Leucokinin and callitachykinin immunoreactive neurons during postembryonic development of calliphora vomitoria (L.) (DIPTERA : CALLIPHORIDAE)

Neurons containing 2 types of myotropic neuropeptides were investigated by immunocytochemistry during postembryonic development of the brain and ventral nerve cord of the blowfly Calliphora vomitoria (Diptera : Calliphoridae). Antisera raised against the insect neuropeptides Callitachykinin II (CavTK II), Locustatachykinin I (LomTK I), and Leucokinin I (LK I) were used. Callitachykinin immunoreactive (CavTK–IR) neurons were detected from the 1st-instar larva throughout development to adult. The number of CavTK–IR cell bodies in the brain was 4–16 in larval stages, 10–84 in pupal stages, and over 140 neurons in the newly emerged fly. With the CavTK antiserum, the fibers of only 4 descending neurons were detected in thoracico–abdominal ganglia throughout development. The antiserum to LomTK displayed the same neurons as that to CavTK II as well as a small number of additional neurons. Notably, there were seen about 14–20 locustatachykinin-like immunoreactive (LomTK-LI) cell bodies in the thoracico–abdominal ganglia throughout development. Leucokinin-like immunoreactive (LK-LI) neurons were labeled throughout postembryonic development. In the brain, 2–4 LK-LI cell bodies were labeled from 1st-instar larva to 8-day-old pupa, and 6 LK-LI cell bodies were labeled in the adult brain. In the abdominal ganglia, 7 pairs of LK-LI cell bodies were labeled from 1st-instar larva to 96-h-old pupa, 8 pairs in 8-day-old pupa, and 9 pairs in newly emerged fly, respectively. The CavTK containing neurons in the brain displayed a drastic increase in numbers from larval stages to adult, which indicates an addition of functional roles for this type of peptide. During earlier pupal stages, the number of CavTK–IR neurons decreased. The LK-LI neurons, however, were strongly immunoreactive throughout postembryonic development. Only one additional pair of cells appeared in the brain and 2 additional pair of cells appeared in the abdominal ganglia of the adult as compared with larvae. The continuous high expression of LK-LI material may suggest a functional role for this type of peptide during development.     

The distribution and activity of tachykinin-related peptides in the blood-feeding bug, Rhodnius prolixus

The invertebrate tachykinin-related peptides (TRPs) with the conserved C-terminal sequence FX1GX2Ramide shows sequence similarity to the vertebrate tachykinins after which they are named, and are hypothesized to be ancestrally related. In this study a polyclonal antiserum generated against a locust tachykinin (LomTK I), was used to demonstrate the presence and describe the distribution of LomTK-like immnoreactivity in the CNS and gut of Rhodnius prolixus. Reverse phase high performance liquid chromatography (RP-HPLC) was used in combination with a sensitive radioimmunoassay (RIA) to demonstrate picomolar amounts of immunoreactive material in the CNS, and femptomolar amounts associated with the hindgut. Furthermore, the results from CNS extracts separated by RP-HPLC, suggest that at least two tachykinin isoforms exist in R. prolixus. A hindgut contraction assay was developed to quantify the myotropic effects of selected LomTKs on R. prolixus hindgut contraction. Both LomTK I and II caused an increase in the frequency of hindgut contractions with EC50 values of 3.6x10(-8)M and 3.8x10(-8)M for LomTK I and II, respectively.     

Tachykinin-related neuropeptide in the crayfish olfactory midbrain

Immunoreactivity indicative of tachykinin-related peptide (TRP) was detected in the olfactory midbrain of the crayfish Pacifastacus leniusculus when using an antiserum to the insect neuropeptide locustatachykinin I (LomTK-I). A monoclonal antibody to the mammalian tachykinin substance P was shown in double-labeling experiments to label structures in the crayfish brain identical to those labeled with the LomTK antiserum. Within the midbrain LomTK-like immunoreactive (LomTK-LI) material was observed in a limited population of neuronal somata and their varicose processes. A single pair of large interneurons gave rise to numerous varicose LomTK-LI processes innervating a cluster of cell bodies (cluster 10) as well as the olfactory neuropils. The latter neuropil was also innervated by a population of LomTK-LI globuli cells with cell bodies in cluster 9. Radioimmunoassay (RIA), utilizing the LomTK antiserum, and reverse-phase high-performance liquid chromatography (HPLC) were used to partially characterize the immunoreactive material in extract of the portion of the midbrain that houses the olfactory (OL) and accessory (AL) lobes and cell clusters 9 and 10 on the one hand, and in extract of the remaining parts of the brain on the other. Approximately the same amounts of LomTK-LI material were observed for the two extracts. RIA showed that the immunoreactive material of both extracts diluted roughly in parallel to synthetic LomTK-I and HPLC analysis of the extracts revealed immunoreactive material in both tissues which eluted with retention times in the range of synthetic LomTK-I and LomTK-II. These results suggest that TRPs similar to LomTKs are present in the olfactory midbrain of Pacifastacus. The distribution of immunolabeled neuronal structures suggests that in the crayfish, peptide(s) closely related to insect TRPs may act as a neuroactive substance released from nerve fibers in olfactory neuropil areas and at certain neuronal cell bodies.     

Locustatachykinin isoforms in the locust: distribution and quantification in the central nervous system and action on the oviduct muscle.

The presence of locustatachykinin (LomTK)-like immunoreactivity is demonstrated in the central nervous system (CNS) of Locusta migratoria with the use of a polyclonal antiserum raised against LomTK1. By developing a radioimmunoassay with the same antiserum, we have demonstrated picomolar amounts of LomTK-like material in the tissues of the central nervous system. In contrast, only femptomolar amounts of LomTK-like material are associated with the oviduct tissue. The relative amounts of the different LomTK isoforms in the brain and the abdominal ganglionic chain were examined by separating the native peptides on high-performance liquid chromatography and comparing their retention times to synthetic LomTK standards. The amounts of the different isoforms of LomTK differed between and within the two regions of the central nervous system. However, the ratios of the different isoform amounts were similar between the two regions. The myostimulatory activities of LomTKs 1 to 4 were characterized by using the locust oviduct bioassay. LomTKs 1, 2, and 3 appeared to be more efficacious than LomTK4.     

Distribution of tachykinin-related neuropeptide in the developing central nervous system of the moth Spodoptera litura

Neuropeptides with similarities to vertebrate tachykinins, designated tachykinin-related peptides (TRPs), have been identified in several insect species. In this investigation we have utilized an antiserum raised to one of the locust TRPs, locustatachykinin-I (LomTK-I), to determine the distribution pattern of LomTK-like immunoreactive (LTKLI) neurons in the developing nervous system of the moth Spodoptera litura. A number of LTKLI neurons could be followed from the larval to the adult nervous system: a set of median neurosecretory cells (MNCs) in the brain, a pair of brain descending neurons and a few sets on neurons in the ventral nerve cord. The distribution of LTKLI neurons in the adult brain is very similar to that seen in other insect species with prominent arborizations in the central body, antennal lobes, mushroom body calyces, optic lobe neuropils and other distinct neuropil areas in the protocerebrum and tritocerebrum. A new finding is the presence of LTKLI neurosecretory cells with axon terminals in the anterior aorta and corpora cardiaca, suggesting for the first time a neurohormonal role of tachykinin-related peptide(s) in insects. During postembryonic development the number of LTKLI neurons in the ventral nerve cord decreases somewhat, whereas the number increases in the brain. Thus the functional roles of TRPs may change to some extent during development.     

Tachykinin-related peptides in invertebrates: a review

Peptides with sequence similarities to members of the tachykinin family have been identified in a number of invertebrates belonging to the mollusca, echiuridea, insecta and crustacea. These peptides have been designated tachykinin-related peptides (TRPs) and are characterized by the preserved C-terminal pentapeptide FX1GX2Ramide (X1 and X2 are variable residues). All invertebrate TRPs are myostimulatory on insect hindgut muscle, but also have a variety of additional actions: they can induce contractions in cockroach foregut and oviduct and in moth heart muscle, trigger a motor rhythm in the crab stomatogastric ganglion, depolarize or hyperpolarize identified interneurons of locust and the snail Helix and induce release of adipokinetic hormone from the locust corpora cardiaca. Two putative TRP receptors have been cloned from Drosophila; both are G-protein coupled and expressed in the nervous system. The invertebrate TRPs are distributed in interneurons of the CNS of Limulus, crustaceans and insects. In the latter two groups TRPs are also present in the stomatogastric nervous system and in insects endocrine cells of the midgut display TRP-immunoreactivity. In arthropods the distribution of TRPs in neuronal processes of the brain displays similar patterns. Also in coelenterates, flatworms and molluscs TRPs have been demonstrated in neurons. The activity of different TRPs has been explored in several assays and it appears that an amidated C-terminal hexapeptide (or longer) is required for bioactivity. In many invertebrate assays the first generation substance P antagonist spantide I is a potent antagonist of invertebrate TRPs and substance P. Locustatachykinins stimulate adenylate cyclase in locust interneurons and glandular cells of the corpora cardiaca, but in other tissues the putative second messenger systems have not yet been identified. The heterologously expressed Drosophila TRP receptors coupled to the phospholipase C pathway and could induce elevations of inositol triphosphate. The structures, distributions and actions of TRPs in various invertebrates are compared and it is concluded that the TRPs are multifunctional peptides with targets both in the central and peripheral nervous system and other tissues, similar to vertebrate tachykinins. Invertebrate TRPs may also be involved in developmental processes.     

FMRFamide-related peptides in the gut of Locusta migratoria L.: a comprehensive map and developmental profile

The gut tissues and associated nervous system of the African migratory locust, Locusta migratoria, were found to contain FMRFamide-like immunoreactive (FLI) material throughout the five larval instars and 2 weeks into the adult stage in both males and females. FMRFamide-like immunoreactivity associated with the locust gut was described using camera lucida techniques. FMRFamide-like immunoreactivity is observed in the frontal connectives, recurrent nerve, and oesophageal nerves; projections from the ingluvial ganglion onto the anterior midgut, and from the proctodeal nerve onto the hindgut and posterior midgut; in the neuropils of the frontal ganglion, hypocerebral ganglion and ingluvial ganglia; 30 cell bodies in the frontal ganglion; multipolar sensory cells on the foregut; and endocrine-like cells in the gastric caecae and midgut. Radioimmunoassay (RIA) was used to determine the quantities of FLI material in foreguts, gastric caecae, anterior and posterior midguts, and hindgut of first-fifth instar larvae, 1-3- and 14-17-day male and female adult locusts. As expected, as the tissue size (assessed by total protein content) increases, so does the amount of FLI material in each tissue. Normalizing for tissue size reveals significant differences in FLI content among the stages for each tissue tested. Reversed phase-high pressure liquid chromatography (RP-HPLC) followed by RIA has identified four groups of FLI fractions present in the gut, and different members of these groups are present in the various gut tissues.     

Identification of an urotensin I-like peptide in the pituitary of the lungfish Protopterus annectens: immunocytochemical localization and biochemical characterization

In the present study we have investigated the localization and biochemical characteristics of urotensin I (UI)-like and urotensin II (UII)-like immunoreactive peptides in the central nervous system (CNS) and pituitary of the lungfish, Protopterus annectens, by using antisera raised against UI from the white sucker Catostomus commersoni and against UII from the goby Gillichythys mirabilis. UI-like immunoreactive material was found within the melanotrope cells of the intermediate lobe of the pituitary. By contrast, no UI-immunoreactive structures were found in the brain. No UII-like peptides structurally similar to goby UII were found in the brain and pituitary of P. annectens. The UI-immunoreactive material localized in the pituitary was characterized by combining reversed-phase high-performance liquid chromatography (HPLC) analysis and radioimmunological detection. The UI-like immunoreactivity contained in a pituitary extract eluted as a single peak with a retention time intermediate between those of sucker UI and rat corticotropin-releasing factor (CRF). Control tests on adjacent sections of pituitary showed that the UI antiserum cross-reacted with the frog skin peptide sauvagine, but lungfish UI did not co-elute with synthetic sauvagine on HPLC. On the contrary, no cross-reaction was observed between the UI antiserum and CRF or alpha-melanocyte-stimulating hormone (alpha-MSH). The occurrence of an UI-like peptide in the intermediate lobe of the pituitary of P. annectens suggests that, in lungfish, this peptide may act as a classic pituitary hormone or may be involved in the control of melanotrope cell secretion.     

Distribution of locustamyotropin-like immunoreactivity in the nervous system of Locusta migratoria.

Locustamyotropin-like immunoreactivity was visualized in the nervous system of Locusta migratoria by means of the peroxidase antiperoxidase method. Highly specific antibodies to the carboxy-terminus of the locustamyotropins were obtained by elution through an affinity column to which Lom-MT II was covalently bound. Specific cells in the nervous system of Locusta migratoria contain substances immunoreactive to anti-locustamyotropin. In total, about 100 cells immunoreactive to the Lom-MT-II antiserum were detected in the head ganglia, in the abdominal neuromeres of the metathoracic ganglion, and in the five free abdominal ganglia. In the brain, immunoreactive cell groups were situated in the inner and outer edge of the tritocerebrum. Prominent axon bundles tightly surround the tractus I to the corpora cardiaca. The corpora allata were innervated by the nervus corporis allati I coming from the corpora cardiaca and by fibers in the nervus corporis allati II originating from cell bodies in the suboesophageal ganglion. Immunoreactive cell bodies in the suboesophageal and abdominal ganglia are distributed along the anterior posterior midline axis, both dorsally and ventrally. The processes of the cell bodies in the abdominal ganglia leave the ganglia and were traced in the respective median nerves into the neurohaemal organs. Since the Lom-MT-II antiserum cross-reacts with all peptides of the locustamyotropin family that have a carboxy-terminus in common, these cells may contain one or several locustamyotropins. The Lom-MT antiserum also recognizes pheromone biosynthesis activating neurohormone, as was revealed by the intensive labeling of suboesophageal cell bodies in Bombyx mori.     

Cardioacceleratory action of tachykinin-related neuropeptides and proctolin in two coleopteran insect species

Several cardioactive peptides have been identified in insects and most of them are likely to act on the heart as neurohormones. Here we have investigated the cardioactive properties of members of a family of insect tachykinin-related peptides (TRPs) in heterologous bioassays with two coleopteran insects, Tenebrio molitor and Zophobas atratus. Their effects were compared with the action of the pentapeptide proctolin. We tested the cardiotropic activity of LemTRP-4 isolated from the midgut of the cockroach Leucophaea maderae, CavTK-I and CavTK-II isolated from the blowfly Calliphora vomitoria. The semi-isolated hearts of the two coleopteran species were strongly stimulated by proctolin. We observed a dose dependent increase in heartbeat frequency (a positive chronotropic effect) and a decrease in amplitude of contractions (a negative inotropic effect). In both beetles the TRPs are less potent cardiostimulators and exert lower maximal frequency responses than proctolin. LemTRP-4 applied at 10(-9)-10(-6) M was cardiostimulatory in both species inducing an increase of heart beat frequency. The amplitude of contractions was stimulated only in Z. atratus. CavTK-I and CavTK-II also exerted cardiostimulatory effects in Z. atratus at 10(-9)-10(-6) M. Both peptides stimulated the frequency, but only CavTK-II increased the amplitude of the heart beat. In T. molitor, however, the CavTKs induced no significant effect on the heart.Immunocytochemistry with antisera to the locust TRPs LomTK-I and LomTK-II was employed to identify the source of TRPs acting on the heart. No innervation of the heart by TRP immunoreactive axons could detected, instead it is possible that TRPs reach the heart by route of the circulation. The likely sources of circulating TRPs in these insects are TRP-immunoreactive neurosecretory cells of the median neurosecretory cell group in the brain with terminations in the corpora cardiaca and endocrine cells in the midgut.In conclusion, LemTRP-4, CavTK-I and CavTK-II are less potent cardiostimulators than proctolin and also exert stimulatory rather than inhibitory action on amplitude of contractions. The differences in the responses to proctolin and TRPs suggest that the peptides regulate heart activity by different mechanisms.     

A newly developed enzyme-immunoassay for measuring the tissue contents of PACAP in fish

We have developed a novel and easy enzyme-immunoassay (EIA) for pituitary adenylate cyclase-activating polypeptide (PACAP). We used it to determine immunoreactive PACAP levels in the central nervous system (CNS) and peripheral tissues of two fishes, a teleost (the stargazer) and an elasmobranch (a stingray). An antiserum was raised in a white rabbit immunized with a conjugate of synthetic stargazer PACAP27 plus keyhole limpet hemocyanin. The EIA system used an antiserum/biotin-labeled PACAP/avidin/biotin-conjugated enzyme complex, and a double antibody method was used to precipitate the immune complexes. We call the system the avidin-biotin complex detectable EIA (ABCDEIA) for PACAP. ABCDEIA with biotin-labeled PACAP27 detected only PACAP27, recognizing neither the longer forms of PACAP nor any other peptides. PACAPs with 27, 38, and 44 residues cross-reacted in another ABCDEIA with biotin-labeled PACAP38 or PACAP44. Whole brains of both fishes contained much higher levels of PACAP, 6-30 times as high as the levels in the mammalian brain, but unexpectedly, no immunoreactive PACAP27 was found in any CNS or peripheral tissue in either fish. The gastrointestinal tracts of fish also contained lower, but significant amounts of PACAP.     

Characterization of endozepine-related peptides in the central nervous system and in peripheral tissues of the rat

Endozepines represent a novel family of regulatory peptides that have been isolated by their ability to displace benzodiazepines from their binding sites. All endozepines derive from an 86 amino acid precursor polypeptide called diazepam binding inhibitor (DBI), which generates, through proteolytic cleavage, several biologically active endozepines. The aim of the present study was to compare the molecular forms of endozepines present in different regions of the rat brain and in various peripheral organs using an antiserum raised against the central (biologically active) region of DBI. Combination of HPLC analysis and RIA detection revealed the existence of two major forms (peaks I and II) of endozepine-immunoreactive peptides. The retention times of the two peaks (36 and 39 min, respectively) were identical in all tissues or organs tested. Western blotting analysis of cerebral cortex extracts confirmed the existence of two immunoreactive species with apparent molecular weights 4000 and 6000 Da, which respectively correspond to peaks I and II. Tryptic digestion of peaks I and II generated a single immunoreactive peptide that coeluted with the synthetic octadecaneuropeptide ODN [DBI(33–50)]. These results show that, in different parts of the brain and in various peripheral organs, DBI is rapidly processed to generate two peptides of apparent molecular weight of 4000 and 6000 Da, which both possess the biologically active determinant of endozepines.     

NPY-like peptides occur in the nervous system and midgut of the migratory locust, Locusta migratoria and in the brain of the grey fleshfly, Sarcophaga bullata

The distribution of the NPY-like substances in the nervous system and the midgut of the migratory locust, Locusta migratoria and in the brain of the grey fleshfly, Sarcophaga bullata was determined by immunocytochemistry using an antiserum directed against synthetic porcine NPY. The peroxidase-antiperoxidase procedure revealed that NPY immunoreactive cell bodies and nerve fibers were observed in the brain, optic lobes, corpora cardiaca, suboesophageal ganglion and ventral nerve cord of the locust and in the brain, optic lobes and suboesophageal ganglion of the fleshfly. In the locust midgut, numerous endocrine cells and nerve fibers penetrating the outer musculature contained NPY-like immunoreactivity. The concentrations of NPY immunoreactive material in acetic acid extracts of locust brain, optic lobes, thoracic ganglia, ovaries and midguts was measured using a specific radioimmunoassay technique. The dilution curves of the crude tissue extracts were parallel to the standard curve. The highest amount of NPY-like immunoreactivity was found in the locust ovary and midgut. Reverse-phase high-performance liquid chromatography (RP-HPLC) and radioimmunoassay were used to characterize the NPY-like substances in the locust brain and midgut. HPLC-analysis revealed that NPY-immunoreactivity in the locust brain eluted as three separate peaks. The major peak corresponded to a peptide less hydrophobic than synthetic porcine NPY. RP-HPLC analysis of midgut extracts revealed the presence of an additional NPY-immunoreactive peak which had a retention time similar to the porcine NPY standard. The present data show the existence of a widespread network of NPY immunoreactive neurons in the nervous system of the locust and the fleshfly. Characterization of the immunoreactive substances indicates that peptides similar but not identical to porcine NPY are present in the central nervous system and midgut of insects.     

Immunoreactivity to molluskan neuropeptides in the central and stomatogastric nervous systems of the earthworm, Lumbricus terrestris L.

Polyclonal antisera against two related command neuropeptides (CNP2 and CNP4) described in neurons of the terrestrial snail Helix were used in a study of the nervous system of the earthworm Lumbricus. The CNP-like peptides belong to the same neuropeptide subfamily and bear a C-terminal signature sequence Tyr-Pro-Arg-X. The distribution patterns of immunoreactive (IR) neurons were studied in the central nervous system (CNS), skin, and stomatogastric nervous system of the earthworm. IR neurons were found in all CNS ganglia, the patterns being similar for both antibodies used. Several clusters of IR cells were observed in the cerebral and subesophageal ganglia. In the ventral cord ganglia, the number of IR cells decreased in the rostro-caudal direction, and the IR cells sent their fibers mostly into the median fiber bundle. Segmental nerves contained no IR fibers. After injury of the worm body, the number of IR neurons in the CNS significantly increased. In the skin, IR sensory neurons were present in sensory buds. The stomatogastric ganglia only contained IR fibers. Numerous scattered IR neurons were found in the inner subepithelial layer of the esophagus and formed the enteric plexus in which the cell bodies displayed a segmentally repeated pattern. Possible involvement of CNP-like-IR neurons in central integratory processes, sensory processes, and the regulation of feeding is discussed.This work was supported by INTAS (grant 01-2117), CRDF (grant RB1-2321-MO-02), and the Russian Foundation for Basic Research (grants 05-04-48724 and 03-04-48179).     

Mapping of serotonin-immunoreactive neurons in the larval nervous system of the flies Calliphora erythrocephala and Sarcophaga bullata

Summary Serotonin-immunoreactive (5-HTi) neurons were mapped in the larval central nervous system (CNS) of the dipterous flies Calliphora erythrocephala and Sarcophaga bullata. Immunocytochemistry was performed on cryostat sections, paraffin sections, and on the entire CNS (whole mounts).The CNS of larvae displays 96–98 5-HTi cell bodies. The location of the cell bodies within the segmental cerebral and ventral ganglia is consistent among individuals. The pattern of immunoreactive fibers in tracts and within neuropil regions of the CNS was resolved in detail. Some 5-HTi neurons in the CNS possess axons that run through peripheral nerves (antenno-labro-frontal nerves).The suboesophagealand thoracico-abdominal ganglia of the adult blowflies were studied for a comparison with the larval ventral ganglia. In the thoracico-abdominal ganglia of adults the same number of 5-HTi cell bodies was found as in the larvae except in the metathoracic ganglion, which in the adult contains two cell bodies less than in the larva. The immunoreactive processes within the neuropil of the adult thoracico-abdominal ganglia form more elaborate patterns than those of the larvae, but the basic organization of major fiber tracts was similar in larval and adult ganglia. Some aspects of postembryonic development are discussed in relation to the transformation of the distribution of 5-HTi neurons and their processes into the adult pattern.     

Neurochemical and Immunocytochemical Studies on the Distribution of N-Acetyl-Aspartylglutamate and N-Acetyl-Aspartate in Rat Spinal Cord and Some Peripheral Nervous Tissues

HPLC analysis of rat spinal cord revealed a uniform distribution of N-acetyl-aspartate (NAA) across both longitudinal and dorsoventral axes. In contrast, ventral cord N-acetyl-aspartylglutamate (NAAG) levels were significantly higher than those measured in dorsal halves of cervical, thoracic, and lumbar segments. Immunocytochemical studies using an affinity-purified antiserum raised against NAAG-bovine serum albumin revealed an intense staining of motoneurons within rat spinal cord. Along with the considerable NAAG content in ventral roots, these results suggest that NAAG may be concentrated in motoneurons and play a role in motor pathways. NAAG was also present in other peripheral neural tissues, including dorsal roots, dorsal root ganglia, superior cervical ganglia, and sciatic nerve. It is interesting that NAA levels in peripheral nervous tissues were lower than those in CNS structures and that NAA levels in ventral roots and sciatic nerve were lower than NAAG levels. These findings further document a lack of correlation between NAAG and NAA levels in both central and peripheral nervous tissues. Taken together, these data demonstrate the presence of NAAG in nonglutamatergic neuronal systems and suggest a more complex role of NAAG in neuronal physiology than previously postulated.     

Chromatographic characterisation and biological activity of neuropeptides immunoreactive to antisera against Met5-enkephalin-Arg6-Phe7 (YGGFMRF) extracted from the blowfly Calliphora vomitoria (Diptera).

Neuropeptides identified with a radioimmunoassay specific for the C-terminus of Met5-enkephalin-Arg6-Phe7 (YGGFMRF) have been extracted from nervous tissues of the blowfly Calliphora vomitoria and also from whole flies. Chromatographic characterisation, based on criteria of molecular weight, charge and hydrophobicity, reveals a complex multiplicity of immunoreactive peptides. Variations in the amounts and types of peptides found within different nervous tissues is evidence that the cellular precursor processing is selective. Physiological studies on the isolated blowfly salivary gland show that synthetic YGGFMRF is a potent secretagogue with a maximal rate of fluid secretion induced at a concentration of between 10(-13) and 10(-12) M. The tetrapeptide comprising the last four residues of the C-terminus of YGGFMRF, Phe-Met-Arg-Phe, is equally potent. However, the carboxyamidated variants, YGGFMRF-NH2 and the molluscan cardioacceleratory peptide FMRF-NH2, as well as the opioid peptides Met5- and Leu5-enkephalin, have no activity. Partially purified YGGFMRF-immunoreactive peptides from the blowfly have ED50 values in the bioassay approximating to 0.3 thoracic ganglion, 2.1 hypocerebral ganglion and 3.0 brain equivalents.