FMRFamide-like Immunoreactivity Research Articles

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.

Modulation of ecdysis in the moth Manduca sexta: the roles of the suboesophageal and thoracic ganglia.

The sequential behaviours shown by insects at ecdysis are due to the sequential release of various hormones, but the transition from one phase to the next can be fine-tuned by inhibitory influences. The ecdysis sequence in the moth Manduca sexta was initiated by injecting sensitive animals with the neuropeptide ecdysis-triggering hormone (ETH). Exposure to ETH stimulates the release of eclosion hormone (EH) which, in turn, activates a set of neurons containing crustacean cardioactive peptide (CCAP) by elevating their levels of intracellular cyclic GMP. We characterized a set of non-CCAP containing neurons that also appear to be EH targets because of their response to cyclic GMP at ecdysis. The neurons did not display leucokinin-, diuretic-hormone- or FMRFamide-like immunoreactivity. They are probably the bursicon-containing cells described previously. After release of EH, there is a transient inhibition of the abdominal centers responsible for ecdysis. Transection experiments suggested that this suppression is via descending inhibitory units from the suboesophageal and thoracic ganglia. The duration of this inhibition appears to depend on the levels of cyclic GMP and can be extended by pharmacologically suppressing cyclic GMP breakdown. We further found that brief exposure to CO(2) caused premature ecdysis. Since the CO(2) treatment was effective only after EH release, it probably acts by suppressing descending inhibition. Studies on adult eclosion suggest that CO(2), given at the appropriate time, can uncouple the basic larval motor program from modulatory influences provided by the adult pterothoracic ganglion. CO(2) therefore appears to be a novel and non-invasive tool for studies of ecdysis behavior in insects.

Evidence for the association of FMRFamide-related peptides with the spermatheca of Locusta migratoria

The association of FMRFamide-related peptides (FaRPs) with the spermatheca of Locusta migratoria was demonstrated using radioimmunoassay and immunohistochemical techniques. The physiological effects of various FaRPs on the neurally evoked contractions of the spermatheca were also examined. FMRFamide-like immunoreactivity (FLI) was demonstrated in processes and cell bodies situated in the VIIIth (terminal) abdominal ganglion. These included an anterior, central and posterior pair of ventral cell bodies positioned near the midline of the ganglion, in addition to two bilaterally paired dorsal cell bodies in the posterior region of the VIIIth abdominal ganglion. Two axons displaying FLI proceed down the ventral ovipositor nerve (VON) and into the receptaculum seminis nerve which innervates the anterior regions of the spermatheca. FLI was also noted in processes on the spermathecal muscle with the highest density occurring on the spermathecal sac and coil duct. FaRPs applied to the spermathecal muscle included GQERNFLRFamide, NFIRFamide, ADDRNFIRFamide, YGGFMRFamide, FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide (PDVDHVFLRFamide). Dose-dependent physiological effects were only noted for FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide. FMRFamide led to a dose-dependent increase in the amplitude of neurally evoked contractions with a threshold of approximately 5 × 10 −7 M. SchistoFLRFamide, and ADVGHVFLRFamide, had an inhibitory effect, decreasing the amplitude of neurally evoked spermathecal contractions.

Seven novel FMRFamide-like neuropeptide sequences from the eyestalk of the giant tiger prawn Penaeus monodon

FMRFamide-like immunoreactivity (FLI) was localized in the eyestalk of Penaeus monodon by immunohistochemistry using a combination of three anti-FMRFamide-like peptide (FLPs) monoclonal antibodies. Approximately 3000 small neuronal cell bodies in the lamina ganglionalis; 100 medium to large size at the ganglion between the medulla interna and the medulla terminalis; and 250 medium size around the medulla terminalis were stained intensely. The neuronal processes in neuropils of the medulla externa, medulla interna, medulla terminalis, sinus gland and some nerve fibers in the optic nerve were also recognized. The small cell bodies, approximately 1500 cells, anterior to the medulla externa were stained inconsistently and the neuronal processes were not observed from these cells. Isolation of FLPs from 9000 eyestalks was performed using methanol/acetic/water (90:1:9) extraction. After the extract was partially purified using C18 cartridges, it was further purified by five to seven steps of RP-HPLC using three kinds of columns: C18; C8; and cyano, and three solvent systems: acetonitrile/trifluoro acetic acid; aceonitrile/heptafluoro butyric acid; and acetonitrile/triethyl ammonium acetate. Dot-ELISA using the combination of the same antibodies was used to monitor FLPs in the fractions during purification processes. Seven new sequences of FLPs were identified which can be divided into four subgroups according to the primary structure of the C-terminus: (1) GDRNFLRFamide; (2) AYSNLNYLRFamide; (3) AQPSMRLRFamide, SQPSMRLRFamide, SMPSLRLRFamide and DGRTPALRLRFamide; and (4) GYRKPPFNGSIFamide. These data indicate the high complexity of this peptide family in which multiple forms are usually exist.

FMRFamide in the amphibian brain: A comprehensive survey

Mapping of FMRFamidergic neural circuitry in the amphibian brain has been done by immunohistochemical methods. Comparative evidence suggests that there are similarities and differences in the overall pattern of distribution of FMRFamide-ir elements in the brain among the three amphibian orders and within each order. FMRFamide is expressed in neurons in some circumscribed areas of the brain. A part of these neurons is concentrated in classical neurosecretory areas of the hypothalamus in a bilaterally symmetrical fashion. Similar neurons occur occasionally in the midbrain, but are virtually absent from the hindbrain. Anurans are unique among amphibians to show FMRFamide neurons in the medial septum and diagonal band of Broca. A viviparous gymnophione is known to possess a small population of such neurons in the dorsal thalamus. Together, the FMRFamide neurons contribute to an extensive fiber network throughout the amphibian brain. Descriptive developmental studies suggest that the rostral forebrain-located FMRFamide neurons originate in the olfactory placode and then migrate into the brain along the route of the vomeronasal-olfactory-terminal nerve complex. Olfactory placodal ablation in an anuran and a urodele provide experimental support to this contention. Other FMRFamide neuronal cell groups, in the hypothalamus and dorsal thalamus, are supposed to arise from non-placodal precursors. The neuroanatomical distribution (projection of immunoreactive processes to areas of the fore-, mid-, and hindbrain as well as to cerebrospinal fluid, co-localization with other neuropeptides, and presence in the median eminence) has furnished morphological correlates of possible functions of FMRFamide in the amphibian CNS. While amphibian FMRFamide-like or structurally related peptides remain to be isolated and characterized, the sum of the distribution pattern of FMRFamide-like immunoreactivity suggests that it may act as a neurotransmitter or a neuromodulator, and also may have endocrine regulatory functions.

Localization of molluscan cardioexcitatory tetrapeptide in the brain of African Cichlid fish ( Haplochromis burtoni) revealed by immunocytochemistry

The FMRFamide-like immunoreactivity was investigated in the brain of African cichlid fish, Haplochromis burtoni, in which sexual maturation is under social control. In both dominant and subdominant males and females, the FMRFamide immunoreactive (ir) cells were found only in the nucleus olfacto-retinalis and in the nucleus of the midbrain tegmentum. However, several FMRFamide-ir fibers were seen in the olfactory bulb and throughout the entire brain of both male morphs and female fish. As the role of nucleus olfacto-retinalis is well known in chemoreception, these results suggest the involvement of FMFRamide-like peptide in the chemosensory control of reproductive behavior in this species.

Feeding state influences the content of FMRFamide- and tachykinin-related peptides in endocrine-like cells of the midgut of Locusta migratoria☆

The midgut of 5th instar male African migratory locust, Locusta migratoria, was found to contain endocrine-like cells that stained positively for FMRFamide-like immunoreactivity. These cells have cell bodies which are tear-drop in shape with processes extending from the cell body. FMRFamide-like immunoreactivity has been described in similar cells in adult midgut tissue [16]. The midgut tissue content of FMRFamide-like immunoreactivity is differentially distributed throughout various regions of the midgut (gastric cecae, anterior and posterior midgut) in 5th instar and varied ages of adult. FMRFamide-like immunoreactivity in midgut tissues decreases significantly by 24 h of starvation, whereas locustatachykinin I-like immunoreactivity does not decrease until 48 h of starvation indicating that there are differential timing effects of these two peptide families on midgut content. HPLC analysis, combined with RIA, of different regions of the midgut tissue from both fed and starved locusts revealed that the relative proportions of the members of the two peptide families vary depending upon the feeding state. These results indicate that the contents of these endocrine-like cells appears to be differentially influenced by the feeding state of the locust.

Localization of FMRFamide-Like Immunoreactivity in the Brain of the Viviparous Skink (Chalcides chalcides)

Neuroanatomical distribution of FMRFamide-like immunoreactivity was investigated in the brain and olfactory system of the viviparous skink, Chalcides chalcides. In the adult brain FMRFamide immunoreactive (ir) perikarya were observed in the diagonal band of Broca, medial septal nucleus, accumbens nucleus, bed nucleus of the anterior commissure, periventricular hypothalamic nucleus, lateral forebrain bundle, and lateral preoptic, subcommissural, suprachiasmatic and lateral hypothalamic areas. This pattern was seen in both male and female brains. Though all major brain areas showed FMRFamide-ir innervation, the densest ir fiber network was observed in the hypothalamus. During development, ir elements were observed for the first time in embryos at mid-pregnancy. FMRFamide perikarya were located along the ventral surface of the vomeronasal nerve, in the olfactory peduncle mediobasally, as well as in the anterior olfactory nucleus and olfactory tubercle. Furthermore, some ir neurons were observed in the rhombencephalic reticular substance; however, the ir fiber network was poorly developed. Later in development FMRFamide-ir neurons appeared also in the bed nucleus of the anterior commissure as well as the rhombencephalic nucleus of solitary tract and the dorsal motor nucleus of vagus nerve. In juveniles, the distribution profile of FMRFamide immunoreactivity was substantially similar to that of the adults, with a less widespread neuronal distribution and a more developed fiber network. Ontogenetic presence of FMRFamide immunoreactivity in the nasal area has been linked to the presence of a nervus terminalis in this reptile.

Distribution of FMRFamide-like immunoreactivity in the amphibian brain: Comparative analysis

FMRFamide is a small neuropeptide present in particular neurons of the basal forebrain and midbrain of the vertebrate groups studied, especially fishes and mammals. In order to assess interspecies variation, the distribution of FMRFamide-like immunoreactivity was studied in the brains of 13 species of amphibian. Although FMRFamide-immunoreactive (IR) terminals occurred throughout much of the brain, IR cell groups were noted in circumscribed regions of the CNS. In the eight anuran species studied, two major populations of labeled perikarya were observed: one in the septopreoptic area and another one in the caudal portion of the diencephalon. The rostrocaudal extent of both and the number of labeled somata in each neuronal group displayed species-specific differences. In urodeles and gymnophiones, labeled perikarya were located in the diencephalon, but there were remarkable species differences in the number of such cells. It is discussed whether sex or season of collection may account for some of the differences observed. The distribution of FMRFamide-IR perikarya, fibers, and pathways in the brain of anurans, urodeles, and gymnophiones was compared. The existence of FMRFamide perikarya in the anterior preoptic neuropil and medial septum appeared to be a feature common to all anurans; labeled neurons in the dorsal thalamus, however, may be present only in the (viviparous) gymnophione Typhlonectes compressicauda. Cerebrospinal fluid contacting FMRFamide neuronal cell bodies and fibers were observed in each of the three taxonomic orders. The data are compared with those previously obtained for other groups of vertebrates.

Distribution of FMRFamide‐like immunoreactivity in the amphibian brain: Comparative analysis

FMRFamide is a small neuropeptide present in particular neurons of the basal forebrain and midbrain of the vertebrate groups studied, especially fishes and mammals. In order to assess interspecies variation, the distribution of FMRFamide-like immunoreactivity was studied in the brains of 13 species of amphibian. Although FMRFamide-immunoreactive (IR) terminals occurred throughout much of the brain, IR cell groups were noted in circumscribed regions of the CNS. In the eight anuran species studied, two major populations of labeled perikarya were observed: one in the septopreoptic area and another one in the caudal portion of the diencephalon. The rostrocaudal extent of both and the number of labeled somata in each neuronal group displayed species-specific differences. In urodeles and gymnophiones, labeled perikarya were located in the diencephalon, but there were remarkable species differences in the number of such cells. It is discussed whether sex or season of collection may account for some of the differences observed. The distribution of FMRFamide-IR perikarya, fibers, and pathways in the brain of anurans, urodeles, and gymnophiones was compared. The existence of FMRFamide perikarya in the anterior preoptic neuropil and medial septum appeared to be a feature common to all anurans; labeled neurons in the dorsal thalamus, however, may be present only in the (viviparous) gymnophione Typhlonectes compressicauda. Cerebrospinal fluid contacting FMRFamide neuronal cell bodies and fibers were observed in each of the three taxonomic orders. The data are compared with those previously obtained for other groups of vertebrates. J. Comp. Neurol. 414:275–305, 1999. © 1999 Wiley-Liss, Inc.

Regulation of pharyngeal motility by FMRFamide and related peptides in the medicinal leech, Hirudo medicinalis.

The medicinal leech possesses FMRFamide-like immunoreactivity in neural processes and somata associated with the pharynx and pharyngeal ganglia. The pharynx possessed about 25 immunoreactive somata; about half of the approximately 20 neurons of the pharyngeal ganglia were immunoreactive. We provide brief descriptions of several neurons located in the first neuromere of the subesophageal ganglion involved in controlling pharyngeal motility. Double-labeling experiments indicate that one of these cells, named Swallow neuron 1 (SW1), contains a FMRFamide-like peptide. Stimulation of SW1 caused the mouth to open and the pharynx to dilate. Upon termination of SW1 stimulation, the mouth closed, and a peristaltic wave progressed from the mouth down the length of the pharynx. Stimulation of SW1 did not produce 1:1 postsynaptic potentials in pharyngeal muscle cells. Thus, SW1 is apparently not a motor neuron. The pharynx responded to application of FMRFamide and related peptides by producing a series of 20- to 35-s phasic contractions superimposed upon an increase in basal tonus. The peptide-induced response was quantified by measuring increases in basal tonus, peak tension, and integrated area. Although there were some differences in the order of potency depending upon which parameter was considered, the approximate order of potency of RFamide peptides tested was: pQDPFLRFamide > or = FMRFamide approximately YGGFMRFamide > or = YMRFamide approximately FLRFamide approximately GGKYMRFamide approximately YLRFamide > leucomyosuppressin approximately perisulfakinin. Except for differences in potency, each of the RFamide peptides produced similar contractile waveforms. FMRFamide-induced responses were reduced by the protein kinase C inhibitor bisindolylmaleimide I (10 microM), the nonspecific protein kinase inhibitor H-7 (50 microM), and were increased by the protein phosphatase inhibitor okadaic acid (1 microM). However, the FMRFamide-induced response was unaffected by the protein kinase A inhibitor H-89 (1 microM), the phosphodiesterase inhibitor theophylline (1 mM), the phospholipase A(2) inhibitor OBAA (0.1 microM) or the cation channel blocker amiloride (100 microM).

Effects of food nutrient content, insect age and stage in the feeding cycle on the FMRFamide immunoreactivity of diffuse endocrine cells in the locust gut.

We have studied the influence of variations in dietary protein and digestible carbohydrate content, of insect age and of time during the feeding cycle on the endocrine cells of the ampullar region of the midgut in the African migratory locust Locusta migratoria L. Morphometric analysis of FMRFamide-like immunoreactivity was used as an indirect measure of the amount of FMRFamide-related peptides (FaRPs) stored in the gut endocrine cells. There was a highly significant correlation between FaRP content and the nutritional quality of the food, measured relative to the concentrations and ratio of protein to digestible carbohydrate in a nutritionally optimal diet. The direction of the relationship between FaRP content and diet quality varied with age during the fifth stadium. On day 1, FaRP levels increased with the nutritional quality of the food, while on day 4 the opposite relationship was observed. Release of peptide was triggered by the onset of a meal during ad libitum feeding, with cell FaRP levels returning to premeal values within 15 min of the meal ending. The results also suggested that cell contents were released during food deprivation beyond the normal intermeal interval. Locusts switched for a single meal during ad libitum feeding on day 4 from a low- to a high-carbohydrate food did not respond by reducing endocrine cell FaRP content. Our results show a relationship between the diffuse gut endocrine system and feeding and nutrition in locusts. The ampullar endocrine cells are in three-way contact with the midgut luminal contents, with the primary urine from the Malpighian tubules and with the haemolymph. They are thus ideally positioned to play an integrative receptor-secretory function in the regulation of a variety of post-ingestive processes, such as enzyme secretion, absorption, gut motility or nutrient metabolism.

FMRFamide-like Immunoreactivity in the Olfactory System Responds to Morphine Treatment in the TeleostClarias batrachus:Involvement of Opiate Receptors

In view of the close relationship between the FMRF-related peptides and the central opiate-sensitive system, we investigated the effects of morphine, alone and in combination with naloxone, on the FMRFamide-like immunoreactivity in the olfactory system of the teleost,Clarias batrachus.In the olfactory system of normal and untreated fish, FMRFamide-like immunoreactivity was confined to the ganglion cells and fibers of the terminal nerve; the cells in the olfactory epithelium per se or the olfactory nerve were not immunoreactive. Intensely immunoreactive cells appeared in the olfactory epithelium following 2 h of intracranial morphine administration. FMRFamide-like immunoreactivity also appeared in the olfactory nerve fibers as they ran caudally and arborized in the glomerular layer of the bulb. However, immunoreactivity in the ganglion cells of the terminal nerve and the ensuing fibers was abolished, suggesting the transport/release of the immunoreactive material. Pretreatment with naloxone, a potent opiate receptor antagonist, reversed the effects of morphine, suggesting the involvement of opiate receptors in the regulation of the ganglion cells of the terminal nerve. The results provide initial immunocytochemical evidence in favor of a relationship between the opiates and FMRFamide-containing systems within the framework of the olfactory system.

The Effects of SchistoFLRFamide on Contractions of Locust Midgut

Lange, A. B. and I. Orchard The effects of SchistoFLRFamide on contractions of locust midgut. Peptides 19(3) 459–467, 1998.—The midgut of insects has recently been shown to contain numerous endocrine-like cells and the midgut is now considered one of the largest endocrine organs in the insect. Using immunohistochemistry, radioimmunoassay, and muscle bioassay techniques, the midgut of the adult locust, Locusta migratoria, has been investigated for the distribution and possible function of FMRFamide-related peptides contained within these endocrine-like cells and innervation. Endocrine-like cells containing RFamide-like immunoreactivity were observed to be unequally distributed throughout the midgut. RFamide-like immunoreactivity was also seen in the ingluvial ganglion and in the nerves projecting posteriorly to the midgut. These axonal tracts resulted in extensive arborizations over the posterior midgut which were RFamide-like immunoreactive. Radioimmunoassay indicated larger amounts of FMRFamide equivalents in female locust midgut as compared to males with an unequal distribution of FMRFamide-like immunoreactivity in the gastric caeca and in the anterior and posterior parts of the midgut. Circular muscle contraction of the midgut was monitored using a ring-type preparation. Structure/activity studies have shown that the only FMRFamide-related peptides tested that alter circular muscle contraction of the midgut are those that belong to the subfamily referred to as myosuppressins. SchistoFLRFamide, leucomyosuppressin, and ManducaFLRFamide were each capable of lowering basal tonus and inhibiting spontaneous and proctolin-induced contractions of midgut muscle. Further structure/activity studies indicated that HVFLRFamide is the minimum sequence required to achieve inhibition comparable to the parent compound. This work suggests that a possible function for the FMRFamide-related peptides contained within the endocrine cells and innervation of the midgut of the locust may be in modulating midgut contraction and thereby playing a role in digestion.

Co-localization of serotonin and FMRFamide-like immunoreactivities in the central nervous system of the earthworm, Eisenia Jetida

In the present study co-localization of serotonin and FMRFamide-like immunoreactivities was studied in the central nervous system of the earthworm, Eisenia fetida. Alternate serial sections were stained with antisera raised against serotonin and FMRFamide, using the peroxidase-antiperoxidase method. The immunostained consecutive sections were compared by light-microscopy and on reconstructed images using NIH Image and Neurolucida programs. Although there was a large number of serotonin and FMRFamide-like immunoreactive neurons in the central nervous system of Eisenia, co-localization of immunostaining was relatively rare. In the cerebral ganglion no cells were found that stained for both antisera. In the subesophageal and ventral cord ganglia the neurons reacting for both antisera represented approximately 17-23% and 10-14% of the serotonin- and 7-11% and 9-17% of the FMRF-amide-like immunoreactive cells, respectively. It is suggested, that FMRFamide-related peptides act as neuromodulators and may also influence the activity of serotonergic neurons.

GABA-immunoreactive neurones and interactions of GABA with serotonin and FMRFamide in a peripheral sensory ganglion of the pond snail Lymnaea stagnalis

The osphradium is a putative chemosensory organ of aquatic molluscs. Previously, we identified cells with serotonin (5-HT) and FMRFamide (FMRFa)-like immunoreactivity in the osphradial ganglion of Lymnaea stagnalis. The present investigation has established the presence of cells immunoreactive to γ-aminobutyric acid (GABA). Some of these cells send processes to the sensory epithelium and are thus considered to be primary sensory neurones. Colocalisation of GABA and FMRFamide-like immunoreactivities was found in some of these and other neurones. The responses of the osphradial output electrical activity to the single and combined application of the above neuroactive substances were examined. 5-HT slightly increased and FMRFa decreased the activity. GABA alone was generally ineffective; however, it had a consistent stimulating effect after pretreatment with 5-HT. In its turn, pretreatment with GABA significantly increased the inhibitory action of FMRFa. Primary sensory neurones giving this kind of responses in the nerve were identified electrophysiologically and morphologically in the osphradial ganglion. Our results indicate that GABA takes part in relay of sensory signals into the central nervous system, and transmitter interactions involving GABA, 5-HT, and FMRFa are considerable for the final output pattern of the osphradial sensory network.

FMRF amide-like-immunoreactive primary sensory neurons in the olfactory system of the terrestrial mollusc, Limax marginatus.

The distribution of FMRF amide-like immunoreactivity was investigated in the olfactory organs in the tentacle tip of the terrestrial slug, Limax marginatus. Approximately 0.7% of the neurons in the lobules of the tentacle ganglia demonstrated FMRF amide-like immunoreactivity. Most of the FMRF amide-like-immunoreactive somata lay at superficial positions within the lobules, and dendritic processes extended to the outer surface of the sensory epithelium, whereas the axons traveled toward the cerebral ganglion through the ventral part of the tentacle nerve. From their morphological features, FMRF amide-like-immunoreactive cells were considered to be primary sensory neurons.

Cholinergic and Peptidergic Regulation of Siphon/Mantle Function in the Zebra Mussel, Dreissena polymorpha

Neurotransmitter regulation of the siphon and adjacent mantle region of bivalves has not previously been examined. In the biofouling bivalve, Dreissena polymorpha, acetylcholine and FMRFamide both elicited contractions of siphon/mantle preparations. Hexamethonium bromide inhibited acetylcholine-elicited contractions but had no effect on FMRFamide-elicited contractions. FMRFamide-like immunoreactivity and chromatographic evidence for acetylcholine were found in central ganglia and the siphon/mantle region. Extracts of siphons, gonads, and gills, separated on Sephadex G-25, also contained macromolecules larger than acetylcholine and FMRFamide that caused siphon/mantle contraction. These results demonstrate regulation of contraction by several potential neurotransmitter agents in a new bivalve preparation, the siphon/mantle.

Localization and Neurohemal Release of FMRFamide-Related Peptides in the Stick Insect Carausius morosus

Miksys, S., A.B. Lange, I. Orchard and V. Wong. Localization and neurohemal release of FMRFamide-related peptides in the stick insect Carausius morosus. Peptides 18(1) 27–40, 1997.—FMRFamide-like immunoreactivity was localized immunohistochemically in the central and stomatogastric nervous systems, visceral tissues, and the neurohemal corpora cardiaca, transverse, and segmental nerves. Each of these neurohemal areas contains one morphologically distinct type of immunoreactive neurosecretory granule. The hemolymph level of FMRFamide-like peptides, quantified by RIA, is higher in animals sampled 2 h into the dark cycle, relative to those sampled at mid-light cycle or 9 h into the dark cycle. High potassium depolarization evokes the calcium-dependent release of FMRFamide-like peptides from neurohemal areas in vitro and HPLC fractionation of hemolymph, corpora cardiaca, and their bathing medium suggests that these organs contribute a single peptide to the FMRFamide-related peptides circulating in the hemolymph of active animals.

Distribution of presumptive chemosensory afferents with FMRFamide- or substance P-like immunoreactivity in decapod crustaceans

In five species of decapod crustaceans — Cherax destructor (crayfish), Carcinus maenas (crab), Homarus americanus (clawed lobster), Eriocheir sinensis (crab), Macrobrachium rosenbergii (shrimp) — immunocytochemical stainings revealed the presence of sensory afferents with FMRFamide-like immunoreactivity in the central nervous system. These afferents were extremely thin, very numerous, and innervated all sensory neuropils except the optic and olfactory lobes. In their target neuropils they gave rise to condensed net- or ball-like terminal structures. Only in Homarus americanus but not in any other studied species immunocytochemistry revealed a separate, non-overlapping class of sensory afferents with substance P-like immunoreactivity. Also the afferents with substance P-like immunoreactivity were very thin and numerous, innervated all sensory neuropils except optic and olfactory lobes, and gave rise to condensed terminal structures. From their morphological characteristics it can be concluded that likely both classes of afferents are chemosensory. The substance P-like immunoreactivity suggests a link with the nociceptor afferents of vertebrates, with which both classes of afferents share several other morphological features.