Functional Characterization of Substance P Receptors on Cultured Human Spinal Cord Astrocytes: Synergism of Substance P With Cytokines in Inducing Interleukin-6 and Prostaglandin E 2 Production CARLA PALMA, 1 LUISA MINGHETTI, 2 MARA ASTOLFI, 1 ELENA AMBROSINI, 2 FRANCESCA CECCHERINI SILBERSTEIN, 2 STEFANO MANZINI, 1 GIULIO LEVI, 2 AND FRANCESCA ALOISI, 2 * 1 Department of Pharmacology, Menarini Ricerche, Pomezia, Italy 2 Laboratory of Organ and System Pathophysiology, Istituto Superiore di Sanita ` , Rome, Italy KEY WORDS glia; tachykinin; transforming growth factor-; tumor necrosis fac- tor-; lipid mediator ABSTRACT Following brain injury, astrocytes express receptors for cytokines and neuropeptides and secrete several regulatory mediators that have a well established role in inflammation, immunity, and tissue development or repair. To elucidate the role of substance P (SP), a neurotransmitter peptide of the tachykinin family, in inducing astrocyte secretory activities, we have examined the expression of SP receptors and the functional consequences of their activation in cultured astrocytes from the human embryonic brain or spinal cord. Radioligand binding studies revealed that only one type of SP receptors, the high affinity NK-1 receptor, was present on human astrocytes and that spinal cord astrocytes expressed about 6 times as many SP binding sites as brain astrocytes. Following SP treatment, a substantial inositol phosphate formation was observed in spinal cord astrocytes only. Stimulation of spinal cord astrocytes with SP alone did not induce secretion of cytokines [interleukin-6 (IL-6), granulocyte-macrophage- CSF, macrophage chemoattractant protein-1 or leukemia inhibitory factor] or prostaglan- din E 2 (PGE 2 ). Interestingly, however, SP selectively potentiated the inducing effect of IL-1 on IL-6 and PGE 2 secretion by spinal cord astrocytes without affecting the IL-1--evoked secretion of other cytokines. SP also enhanced the small inducing effect of tumor necrosis factor- (TNF-) on IL-6 and PGE 2 secretion and that of transforming growth factor- on PGE 2 secretion. These results suggest that SP can enhance immuno- regulatory and neurotrophic astroglial functions mediated by IL-6 and PGE 2 by acting in concert with a set of cytokines whose cerebral expression has been reported during development and in a variety of diseases. GLIA 21:183–193, 1997.  1997 Wiley-Liss, Inc. INTRODUCTION Astrocytes, the major glial cell population of the central nervous system (CNS), are thought to be in- volved in the control of brain inflammation and tissue repair through the upregulation of a number of cellular functions that are characteristic of reactive astrocytes Contract grant sponsor: Project on AIDS of the Italian Ministry of Health; Contract grant number: 940-J; Contract grant sponsor: Project on Multiple Sclerosis of the Istituto Superiore di Sanita ` ; Contract grant sponsor: Istituto Mobiliare Italiano; Contract grant number: 56665. *Correspondence to: F. Aloisi, Neurophysiology Unit, Laboratory of Organ and System Pathophysiology, Istituto Superiore di Sanita `, Viale Regina Elena 299, 00161 Rome, Italy. E-mail: FOS4@ISS.IT Received 26 November 1996; Accepted 24 February 1997 GLIA 21:183–193 (1997)  1997 Wiley-Liss, Inc.