Ny. Wu et al., EFFECTS OF D-AMPHETAMINE ON THE FREQUENCY OF THE SPONTANEOUS CONTRACTION OF THE PORTAL-VEIN IN RAT, General pharmacology, 30(5), 1998, pp. 669-683
1. Effects of d-amphetamine on the frequency of spontaneous contractio
n of the longitudinal muscle of the portal vein were studied in Wistar
rats. Its effects on the circular muscles of the pulmonary artery and
stomach also were tested, 2. d-Amphetamine increased the frequency of
the spontaneous contraction of the portal vein. The ratio of the freq
uency of the spontaneous contraction of the portal vein before and aft
er d-amphetamine treatment also was increased. The effect was not affe
cted in the presence of prazocin, (+)-lysergic acid diethylamide, atro
pine and haloperidol. These results suggested that the d-amphetamine-e
licited response was not due mainly to the activation of adrenergic, s
erotoninergic (5-HT), cholinergic or dopaminergic receptors. 3. Increa
sing extracellular calcium or sodium ion concentrations decreased the
frequency of the spontaneous contraction of the portal vein. However,
the ratios of the frequency of the spontaneous contraction of the rat
portal vein before and after d-amphetamine treatment in media containi
ng different extracellular calcium or sodium concentrations were not s
ignificantly altered. Tetrodotoxin did not alter the effect of d-amphe
tamine on the frequency of spontaneous contractions. It appeared that
calcium and sodium ions may not take part in the effects of d-amphetam
ine on the frequency of the portal vein. 4. An increase in extracellul
ar potassium ion concentrations increased the frequency of the spontan
eous contractions of the portal vein. In addition, the ratios of the f
requency of the spontaneous contractions of the rat portal vein before
and after d-amphetamine treatment in media containing different extra
cellular potassium ion concentrations were significantly altered. Tetr
aethylammonium chloride (TEA) and 4-aminopyridine (4-AP) increased the
spontaneous contractions of the portal vein. However, TEA and 4-AP di
d not increase the d-amphetamine elicited increasing effect on the fre
quency of spontaneous muscle contractions. 5. Levochromakalim, a potas
sium channel opener, decreased the frequency of the spontaneous contra
ctions of the portal vein. Levochromakalim also decreased the effect o
f d-amphetamine on the frequency of spontaneous contractions of the mu
scle. It appeared that potassium ion may be associated with the effect
s of d-amphetamine on the activity of the portal vein. 6. d-Amphetamin
e potentiated, whereas prazosin decreased, the noradrenaline-elicited
contracture of the rat pulmonary artery in a dose-dependent manner. 7.
d-Amphetamine elicited contracture of the circular muscle of rat stom
ach, whereas it did not alter the frequency of the spontaneous contrac
tion of the muscle. 8. Both 5-HT and d-amphetamine elicited the contra
cture of the circular muscle of rat stomach. Ketanserin decreased the
5-HT-elicited response, whereas it did not alter the d-amphetamine-eli
cited response in the muscle. d-Amphetamine did not alter the frequenc
y of the spontaneous contraction of the stomach. 9. It is concluded th
at d-amphetamine has different effects on the frequency of spontaneous
smooth muscle contractions. It increased the frequency in the portal
vein, but it did not alter the frequency in stomach circular muscle. (
C) 1998 Elsevier Science Inc.