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Del Rianco P L, Fancinllacci M, Franchi G. Sicuteri F. 
“Human 5-Hydroxytryptamine Venomotor Receptors.”. 
Pharmacol.Res.Commun.. 1975.
Serotonin venomotor receptors were studied in man. 140 Subjects (aged 20-55 yr) were studied and were untreated except for chronic administration of serotonin antagonists, MAO inhibitors, reserpine or fenclonine as required for headache, depression or arterial hypertension. The venous constriction test (VCT), recording local venospasm after injection of low doses of serotonin, noradrenaline or adrenaline via a needle inserted orthodromically into the vein, was performed on the hand in each subject. The effects of different concentrations of serotonin (Farmitalia) alone or combined with nicergoline (Sermion, Farmitaria), LSD-25, methysergide (Deserril), BOL-148, 1-methylcycloheptathiophene (BC-105, Sandomigran), 1-methyl ergotamine (My 25) (all from Sandoz), cyproheptadine (Periactin, Merck-USA), phenelzine (Nardil, Warner), pargyline (Eutonyl, Abbott), noradrenaline (Noradrec),adrenaline (both Recordati), fenclonine (Falorni), reserpine (Serpasil, CIBA) and human serum and plasma were determined. Results - Threshold values of the receptor sensitivity to serotonin varied between subjects in the range 50 ng-2 pa, with regard to venous constriction. Serotonin was more active than noradrenaline and the latter more active than adrenaline. Serum showed venoconstrictor activity due to endogenous serotonin. Methysergide (250 mcg) blocked the effects of serotonin and serum. Post-ischemic plasma also constricted the vein. Sensitivity to serotonin was enhanced in about 500f the patients treated with phenelzine (75 mg/day for 10 days) and pargyline (50 mg/day p.o. for 7 days). Hypersensitivity to catecholamines was also produced. LSD-25 and BOL-148 inhibited the serotonin venospasm, irrespective of the time of drug administration with respect to serotonin. Nicergoline, cyproheptadine and MY-25 also antagonized the action of serotonin. Sensitivity to serotonin was increased 2-3 fold by reserpine (0.5 mg/day for 1-2 wk) in 5/7 subjects. Fenclonine (0.8 g/day p.o. for 1-2 wk) increased sensitivity to serotonin, but not to adrenaline or noradrenaline. Conclusion The VCT affords an excellent and safe way of testing monoamine venomotor responses in man.
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