Tissue & Cell, 1997 29 (3) 347-354 © 1997 Pearson Professional Ltd. Distribution of sulfakinin-like peptides in the central and sympathetic nervous system of the American cockroach, Periplaneta americana (L.) and the field cricket, Teleogryllus commodus (Walker) P. D. East 1, D. F. Hales 2, P. D. Cooper 3 Abstract. We describe the distribution of sulfakinin-like neuropeptides in the central and sympathetic ner- vous system of the American cockroach Periplaneta americana (L.) (Blattodea) and the field cricket Teleogryllus commodus (Walker) (Orthoptera), using an antisulfakinin primary antibody and confocal laser scanning microscopy. We conclude that, in the cockroach, sulfakinin-like material is produced in ten pairs of anterior cells in the pars intercerebralis, as well as two pairs of medial and one major pair of lateral posterior brain cells. This contrasts with findings in other insects, including the cricket, where only the posterior cell groups express sulfakinin-immunoreactive material. Extensive arborization of dendrites contain- ing sulfakinin-like peptides occurs within the neuropile of both species, suggesting a neurotransmitter/ neuromodulator function. In the cockroach, there is clear evidence of direct distribution of sulfakinin-like peptides along axons to the foregut tissue, and a plexus of retrocerebral nerves is likely to serve as a neurohaemal release site. Neurohaemal release into the dorsal aorta is also postulated. Sulfakinin- immunoreactive axons do not innervate the hindgut in either cockroaches or crickets. Sulfakinin may function as a gut myotropin in the Blattodea, in addition to functioning as a neurotransmitter within the central nervous system. This latter function appears to be general across insect orders, while the neurohaemal distribution and myotropic activity are restricted to the Blattodea. Keywords" Cockroach, cricket, sulfakinin, neuropeptide, confocal microscopy Introduction In recent years, a wide range of neuropeptides has been identified in the central and sympathetic nervous system of insects, the initial evidence often coming from detec- CSIRO Division of Entomology, GPO Box 1700, Canberra, ACT 2601, Australia. 2 School of Biological Sciences, Macquarie University, NSW 2109, Australia. 3 Division of Botany and Zoology, Australian National University, Canberra, ACT 0200, Australia. Received 19 August 1996 Accepted 5 February 1997 Correspondence to: Dr P. East, Tel: +61 6 246 4127; Fax: 4-61 6 246 4173; E-mail: petere@ento.csiro.au tion of immunoreactivity when antisera to vertebrate peptides were applied to insect material. For example, certain neurones in insects react with anti-gastrin and anti-cholecystokinin antisera (Dockray et al., 1981; Duve & Thorpe, 1981, 1984; Nfissel et al., 1988; Tamarelle et al., 1990). Many insect neuropeptides have now been sequenced, and some of these show apparent structural homology with vertebrate peptides (Nachman & Holman, 1991; De Loof & Schoofs, 1990). Nachman et al. (1986b) were the first to sequence a sulfakiniu, using head extracts prepared from the cockroach Leucophaea maderae as starting material, and they showed it to be a sulfated peptide of 11 amino acids 347