Psychopharmacology
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Comparative Study Clinical Trial
Comparison of pramipexole and amisulpride on alertness, autonomic and endocrine functions in healthy volunteers.
In a previous study in healthy volunteers, the anti-Parkinsonian drug pramipexole caused sedation and pupil dilatation, consistent with the stimulation of inhibitory D(2)/D(3) autoreceptors on the ventral tegmental area dopaminergic neurones. The sedation may be related to the removal of the dopaminergic excitation of the locus coeruleus (via the meso-coerulear pathway), whereas the pupil dilatation may be due to the removal of the dopaminergic excitation of the Edinger-Westphal nucleus (via a putative meso-pupillomotor pathway). ⋯ The opposite effects of pramipexole and amisulpride on alertness, pupillary function and pituitary hormone levels are consistent with their interactions with inhibitory D(2)/D(3) receptors on VTA neurones and in the tuberoinfundibular system.
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Comparative Study
Differential role of 5-HT1A and 5-HT1B receptors on the antinociceptive and antidepressant effect of tramadol in mice.
Tramadol, (1RS,2RS)-2-[(dimethylamine)-methyl]-1-(3-methoxyphenyl)-cyclohexanol hydrochloride, is an atypical analgesic which binds weakly to ì-opioid receptors and enhances the extra-neuronal concentration of noradrenaline and serotonin by interference with both the uptake and release mechanisms. ⋯ These findings suggest that 5-HT1A receptors modulate the analgesic and the antidepressant-like effects of tramadol in differing ways. The results suggest the involvement of the 5-HT1A autoreceptors from the raphe nuclei and spinal 5-HT1A receptors in the antinociceptive effect. In contrast, the 5-HT1A receptors located in the forebrain may be responsible for the blockade of the antidepressant-like effect of tramadol. 5-HT1B receptors seem not to modify these effects in the models investigated.