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At least 1,063 records · Page 59Linked to original sources
PubMed1985

Calcium regulation in blowflies: absence of a role for midgut.

Adult blowflies (Calliphora vicina) survive many days without increased mortality if fed 12.5 mM CaCl2 solution in place of water. Initially the calcium content of these flies rapidly increases to more than double the original content but then remains stable for many days afterward. Calcium absorption continues at a similar rate throughout this time. Midguts isolated from flies fed either 12.5 mM CaCl2 solution or distilled water have the same capacity to absorb calcium. Dopamine, octopamine, proctolin, and 5-hydroxytryptamine, at pharmacological doses, do not affect calcium absorption by the isolated midgut. Malpighian tubules are the site of most rapid calcium turnover when flies are fed excess calcium. It is concluded that excretion and not absorption is the major site of hemolymph calcium regulation in C. vicina. This contrasts to the situation in mammals where transcellular calcium absorption by the duodenum is precisely controlled. It is suggested that to avoid high luminal calcium concentrations, fast calcium absorption from the blowfly midgut is adapted to remove calcium from the lumen rather than to regulate hemolymph calcium concentration.

Animals↗
PubMed1989

Mechanics of stretch in activated crustacean slow muscle. I. Factors affecting peak force.

1. The active stiffness of ventral superficial abdominal muscle (VSM) of the hermit crab, Pagurus pollicarus, was measured with ramp stretches of different amplitudes and velocities. Active stiffness was calculated by subtracting the peak force produced by passive stretch and the isometric force just before stretch from the peak force produced by stretching active muscle. The result was then divided by stretch length to give stiffness. 2. The relationship between force just before stretch (the level of activation) and active stiffness was curvilinear and was found to apply under a variety of experiment conditions. For pooled data from eight experiments, active stiffness (GN.m-2.m-1) = 3.2*stress (MN/m2)-7.6*stress2. Decreasing the number of motor units or activating the inhibitor did not alter this relationship nor did the addition of proctolin, octopamine, or 5-HT to the bath. The relationship also applied during the rising phase of isometric tension. However, stiffness declined more rapidly than predicted by this relationship after the end of tetanus. 3. Active stiffness varied inversely with stretch amplitude for fast stretches, and the slope of this relationship increased with increasing muscle activation. At lower stretch velocities, the slope was much less than at rapid stretch velocities, so at low levels of activation and stretch velocity, active stiffness was essentially independent of stretch length. 4. Active stiffness covaried with muscle force as both were sampled at shorter and shorter lengths on the ascending limb of the length-tension curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Action of locust neuromodulatory neurons is coupled to specific motor patterns.

1. Many muscles of the locust are supplied by dorsal unpaired median neurons (DUM neurons) that release octopamine and alter the contractions caused by spikes in motor neurons. To determine when these neuromodulatory neurons are normally activated during behaviour, intracellular recordings were made simultaneously from them and from identified motor neurons during the specific motor pattern that underlies kicking. A kick consists of a rapid and powerful extension of the tibia of one or both hind legs that is produced by a defined motor pattern. Only 3 identified DUM neurons of the 20 in the metathoracic ganglion spike during a kick, and they supply muscles involved in generating the kick. Their spikes occur in a distinctive and repeatable pattern that is closely linked to the pattern of spikes in the flexor and extensor tibiae motor neurons. When the extensor and flexor muscles cocontract, these three DUM neurons produce a burst of spikes at frequencies that can rise to 25 Hz, and with the number of spikes (3-15) related to the duration of this phase of the motor pattern. The spikes stop when the flexor muscle is inhibited and therefore before the tibia is extended rapidly. The other DUM neurons which supply muscles that are not directly involved in kicking are either inhibited or spike only sporadically. 2. The activation of a specific subset of DUM neurons during kicking may thus be timed to influence the action of the muscles that participate in this movement and appear to be controlled by the same circuits that determine the actions of the participating motor neurons. These modulatory neurons thus have specific individual actions in the control of movement.

Animals↗
PubMed1998

Temporal dynamics of convergent modulation at a crustacean neuromuscular junction.

At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and -allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and allatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and -allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; -allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation-contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.

Animals↗
PubMed1991

Dopamine beta-hydroxylase deficiency. A genetic disorder of cardiovascular regulation.

Dopamine beta-hydroxylase (DBH) deficiency is a genetic disorder in which affected patients cannot synthesize norepinephrine, epinephrine, and octopamine in either the central nervous system or the peripheral autonomic neurons. Dopamine acts as a false neurotransmitter in their noradrenergic neurons. Neonates with DBH deficiency have had episodic hypothermia, hypoglycemia, and hypotension, but survivors sometimes cope relatively well until late childhood when overwhelming orthostatic hypotension profoundly limits their activities. The hypotension may be so severe that clonic seizures supervene. Most currently recognized patients are young or middle-aged adults. The diagnosis is established by the observation of severe orthostatic hypotension in a patient whose plasma norepinephrine/dopamine ratio is much less than one.

Adult↗
PubMed1987

Serotonin phase-shifts the circadian rhythm of locomotor activity in the cockroach.

Serotonin, a putative neurotransmitter in insects, was found to cause consistent phase shifts of the circadian rhythm of locomotor activity of the cockroach Leucophaea maderae when administered during the early subjective night as a series of 4-microliters pulses (one every 15 min) for either 3 or 6 hr. Six-hour treatments with dopamine also caused significant phase shifts during the early subjective night, but 3-hr treatments with dopamine had no phase-shifting effect. Other substances tested in early subjective night (norepinephrine, octopamine, gamma-aminobutyric acid, glutamate, carbachol, histamine, tryptophan, tryptamine, N-acetyl serotonin, or 5-hydroxyindole-3-acetic acid) did not consistently cause phase shifts. The phase-shifting effect of serotonin was found to be phase-dependent. The phase response curve (PRC) for serotonin treatments was different from the PRC for light. Like light, serotonin caused phase delays in the late subjective day and early subjective night, but serotonin did not phase-shift rhythms when tested at phases where light causes phase advances.

Animals↗
PubMed2004

Citrus aurantium, an ingredient of dietary supplements marketed for weight loss: current status of clinical and basic research.

Seville orange (Citrus aurantium) extracts are being marketed as a safe alternative to ephedra in herbal weight-loss products, but C. aurantium may also have the potential to cause adverse health effects. C. aurantium contains synephrine (oxedrine), which is structurally similar to epinephrine. Although no adverse events have been associated with ingestion of C. aurantium products thus far, synephrine increases blood pressure in humans and other species, and has the potential to increase cardiovascular events. Additionally, C. aurantium contains 6',7'-dihydroxybergamottin and bergapten, both of which inhibit cytochrome P450-3A, and would be expected to increase serum levels of many drugs. There is little evidence that products containing C. aurantium are an effective aid to weight loss. Synephrine has lipolytic effects in human fat cells only at high doses, and octopamine does not have lipolytic effects in human adipocytes.

Animals↗
PubMed2004

Substantial changes in central nervous system neurotransmitters and neuromodulators accompany phase change in the locust.

Desert locusts (Schistocerca gregaria) can undergo a profound transformation between solitarious and gregarious forms, which involves widespread changes in behaviour, physiology and morphology. This phase change is triggered by the presence or absence of other locusts and occurs over a timescale ranging from hours, for some behaviours to change, to generations, for full morphological transformation. The neuro-hormonal mechanisms that drive and accompany phase change in either direction remain unknown. We have used high-performance liquid chromatography (HPLC) to compare amounts of 13 different potential neurotransmitters and/or neuromodulators in the central nervous systems of final instar locust nymphs undergoing phase transition and between long-term solitarious and gregarious adults. Long-term gregarious and solitarious locust nymphs differed in 11 of the 13 substances analysed: eight increased in both the brain and thoracic nerve cord (including glutamate, GABA, dopamine and serotonin), whereas three decreased (acetylcholine, tyramine and citrulline). Adult locusts of both extreme phases were similarly different. Isolating larval gregarious locusts led to rapid changes in seven chemicals equal to or even exceeding the differences seen between long-term solitarious and gregarious animals. Crowding larval solitarious locusts led to rapid changes in six chemicals towards gregarious values within the first 4 h (by which time gregarious behaviours are already being expressed), before returning to nearer long-term solitarious values 24 h later. Serotonin in the thoracic ganglia, however, did not follow this trend, but showed a ninefold increase after a 4 h period of crowding. After crowding solitarious nymphs for a whole larval stadium, the amounts of all chemicals, except octopamine, were similar to those of long-term gregarious locusts. Our data show that changes in levels of neuroactive substances are widespread in the central nervous system and reflect the time course of behavioural and physiological phase change.

Acetylcholine↗
PubMed1988

The action of vasoactive intestinal peptide antagonists on peptidergic modulation of the squid Schwann cell.

1. The effects of two specific antagonists of vasoactive intestinal peptide (VIP) receptors were investigated on the VIP-induced hyperpolarization of the membrane potential of the Schwann cell of the giant nerve fibre of the tropical squid. 2. Both (pCl-D-Phe6,Leu17)VIP and (N-Ac-Tyr1,D-Phe2)-GRF(1-29)amide competitively and reversibly blocked the effects of VIP in this preparation with the former compound being more potent than the latter. 3. The blocking actions of both antagonists were specific for the responses of this preparation to VIP. They did not block the actions of carbachol, DL-octopamine or substance P. 4. Both antagonists also reduced the effectiveness of an endogenous VIP-like component in the normal hyperpolarizing action of giant axon activity on the membrane potential of the Schwann cell, with the same potency ratio as for their actions on the effects induced by the exogenous application of VIP.

Animals↗
PubMed1994

The effects of myomodulin and structurally related neuropeptides on skeletal neuromuscular transmission in the locust.

1. The modulatory actions of myomodulin A on tension generated in the extensortibiae muscle of the locust hindleg by stimulation of the slow excitatory motoneurone (SETi) depend upon the frequency of stimulation. Myomodulin A has no consistent effect on the tension induced by the fast extensor motoneurone (FETi) or upon the myogenic rhythm present in the extensor. The effects of a range of structurally related neuropeptides have also been assessed. 2. At low frequencies of SETi stimulation (1 Hz and below), the predominant modulatory effects are increases in the amplitude, contraction rate and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), these effects are superimposed upon an increase of maintained tension. 3. The modulatory actions of myomodulin-like peptides show some similarities to and some differences from the modulatory actions of octopamine, proctolin and FMRFamide-like neuropeptides in this preparation, but are likely to be mediated via a distinct set of receptors. 4. The results of the present study, taken together with the localization of myomodulin-like immunoreactivity in specific sets of neurones in the locust nervous system, suggest the presence of a novel modulatory system in insects that uses myomodulin-like neuropeptides. It also indicates that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.

Animals↗
PubMed1997

Possible mechanisms of control of vascular resistance in the lobster Homarus americanus

In Homarus americanus, the resistance to fluid flow through each of the arteries leaving the heart, including the complete hemocoelic return pathways, can be controlled. Each of the five arterial types (anterior median, paired anterior lateral, paired hepatic, sternal and dorsal abdominal) exhibits a unique spectrum of responses to a battery of neurotransmitters (acetylcholine, glutamic acid, -aminobutyric acid) and neurohormones (dopamine, octopamine, 5-hydroxytryptamine, crustacean cardioactive peptide, FLRFamide-related peptides F1 and F2, and proctolin). Acetylcholine causes increases in resistance in all arteries except the anterior median artery; in the dorsal abdominal artery, this increase is antagonized by -aminobutyric acid. All neurohormones that are effective in a particular artery cause increases in resistance to flow. The sites of action of these compounds in the dorsal abdominal artery are valves located at major branch points; the sites of control in the other arteries are not known. It is concluded that the control of arterial resistance is a mechanism which the animal can exploit to produce different flow patterns among the various arteries.

Journal Article↗
PubMed1997

The anaerobic endproduct lactate has a behavioural and metabolic signalling function in the shore crab

This study presents the first evidence that, in invertebrates, the anaerobic endproduct lactate has an alarm signal function and induces metabolic and behavioural responses as in the anuran Bufo marinus. In support of this function, behavioural hypothermia was demonstrated in the shore crab Carcinus maenas. The animals moved to a cooler environment when exposed to hypoxic conditions. A decrease in preferred temperature of the same magnitude was also found when normoxic animals were injected with an iso-osmotic lactate solution resulting in a haemolymph concentration of approximately 12 mmol l-1. Under normoxic (PO2=>18 kPa) and moderately hypoxic conditions (PO2=12 kPa), injection of this lactate solution also caused a significant increase in the rate of oxygen consumption (100 and 50 % respectively). The increase in the rate of oxygen consumption was smaller and delayed, but lasted longer, under hypoxic conditions compared with normoxic conditions. Low but significant correlations between levels of lactate and levels of adrenaline, octopamine and tryptophan suggest the involvement of biogenic amines in the mediation of the signal.

Journal Article↗
PubMed1999

Patterned activation of unpaired median neurons during fictive crawling in manduca sexta larvae

The unpaired median neurons are common to the segmental ganglia of many insects. Although some of the functional consequences of their activation, among them the release of octopamine to modulate muscle contraction, have been described, less is understood about how and when these neurons are recruited during movement. The present study demonstrates that peripherally projecting unpaired median neurons in the abdominal and thoracic ganglia of the larval tobacco hornworm Manduca sexta are recruited rhythmically during the fictive crawling motor activity that is produced by the isolated central nervous system in response to pilocarpine. Regardless of the muscles to which they project, the efferent unpaired median neurons in all segmental ganglia are depolarized together during the phase of the crawling cycle when the thoracic leg levator motoneurons are active. During fictive crawling, therefore, the unpaired median neurons are not necessarily active in synchrony with the muscles to which they project. The rhythmical synaptic drive of the efferent unpaired median neurons is derived, at least in part, from a source within the subesophageal ganglion, even when the motor pattern is evoked by exposing only the more posterior ganglia to pilocarpine. In pairwise intracellular recordings from unpaired median neurons in different ganglia, prominent excitatory postsynaptic potentials, which occur with an anterior-to-posterior delay in both neurons, are seen to underlie the rhythmic depolarizations. One model consistent with these findings is that one or more neurons within the subesophageal ganglion, which project posteriorly to the segmental ganglia and ordinarily provide unpatterned synaptic inputs to all efferent unpaired median neurons, become rhythmically active during fictive crawling in response to ascending information from the segmental pattern-generating network.

Journal Article↗
PubMed1999

Venom of a parasitoid wasp induces prolonged grooming in the cockroach

The parasitoid wasp Ampulex compressa hunts cockroaches Periplaneta americana, stinging them first in the thorax and then in the head, the sting penetrating towards the subesophageal ganglion. After being stung the cockroach grooms almost continuously for approximately 30 min, performing all the normal components of grooming behavior. This excessive grooming is only seen after the head sting and cannot be attributed to stress, to contamination of the body surface or to systemic or peripheral effects. This suggests that the venom is activating a neural network for grooming. We suggest that the venom induces prolonged grooming by stimulating dopamine receptors in the cockroach, for the following reasons. (1) Reserpine, which causes massive release of monoamines, induces excessive grooming. (2) Dopamine injected into the hemocoel also induces excessive grooming and is significantly more effective than octopamine or serotonin. In addition, the dopamine agonist SKF 82958 induces excessive grooming when injected directly into the subesophageal ganglion. (3) Injection of the dopamine antagonist flupenthixol greatly reduces venom-induced grooming. (4) Dopamine, or a dopamine-like substance, is present in the venom.

Journal Article↗
PubMed1996

The monoamine regulon including syntheses of arylsulfatase and monoamine oxidase in bacteria.

Bacterial cells respond to monoamine compounds, such as tyramine, dopamine, octopamine, or norepinephrine, and induce the syntheses of tyramine oxidase encoded by tynA and monoamine oxidase encoded by maoA. These monoamine compounds also derepress the synthesis of atsA-specified arylsulfatase that is repressed by sulfur compounds. These complex mechanisms of regulons regulated by monoamine and sulfur compounds has been analyzed by cloning and characterization of genes that are involved in the repression and derepression of the synthesis of arylsulfatase. The atsA gene forms an operon with the atsB gene, which encodes an activator of the expression of atsA. The negative regulator gene for arylsulfatase was found to code for dihydrofolate reductase (folA). The maoA gene forms an operon with the maoC gene, which has similarity to a dehydrogenase involved in the tyramine metabolism. The moaF gene encoding a 30-kDa protein, which is induced by tyramine, also forms an operon with the moaE gene. Finally, the moaR gene, which is induced by monoamine, was found to play a central role in the positive regulation of the expression of the monoamine regulon (moa) including the atsBA, maoCA, moaEF, and tyn operons. The moaR expression is subject to autogenous regulation and to cAMP-CRP control. The MoaR protein has a helix-turn-helix motif in its C terminus. Thus, the MoaR protein probably regulates the operons by binding to the regulatory region of the moa regulon.

Arylsulfatases↗
PubMed1976

Biochemical and physiological effects of chlordimeform.

Chlordimeform is a relatively new acaricide/insecticide, whose mode of action we have investigated. It appears to interfere with amine-mediated control of nervous and endocrine systems in a variety of ways. Specifically, chlordimeform causes a build-up of the amines 5-hydroxytryptamine and to a lesser extent norepinephrine in the rat brain in vivo, antagonizes the in vivo action of reserpine in the rat (reserpine depletes amine stores in the CNS), inhibits monoamine oxidase from rat liver in vitro, and causes hypotension in rabbits. In the American cockroach it directly stimulates the heart in situ, acts synergistically with tryptamine in vivo, inhibits amine-N-acetyltransferase from cockroach head in vitro, causes accumulation of indolamines in cockroaches in vivo, and blocks the stimulation of adenylate cyclase by octopamine in the cockroach CNS in situ. It also inhibits tryptamine metabolism in whole mites in vitro.

Amidines↗
PubMed2005

Experiential effects of appetitive and nonappetitive odors on feeding behavior in the blowfly, Phormia regina: a putative role for tyramine in appetite regulation.

In humans, appetite is affected by food experiences and food flavors. In the blowfly Phormia regina, we found that feeding threshold to sugar increased in the presence of the odor of D-limonene and decreased in the presence of the odor of dithiothreitol (DTT). Using these odors as representative nonappetitive and appetitive flavors, we demonstrated the role played by tyramine (TA) in appetite regulation by experiences of food flavors. When fed with sucrose flavored with D-limonene for 5 d after emergence, flies showed subsequent decreased appetite to plain sucrose, whereas when they were fed with sucrose flavored by DTT they showed increased appetite. However, mushroom body (MB)-ablated flies did not show these patterns. This suggests that MB, one of the primary memory centers of the insect brain, is necessary for the flies to apply previous experiences of food flavors to appetitive learning behaviors. In addition, flies' previously acquired decreased or increased appetites showed parallel changes with both octopamine (OA) and tyramine levels in the brain. However, injection experiments with OA, TA, or their agonist and antagonist indicated that TA more directly mediates feeding threshold determination, which was affected by acquired memories of food flavors.

Animals↗
PubMed2006

Coordination and modulation of locomotion pattern generators in Drosophila larvae: effects of altered biogenic amine levels by the tyramine beta hydroxlyase mutation.

Forward locomotion of Drosophila melanogaster larvae is composed of rhythmic waves of contractions that are thought to be produced by segmentally organized central pattern generators. We present a systematic description of spike activity patterns during locomotive contraction waves in semi-intact wild-type and mutant larval preparations. We have shown previously that Tbetah(nM18) mutants, with altered levels of octopamine and tyramine, have a locomotion deficit. By recording en passant from the segmental nerves, we investigated the coordination of the neuronal activity driving contraction waves of the abdominal body-wall muscles. Rhythmic bursts of activity that occurred concurrently with locomotive waves were frequently observed in wild-type larvae but were rarely seen in Tbetah(nM18) mutants. These centrally generated patterned activities were eliminated in the distal stumps of both wild-type and Tbetah(nM18) larvae after severing the segmental nerve from the CNS. Patterned activities persisted in the proximal stumps deprived of sensory feedback from the periphery. Simultaneous recordings demonstrated a delay in the bursting activity between different segments, with greater delay for segments that were farther apart. In contrast, bilateral recordings within a single segment revealed a well synchronized activity pattern in nerves innervating each hemisegment in both wild-type and Tbetah(nM18) larvae. Significantly, rhythmic patterns of bursts and waves could be evoked in Tbetah(nM18) mutants by head or tail stimulation despite their highly irregular spontaneous activities. These observations suggest a role of the biogenic amines in the initiation and modulation of motor pattern generation. The technique presented here can be readily extended to examine the locomotion motor program of other mutants.

Abdominal Wall↗