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Biomedical subjects

J Fontaine

Publications and source records attributed to J Fontaine.

At least 127 records · Page 7Linked to original sources
PubMed1984

Potentiation by sulphydryl agents of the responses of guinea-pig isolated ileum to various agonists.

Sulphydryl agents (dithiothreitol, mercaptoethanol, monothioglycerol, cysteine, glutathione) increase non-specifically the potency of various agonists (acetylcholine, 5-hydroxytryptamine, nicotine, bradykinin, prostaglandin E2) on the guinea-pig ileum. These effects are of non-cholinergic origin and are not related to prostaglandin synthesis. Sulphydryl agents act directly on the smooth muscle cells of the guinea-pig ileum most probably by reducing disulphide bonds located on the membrane surface and by this mechanism modulate the muscular contractile activity.

Acetylcholine↗
PubMed1984

Effect of dopamine on dog distal colon in-vitro.

The effects of dopamine, isoprenaline, adrenaline and noradrenaline in dog isolated colon strips were studied. All these drugs produced in the preparation relaxations which were inhibited by propranolol and sotalol or, in the case of noradrenaline, by a mixture of propranolol and phentolamine. A selective beta 1-adrenergic antagonist, practolol, had the same inhibitory effects on the relaxations induced by all the agonists, suggesting the existence of beta 1- and beta 2-adrenoceptor subtypes in the dog distal colon. There is no evidence for the presence of specific dopaminergic receptors in this preparation.

Animals↗
PubMed1983

The cardiac inotropic response to secretin is lower in genetically obese (fa/fa) than in lean (fa/?) Zucker rats.

The efficacy and potency of secretin in rat heart was documented by comparing secretin and D,L-isoproterenol effects on: 1. the inotropic response of papillary muscles electrically stimulated in vitro, and 2. adenylate cyclase activity in a crude membrane preparation from heart ventricle. In male adult lean (FA/?) Zucker rats, the extent of the positive inotropic response and the stimulatory effect on adenylate cyclase were similar in magnitude for secretin and D,L-isoproterenol, the two corresponding EC50 values for inotropic effects being 5- to 10-fold lower than the EC50 values for adenylate cyclase stimulation. In male adult obese (fa/fa) Zucker rats, the stimulatory effects exerted by secretin on the inotropic response and adenylate cyclase activity were reduced by 73% and 70%, respectively, while the extent of similar D,L-isoproterenol responses were reduced, respectively, by 29% and 25% only. With D,L-isoproterenol, the EC50 value for the inotropic effect was 5-fold lower than the EC50 value for adenylate cyclase activation whereas both EC50 values were comparable when secretin was used as a stimulant.

Adenylyl Cyclases↗
PubMed1983

Naloxone and alcohol intoxication in the dog.

1 The effects of naloxone upon ethanol-induced coma have been investigated in dogs. In a double blind study, 15 mongrel dogs received ethanol i.v. (4 g/kg) followed by a single dose of naloxone (12 micrograms/kg). 2 Naloxone failed to affect either the duration of respiratory arrest or the time to recovery of motor coordination. In similar animals treated with the narcotic analgesic, fentanyl, naloxone induced a dramatic and complete reversal of the narcotic effects within 30 seconds. 3 It is concluded that, if naloxone has any effect in alcoholic coma, it is not comparable with its dramatic action in narcotic coma.

Alcoholic Intoxication↗
PubMed1982

Naloxone and ethanol intoxication.

Naloxone has been said to be an antidote of acute ethanol intoxication in man. Experimental and clinical studies are however not convincing and contradictory. We have used naloxone to antagonize the effect of ethanol in mice. Results are compared to those obtained with morphine intoxication. Even at high doses (5 mg/kg) naloxone is not a good antagonist of ethanol intoxication in mice.

Alcoholic Intoxication↗
PubMed1980

The effects of substituted benzamides on frog rectus abdominis.

The substituted benzamides metoclopramide, bromopride, tiapride and sulpiride (10(-5) and 10(-4) M) significantly increased the sensitivity of frog rectus abdominis muscle to exogenous acetylcholine but not to carbachol. This supersensitivity could be correlated with the anticholinesterase activity of these drugs measured in homogenates from frog skeletal muscle. Sultopride, like procainamide, has only inhibitory effects on the responses of the rectus abdominis to acetylcholine and has no anticholinesterase activity in this preparation.

Amisulpride↗
PubMed1980

A study of the effects of amodiaquine on the guinea-pig isolated ileum.

Amodiaquine (3.5 . 10(-7) mol/l), a 4-amino-quinoline antimalarial, increases the responses of the guinea-pig isolated ileum to direct (acetylcholine, histamine, barium, chloride), partially (5-hydroxytryptamine, PGE1 and F2 alpha) and totally (electrical stimulations, nicotine) indirect agonists. Moreover it reverses inhibitions of the electrical induced contractions by acetylcholine antagonists (atropine), acetylcholine release blocking agents (morphine, tetrodotoxin, procaine, noradrenaline) and prostaglandin synthesis inhibitors (indomethacin, ibuprofen, flufenamine acid, hydrocortisone). From 2.7 . 10(-6) mol/l, it induces dose-related tonic contractions which are totally and reversibly abolished by indomethacin as well as by the prostaglandin antagonist, polyphloretin phosphate, but not by atropine, morphine and tetrodotoxin. This indicates that amodiaquine exerts both a direct muscular non selective ileal sensitization to various agonists and, but at higher concentrations, a contractile effect apparently dependent on prostaglandin synthesis and release. At even higher concentrations (5.4 . 10(-6) mol/l) an effect of amodiaquine on acetylcholine release was demonstrated by the observation of phasic contractions inhibited by atropine, morphine and tetrodotoxin. These effects are different from those found by us with several other antimalarial compounds in the same preparation.

Amodiaquine↗
PubMed1979

The effects of antiinflammatory steroids on the response of the guinea-pig isolated ileum to acetylcholine, histamine, nicotine, 5-hydroxytryptamine and electrical stimulation.

High concentrations of antiinflammatory steroids (2.5-40 microgram/ml) reversibly inhibited the electrically induced contractions of the guinea-pig isolated ileum. At 40 microgram/ml they also reversibly inhibited contractions elicited by acetylcholine, histamine nicotine and 5-hydroxytryptamine. PGE1 (2.5 ng/ml), PGE2 (2.5 ng/ml) and PGF 2 alpha (25 ng/ml) antagonized these effects. The inhibition of contractions elicited by direct agonists were less pronounced than those elicited by indirect or partly indirect agonists. The inhibitory effect of steroids may be related to non-specific actions on biological membranes. An overall sensitization of the smooth muscle by PG's may explain their antagonism to inhibition by steroids.

Acetylcholine↗
PubMed1979

Potentiation by D-penicillamine and other sulfhydryl agents of the vascular response to histamine in the anaesthetized dog.

D-penicillamine (80 mg/kg) potentiates the fall in blood pressure produced by an i.v. injection of histamine in the anaesthetized dog but is inactive on the effects of acetylcholine and prostaglandin E1. Other sulfhydryl agents (alpha-thioglycerol, 2-mercaptoethanol, 2,3-dimercapto-l-propanol, DL-cysteine, glutathione, diethyldithiocarbamate) can similarly modify the effects of histamine on blood pressure but two metal complexing agents (CaNa2 EDTA and orthophenantroline) are inactive. After pretreatment with indomethacin (10 mg/kg) or cimetidine (0.5 mg/kg/min) D-penicillamine still increases the effect of histamine but not after pretreatment with pyrilamine maleate (1 mg/kg). Moreover D-penicillamine does not modify the blood pressure drop due to dimaprit but increases that to 2-(2-pyridyl) ethylamine. It is concluded that D-penicillamine and some other sulfhydryl agents can increase the blood pressure lowering effects of histamine at the level of vascular H1-receptors by a sensitizing mechanism which might involve the rupture of a disulfide bridge.

Anesthesia↗
PubMed1979

Pharmacological analysis of the effects of metoclopramide on the transmurally stimulated guinea-pig ileum.

The effects of metoclopramide (Mcp), a benzamide derivative, have been quantitatively analyzed on the responses of the isolated guinea-pig ileum to transmural stimulation. Mcp (0.03 microgram ml-1 upwards) increased these responses but this effect which was calcium-dependent was not concentration-dependent (up to 30 micrograms ml-1). Mcp antagonized the inhibitor effects of noradrenaline, dopamine, procaïne, adenosine triphosphate, bufexamac and hydrocortisone on the ileal responses, but not those of tetrodotoxin and verapamil.

Animals↗