Ej. Whalen et al., Functional evidence for the rapid desensitization of 5-HT3 receptors on vagal afferents mediating the Bezold-Jarisch reflex, BRAIN RES, 873(2), 2000, pp. 302-305
The aim of this study was to determine whether 5-hydroxytryptamine (5-HT)(3
) receptors on cardiopulmonary afferents mediating the Bezold-Jarisch refle
x (BJR) desensitize upon repeated exposure to selective agonists. BJR-media
ted falls in heart rate, diastolic arterial blood pressure and cardiac outp
ut elicited by the 5-HT3-receptor agonists, phenylbiguanide (100 mu g/kg, i
.v.) or 2-methyl-5-HT (100 mu g/kg, i.v.), progressively diminished upon re
peated injection in conscious rats. The BJR responses elicited by 5-HT (40
mu g/kg, i.v.) were markedly reduced in rats which had received the above i
njections of phenylbiguanide or 2-methyl-5-HT whereas the BJR responses eli
cited by L-S-nitrosocysteine (10 mu mol/kg, i.v.) were similar before and a
fter the injections of the 5-HT3 receptor agonists. These findings suggest
that tachyphylaxis to 5-HT3 receptor agonists may be due to the desensitiza
tion of 5-HT3 receptors on cardiopulmonary afferents rather than the impair
ment of the central or peripheral processing of the BJR. (C) 2000 Elsevier
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