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Buspirone, but not sumatriptan, induces miosis in humans: Relevance for a serotoninergic pupil control
Author(s) -
Fanciullacci Marcello,
Sicuteri Riccardo,
Alessandri Massimo,
Geppetti Pierangelo
Publication year - 1995
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1016/0009-9236(95)90161-2
Subject(s) - miosis , buspirone , sumatriptan , pupil , agonist , medicine , pharmacology , phenylephrine , anesthesia , blood pressure , heart rate , serotonergic , receptor , psychology , serotonin , neuroscience
Background and objective Drugs that act on the serotoninergic system have been shown to influence the pupil size. However, the 5‐hydroxytryptamine (5‐HT) receptor type or subtype that affects pupil diameter has not been defined in humans. With a placebo‐controlled, double‐blind randomized design, we investigated in healthy volunteers the effect on pupil size of buspirone and sumatriptan, which mainly act on 5‐HT 1A − and the 5‐HT 1 − like receptors, respectively. Methods The pupil area was measured by means of a videopupillometer before and after a single oral administration of placebo or of three different doses of active drugs. Heart rate and arterial blood pressure were recorded after pupil area measurement. Results Buspirone (5, 10, and 20 mg) caused a dose‐dependent miosis. Sumatriptan (50, 100, and 200 mg) did not affect the pupil size. Twenty milligrams of buspirone reduced the mydriasis induced by pretreatment with homatropine eyedrops. A 20 mg dose of buspirone reduced blood pressure without change in heart rate, whereas buspirone, at doses lower than 20 mg, and sumatriptan did not affect heart rate and blood pressure. Conclusions This study suggests that buspirone, but not sumatriptan, the selective agonist of 5‐HT 1 ‐like receptors, causes miosis in humans by activation of 5‐HT 1A receptors, possibly located in the central nervous system where they inhibit iris sympathetic pathways. Measurement of pupil size seems to provide a valuable and sensitive index of 5‐HT 1A receptor function in humans. Clinical Pharmacology & Therapeutics (1995) 57 , 349–355; doi: