. Based on these results, we conclude that prostacyclin could play an important role in preserving cell integrity of the lung and prevention of increased lung vascular permeability following pulmonary microembolization.

6-Ketoprostaglandin F1 alpha↗

PubMed1983

Protective effect of a thromboxane synthetase inhibitor, OKY-1581, on increased lung vascular permeability in pulmonary microembolization in dogs.

To evaluate the potential beneficial effect of a thromboxane synthetase inhibitor, OKY-1581, on increased pulmonary vascular permeability in pulmonary microembolization, we have measured the filtration coefficient in the nonembolized lung after unilateral microembolization in dogs. The unilateral microembolization caused marked elevations in pulmonary artery pressure and blood flow to the nonembolized lung, while pulmonary venous pressure in nonembolized lung did not change. The pulmonary vascular resistance in nonembolized lung did not increase significantly. The filtration coefficient (Kf) in nonembolized lung increased to 0.14 +/- 0.02 from the baseline value of 0.07 +/- 0.01 ml/min/mmHg/100g at 30 min after microembolization when the initial hemodynamic changes reduced toward the baseline value. In OKY-1581 treated dogs, similar hemodynamic changes did not result in the increase in the filtration coefficient in nonembolized lung. Platelet aggregation was also inhibited after microembolization in OKY-1581 treated dogs. Based on these results, we could conclude that OKY-1581 could prevent the increase in pulmonary vascular permeability following pulmonary microembolization by inhibiting platelet aggregation and possibly by preventing the release of thromboxane A2.

Acrylates↗

PubMed1982

Actions of prostaglandins and indomethacin on the electrical and mechanical properties of smooth muscle cells of the guinea-pig ileocecal junction.

The effects of prostaglandins (PGs) and indomethacin on the mechanical and membrane properties of the smooth muscle cells of the guinea-pig ileocecal junction were studied using microelectrode and tension recording techniques and radioimmunoassay to determine levels of PGs. In the guinea-pig ileocecal junction, we found two distinct cell populations-cells with, and without spontaneous electrical and mechanical activities. PGs (PGE1, PGE2, PGF2 alpha) in low concentrations suppressed spontaneous mechanical activity. Correspondingly, PGs (greater than 10-7 M) suppressed both spontaneously generated spikes and evoked spikes, presumably due to an increase in the threshold for generation of action potential. On the contrary, indomethacin evoked rhythmic spontaneous contractions in the mechanically quiescent muscle preparations and reduced the PGE and PGF content of the muscle. Spontaneous spike discharges occurred during the indomethacin-induced contractions. The spontaneous electrical and mechanical activities induced by indomethacin were suppressed by PGs, in low concentrations. These results indicate that under physiological conditions, the endogenous PGs in the muscle may play an important role in regulation muscle tone as well as the membrane properties, thereby contributing to the regulation of motility of the intestine and possibly the sphincter.

Animals↗

PubMed1982

A possible role of a nonadrenergic inhibitory nervous system in airway hyperreactivity.

To investigate a possible role of a nonadrenergic inhibitory nervous system in airway hyperreactivity, we measured changes in RL and CL caused by electrical stimulation of cervical vagus nerve during the infusion of 5-HT, after treatment with atropine and propranolol in 18 cats. RL decreased to 56 +/- 3% (mean +/- SE) and CL increased to 186 +/- 13% of the prestimulated values, respectively, after stimulation. Hexamethonium diminished these responses significantly. Airway reactivity to 5-HT was reduced by continuous electrical stimulation of cervical vagus nerve in cats pretreated with atropine and propranolol. Hexamethonium potentiated airway reactivity to 5-HT. These results suggest that a nonadrenergic inhibitory nervous system could play an important role in the control of the bronchomotor tone and contribute to airway hyperreactivity.

Airway Resistance↗