Neuropharmacology 44 (2003) 117–124 www.elsevier.com/locate/neuropharm A tachykinin-like factor increases glutamate toxicity in rat cerebellar granule cells Cinzia Severini a , Maria Teresa Ciotti a , Delio Mercanti a , Christian Barbato a,b , Pietro Calissano a,b,* a Istituto di Neurobiologia e Medicina Molecolare, CNR, Viale Marx 15/43, I-00137 Rome, Italy b Dipartimento di Neuroscienze, Universita ` di Roma Tor Vergata, Via di Tor Vergata 135, 00173 Rome, Italy Received 17 May 2002; received in revised form 8 August 2002; accepted 23 August 2002 Abstract Tachykinins (TKs), which include substance P, neurokinin A and neurokinin B, constitute a group of neuropeptides widely expressed in the CNS where they play several functions connected with neural modulation often in synergy with glutamate excitatory transmission. The aim of this study was to assess whether TKs modulate glutamate response of in vitro cultured cerebellar granule neurons and whether GSA (glutamate-sensitizing activity), a peptide released by these neurons, belongs to the TKs family. Treatment with substance P and other neurokinin 1 receptor (NK1) agonists does not affect the response of cerebellar granule neurons to glutamate toxicity. On the contrary, agonists neurokinin 2 receptor (NK2) and neurokinin 3 receptor (NK3) agonists increase, in a dose and time dependent fashion, the response of the same neurons to glutamate. MEN 10,627, a selective NK2 receptor antagonist, and (Trp 7 ,βAla 8 ) NKA (4–10), a selective NK3 receptor antagonist inhibit not only the sensitizing action to glutamate of their respective agonists. These antagonists almost equally reduce the glutamate-sensitizing activity of GSA. Such activity is also abol- ished in the presence of a polyclonal antibody directed against neurokinin B (NKB). These findings indicate that TKs increase glutamate sensitivity in cerebellar granule neurons and that the GSA previously detected in conditioned media of the same cultured neurons belongs to the TK family although its primary structure as compared to known TKs remains to be established.  2002 Elsevier Science Ltd. All rights reserved. Keywords: Glutamate-sensitizing activity; Excitotoxicity; Neurokinin A; Neurokinin B Abbreviations BME basal medium Eagle’s with Earle’s salts CGCs cerebellar granule cells ELE eledoisin FCS fetal calf serum GSA glutamate-sensitizing activity HEPES N-(2-hydroxyethyl)piperazine-N 1 -(2- ethanesulphonic acid) KASS kassinin NK1 neurokinin receptor 1 NK2 neurokinin receptor 2 NK3 neurokinin receptor 3 NKA neurokinin A * Corresponding author. Tel.: +39-06-8609-0248; fax.: +39-06- 8609-0370. E-mail address: calissano@in.rm.cnr.it (P. Calissano). 0028-3908/03/$ - see front matter  2002 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0028-3908(02)00274-5 NKB neurokinin B NMDAR1 NMDA receptor type 1 PHYS physalaemin RTKA ranatachykinin A SP substance P TKs tachykinins 1. Introduction Tachykinins (TKs) are a family of neuropeptides widely distributed both in the central and peripheral ner- vous system of mammals (Helke et al., 1990). Tachyki- nin neuropeptides, which include substance P (SP), neu- rokinin A (NKA), and neurokinin B (NKB), interact with three distinct types of surface receptors defined respect- ively NK1, NK2, and NK3 (Maggi et al., 1993; Mussap et al., 1993; Buch, 1994). All these receptors belong to