Metabolic fate of injected radiolabelled dopamine and 2-fluorodopamine in rats.

In evaluating positron-emitting analogs of dopamine (DA) as possible imaging agents for visualizing tissue sympathetic innervation and function, the metabolic fate of systemically injected [3H]-DA or [14C]-DA was compared with that of [3H]-2-fluoroDA in plasma and in sympathetically innervated tissues (left ventricle, spleen and salivary glands) of rats. By 60 min after the injection of [3H]-DA or [3H]-2-fluoroDA, concentrations of [3H]-DA. [3H]-2-fluoroDA, [3H]-norepinephrine ([3H]-NE) and [3H]-2-fluoroNE in tissue exceeded concentrations in plasma by up to several thousand-fold.

Modification of alpha-2 presynaptic receptor activity and catecholamine release following chronic MAO inhibition.

Neuronal release of noradrenaline from the isolated rat vas deferens has been studied following long-term MAO inhibition. Fractional release of 3H-noradrenaline in response to electrical field stimulation was reduced following chronic clorgyline treatment, but yohimbine equalised the fractional release to that of control animals. Endogenous release of noradrenaline was increased 1.

Effects of monoamine oxidase inhibitors on levels of catechols and homovanillic acid in striatum and plasma.

Levels of homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC) and dihydroxyphenylglycol (DHPG) in plasma and the striatium were measured after inhibition of monoamine oxidase type A (MAO-A) by clorgyline (4 mg/kg i.p.), MAO-B by (-)deprenyl (1 mg/kg i.

Neuronal uptake and metabolism of 2- and 6-fluorodopamine: false neurotransmitters for positron emission tomographic imaging of sympathetically innervated tissues.

The neuronal uptake and metabolism of 2-fluorodopamine (2F-dopamine), 6-fluorodopamine (6F-dopamine) and tritium-labeled dopamine were compared in heart, submaxillary gland and spleen of rats to assess the utility of 18F-labeled 2F- or 6F-dopamine for positron emission tomographic imaging of sympathetically innervated tissues. Tritiated dopamine with and without 2F- or 6F-dopamine, or tritiated 2F-dopamine alone, were injected i.v.

Chronic inhibition of monoamine oxidase reduces noradrenaline release in rat vas deferens and anococcygeus muscle.

Rats were treated once (acute) or once daily for 21 days (chronic) with clorgyline (2 mg/kg) or nialamide (50 mg/kg). (-)Deprenyl (1 mg/kg) was given for 21 days. One day after the last injection, vas deferens and anococcygeus muscles were removed and noradrenaline stores labelled with 3H-noradrenaline.

Effect of acute and chronic exposure to heat on pharmacokinetic parameters of digoxin in rats.

Digoxin pharmacokinetic parameters in acute heat-exposed male rats (AHE) maintained for 3 hours at 35 degrees C, and chronic heat-exposed rats (CHE) maintained at 35 degrees C for 4 weeks, were compared to control rats (C) maintained at 22 degrees C. Digoxin concentration in the plasma was measured by radioimmunoassay which gave values similar to thin layer chromatography method. The half life time of digoxin during the elimination phase of the drug (t 1/2 beta) was similar in all three experimental groups (2.

Toxicity of digoxin in acutely and chronically heat-exposed rats.

Rats exposed acutely or chronically to high ambient temperatures (35 degrees C) were much more susceptible to digoxin toxicity than rats kept at 22 degrees C. LD 50 values were 8.8 +/- 1.