Action and immunoreactivity of neuropeptides in the buccal neuromuscular system of a prosobranch mollusc,Rapana thomasiana

Summary In a prosobranch mollusc, Rapana thomasiana, the catch-relaxing peptide H-Ala-Met-Pro-Met-Leu-Arg-Leu-NH₂ (CARP) was found to depress the contraction of the radula protractor and retractor elicited by electrical stimulations. The action of CARP was in contrast to that of other neuropeptides, H-Phe-Met-Arg-Phe-NH₂ (FMRFamide) and H-Phe-Leu-Arg-Phe-NH₂ (FLRFamide), which enhanced the contraction of the radula protractor and retractor, respectively. By immunohistochemical examinations, FMRFamide-like immunoreactive neurons were found on the rostral side of the right buccal ganglion and the caudal side of the left ganglion, where some CARP-like immunoreactive neurons were also distributed, indicating a possible coexistence of FMRFamide and CARP. FMRFamide- and CARP-like immunoreactivities were also detected in the neuropile of buccal ganglia, radula nerves arising from the ganglia, and nerve fibers in the radula muscles. The present results suggest that FMRFamide- and CARP-like peptides are involved in the regulation of the contraction of the radula muscles.     

A comparative study of leucokinin-immunoreactive neurons in insects

Antisera were raised against leucokinin IV, a member of the leucokinin peptide family. Immunohistochemical localization of leucokinin immunoreactivity in the brain of the cockroach Nauphoeta cinerea revealed neurosecretory cells in the pars intercerebralis and pars lateralis, several bilateral pairs of interneurons in the protocerebrum, and a group of interneurons in the optic lobe. Several immunoreactive interneurons were found in the thoracic ganglia, while the abdominal ganglia contained prominent immunoreactive neurosecretory cells, which projected to the lateral cardiac nerve. The presence of leucokinins in the abdominal nerve cord was confirmed by HPLC combined with ELISA. Leucokinin-immunoreactive neurosecretory cells were also found in the pars intercerebralis of the cricket Acheta domesticus and the mosquito Aedes aegypti, but not in the locust Schistocerca americana or the honey bee Apis mellifera. However, all these species have leucokinin-immunoreactive neurosecretory cells in the abdominal ganglia. The neurohemal organs innervated by abdominal leucokinin-immunoreactive cells were different in each species.     

Partial Characterization of a Novel Cardioinhibitory Peptide from the Brain of the Snail Helix aspersa

1. We report the isolation of a peptide from the brain of the snail Helix aspersa by radioimmunoassay using an antisomatostatin.2. The sequencing of an immunopositive fraction showed the presence of a new tridecapeptide, termed Helix cardioinhibitory peptide (HCIP), with the following primary structure : H-Val-Phe-Gln-Asn-Gln-Phe-Lys-Gly-Ile-Gln-Gly-Arg-Phe-NH₂. It is structurally related to the Achatina cardioexcitatory peptide (ACEP-1) and the terminal-ammo acid sequence of HCIP is identical to that of FMRFamide family peptides.3. The synthetic HCIP was tested on heart and neuronal activities and it was found to have inhibitory actions not only on the ventricle but also on visceral neurons of the central nervous system of Helix. Immunocytochemical investigation indicates its presence in visceral and parietal ganglia, in which cells taking part in the regulation of the heartbeat have been previously identified .     

Developmental and regional-specific expression of FLRFamide peptides in the tobacco hornworm,Manduca sexta,suggests functions at ecdysis

The developmental profile of a family of three FLRFamide (Phe-Leu-Arg-Phe-NH₂) peptides in the tobacco hornworm, Manduca sexta, revealed regional-specific expression patterns within the segmental ganglia. Levels of the three peptides—F7G (GNSFLRFamide), F7D (DPSFLRFamide), and F10 (pEDVVHSFLRFamide)—were always higher in the thoracic than abdominal ganglia. The predominant peptide also differed regionally, with F7G being highest in the thoracic ganglia and F7G and F10 being equivalent in the abdominal ganglia. Furthermore, we found regional-specific transient declines in ganglion peptide levels temporally correlated to ecdysis. Thoracic ganglion peptide levels declined at each molt, while abdominal ganglion levels declined over a period of 2 days after ecdysis. The decline in central levels was accompanied by an increase in levels in peripheral neurohemal sites, the transverse nerves (TNs). These observations suggest peptides were released from neurosecretory cells (NSCs) at ecdysis. Distinct sets of thoracic and abdominal NSCs and their processes in peripheral neurohemal sites were immunoreactive, supporting the biochemical data. These results also suggest the regional differences may arise from cellular-specific expression patterns for this family of peptides. In addition, fine immunoreactive processes were observed traveling between TNs and skeletal muscles, suggestive of myotropic actions. We propose that the release of different M. sexta FLRFamides from regionally distinct NSCs leads to a coordinated modulation of skeletal and visceral muscles that facilitate ecdysis. © 1998 John Wiley & Sons, Inc. J Neurobiol 37: 469–485, 1998     

Peptidergic innervation of leg muscles of the cockroach,Periplaneta americana (L.), and a possible role in modulation of muscle contraction

FMRFamide-related peptides of insects are particularly important because of their possible function as neurohormones and neuromodulators on a wide variety of tissues. Part of this study was an investigation of the immunofluorescent staining of motor nerves which arise in the metathoracic ganglion, examined in wholemount using an antiserum that recognizes extended -RFamide peptides (generally recognized to be of the FMRFamide family). This antiserum revealed immunochemical staining of numerous cell bodies in the metathoracic ganglion and of axons in peripheral nerve 5, a large nerve which contains both motor and sensory fibres. Axons staining positive for FMRFamide-related peptides were traced in nerve 5 as far as the femur-tibia joint, and into the first (sensory-motor) and third (motor only) ramus of nerve 5. Reverse-phase HPLC with radioimmunoassay revealed a peak of FMRFamide-related peptide activity in nerve 5 that was coincident with a peak found when thoracic ganglia were processed in the same fashion. A physiological assay was devised to test the ability of various non-native peptides to alter the characteristics of contraction of skeletal muscles of the legs. Using neurally evoked contractions of coxal depressor muscles of the metathoracic leg it was determined that several non-native peptides could potentiate muscle contractions.The results of this study suggest that muscles of the legs receive innervation by identifiable, FMRFamide-related peptide-containing neurons and that the release of peptide(s) at the muscle may be yet another method of modulating the mechanics of muscle contraction.Abbreviations D _f fast depressor motor neuron - D _s slow depressor motor neuron - DU M dorsal unpaired median - FaRPs FMRFamide related peptides - FEFe fast extensor of the femur - FFFe fast flexor of the femur - FITC fluorescein isothiocyanate - FPC fast promotor of the coxa - FPT fast flexor of the pretarsus - I _1–3 inhibitory motor neurons - LMS leucomyosuppressin, N5 nerve 5 - N5r1 first ramus of nerve 5 - PBS phosphate buffered saline - PLCl posterior lateral cluster - RIA radioimmunoassay - SETi slow extensor of the tibia - SFTi slow flexor of the tibia - TFA trifluoroacetic acid - VMCl ventral median cluster     

An FMRFamide antiserum differentiates between populations of antigens in the ventral nervous system of the locust,Schistocerca gregaria

Summary The distribution of FMRFamide immunoreactive neurones in the ventral nerve cord of the locust, Schistocerca gregaria, is described. These neurones are found only in the suboesophagael and thoracic ganglia, although immunoreactive processes are found in the neuropils of the abdominal ganglia. Many of these neurones also react with an antiserum raised against bovine pancreatic polypeptide (BPP), but this antiserum also reveals another population of cells in the abdominal ganglia. The staining obtained with the BPP antiserum is blocked by preabsorption of the antiserum with FMRFamide; the converse is not true: FMRFamide-like immunoreactivity is not suppressed by preincubation with BPP. These results suggest that there are at least two endogenous peptide antigens in the locust nerve cord: one is found in cells of the suboesophageal and thoracic ganglia, and the other is found in cells of the abdominal ganglia.     

Properties of proton and sugar transport at the tonoplast of tomato (Lycopersicon esculentum) fruit

Tonoplast vesicles were isolated from tomato (Lycopersicon esculentum Mill.) fruit pericarp and purified on a discontinuous sucrose gradient. ATPase activity was inhibited by nitrate and bafilomycin A₁ but was insensitive to vanadate and azide. PPase hydrolytic activity was inhibited by NaF but was insensitive to nitrate, bafilomycin A₁ vanadate and azide. Kimetic studies of PPase activity gave an apparent K_m, for PP₃ of 18 μM. Identical distributions of bafilomycin- and NO₃-sensitive ATPase activities within continuous sucrose density gradients, confirmed that bafilomycin-sensitive ATPase activity is a suitable marker for the tonoplast. By comparing the distribution of bafilomycin-sensitive ATPase activity with that of PPase activity, it was possible to locate the PPase enzyme exclusively at the tonoplast. The apparent density of the tonoplast did not change during fruit development. Measurements of tonoplast PPase and ATPase activities during fruit development over a 35-day period revealed an 80% reduction in PPase specific activity and a small decrease in ATPase specific activity. ATP- and PP₁-dependent ΔpH generation was measured by the quenching of quinacrine fluorescence in tonoplast vesicles prepared on a discontinuous Dextran gradient. No H⁺ efflux was detected on the addition of sucrose to energized vesicles. Therefore a H⁺/sucrose antiport may not be the mechanism of sucrose uptake at the tomato fruit tonoplast. Similar results were obtained with glucose, fructose and sorbitol. The lack of ATP (or PP₁) stimulation of [¹⁴C]-sucrose uptake also suggested that an antiport was not involved. Initial uptake rates of radiolabelled glucose and fructose were almost double that for sucrose. The inhibition of hexose uptake by p-chloromercuribenzene sulphonate (PCMBS) implicated the involvement of a carrier. Therefore storage of hexose in the tomato fruit vacuole and maintenance of a downhill sucrose concentration gradient into sink cells is likely to be regulated by the activity of sucrose metabolizing enzymes, rather than by energy-requiring uptake mechanisms at the tonoplast.     

Hormone-Carrier-Neurosecretory Granule Association in the Urophysis of the Goby Gillichthys mirabilis*

Nishioka, R. S., Bern, H. A., Gunther, R. L. 1980. Hormone-carrier-neurosecretory granule association in the urophysis of the goby Gillichthys mirabilis. (Department of Zoology and Cancer Research Laboratory, University of California, Berkeley, California, N.S.A.) — Acta zool. (Stockh.) 61(1): 29–38. The caudal neurosecretory system of the mudsucker, Gillichthys mirabilis, was investigated using continuous sucrose density gradient centrifugation, electron microscopy, polyacrylamide gel electrophoresis, and bioassay. A strong light-scattering band near the 41 % sucrose concentration was shown to contain neurosecretory granules by electron microscopy and urotensin II activity by bioassay. Aliquots of this band were run in polyacrylamide gel electrophoresis and the selected regions of the gel containing those bands unique to urophysial tissue were cut out and eluted after the gel had been sliced longitudinally. The eluate from the region of the unique band (rf 0.46) gave the highest urotensin II bioassay activity when compared to adjacent areas. The remaining half of the gel was stained to confirm the localization of the unique bands. Gels made from regions adjacent to the 41 % sucrose concentration showed less stainability of the bands, and eluate of regions from its unique bands contained correspondingly less bioactivity.     

Comparative potency of some extended peptide chain members of the RFamide neuropeptide family,assessed on the hearts of<Emphasis Type="Italic"> Busycon canaliculatum</Emphasis> and<Emphasis Type="Italic"> Buccinum undatum</Emphasis>

Twenty different RFamide neuropeptide analogues were examined for their relative potencies on the ventricles of Busycon canaliculatum and Buccinum undatum and on the atrium of Busycon to determine the essential requirements for activity at the RFamide receptor. None of the neuropeptide studies was inhibitory to natural cardiac rhythmicity or to FMRFamide (Phe-Met-Arg-Phe-NH₂) or FLRFamide (Phe-Leu-Arg-Phe-NH₂) responses. Two tripeptides studied were completely without effect, indicating that a minimum of four amino acids in the peptide chain length was essential for any activity. The original parent tetrapeptide FMRFamide was surprisingly less potent than many of the extended chain peptides such as the penta, hepta and decapeptides. These RFamide neuropeptides were strongly inotropic on both ventricles and the atrium, while on the latter they were strongly chronotropic despite several of these peptides being of a non-molluscan origin. Chain length seems to be of little importance for activity at the receptor. Surprisingly, SCP_B (small cardioactive Peptide B) was not very effective in either Busycon or Buccinum ventricle. What was also clear was that the configuration of the carboxyl terminal was important for activity. Two neuropeptides in this study possessed an Arg-Met carboxyl terminal and were much less effective than FMRFamide, suggesting that an Arg-Phe terminal is most effective in receptor activation.Abbreviations Ala alanine - Arg arginine - Asn asparagine - Asp aspartic acid - FLRFamide Phe-Leu-Arg-Phe-NH₂ - FMRFamide Phe-Met-Arg-Phe-NH₂ - Glu glutamic acid - Gly glycine - His histidine - Leu leucine - LMS leucomyosuppressin - Met methionine - Nle norleucine - Phe phenylalanine - Pro proline - SCP_B Small cardioactive peptide B - Ser serine - Thr threonine - Trp tryptophan - Tyr tyrosine - Val valineCommunicated by G. HeldmaierPart of this work was presented at the Society for Experimental Biology 1999 Annual conference (Huddart et al. 1999)     

An initial screen of a series of neuroactive peptides for activity on identified central neurones of Helix aspersa

1. Intracellular recordings were made from identified neurones in the suboesophageal ganglia of Helix aspersa. Seven neuropeptides were tested for activity and their actions compared with acetylcholine and FMRFamide.2. Three peptides isolated from nematodes, AF-1, AF-2 and PAN-1 had mainly inhibitory effects with thresholds of around 1 nM. This inhibition was due to an increase in potassium conductance.3. The molluscan neuropeptides LSSFVRIamide, CARP and ACEP-1 were all active on certain neurones; the first two showed only inhibitory effects while ACEP-1 was mainly excitatory. The thresholds in each case were 0.1–10 μM. When norleucine replaced methionine in CARP, the potency was reduced by at least 100 times.4. The echinoderm peptide, SALMF-1, only excited neurones but with a very low threshold, around 1.0 fM.5. There was no obvious correlation between the action of these peptides and either acetylcholine or FMRFamide.     

Evidence for homologous peptidergic neurons in the buccal ganglia of diverse nudibranch mollusks

The buccal ganglia of seven nudibranches (Aeolidia papillosa, Armina californica, Dirona albolineata, D. picta, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea) were examined to explore possible homologies between large cells that reacted with antibodies directed against small cardioactive peptide B (SCP_B). The buccal ganglion of each species possessed a pair of large, dorsal–lateral, whitish neurons that contained an SCP_B-like peptide. We refer to these neurons as the SLB (SCP_B-immunoreactive Large Buccal) cells. In all species examined, the SLB cells project out the gastroesophageal nerves and appear to innervate the esophagus. In each species, an apparent rhythmic feeding motor program (FMP) was observed by intracellular recording from both SLB neurons and other neurons in isolated preparations of the buccal ganglia. SLB cells often fire at a high frequency, and usually burst in a specific phase relation to the FMP activity. Stimulation of SLB cells enhances expression of the feeding motor program, either by potentiating existing activity or eliciting the FMP in quiescent preparations. Finally, perfusion of isolated buccal ganglia with SCP_B excites the SLB cells and activates FMPs. Thus, both the immunohistochemical and electrophysiological data suggest that the SLB cells within three suborders of the opistobranchia (Dendronotacea, Arminacea, and Aeolidacea) are homologous. A comparison of our data with previously published studies indicates that SLB cell homologs may exist in other gastropods as well.     

Small cardioactive peptide-like immunoreactivity and its colocalization with FMRFamide-like immunoreactivity in the central nervous system of the leech Hirudo medicinalis

Summary The distributions of small cardioactive peptide (SCP)- and FMRFamide-like immunoreactivities in the central nervous system of the medicinal leech Hirudo medicinalis were studied. A subset of neurons in the segmental ganglia and brains was immunoreactive to an antibody directed against SCP_B. Immunoreactive cell bodies were regionally distributed throughout the nerve cord, and occurred both as bilaterally paired and unpaired neurons. The majority of the unpaired cells displayed a tendency to alternate from side to side in adjacent ganglia. A small number of neurons were immunoreactive only in a minority of nerve cords investigated. Intracellular injections of Lucifer yellow dye and subsequent processing for immunocytochemistry revealed SCP-like immunoreactivity in heart modulatory neurons but not in heart motor neurons. FMRFamide-like immunoreactivity was also detected in cell bodies throughout the central nervous system. A subset of neurons contained both SCP- and FMRFamide-like immunoreactivities; others stained for only one or the other antigen. These data suggest that an antigen distinct from FMRFamide is responsible for at least part of the SCP-like immunoreactivity. This antigen likely bears some homology to the carboxyl terminal of SCP_A and SCP_B.     

Purification and Characterization of a Cardioexcitatory Neuropeptide from the Central Ganglia of a Bivalve Mollusc

Abstract

We have purified a cardioexcitatory substance, previously designated peak C, from ganglia of the Sunray Venus clam, Macrocallista nimbosa. Low concentrations (10^?9 -10^?8M) of this substance not only excite the isolated clam heart, but also produce tonic contractions of the isolated radula protractor muscle of the whelk, Busycon contrarium. These two muscle preparations have therefore been used as a parallel bioassay for peak C. Peak C is inactivated by proteolytic enzymes, has an isoelectric point greater than pH 10 and has an ultraviolet absorption spectrum similar to that of phenylalanine. On thin layer chromatograms, peak C separates into two components; one of these is probably a partially oxidized form produced during purification. Both components react with ninhydrin and with the Sakaguchi reagent for guanidino groups. The amino acid composition of peak C is Phe_2.00 Met_0.81 Arg_1.12. N-terminal analysis, one round of Edman-dansyl degradation, and tryptic digestion are consistent with the identification of Macrocallista peak C as a tetrapeptide amide: Phe-Met-Arg-Phe-NH₂ (FMRFamide).     

Distribution of FMRFamide-like immunoreactivity in the brain and suboesophageal ganglion of the sphinx mothManduca sexta and colocalization with SCPB-, BPP-, and GABA-like immunoreactivity

Summary Using an antiserum against the tetrapeptide FMRFamide, we have studied the distribution of FMRFamide-like substances in the brain and suboesophageal ganglion of the sphinx mothManduca sexta. More than 2000 neurons per hemisphere exhibit FMRFamide-like immunoreactivity. Most of these cells reside within the optic lobe. Particular types of FMRFamide-immunoreactive neurons can be identified. Among these are neurosecretory cells, putatively centrifugal neurons of the optic lobe, local interneurons of the antennal lobe, mushroom-body Kenyon cells, and small-field neurons of the central complex. In the suboesophageal ganglion, groups of ventral midline neurons exhibit FMRFamide-like immunoreactivity. Some of these cells have axons in the maxillary nerves and apparently give rise to FMRFamide-immunoreactive terminals in the sheath of the suboesophageal ganglion and the maxillary nerves. In local interneurons of the antennal lobe and a particular group of protocerebral neurons, FMRFamide-like immunoreactivity is colocalized with GABA-like immunoreactivity. This suggests that FMRFamide-like peptides may be cotransmitters of these putatively GABAergic interneurons. All FMRFamide-immunoreactive neurons are, furthermore, immunoreactive with an antiserum against bovine pancreatic polypeptide, and the vast majority is also immunoreactive with an antibody against the molluscan small cardioactive peptide SCP_B. Therefore, it is possible that more than one peptide is localized within many FMRFamide-immunoreactive neurons. The results suggest that FMRFamide-related peptides are widespread within the nervous system ofM. sexta and might function as neurohormones and neurotransmitters in a variety of neuronal cell types.Abbreviations AL antennal lobe - BPPLI bovine pancreatic polypeptide-like immunoreactivity - FLI FMRFamide-like immunoreactivity - GLI GABA-like immunoreactivity - NSC neurosecretory cell - SCP _B LI small cardioactive peptide_B-like immunoreactivity - SLI serotonin-like immunoreactivity - SOG suboesophageal ganglion     

Immunocytochemical localization of FMRFamide in the central nervous system and the kidney of Helisoma duryi (Mollusca): its possible antidiuretic role

The distribution of FMRFamide-immunoreactive neurons in the central nervous system of the freshwater pulmonate, Helisoma duryi is described. All parts of the central nervous system except the two pleural and the right parietal ganglia, contain immunoreactive neurons. By immunogold techniques, only one kind of neurosecretory FMRFamide-immunoreactive cell (previously identified as the type-3 cell) was localized in the visceral and left parietal ganglia. This cell type has been previously implicated in an antidiuretic role. FMRFamide-immunoreactive material is found in the whole mount of the kidney as well as in kidney sections. Electron microscopic examination shows that the axons innervating either the smooth muscles of the kidney or the kidney itself contain neurosecretory granules morphologically similar to type-3 cells of the visceral and left parietal ganglia. When incubated in saline containing nanogram quantities of FMRFamide, the wet weight of the kidney increased. It is suggested that FMRFamide-like substance may function as an antidiuretic factor and that the kidney is a target organ of this peptide for osmoregulation.     

Physiological and anatomical properties of Leydig cells in the segmental nervous system of the leech

Summary Each of the 21 segmental ganglia in the American leechMacrobdella decora contains a pair of Leydig cells (ca. 45 m) each of which is located in a posteriolateral glial packet. Leydig cells exhibit spontaneous action potentials (1–10/s) whose duration and undershoot depend upon membrane polarization. The two Leydig cells within each ganglion are bidirectionally-coupled (V ₂/V ₁0.3). Pairs of ipsilateral Leydig cells within adjacent ganglia are mutually excitatory such that an impulse in one generates an impulse in the other. The interganglionic latency for any cell pair is constant regardless of the direction of impulse conduction and is unchanged by 20 mM Mg²⁺ saline. These data indicate that the interactions are not mediated by chemical synapses. Additionally, the results of collision experiments lead us to infer that ipsilateral Leydig cell pairs utilize common axonal pathways for interganglionic interactions. If Leydig cells are driven by current injection to fire impulses at frequencies of six to ten per s, cells in adjacent ganglia exhibit impulse failures. The combination of spontaneous activity, intraganglionic coupling and interganglionic interactions results in the generation of constant, low frequency impulse activity and can cause impulse reverberations.The branching pattern of Leydig cells filled with HRP is consistent with their functional properties and connectivity. Each cell sends axons to both adjacent ganglia through the ipsilateral connectives and projects to the periphery only by the lateral roots of these adjacent ganglia. This unusual morphology was verified Lucifer Yellow CH.In addition to intraganglionic dye-coupling, dye coupling was occasionally evident between ipsilateral cells in adjacent ganglia. Electron microscopy of Leydig cells depicts abundant 100 nm granules in both their somata and neuropilar processes. Although this fine structure suggests a neurosecretory role, we were unable to discern a peripheral function for these neurons.Abbreviation H R P horseradish peroxidase     

Excitation evoked by FMRFamide and FLRFamide in the heart of Buccinum undatum and evidence for inositol 1,4,5-trisphosphate as an RF-tetrapeptide second messenger

In this study the relative potencies of four established molluscan cardioexcitatory agents were examined on Buccinum heart. The potencies were, in decending order: phenylalanine-leucine-arginine-phenylalanine-NH₂ (FLRFamide) > phenylalanine-methionine-arginine-phenylalanine-NH₂ (FMRFamide; 80% of maximum) > 5-hydroxytryptamine (5HT; 60% of maximum) > guanosine triphosphate (GTP; 15% of maximum). FMRFamide and FLRFamide had similar dose-response curve patterns with thresholds at 10⁻⁹ mol l⁻¹ but FLRFamide was more potent than FMRFamide. The superfused atrium was much less sensitive to all agonists than the internally perfused ventricle. FLRFamide and FMRFamide induced small depolarizations (1–2 mV) which triggered a burst of action potentials of about 5 mV which on reaching 4 mV triggered a burst of fast twitch contractions. Lithium, at high concentrations inhibited FMRFamide and 5-HT responses of internally perfused ventricles. Neomycin also inhibited peptide responses, but was without effect on 5-HT responses. Heparin, however, for technical reasons was without effect on ventricular responses to all three agonists. FMRFamide and FLRFamide appear to share a common receptor, the potency difference being due to the substitution of leucine for methionine in FLRFamide. The RF N-terminal sequence appears crucial for receptor activation. The Phospholipase C inhibitor neomycin equally inhibits responses to the two peptides while 5-HT responses are unaffected. This implicates a peptide/receptor interaction which activated inositol 1,4,5-trisphosphate (IP₃) as a second messenger. Accepted: 22 March 2000     

Blood pressure elevation in rats by peripheral administration of TyrGlyPheMetArgPhe and the invertebrate neuropeptide,PheMetArgPheNH2

PheMetArgPheNH₂ (FMRFamide), injected at < μmol/kg intravenously in the anesthetized rat, produces sharp elevations of blood pressure and changes in respiration. The effects were dependent on the carboxyterminal ArgPhe (RF) configuration and were stereospecific for these two amino acids. A related peptide with RF carboxyterminus, ^γ₁-melanotropic stimulating hormone, also had potent blood pressure stimulating activity. The mechanisms underlying the pressor effect of FMRFamide have not yet been established but this pressor action was not significantly attenuated by standard pharmacologic antagonists or prevented by removal of the adrenal or pituitary gland.     

FMRFamide immunoreactive neurons in the central nervous system of the snail,Achatin a fulica

• 1.1. FMRFamide immunoreactive neurons were detected in the central nervous system of the snail, Achatina fulica.
• 2.2. FMRFamide immunoreactive neurons were found in all the ganglia comprising the central nervous system. In particular, the immunoreactivity was recognized in both the ordinary and giant neurons of the visceral and right parietal ganglia.
• 3.3. In the cerebral and pleural ganglia, FMRFamide immunoreactive neurons were found only in the ordinary neurons. The immunoreactivity was shown to have a tendency to form a group in the cerebral and pedal ganglia.