Ag. Ramage et Mg. Wyllie, A COMPARISON OF THE EFFECTS OF DOXAZOSIN AND TERAZOSIN ON THE SPONTANEOUS SYMPATHETIC DRIVE TO THE BLADDER AND RELATED ORGANS IN ANESTHETIZED CATS, European journal of pharmacology, 294(2-3), 1995, pp. 645-650
The effects of i.v. infusion of the alpha(1)-adrenoceptor antagonists
doxazosin and terazosin (2 mg kg(-1) h(-1)) on spontaneous hypogastric
, renal and inferior cardiac nerve activity, spontaneous bladder contr
actions, blood pressure, heart rate and femoral arterial flow were inv
estigated separately in alpha-chloralose-anaesthetized cats. Both drug
s caused a reduction in hypogastric nerve activity associated with no
overt changes in spontaneous bladder contractions. Doxazosin was more
potent than terazosin, in that there was a significant reduction in hy
pogastric nerve activity after 20 min (0.67 mg kg(-1)) of infusion, wh
ile for terazosin this occurred after 40 min (1.33 mg kg(-1)). Both dr
ugs also caused significant falls in blood pressure of 34 +/- 3 mm Hg
and 33 +/- 4 mm Hg after 60 min. This was associated with no change in
heart rate for doxazosin while terazosin caused an initial and signif
icant increase in heart rate of 20 +/- 3 beats min(-1) by 5 min, decli
ning by 30 min to 1 +/- 5 beats min(-1). This terazosin-induced tachyc
ardia was associated with a significant increase in cardiac nerve acti
vity of 128 +/- 22%. Both drugs caused increases in renal nerve activi
ty however only for doxazosin was this increase significant. Femoral a
rterial conductance was also increased by both drugs, however, for dox
azosin this increase was immediate and larger over the infusion period
. These results demonstrate that alpha(1)-adrenoceptor antagonists can
reduce sympathetic drive to the bladder and related organs.