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Biomedical subjects

L Tocco

Publications and source records attributed to L Tocco.

12 recordsLinked to original sources
PubMed1987

Peripheral dopamine receptors in the antihypertensive action of dihydroergotoxine in humans.

The effect of the intravenous administration of dihydroergotoxine (6 micrograms/kg) on arterial blood pressure, heart rate, and plasma concentrations of norepinephrine and 3,4-dihydroxyphenylacetic acid (the deaminated dopamine metabolite) was studied in 20 subjects with essential hypertension (8 men and 12 women aged 32-68 years old, World Health Organization Class I-II). In supine resting subjects, dihydroergotoxine significantly decreased systolic blood pressure (from 175 +/- 5 to 156 +/- 4 mm Hg; p less than 0.001), diastolic blood pressure (from 109 +/- 4 to 95 +/- 3 mm Hg; p less than 0.001), and heart rate (from 71 +/- 2 to 63 +/- 2 beats/min; p less than 0.001) as compared with the results of placebo treatment. Moreover, dihydroergotoxine reduced plasma levels of norepinephrine (from 368 +/- 39 to 238 +/- 33 pg/ml; p less than 0.001) and 3,4-dihydroxyphenylacetic acid (from 1.57 +/- 0.21 to 1.22 +/- 0.13 ng/ml; p less than 0.01). The time course of the blood pressure decrease paralleled that of plasma norepinephrine concentration. Dihydroergotoxine did not suppress the cardiovascular and plasma norepinephrine concentration. Dihydroergotoxine did not suppress the cardiovascular and plasma norepinephrine response to standing. The effect of domperidone, a peripheral presynaptic dopamine receptor antagonist, on dihydroergotoxine response was studied in six of the 20 subjects (3 men and 3 women 48-64 years old). The intravenous administration of domperidone (0.3 mg/kg) prevented the dihydroergotoxine-induced reduction in blood pressure and heart rate and the fall in plasma norepinephrine and 3,4-dihydroxyphenylacetic acid levels. Domperidone administered alone failed to significantly modify any measured variables.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Bromocriptine reduces plasma noradrenaline and 3,4-dihydroxyphenylacetic acid in normal and hypotensive subjects.

The effect of a single oral dose of bromocriptine 2.5 mg was evaluated in 11 normotensive and 6 hypertensive volunteers. 150 min after drug administration, a significant decrease in plasma noradrenaline concentration from 202 to 124 pg/ml in normotensive and from 197 to 119 pg/ml in hypertensive patients was observed. Plasma 3,4-dihydroxyphenylacetic acid, a major metabolite of dopamine, fell from 1132 to 956 pg/ml in normal subjects and from 1242 to 807 pg/ml in hypertensives. No change in plasma adrenaline was found. At the same time, mean arterial pressure showed a significant decrease from 90 to 81 and from 132 to 111 mmHg in normotensive and hypertensive subjects, respectively. Bromocriptine also inhibited the increase in noradrenaline level that occurred when the subjects changed from the supine to the standing position. The inhibition was more evident in hypertensive subjects. It is suggested that the hypotensive effect of bromocriptine is mediated by the inhibition of noradrenaline release due to the stimulation of dopamine receptors on noradrenergic nerve terminals.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1980

[Pulmonary ventilation during passive leg movements].

Passive leg movements induced in man at a frequency of 1 Hz by an electric cycle increase pulmonary ventilation after a delay of 200-400 msec. No chemical stimuli can account for this effect since a longer delay of 1 to 5 respiratory acts (7) is required for them to drive the respiratory system. Consequently the hypothesis is made that a neural mechanism, put into action by the moving legs, provides the adequate stimuli.

Adult↗
PubMed1979

[Respiration during isometric contraction of the flexor or extensor muscles of the arm in humans].

An increase in the instantaneous pulmonary flow and a decrease in the respiratory frequency has been found in man as a consequence of isometric contraction of either flexor or extensor muscles of the elbow. The delay of 200 to 900msec between the onset of the muscle contraction and the beginning of the flow increment suggests that the respiratory system increases its activity due to the proprioreceptor activation. As there is no significant difference in the results obtained during flexor or extensor contraction, the contribution of the two different receptor groups appears to be the same.

Adult↗
PubMed1979

[Effects of passive movement of the arm on respiration in humans].

Cyclic passive movements of the right arm at 1Hz induce an increase in pulmonary ventilation in man. This results from an increase in frequency of the respiratory cycles, mainly due to a shortening of the expiratory phase, and from an increase of the instantaneous flow. The delay between the beginning of the arm movements and the onset of the increase in flow is about 450msec.

Adult↗
PubMed1979

Respiratory ventilation during muscular contraction in man.

Brief contraction of arm muscles affects respiratory ventilation either by increasing respiratory frequency or by increasing the instantaneous flow. Both these changes occur at a time subsequent to muscle contraction and can be attributed to a reflex mechanism originating from the muscles.

Adult↗