NEUROPEPTIDES IN NORMAL AND PATHOLOGICAL FUNCTION 45 laminae of the dorsal horn. Light microscopic examina- tion of HRP anterogradely labelled fibres in the rat dorsal horn showed that fine caliber stem fibres give rise to six morphological types of terminal arbors, each having a pre- cise location in laminae I and II (1). We have used a method of combined ultrastructural HRP anterograde tracing and peptide immunogold labelling of primary afferents (2) to investigate the electron microscopic distribution of CGRP and substance P (SP) immunoreactive (Ir) primary affer- ents in laminae I-II, of the rat dorsal horn. Ir-fibres were visualized in the lateral, middle and medial parts of such laminae, more abundant in the lateral third. Here CGRP- and/or SPIr fibres were detected at the light level in the plexus of parallel fibres with side branches (1). Immunolabelled boutons depicted a moderately scalloped contour and were filled with tightly packed small diame- ter agranular and large granular vesicles (LGVs). Peptide- Ir was consistently restricted to LGVs in which SP and CGRP co-localised. The immuno-plus HRP-labelled profiles were usually pre-synaptic to large dendrites. In the middle and medial part of laminae I-IIo, immunos- tained afferent fibres occurred, respectively, in the HRP- labelled network and dichotomizing plexuses (l), which however contained only a few peptide-Ir LGVs. These results suggest that differences in the morphol- ogy of primary afferent terminals may reflect some het- erogeneity in their neurochemical content. 1. Cruz et al. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1987). J. Comp. Neural. 261,221. 2. Merighi et al. (1992). J. Neurosci. Methods (in press). zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED Localization of Tachykinin Receptors in Rat Peripheral Tissues by Immunocytochemistry K. Moller*, F. Sundler* and J. Sundelint *Dept. of Medical Cell Research, University of Lund, Biskopsgatan 5, S-223 62 Lund, Sweden; tDept. of Medical and Physiological Chemistry, University of Lund, Box 94, S-221 00 Lund, Sweden Tachykinins are neuropeptides widely distributed both within the central nervous system and in the periphery. They are important sensory transmitters, e.g. in nocicep- tion, furthermore they are inducers of smooth muscle con- traction. In certain pathological conditions such as rheumatoid arthritis, neurogenic inflammation and mb Crohn, tachykinins serve many important functions. The bovine, rat, mouse and human receptors for the hitherto known mammalian tachykinins, i.e. substance P, neu- rokinin A and neuromedin K have recently been cloned and fully sequenced at the cDNA level. Our aim was to localize substance P- (SPR) and neurokinin A-receptor (NKAR) expression in certain peripheral rat tissues by immunocytochemistry. We used two different polyclonal rabbit-antibodies for this purpose. One is reactive against the C-terminal part of the SPR whereas the other one is raised against the C-terminal part of the NKAR. The spinal cord displayed distinct SPR and NKAR immunoreactive neurons scattered in the gray matter in the dorsal horn area. In the urinary bladder the urothelium was intensely stained for both SPR- and NKAR whereas the staining within the underlying smooth muscle was much less pronounced. In the GI-tract in the rat SPR and NKAR-immunore- activity could be observed in the chief-cell rich fimdic region of the stomach. Furthermore we observed that NKAR-immunoreactivity in the underlying smooth mus- cle but no labelling for SPR. In joints from rats with induced, rheumatoid arthritis we observed a pronounced increase in the number of SPR and NKAR-positive inflammatory cells in the synovium compared to normal control tissue. On the whole the immunocytochemical results agree with those previously reported for receptor mRNA-abun- dance and for ligand binding autoradiography. Thus immunocytochemistry seems to be a useful technique for visualizing tachykinin receptors. Effect of Tachykinin Selective Receptor Antagonists on the Growth of Cultured Human Skin Fibroblasts L. Morbidelli, C. Maggi* and M. Ziche Department of Pharmacology, School of Medicine, University of Florence and *Pharmacology Department, Res. Labs., Menarini Pharmaceuticals, Florence, Italy Among the multiple actions produced by substance P, it has also been reported the growth stimulant effect on cul- tured connective tissue cells. Using synthetic selective tachykinin receptor agonists we have recently demon- strated that human fibroblast (HF) proliferation could be reproduced by the selective NKl receptor agonist which appeared to be even more potent than SP itself. In order to verify and complete the receptor characterization, syn- thetic selective receptor antagonists for the NKl [GR71251 (Glaxo), andL668,169 (Peninsula)] orNK2 [L 659,877 (Peninsula)] receptor were studied on the growth of cultured HF and tested against SP, a selective NKl receptoragonist andbasicFGF.BothselectiveNKl recep- tor antagonists at a concentration of 1O-5M induced a significant displacement to the right of the dose response curves of the proliferation induced by SP and the selec- tive NKl receptor agonist. The selective NK2 receptor antagonist did not modify the proliferative response. The growth promoting effect of b-FGF was not modified by either of the tachykinin antagonists. Basic Fibroblast Growth Factor (b-FGF) Effect on Cultured Human Skin Fibroblast is Potentiated by Substance P L. Morbidelli, A. Parenti, C. A. Maggi * and M. Ziche Dept. of Pharmacology, School of Medicine, University of Florence and *A. Menarini Pharmaceuticals, Florence, Italy We have previously reported that substance P (SP) stim- ulates the proliferation of cultured human fibrob’lasts and