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The physiological importance of brain alpha 2-adrenoceptors in controlling the activity of tyrosine hydroxylase in noradrenergic regions was investigated using the accumulation of 3,4-dihydroxyphenylalanine (DOPA) after decarboxylase inhibition as a measure of the rate of tyrosine hydroxylation (and synthesis of noradrenaline) in vivo. In the hypothalamus(More)
Methionine-enkephalin and leucine-enkephalin, administered into the lateral ventricle of intact rats, increased the accumulation of DOPA by a naloxone-sensitive mechanism in different brain regions after inhibition of the aromatic L-amino acid decarboxylase. Because of the rapid enzymatic degradation of both enkephalins large doses (500 pg) were required to(More)
The isolated field-stimulated vas deferens of the rat (0.1 Hz, 3 ms, 30-40 V) was used to study the relationship between the in vivo inhibition of neuronal uptake of noradrenaline (NA) by cyclic antidepressant drugs and the subsequent activation/desensitization of presynaptic alpha 2-adrenoceptors. Receptor activation was indirectly measured by quantifying(More)
Antiotensin II facilitated in a concentration-dependent manner the potassium-evoked 3H-noradrenaline over-flow from the rabbit hypothalamus. This effect which is probably mediated through presynaptic angiotensin facilitatory receptors on noradrenergic nerve terminals was blocked by the specific angiotensin receptor antagonist, saralasin. These results(More)
After twp weeks of twice-daily administration of amitriptyline to rats, the binding of [3H]clonidine to presynaptic a2-adrenoreceptors was decreased in membranes isolated from 5 areas of the rat brain. After one day of treatment, binding did not differ from saline treated controls. In vitro, a high concentration of amitriptyline caused a competitive(More)
The existence of a functional interaction between presynaptic receptors modulating the release of noradrenaline was studied in the rabbit heart. Isolated right atria were prelabelled with 3H-noradrenaline and the overflow of tritium was induced by field stimulation (2 Hz, 0.1 ms duration, supramaximal voltage for a total of 180 pulses). In atria superfused(More)
Intracerebroventricularly administered Arg-Pro-Lys-Pro-Gln-Gln-Phe-Gly-Leu-Met-NH2 (substance P, SP) enhanced the accumulation of DOPA after inhibition of the aromatic L-amino acid decarboxylase in the rat brain. SP also stimulated locomotor activity in a dose-dependent manner. A total of 31 structural analogues of SP were evaluated with respect to the(More)
Uptake mechanisms in the rat vas deferens have not yet been thoroughly investigated. In this study we show that uptake inhibition by cocaine, amantadine and desmethylimipramine induces increases in sensitivity that are greater for adrenaline than for noradrenaline. However, this does not occur when guanethidine is used. These results are clearly in(More)