Plasma dopamine in regulation of canine renal blood flow.

Studies were performed in pentobarbital-anesthetized dogs to determine whether circulating plasma dopamine (DA) is involved in renal blood flow (RBF) regulation. During graded reductions in renal perfusion pressure (RPP), total renal venous (RV) DA content significantly increased at RPPs below the autoregulatory range. The RBF response to decrements in RPP was also examined during control, infusion of DA (1.

Effects of cocaine and nomifensine on canine renal venous norepinephrine and dopamine content during electrical stimulation of the renal nerves.

Dopamine has been suggested to play a role in the regulation of renal blood flow following its neuronal release from within the kidney. Skepticism remains, however, as to whether a vascular dopaminergic innervation plays a physiologic role in renal blood flow regulation. Thus, to investigate this possibility, we examined whether electrical stimulation of the renal nerves evokes an overflow of dopamine into renal venous blood that could be augmented by cocaine or nomifensine, two inhibitors of presynaptic uptake.

Stereoselectivity of S- and R-sulpiride for pre- and postsynaptic dopamine receptors in the canine kidney.

The stereoselectivity of S (S)- and R (R)-sulpiride for the pre-(prereceptor) and post (postreceptor) synaptic dopamine receptors has been examined in various tissues. In the present study, the effects of S and R on the pre- and postreceptor in the canine kidney were investigated. The left renal artery of pentobarbital-anesthetized dogs was exposed and mean arterial pressure and renal blood flow were monitored.

Controversial evidence regarding the functional importance of presynaptic alpha receptors.

alpha-Adrenergic agonists have been reported to decrease the release of neuronal norepinephrine (NE) via presynaptic alpha 2 receptors when studied under in vitro conditions. Within the last several years studies have been performed in the intact animal to determine whether this presynaptic mechanism is a pharmacological artifact or whether it plays a functional role in cardiovascular physiology. In the intact renal vascular bed clonidine, oxymetazoline, and NE did not decrease stimulation-induced vasoconstrictor responses relative to constrictor responses produced by exogenous NE.

Evaluation of presynaptic histamine receptors in the canine renal vascular bed.

Histamine has been shown to increase renal blood flow via H1- and H2-receptors. Furthermore, H2-receptors have been demonstrated to attenuate stimulation-induced release of norepinephrine. The present studies examined whether histamine has a presynaptic effect on sympathetic nerves in the canine renal vascular bed.

The cardiac and vascular effects of sodium glutamate.

1. The cardiovascular effects of sodium glutamate were investigated in anaesthetized dogs with bolus injections, intravenous infusions and rabbit isolated papillary muscles. 2.

Evaluation of presynaptic alpha-receptor function in the canine renal vascular bed.

The functional significance of presynaptic alpha-receptor modulation of sympathetic nerves was examined in vivo in the canine renal vascular bed. In pentobarbital-anesthetized dogs, the vasoconstrictor response to renal nerve stimulation and exogenous norepinephrine was compared before and during intra-arterial infusions of epinephrine, oxymetazoline, clonidine, and norepinephrine. Only epinephrine produced a modest decrease in stimulation-induced vasoconstriction at 1 Hz.

Presynaptic inhibition of canine renal adrenergic nerves by acetylcholine in vivo.

Experiments were performed in anesthetized dogs to determine whether previously reported in vitro inhibition of sympathetic neurotransmitter release by acetylcholine could be demonstrated in the renal vasculature of the intact animal. Vasoconstrictor responses to renal sympathetic nerve stimulation at varying frequencies were compared to intra-arterial injections of norepinephrine before and during intra-arterial infusions of acetylcholine, 2.5--80 micrograms/min.

Intrarenal mechanism for renal vasoconstriction resulting from stimulation of the ureter in the dog.

1. The mechanism responsible for ipsilateral renal vasoconstriction resulting from mechanical stimulation of the ureter was examined using the pharmacological antagonists saralasin, SQ20881, indomethacin, atropine and phentolamine. 2.

Effects of minoxidil and nitroprusside on reflex increases in myocardial contractility.

1 The effects of nitroprusside and minoxidil on increases in myocardial contractility resulting from carotid artery occlusion were investigated in anaesthetized dogs. The results were compared with those produced by intravenous influsion of noradrenaline. 2 Nitroprusside and minoxidil attenuated the pressor responses produced by carotid artery occlusion.

Evaluation of drug-induced reno-renal vasomotor reflex in the dog.

1. Renal arterial infusions of endogenous vasoactive compounds were administered, and elctromagnetic flow probes were used to measure simultaneous ipsilateral and contralateral renal blood flow. 2.

Comparative splanchnic blood flow effects of various vasodilator compounds.

We examined the visceral blood flow distribution during infusion of three vasodilators at doses that produced similar depression of systemic arterial pressure. The studies were performed in pentobarbital-anesthetized dogs using the radioactive microspheres technique. Minoxidil did not alter renal, total visceral, or visceral organ flow distribution with the exception of a modest increase in relative stomach blood flow.

Determination of hydralazine and its metabolites by gas chromatography-mass spectrometry.

Metabolism of the vasodilator hydralazine was investigated by in vivo and in vitro studies. Standards to identify metabolic products were synthesized. Determination and quantification of hydralazine and its metabolites were accomplished by gas chromatography-mass spectrometry.

Comparative systemic and regional hemodynamic effects of dopamine and dobutamine.

Dopamine and dobutamine are sympathomimetic amines with divergent peripheral vascular actions. The renal, mesenteric, and femoral vascular and total systemic hemodynamic effects of these amines were compared in pentobarbital-anesthetized dogs. Both agents increased myocardial contractility.