Some pharmacological properties of neuromuscular transmission in the oviduct of the locust,Locusta migratoria

The effects of various pharmacological agents on neurally evoked contractions of the visceral muscles of the oviduct of Locusta migratoria have been examined. The pentapeptide, proctolin, at low concentrations (10^?11 M?10^?10 M), induced an increase in the amplitude of neurally evoked contractions and basal tonus, and induced the appearance and increased the frequency of myogenic contractions. Glutamate, at 10^?4 M, produced a small transient contraction which in some preparations was accompanied by a reduction in amplitude of neurally evoked contractions. Octopamine, at 10^?6 M, reduced the amplitude of neurally evoked contractions and also resulted in a relaxation of the muscles. The octopaminergic effects were inhibited by the α-aminergic antagonist phentolamine. Neurally evoked contractions were unaffected by dopamine, 5-HT or the acetylcholine receptor antagonists atropine and hexamethonium. Acetylcholine increased the amplitude of neurally evoked contractions, but only at the high concentration of 10^?3 M. The possible role of proctolin and glutamate as excitatory neuro-transmitters and the inhibitory action of octopamine is discussed.     

Experimental studies upon a bundle of tonic fibres in the locust extensor tibialis muscle

The bundle of tonic fibres situated at the proximal end of the locust metathoracic extensor tibialis muscle is innervated by the dorsal unpaired median neurone (DUMETi) as well as by the slow excitatory (SETi)) and common inhibitor (CI) neurones. It is not innervated by the fast excitatory neurone (FETi).These fibres contract spontaneously and rhythmically. The myogenic rhythm can be modified by neural stimulation.Spontaneous slow depolarizing potentials resembling the pacemaker potentials of insect cardiac muscle were demonstrated in these fibres.The actions of glutamate on the tonic muscle fibres are not compatible with its being a specific excitatory transmitter. Glutamate can stimulate weak contractions of the muscle, but this action is inhibited when chloride ions are removed from the saline.10^?6 M Octapamine hyperpolarizes the tonic fibre membrane. Octopamine, GABA and glutamate all inhibit the myogenic contractions and reduce the force of the neurally evoked contractions.The tonic muscle is very responsive to proctolin. At 5 × 10^?11 M proctolin enhances the force and increases the frequency of myogenic contractions. At 10^?9 M it depolarizes the muscle membrane potential, and at that and higher concentrations it causes the muscle to contract. At 2 × 10^?7 M proctolin induces contractures which resemble those evoked by sustained high-frequency neural stimulation. Iontophoretic experiments show that proctolin receptors occur at localized sites on the tonic fibre membrane.     

Neuromuscular modulation in Limulus by both octopamine and proctolin

Both octopamine and proctolin potentiate nerve-evoked skeletal muscle contractions in the horseshoe crab, Limulus. The threshold concentration for octopamine was 10^?9 to 10^?8M, while for proctolin it was 3 × 10^?9M. Norepinephrine and dopamine produced effects similar to octopamine but at higher thresholds; tyramine and serotonin were ineffective. Octopamine caused significant increases in amplitudes of excitatory postsynaptic potentials (epsps) of muscle fibers, but had little effect on muscle fiber input resistance or membrane potential. Also, octopamine did not affect depolarization of muscle fibers and subsequent contraction due to the direct action of exogenously applied glutamate. These results suggest that octopamine potentiates nerve-evoked contractions primarily by facilitating release of neuromuscular transmitter. At concentrations above 10^?7M, however, octopamine sometimes caused muscle spikes in response to motoneuron stimulation, a finding that suggests that octopamine may also have some postsynaptic action. Proctolin potentiated the muscle contractions evoked by glutamate but had little effect on glutamate-evoked muscle fiber depolarization, muscle fiber input resistance, or membrane potential. Thus, proctolin appears to act directly on skeletal muscle to enhance contractility. The proctolin-induced potentiations of contraction were sometimes accompanied by modest increases in epsp amplitude, so that unlike lobster skeletal and Limulus cardiac neuromuscular preparations, proctolin may have a secondary direct synaptic effect. Both octopamine and proctolin have been found in Limulus cardiac ganglion. This potential access to the hemolymph and the relatively low threshold concentrations needed for physiological action suggest that octopamine and proctolin could function as hormonal modulators of neuromuscular function in Limulus.     

Peptide actions on oviduct contractions in the large pine weevil,Hylobius abietis

Abstract The peptides proctolin, crustacean cardioactive peptide (CCAP) and FMRFamide, which are known to modulate insect muscle contractions, were assayed for their action on oviduct contractions in Hylobius abietis. A video microscopy technique and computer‐based method of data acquisition and analysis were used to investigate the effects of theses peptides on spontaneous contractions of continuously perfused oviducts. All three peptides tested stimulate spontaneous contraction activity of the pine weevil oviduct, increasing the frequency and amplitude of phasic contractions in a dose‐dependent manner. Proctolin is more potent as a stimulator than CCAP. For proctolin a threshold response of oviduct muscles is at concentration of peptide 10^?11–10^?10 mol/L and for CCAP at concentration range 10^?10–10^?9 mol/L. FMRFamide exerts a weak stimulatory effect on the oviduct, and at higher concentrations of the peptide (above 10^?8 mol/L). The peptides exert different responses on oviduct contractions and they may play a role as functional regulators in such processes as egg movement and oviposition.     

Proctolin's role in neurally evoked contractions of the locust oviducts

The effects of proctolin (RYLPT) on neurally evoked contractions of locust oviduct muscle were studied to examine the role of proctolin as a cotransmitter. Increasing the number of stimuli in a burst (from one to 30 stimuli) resulted in an increase in amplitude of contraction of locust oviduct muscle. Proctolin was capable of increasing the amplitude of neurally evoked contractions at lower-stimulus regimes (one- and two-stimulus bursts) but did not do so at higher-stimulus regimes (five- and 10-stimulus bursts). The effects of proctolin were dose dependent within the one- and two-stimulus regimes, with thresholds at 10⁻⁹ M and maxima at 2.5 × 10⁻⁸ M. Addition of proctolin increased the basal tonus and size of a postcontraction relaxation of the oviduct muscle in a dose-dependent manner during all stimulus regimes. However, the effect of proctolin on basal tonus and the postcontraction relaxation was much less at the higher stimulus regimes. Previously, several proctolin analogues have been tested for their ability to antagonize proctolin-induced contractions of the oviduct muscle. Since proctolin is proposed to be a cotransmitter at this neuromuscular junction, one of these analogues, cycloproctolin, was used to antagonize proctolin's effects on neurally evoked contractions. In the presence of the antagonist, the maximum amplitude induced by application of proctolin was decreased by 22.7%, while the proctolin-induced increase in basal tonus was decreased by 45.8%. Finally, the maximum increase in the size of the postcontraction relaxation caused by proctolin was lowered by 32.0%. The results of the present study show that exogenously applied proctolin is an excitant of the oviduct muscle at lower, rather than higher, stimulus regimes, and this latter inaction may be due to the corelease of endogenous proctolin during increased neural stimulation. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 139–150, 1997     

Effects of leucomyosuppressin on the excitation-concentration coupling of insect Leucophaea maderae visceral muscle

1. Leucomyosuppressin (LMS) inhibited neurally evoked contractions of the hindgut of the cockroach Leucophaea maderae. The threshold for this inhibition of LMS was in the range of 1 × 10⁻¹⁰ M.2. LMS caused a sharp reduction in both l-glutamate and proctolin induced contractions. Dose-response profiles of the effect of LMS (held constant at 10⁻⁸M) on variable amounts of proctolin showed an inhibitory effect at 10⁻⁹ M proctolin and below, but at 5 × 10⁻⁹ M proctolin and above, LMS caused no inhibition.3. Potassium (158 mM) depolarized hindguts treated with LMS (10⁻⁸ M) showed a marked reduction (76% ± 2.1) in the proctolin (10⁻⁸ M) response.4. When calcium depleted preparations were returned to normal calcium levels (2 mM) in the presence of proctolin (10 ⁻⁸ M) a contraction occurred that was 45% ± 4 of the maximum in normal saline solution. However, LMS (10⁻⁸ M) reduced this response to only 28% ± 2 of the maximum.5. Proctolin (10⁻⁸ M) induced contractions in the presence of the manganous ions (2mM) fell to 63% ± 4 of the maximum but on the addition of LMS (10⁻⁸M), such responses fell to only 16% ± 5 of the maximum.6. These results offer evidence for a non-synaptic site of action for LMS and a perturbation of key calcium dependent events in the excitation-contraction coupling sequence of visceral muscle by this peptide.     

Mode of action of proctolin on locust visceral muscle

Proctolin increases the frequency and amplitude of myogenic contractions and results in a sustained contraction of the oviducts of Locusta migratoria. The possible mode of action of proctolin receptors on this visceral muscle has been investigated. Calcium-free saline, containing either 20 mM magnesium ions or 100 μM EGTA, inhibited myogenic contractions, lowered basal tension, and abolished all the effects of proctolin following a 20 min incubation. These effects were reversible upon washing with normal saline. Similar results were obtained with normal saline containing 10 mM cobalt ions. Nifedipine at 50 μM lowered basal tension, abolished myogenic contractions, and reduced the proctolin-induced sustained contraction by 42-62% at 0.5 nM proctolin and by 33-37% at 5 nM proctolin. Similar results were obtained with 100 μM verapamil. Proctolin was still capable of eliciting considerable contractions (25-67% of controls) in preparations depolarized with 100 mM potassium saline. The removal of calcium from the high-potassium saline reversibly abolished the potassium-induced contraction and reversibly blocked the action of proctolin. Nifedipine was ineffective in blocking the action of proctolin in high-potassium saline. Neither cyclic AMP levels nor cyclic GMP levels of the lateral oviducts were elevated by proctolin in the presence of a phosphodiesterase inhibitor. The results indicate that proctolin mediates its effects via an influx of external calcium ions. This calcium appears to enter through two channels, a voltage-dependent channel and a receptor-operated channel. Cyclic nucleotides do not appear to be involved in the action of proctolin in this visceral muscle.     

Electrophysiological studies of the effect of the neuropeptide proctolin on the hyperneural muscle of Periplaneta americana (L.)

The myotropic neuropeptide proctolin is, in additional to its action on proctodaeum and on some other systems, highly effective on the hyperneural muscle of Periplaneta americana and evokes long-term contractions. During this proctolin response the input resistance (R_input) increases by about 25% accompanied by only slight depolarization. These processes require extracellular Ca²⁺ but are still present in Na⁺-free solution.Junction potentials evoked by threshold stimulation of the nerve are not affected by proctolin. Synaptic processes do not seem to be important for the proctolin action on hyperneural muscle. It is more likely that the whole membrane of the muscle fibre serves as target for proctolin. Proctolin reduces the threshold for neurally evoked muscle contractions, the only available route of excitation since the muscle fibres themselves are not electrically excitable.The K⁺-channel blocker 4-aminopyridine may evoke contraction as well as proctolin, but this is only a transitory response. In contrast to proctolin, 4-aminopyridine is still effective after blocking the Ca²⁺-channels by Co²⁺, but the response is smaller. Therefore proctolin seems to be primarily effective via Ca²⁺-channels, whereas 4-aminopyridine exerts its effects via K⁺-channels. The decrease in membrane conductance produced by proctolin could result from a Ca²⁺-dependent reduction of the K⁺-outward current.     

Proctolin and octopamine actions on the contractile systems of insect leg muscles

1. The pentapeptide proctolin produced contractions of the coxal depressor muscle of the cockroach, Periplaneta americana.2. The contraction was dependent upon extracellular calcium and the contraction was completely blocked by a Ca-free EGTA saline.3. Caffeine elicited transient contractions which were unaffected by manganese treatment.4. When the muscle was pre-treated with the conditioning solution with different K⁺ concentrations (1–100 mM), the amplitude of proctolin-induced contractions was reduced in the low K⁺ saline as well as in the high K⁺ saline.5. The results suggest that voltage sensitive calcium channels account for the proctolin-induced contractions.6. Octopamine (OA) reduced the contractions resulting from brief applications of elevated K⁺ concentration and of caffeine.7. The effect of OA on the response to elevated K⁺ concentrations was blocked by the α-adrenergic blocker, phentolamine.     

A peptide action in a lobster neuromuscular preparation

The neuropeptide proctolin causes a sustained contraction of the opener muscle of the dactyl of the lobster walking leg. This substance acts directly on the muscle at concentrations as low as 10^?10M. The contraction is dependent on extracellular calcium. Neither a significant depolarization nor a detectable change in the input resistance accompanies the response. No presynaptic action of proctolin is indicated; excitatory and inhibitory junctional potential sizes and the frequency of spontaneous miniature excitatory junctional potentials are unaffected.     

Acetylcholine-induced contractions in a holothurian (Isostichopus badionotus) smooth muscle are blocked by the calcium antagonists,diltiazem and verapamil

1. The longitudinal muscle of the body wall (LMBW) of the holothurian, Isostichopus badionotus contracted when treated with acetylcholine (ACh). The threshold concentration for initiating a contraction was 10⁻⁸M ACh.2. Inward calcium (Ca²⁺) current blockers, diltiazem and verapamil, blocked contractions induced by ACh suggesting that Ca²⁺ channels are involved. Verapamil caused small rhythmic contractions to occur in some muscle preparations.3. Caffeine initiated contractions only at the high concentration of 10 mM and caused rhythmic contractions in otherwise non-spontaneously beating muscle. The caffeine-contractions were partially blocked by verapamil.     

Effects of FMRFamide-related peptides and morphine on the isolated foregut of the locust schistocerca gregaria

1. Morphine and YAGFMamide were the most effective potentiators of 5-hydroxytryptamine (5-HT)-induced relaxation of the isolated foregut.2. Morphine had no effect on proctolin-induced tissue contraction which was inhibited by YGGF-Mamide and YFMRFamide.3. The differing potency of FaRPs and morphine to potentiate 5-HT effects and reduce proctolin responses suggests that there are two separate FaRP receptor sub types.4. This proposal is supported by the observation that, while naloxone (10⁻⁵ M) is a relatively potent antagonist of FaRP induced inhibition of proctolin contraction, it has less effect on FaRP-induced potentiation of 5-HT-induced relaxation.     

A novel response to propranolol: Contractile response in the isolated rabbit ear artery

Propranolol caused a contractile response in the isolated rabbit ear artery (EA). The concentration of propranolol causing a threshold contraction was 1.76 × 10^?6M while that causing a maximal contraction of 2.2 ± 0.18 g was 3 × 10^?5M. Higher concentrations caused tissue relaxation. Phentolamine, 10^?7 and 10^?6M reduced the propranolol-induced contractions by 50% and 90%, respectively while prazosin, 10^?8, 10^?7 and 10^?6M caused reductions of 54, 74 and 88%, respectively. Reserpinization of the rabbit with 5 mg/kg 24 hours before use eliminated the EA contractile response to tyramine but had no effect on that to propranolol. Desmethylimipramine plus deoxycorticosterone acetate enhanced the submaximal contraction of the EA to propranolol. $\text{In vitro}$ denervation with 6-hydroxydopamine (6-OHDA) decreased the response of the EA to tyramine and propranolol by 96% and 85% respectively but increased that to norepinephrine (NE) by 11%. Rabbit thoracic aorta (TA) did not respond to propranolol. In EA contracted with vasopressin o or 30 mM potassium, propranolol 10^?4 and 3 × 10^?4M caused a 20% and 100% relaxation, respectively. It is concluded that propranolol elicits a contractile response in the EA, at least in part, by direct activation of postsynaptic alpha adrenoceptors.     

Proctolin: a peptide transmitter candidate in insects.

The slow, striated muscles of the proctodeum (hindgut) of the cockroach, $\text{Periplaneta americana}$ (L.), were examined pharmacologically with reference to the responses evoked by nerve stimulation, glutamate, 5-HT, and proctolin, a myotropic peptide from $\text{Periplaneta}$ recently isolated and identified. The graded contractions evoked by repetitive nerve stimulation were simulated by 5-HT and proctolin at threshold concentrations of about 10⁻⁷ and 10⁻⁹ M respectively; responses to glutamate (∼10⁻⁴ M) were not similarly graded. The 5-HT receptors are distinct from other receptors, including the post-synaptic receptors, since they were specifically blocked by bromolysergic acid diethylamide. Proctolin was fully active on TTX-treated or surgically denervated muscle indicating that the proctolin receptors are located on the muscle fibre membrane. Tyramine, at threshold levels 5×10⁻⁸ M, reversibly antagonized the responses evoked by proctolin and by nerve stimulation but was without effect on the 5-HT and glutamate responses. Neurally evoked responses were potentiated by subthreshold concentrations of proctolin but not by glutamate. Pharmacologically, the proctolin and post-synaptic receptors appear to be identical and distinct from the glutamate and 5-HT receptors. Since proctolin is known to be a constituent of an efferent pathway of the proctodeal nerves, the evidence suggests that it may function as an excitatory transmitter substance. Peptidergic transmission is discussed in relation to the ultrastructural organization of the proctodeal nerve terminals which contain neurosectory granules in addition to electron-lucent, synaptic vesicles.     

The oviduct musculature of the cockroach Leucophaea maderae and its response to various neurotransmitters and hormones

The musculature of the oviduct consists of an outer, irregular layer of longitudinal muscle and an inner layer of circular muscle. The four basic modes of activity—compression, segmentation, peristalsis, and reverse peristalsis—were evident in the isolated oviduct. These spontaneous events often occurred in an organized sequence. In fact eggs could be transported down the lateral oviducts by this myogenic activity once the sphincter between the common oviduct and vagina was severed. Myographic recordings were made of only the contractions of the longitudinal muscles. L-glutamate caused a distinct phasic contraction at 2.2 × 10^?5 M. The response became larger and more complex as the concentration of the amino acid was increased. Acetylcholine (1.6 × 10^?5 M) caused either a phasic or tonic response, or a combination thereof. By contrast, 5HT and tyramine simply increased the frequency of small phasic contractions, although in some preparations both monoamines caused an inhibition. The ecdysones, a juvenile hormone analogue (1 × 10^?6 M), and prostaglandin E₂ had no effect on oviduct activity. Initially high KCI solutions (162 mM) without Ca⁺⁺ induced a strong contraction but subsequent additions failed to do so. However, when a high KCI solution (158 mM) with 2 mM Ca⁺⁺ was added to the preparation the response was partially restored. Also the potent calcium antagonist Mn⁺⁺ (2mM) can suppress spontaneous activity.     

Dual effects of proctolin on the rhythmic burst activity of the cardiac ganglion

The neuropeptide proctolin has distinguishable excitatory effects upon premotor cells and motorneurons of Homarus cardiac ganglion. Proctolin's excitation of the small, premotor, posterior cells is rapid in onset (5–10 s) and readily reversible (< 3 min). Prolonged bursts in small cells often produce a “doublet” ganglionic burst mode via interactions with large motorneuron burst-generating driver potentials. In contrast to small cell response, proctolin's direct excitatory effects upon motorneuron are slow in onset (60–90 s to peak) and long-lasting (10–20 min). The latter include: (a) a concentration-dependent (10^?9–10^?7M) depolarization of the somatic membrane potential; (b) increases in burst frequency and (c) enhancement of the rate of depolarization of the interburst pacemaker potential. Experiments on isolated large cells indicate: (a) the slow depolarization is produced by a decrease in the resting G_K and (b) proctolin can produce or enhance motorneuron autorhythmicity. A two-tiered non-hierarchical network model is proposed. The differential pharmacodynamics exhibited by the two cell types accounts for the sequential modes of ganglionic burst activity produced by proctolin.     

The mode of action of phenylhydrazine hydrochloride on the locust neuromuscular system

The action of the carbonyl reagent phenylhydrazine hydrochloride (Phen. HCl) on locust excitatory neuromuscular systems was studied by examining the effects of this compound on the mechanical and electrical properties of the retractor unguis and extensor tibiae muscles of the locust Schistocerca gregaria.Low concentrations of Phen. HCl (10^?9 w/v to 2·5 × 10^?5 w/v) potentiated the muscle contractions and the excitatory post-synaptic potential (EPSP), the optimum concentration being about 10^?5 w/v. 10^?8 w/v Phen. HCl increased miniature EPSP frequency, but this increase became less pronounced as the concentration was raised, and no increase at all was observed at 10^?5 w/v. There was no change in miniature EPSP amplitude at any concentration. Higher concentrations of Phen. HCl (> 2·5 × 10^?6 w/v) depressed the neurally evoked contraction, the EPSP, and the response of the muscle to iontophoretically applied l-glutamate. A gradual increase in muscle input conductance was observed on perfusion with these high concentrations of Phen. HCl. The presence of magnesium in the bathing fluid (15 m-moles/l.) reduced the effectiveness of Phen. HCl in potentiating the EPSP and delayed or reduced the increase in input conductance observed on perfusion with high concentrations of Phen. HCl.The results indicate that low concentrations of Phen. HCl act presynaptically, possibly by depolarizing the excitatory nerve terminals. Higher concentrations may act directly on the post-synaptic glutamate receptors.     

Myonemal contraction of Spirostomum. I. Kinetics of contraction and relaxation

A microphotometric method is introduced that allows measurement of the contraction-relaxation kinetics of Spirostomum in response to electrical stimulation. The time course of contraction includes a rapidly contracting phase of some 4–5 mS during which cells shorten at a rate in excess of 100 cell lengths sec^?1. While a stimulus strength-duration curve determines the threshold of the response, the response to above threshold stimuli of different strengths and to trains of stimuli suggest that contraction of Spirostomum may not be an all-or-none event. The kinetics of relaxation following high stimulating voltages and repetitive after contractions also induced by high voltages are explained by excitation-contraction coupling through a stimulus-dependent intermediate effector, possibly the release of calcium ions. Changes in resting membrane potential detected by intracellular recording do not influence the initiation of contraction, while microinjection of calcium buffers above 10^?5 M Ca²⁺ invariably induces contraction.     

Electrophysiological investigation of the antennal heart of Periplaneta americana and its reactions to proctolin

Some physiological parameters of the antennal heart, an accessory circulatory organ in the head of Periplaneta americana and the effect of the neuropeptide proctolin on it were investigated. The beat frequency of the antennal heart in vivo or semiisolated is about 2–3 times slower than that of the dorsal vessel and not coordinated with the latter. The extracellular ECG of the antennal heart has a simple biphasic shape with a total duration of 588.7 ± 38.2 ms. Intracellularly recorded parameters showed characteristics typical of myogenic rhythmicity: a slow depolarization with a rate of rise of 7.5 ± 0.7 mV/s, followed by an action potential of 54.9 ± 1.2 mV with a relatively long duration of 201.6 ± 10.8 ms, absence of overshoots and resistance to TTX. Proctolin produced a marked enhancement of the frequency of beat of the antennal heart up to about 400% with a high sensitivity (threshold concentrations: 5·10^?9M). The dose-response curve shows a linear relationship between the logarithm of the concentration and the percentage increase in beat frequency. The electrical event most influenced by proctolin was the slow pacemaker depolarization, whose rate of rise was enhanced up to 240%. The action potential remained unchanged; the depolarization of the resting potential was very small and the input resistance did not change. The antennal heart responds to neurohormone D, another neuropeptide in insects, in a similar way as it does to proctolin. The mode of action of proctolin on the antennal heart is discussed in comparison to that found in other systems.     

Myotropic activity and immunolocalization of selected neuropeptides of the burying beetle Nicrophorus vespilloides (Coleoptera: Silphidae)

Burying beetles (Nicrophorus sp.) are necrophagous insects with developed parental care. Genome of Nicrophorus vespilloides has been recently sequenced, which makes them interesting model organism in behavioral ecology. However, we know very little about their physiology, including the functioning of their neuroendocrine system. In this study, one of the physiological activities of proctolin, myosuppressin (Nieve? MS), myoinhibitory peptide (Trica-MIP-5) and the short neuropeptide F (Nicve-sNPF) in N. vespilloides have been investigated. The tested neuropeptides were myoactive on N. vespilloides hindgut. After application of the proctolin increased hindgut contraction frequency was observed (EC50 value was 5.47 x 10-8 mol/L). The other tested neuropeptides led to inhibition of N. vespilloides hindgut contractions (Nicve-MS: IC50 = 5.20 x 10~5 mol/L;Trica-MIP-5: IC50 = 5.95 x 10-6 mol/L;Nicvc-sNPF: IC50 = 4.08 x 10-5 mol/L). Moreover, the tested neuropeptides were immunolocalized in the nervous system of N. vespilloides. Neurons containing sNPF and MIP in brain and ventral nerve cord (VNC) were identified. Proctolin-immunolabeled neurons only in VNC were observed. Moreover, MIP-immunolabeled varicosities and fibers in retrocerebral complex were observed. In addition, our results have been supplemented with alignments of amino acid sequences of these neuropeptides in beetle species. This alignment analysis clearly showed amino acid sequence similarities between neuropeptides. Moreover, this allowed to deduce amino acid sequence of N. vespilloides proctolin (RYLPTa), Nicve-MS (QDVDHVFLRFa) and six isoforms ofNicve-MIP (Nicve-MIP-1一 DWNRNLHSWa;Nicve-MIP-2—AWQNLQGGWa;Nicve-MIP-3—AWQNLQGGWa;Nicve-MlP-4—AWKNLNNAGWa;Nicve-MIP-5—SEWGNFRGSWa;Nicve-MIP-6— DPAWTNLKGIWa;and Nicve-sNPF—SGRSPSLRLRFa).