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Biomedical subjects

G Lambrecht

Publications and source records attributed to G Lambrecht.

At least 127 records · Page 7Linked to original sources
PubMed1982

Depressor effects of isoguvacine propyl ester and isoarecaidine propyl ester due to stimulation of central GABA receptors in the cat.

Upon their simultaneous administration into the left and right vertebral artery of the cat, 2 x 30 micrograms isoarecaidine propyl ester (IAPE) and 2 x 30 micrograms isoguvacine propyl ester (IGPE) induce hypotension and bradycardia. These effects were antagonized by (+)-bicuculline or picrotoxin. IAPE is rapidly hydrolyzed by cat brain tissue in vivo. It is suggested that both IAPE and IGPE are prodrugs and that the corresponding carboxylic acids are GABA agonists and responsible for the cardiovascular effects evoked.

Animals↗
PubMed1982

Centrally induced cardiovascular effects and kinetic behaviour of isoarecaidine propyl ester in the cat.

The present investigation deals with effects of isoarecaidine propyl ester (IAPE) on blood pressure and heart rate of the anaesthetized cat. The kinetic behaviour of the drug in plasma and various brain tissues was also studied. The results indicate that the ester (4 mg.kg-1) induces a depressor effect and bradycardia after i.v. administration. Injection of IAPE (up to 60 micrograms.kg-1) into the left vertebral artery lowers blood pressure in a dose-dependent manner. When administered simultaneously into the left and right vertebral artery, low doses (6 micrograms. kg-1) produce a substantial fall in blood pressure. Although the fall in blood pressure after i.v. injection lasts for more than 60 min, plasma half life is extremely short (t1/2 = 6.3 sec). The possible metabolism of the ester was studied in the pons, medulla oblongata and cerebellum. Thirty min after the injection into the left vertebral artery, IAPE is almost entirely hydrolyzed in the pontomedullary region. This degradation is prevented by pretreatment with paraoxon, that abolishes the depressor action of IAPE. It is suggested that accumulated isoarecaidine in the pontomedullary region is responsible for the depressor response to IAPE. Since IAPE does not seem to influence blood pressure and heart rate via a peripheral mechanism and lowers blood pressure and cardiac frequency by a central action, this drug is considered to be of pharmacological interest. The mechanism of action is discussed.

Animals↗
PubMed1982

[Structure- and conformation-activity relationship of heterocyclic acetylcholine analogs. 13. Cholinergic properties of tertiary and quaternary 4-acetoxyquinuclidines].

In the course of investigations of structure and conformation-activity relationships of heterocyclic acetylcholine analogues, the cholinergic properties of the tertiary (7) and quaternary (8) 4-acetoxyquinuclidine were studied. Both esters have no affinity when tested at the nicotinic receptor, and they are not hydrolyzed by acetylcholinesterase. In the guinea-pig ileum and atrium assay, the heterocyclic analogues 7 and 8 demonstrate agonistic properties, but their potency is three to four orders of magnitude lower than that of acetylcholine. Stereochemical restrictions seem to be responsible for the weak muscarinic potency of both quinuclidine analogues.

Animals↗
PubMed1981

Muscarinic effects of various isoarecaidine esters in sympathetic ganglia.

1 The pressor effects of various tertiary and quaternary isoarecaidine esters in both pithed and anaesthetized rats are reported. In order to elucidate the mechanism of action, various experiments were carried out with the quaternary isoarecaidine methyl ester (Q-4-Me). 2 Treatment with mecamylamine, dexetimide, reserpine and phentolamine abolished or reduced the pressor response to Q-4-Me, whereas pretreatment with cocaine gave rise to a prolonged pressor effect. Plasma noradrenaline levels were significantly increased after the infusion of Q-4-Me. 3 From the results it can be concluded that the pressor effects brought about by the quaternary compounds can be attributed to stimulation of nicotinic and muscarinic receptors in sympathetic ganglia. The consequences of interaction with muscarinic receptors predominate over the effects due to minimal interference with nicotinic receptors by the drug.

Anesthesia↗
PubMed1981

[Structure and conformation-activity relationships of cyclic acetylcholine analogues / 12th communication: Synthesis and cholinergic properties of stereoisomeric 3-acetoxythiacyclohexanes (author's transl)].

In the course of investigations of structure and conformation-activity relationships of cyclic acetylcholine analogues, both the enantiomers of trans-3-acetoxy-1-methylthioniacyclohexane were prepared. These two esters and the corresponding racemate of the cis-ester were tested for nicotine- and muscarine-like activity. The stereoisomeric cyclic analogues differ substantially in pharmacological activity. The cis-sulfonium ester shows the highest nicotinic potency (1/25 the nicotinic potency of acetylcholine), and the (+)-trans-ester has no agonistic properties when tested at nicotinic receptors, but it shows the highest muscarinic potency in this series.

Acetylcholine↗
PubMed1980

Structure and conformation activity relationships of heterocyclic acetylcholine analogues. X. The inhibitory effect of 3-quinuclidinyl benzilates on cardiac muscarinic receptors.

The tertiary and quaternary enantiomers of 3-quinuclidinyl benzilate (QNB) were tested for atropine-like activity on the electrically stimulated guinea-pig atrium preparation. The (R)-isomers had higher affinity for muscarine-sensitive acetylcholine receptors than their corresponding (S)-analogues.

Acetylcholine↗