Comparison of the behavioral and neurochemical effects of the two optical enantiomers of medetomidine, a selective alpha-2-adrenoceptor agonist.
J Pharmacol Exp Ther
; 259(2): 848-54, 1991 Nov.
Article
em En
| MEDLINE
| ID: mdl-1682487
ABSTRACT
Medetomidine (MED) is a veterinary sedative whose mode of action is activation of alpha-2 adrenoceptors. Because the carbon atom which separates the two ring systems is methylated, there is a center of stereochemical asymmetry in the molecule. The resulting enantiomers, d-MED and l-MED have recently become available for study. The biological activity of MED, as is now demonstrated in rats in vivo, seems to reside almost exclusively in the d-MED form. Only at extremely high doses (e.g., 10 mg/kg) does l-MED exert any effects, interpreted as alpha-2 adrenoceptor antagonism. In contrast, doses of d-MED as low as 30 micrograms/kg cause sedation, hypothermia and induce neurochemical changes in norepinephrine and 5-hydroxytryptamine metabolism in brain characteristic of alpha-2-agonists (decreases in concentrations of biogenic amine metabolites, turnover and increases in concentration of parent amine). The most sensitive neurochemical indicator of the alpha-2-agonist action of d-MED was the concentration of unconjugated 3-methoxy-4-hydroxy-phenyethylene glycol in rat cerebral spinal fluid, doses of d-MED as low as 10 micrograms/kg caused a significant reduction in this norepinephrine metabolite. Simultaneous administration of the specific alpha-2 adrenoceptor antagonist, atipamezole (1 mg/kg), effectively inhibited the behavioral and most of the neurochemical actions of d-MED (100 micrograms/kg). It is concluded that the enantiomers of MED may be extremely useful in elucidating structure action relationships at alpha-2 adrenoceptors.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Comportamento Animal
/
Encéfalo
/
Agonistas alfa-Adrenérgicos
/
Imidazóis
Limite:
Animals
Idioma:
En
Revista:
J Pharmacol Exp Ther
Ano de publicação:
1991
Tipo de documento:
Article
País de afiliação:
Finlândia