ELSEVIER Life Sciauxs, Vo l. 65, No. 25, pp. 2735~2l41. 1999 copyriro 1999Elmviaso#lceIno. RioosdilltlmUSk Aurig&r.ammd 0024-32osl99hm Ima mallu PI1 S00263205(99)00542-1 DECREASED PLATELET 3H-PAROXETINE BINDING IN UNTREATED PANIC DISORDER PATIENTS Donatella Marazziti’, Alessandra Rossi, Liia na Dell’Osso, Lio n e lla Palego, Giovanni P.A. Pla cidi, Gino Gia nnaccini, Antonio Lu c a c c h in i and Giovanni B. Cassano “Dipartimento di Psichia tria, Neurobiologia, Farmacologia e Biotecnologie”, University of Piss,via Roma67,561OO Piss,Italy (Received in final form August12, 1999) zyxwvutsrqponmlkjihgfedcbaZYXWV Summary Different findings support the involvement of the serotonin (S-HT) system in panic disorder Th e presence of the S-I-IT transporter in bloodpla telets s im ila r to thatin presynaptic serotonergic neurons, permits the investigation of this structure in periphery. We therefore evaluated the biing of 3H-paroxetine, a selective 5-HT reuptake inhibitor which is considered the ligand of choice for la b e lliig the 5-HT transporter, in platelets of 20 drug-free patients with pa nic disorder. Th e same measurement was repeated after one year’s treatment with different drugs. Th e results showed patients to havea lowernumber of 3H- paroxetine sites than a group of age- and sex-matched controls,thus suggesting the involvement of the S-HT transporter in panicdisorder. Th is abnormality reverted after one year of treatment with specific drugs that provoked the symptom remission in a ll c a ses, which wouldsuggest a lin k with the c lin ic a l improvement. Key Words: serotonin, serotonin transporter, platelets, panicdisorder, tricyclics, SSRIs An im a ld a t a a nd pre c lin ic a l findings would sugge st tha t the serotonin (5-I-H) system is involved in anxiety, but the y a re controversial and contradictory, since they report both an increased and a decreased functionality of thissystem (1). The most consistent findings in humans in this regard derive from the observation of the effectiveness in panic disorder of antidepressants, sucha s im ipramine (2), whichinhibits the re-uptake of both norepinephrine and 5-I-H, clom ipramine (3) whichinhibits only 5-I-H re- uptake, and the selective 5-HT reuptake inhibitors (SSRIs)(4,5). Experimental support for the involvement of 5-HT in panic disorder derives from peripheral indicators of serotonergic functions, sucha s cha llenge tests or platelet studies. It has been widely reported that panic disorder patients often present a “biphasic” response with an early ‘Cenesponding author:Dr. DonatelIa Marazziti, D@rtimentodi Psichiatria, Neurobiologia, FarmacoIogia e Biotecnologie, University of piss, via Roma67,561OO piss, Italy. Tel: 39-050/835412; Fa x: 39-050/21581; e- mail:dmamzzi@psico.med.tipi.it.