Effects of benzoyltropine and tropacocaine on several cholinergic processes in the rat brain.
J Pharmacol Exp Ther
; 254(2): 584-90, 1990 Aug.
Article
em En
| MEDLINE
| ID: mdl-1974643
ABSTRACT
Benzoyltropine and tropacocaine are two contaminants of street-cocaine reported to have parasympatholytic activity. Because the mechanism underlying this activity is obscure, we investigated the effects of these compounds on several cholinergic processes sodium-dependent choline uptake, sodium-independent choline uptake, acetylcholine synthesis, acetylcholine release (spontaneous and veratridine-induced) and binding of [3H]quinuclidinyl benzylate to muscarinic receptors. These studies used rat cerebral cortical synaptosomes, except for the receptor-binding studies, which used whole brain plasma membranes. Benzoyltropine and tropacocaine each inhibited sodium-dependent choline uptake and acetylcholine synthesis in a dose-related manner that was competitive with extracellular choline. Benzoyltropine was 4 to 5 times more potent in both actions than tropacocaine. Sodium-independent choline uptake was not affected by either compound. Benzoyltropine (30 microM) had no effect on the sodium-dependent uptake of norepinephrine, gamma-amino-butyric acid, glutamate or serotonin; tropacocaine (30 microM) inhibited only norepinephrine uptake at this concentration. Benzoyltropine and tropacocaine each inhibited the spontaneous and veratridine-induced release of newly synthesized acetylcholine, but not via activation of presynaptic muscarinic receptors. Instead, each compound was able to attenuate the oxotremorine-induced inhibition of the release of acetylcholine, suggesting antimuscarinic activity. Binding experiments showed that benzoyltropine and tropacocaine were, respectively, about 1,000- and 10,000-fold less potent than scopolamine as receptor antagonists. Finally, we demonstrated that benzoyltropine accumulates in the rat brain after its peripheral injection (10 mg/kg i.p.) and remains there with a half-life similar to that of cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Encéfalo
/
Colina
/
Cocaína
/
Anestésicos Locais
Limite:
Animals
Idioma:
En
Ano de publicação:
1990
Tipo de documento:
Article