ISSN:
1440-1681
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Medizin
Notizen:
1. The present study was carried out to determine whether rilmenidine, a recently introduced antihypertensive agent which acts on α2-adrenoceptors, has partial agonist activity on prejunctional α2-adrenoceptors in guinea-pig atria.2. Isolated preparations of guinea-pig atria were incubated with [3H]-noradrenaline and the efflux of radioactivity induced by stimulation of intramural sympathetic nerves was used as an index of release of transmitter noradrenaline.3. Rilmenidine (1 μmol/1) inhibited noradrenaline release evoked by short trains (five, 20 and 50 pulses) of sympathetic nerve stimulation and this inhibitory effect of rilmenidine was antagonized by the α2-adrenoceptor antagonists, idazoxan (0.1 and 0.3 umol/1) and rauwolscine (0.3 umol/1) whereas it was not affected by the α1-adrenoceptor antagonist prazosin (0.1 μmol/1).4. On the other hand, rilmenidine (1 μmol/1) enhanced noradrenaline release evoked by long trains (150 and 300 pulses) of stimulation and this effect was also abolished by idazoxan (0.1 μmol/1).5. These findings suggest that the effects of rilmenidine on transmitter release depend on the degree of auto-inhibition: when the concentration of noradrenaline in the biophase of the prejunctional α2-adrenoceptors is low, rilmenidine acts as an agonist, but when the concentration is high it acts as an antagonist. Thus, rilmenidine, like clonidine, is a partial agonist on prejunctional α2-adrenoceptors in guinea-pig atria.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1440-1681.1988.tb01016.x
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