Search

In rabbit carotid bodies (CBs) superfused during 1–5 h, with an air-equilibrated medium containing no tyrosine (TYR), the dopamine (DA) content decreased by approximately 60% after 1 h and remained constant afterwards. TYR and 3,4-dihydroxyphenylacetic acid (DOPAC) decreased with the same time course. Noradrenaline (NA) content exhibited a biphasic decrease of lesser magnitude than that of DA. Superfusions with a TYR-containing medium did not prevent the reduction in DA and TYR. Large amounts of DA and DOPAC were recovered in the effluent during the first hour of superfusion but after 90 min the two substances had declined below the detection limits (i.e. 0.5 and 1 pmol/5 min, respectively). The DA efflux decreased exponentially during the first hour and was not altered by changing the oxygen partial pressure (PO2) of the medium. The DOPAC efflux declined after 40 min of superfusion and was modulated byPO2. The DA and the DOPAC effluxes were not suppressed by omitting calcium ions from the superfusing medium. In 4 cat CBs equal amounts of DA and NA were recovered from the effluent during the first hour of superfusion. more...

Monoamines and their metabolites have been measured by high performance liquid chromatography with electrochemical detection, in control rabbit carotid bodies and under several experimental conditions: 1) at different times (3 h, 6 h, 24 h, 48 h) after intravenous injection of reserpine (5 mg/kg); 2) 14 days after sympathectomy; 3) 14 days after section of the carotid sinus nerve. The results were analyzed with probability plotting methods. Dopamine was the most important monoamine in the carotid body (CB) and its variations were very large. It was almost entirely depleted by reserpinization without simultaneous increase in 3,4-dihydroxyphenylacetic acid. Sympathectomy increased dopamine content but did not change noradrenaline content. However data analysis suggested that noradrenaline might be compartmented in two pools: one with a large variance, located in the type I cells was increased after sympathectomy, the other, more constant, located in the sympathetic nerve endings was entirely depleted after sympathectomy. Section of the carotid sinus nerve increased dopamine and noradrenaline and quadrupled the serotonin content of the CB. It is proposed that carotid sinus and sympathetic innervations regulate the monoamine metabolism of the CB. more...

Assays capable of concurrently measuring small quantities of noradrenaline, dopamine, serotonin, and several of their metabolites in cerebrospinal fluid (c.s.f.) were developed by the use of high performance liquid chromatography with electrochemical detection. For comparison, cortical subarachnoid, ventricular, cisternal and lumbar c.s.f. were obtained by puncture under barbiturate anaesthesia in sheep. Basal concentrations related to the adrenergic system, including methoxyhydroxyphenylglycol (MHPG), were similar in ventricular, cisternal and lumbar c.s.f., and those of the serotoninergic metabolites, 5‐hydroxyindole‐3‐acetylacetic acid (5‐HIAA), were similar in ventricular and cisternal c.s.f. High concentrations of the dopamine metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were found only in ventricular c.s.f. Monoamine metabolites in ventricular c.s.f. under basal conditions and after various experimental manipulations were then determined over periods of 3 months in two different breeds of sheep fitted chronically with cannulae in lateral ventricles. A dose‐related accumulation of all the acidic monoamine metabolites was recorded during treatment with probenecid. The increase in 5‐HIAA was linear after administration of increased doses of tryptophan and 5‐hydroxytryptophan. The concentrations of dopamine, DOPAC and HVA in the ventricular c.s.f. reflected the response of the dopaminergic system to agents capable of crossing the blood‐brain barrier. It is concluded that cerebral metabolism in conscious sheep could be indirectly approached by recording the concentration of end‐products of dopamine metabolism in ventricular cerebrospinal fluid, obtained under conditions of minimal stress. more...

Postprandial disruption of the migrating myoelectric complex is of longer duration in obese hyperinsulemic Zucker rats than in control rats. No postprandial disruption was seen in an insulin resistant dog. This gives further support to a major role for insulin in control of gut activity. more...

In the rabbit carotid body (CB) in vivo, the rate of dopamine metabolism was estimated to 44.4±3.9 (SD) pmol/CB/h from the decrease in dihydroxyphenylacetic acid content after pargyline inhibition of monoamine oxidase. more...