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PubMedDate not supplied

Central regulation of photosensitive membrane turnover in the lateral eye of Limulus, II: octopamine acts via adenylate cyclase/cAMP-dependent protein kinase to prime the retina for transient rhabdom shedding.

Why photoreceptors turn over a portion of their photoreceptive membrane daily is not clear; however, failure to do so properly leads to retinal degeneration in vertebrates and invertebrates. Little is known about the molecular mechanisms that regulate shedding and renewal of photoreceptive membrane. Photoreceptive cells in the lateral eye of the horseshoe crab Limulus turn over their photoreceptive membrane (rhabdom) in brief, synchronous burst in response to dawn each morning. Transient rhabdom shedding (TRS), the first phase of rhabdom turnover in Limulus, is triggered by dawn, but requires a minimum of 3-5 h of overnight priming from the central circadian clock (Chamberlain & Barlow, 1984). We determined previously that the clock primes the lateral eye for TRS using the neurotransmitter octopamine (OA) (Khadilkar et al., 2002), and report here that OA primes the eye for TRS through a G(s)-coupled, adenylate cyclase (AC)/cyclic adenosine 3',5'-monophosphate (cAMP)/cAMP-dependent protein kinase (PKA) signaling cascade. Long-term intraretinol injections (6-7 h @ 1.4 microl/min) of the AC activator forskolin, or the cAMP analogs Sp-cAMP[s] and 8-Br-cAmp primed the retina for TRS in eyes disconnected from the circadian clock, and/or in intact eyes during the day when the clock is quiescent. This suggests that OA primes the eye for TRS by stimulating an AC-mediated rise in intracellular cAMP concentration ([cAMP]i). Co-injection of SQ 22,536, an AC inhibitor, or the PKA inhibitors H-89 and PKI (14-22) with OA effectively antagonized octopaminergic priming by reducing the number of photoreceptors primed for TRS and the amount of rhabdom shed by those photoreceptors compared with eyes treated with OA alone. Our data suggest that OA primes the lateral eye for TRS in part through long-term phosphorylation of a PKA substrate.

Adenylyl Cyclase Inhibitors↗
PubMed1994

Photoaffinity labeling of a neuronal octopamine receptor.

The invertebrate aminergic neurotransmitter and neuromodulator octopamine (OA) acts at both neuronal and nonneuronal receptors that appear to have distinct pharmacological characteristics. The current work uses a potent and specific OA photoaffinity ligand, tritiated 2(2,6-diethyl-4-azidophenylimino)imidazolidine ([3H]NC-5Z), to identify and characterize a putative neuronal OA receptor protein in membranes from nerve tissue of the desert locust, Schistocerca gregaria. Under nonphotolyzing conditions, [3H]NC-5Z demonstrated high-affinity binding (KD = 2.5 +/- 0.3 nM; Bmax = 702 fmol/mg of protein) to a single class of noninteracting sites. The absolute and rank order potency of binding of both agonists and antagonists was highly correlated (r = 0.99) with their known ability to displace [3H]OA binding to locust neuronal membranes and was consistent with the labeling of a class 3 OA receptor. Under photolyzing conditions, [3H]NC-5Z demonstrated irreversible binding that was resistant to trichloroacetic acid and methanol, displaceable by OA and other octopaminergic agonists and antagonists, soluble in sodium dodecyl sulfate, and only sparingly soluble in nonionic detergents. Membrane-bound [3H]NC-5Z, solubilized with Nonidet P-40, bound specifically only to immobilized concanavalin A or lentil lectin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of photolyzed proteins under reducing conditions revealed a single peak of radioactivity with a molecular mass of 53 +/- 5 kDa. Taken together, these biochemical and pharmacological results support the identity of this protein peak as that of the neuronal OA3 receptor.

Affinity Labels↗
PubMed1986

Impaired effect of dopamine on cardiac output during octopamine infusion.

The hemodynamic effects of octopamine (OCT) were studied before and during dopamine (DA) infusion in six normal dogs. Before OCT infusion, DA significantly increased cardiac index (CI) from 3.24 +/- 0.20 to 4.90 +/- 0.30 L/min X m2 and significantly decreased systemic vascular resistance index (SVRI) from 3700.2 +/- 212.5 to 2618.3 +/- 156.6 dyne X sec/cm5 X m2, without changing heart rate. During OCT infusion, DA failed to increase CI or decrease SVRI; however, it significantly increased heart rate from 153.3 +/- 12.9 to 183.0 +/- 17.0 beat/min. This suppression of a DA-related increase in cardiac output may explain why DA is ineffective in those septic patients with elevated plasma OCT levels.

Analysis of Variance↗
PubMed2006

Molecular cloning and heterologous expression of an alpha-adrenergic-like octopamine receptor from the silkworm Bombyx mori.

A cDNA encoding an octopamine (OA) receptor (BmOAR1) was isolated from the nerve tissue of silkworm (Bombyx mori) larvae. Comparison of amino acid sequences showed that BmOAR1 is highly identical to OA receptors isolated from Periplaneta americana (Pa oa(1)), Apis mellifera (AmOA1), and Drosophila melanogaster (OAMB or DmOA1A). BmOAR1 was stably expressed in HEK-293 cells. OA above 1 microM led to an increase in intracellular cyclic AMP concentration ([cAMP](i)). The synthetic OA-receptor agonist demethylchlordimeform also elevated [cAMP](i) to the same maximal level (approximately 5-fold over the basal level) as that induced by OA. However, other biogenic amines, tyramine and dopamine, and chlordimeform were without effects. The [cAMP](i) level raised by OA was lowered by antagonists; the rank order of antagonist activity was chlorpromazine > mianserin = yohimbine. Cyproheptadine and metoclopramide had little effect. OA above 100 nM induced a transient or sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), depending on the concentration of OA. Sequence homology and functional analysis data indicate that BmOAR1 is an alpha-adrenergic-like OA receptor of B. mori.

Amino Acid Sequence↗
PubMed1987

Specific antisera against the catecholamines: L-3,4-dihydroxyphenylalanine, dopamine, noradrenaline, and octopamine tested by an enzyme-linked immunosorbent assay.

Antisera were raised against L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine (DA), noradrenaline (NA), and octopamine (OA). This was achieved by coupling each molecule to bovine serum albumin or human serum albumin using glutaraldehyde. The conjugated aromatic amines were kept in a reducing medium containing sodium metabisulfite. Antiserum specificity was tested using an enzyme-linked immunosorbent assay method for catecholamines. Competition experiments were done between the immunogen coated on the well plates and each catecholamine, either in the free state or in conjugated form, previously incubated with an antiserum. In each case, the nonconjugated compound was poorly recognized. The nonreduced conjugates of L-DOPA and DA were well recognized, whereas those of NA and OA were poorly immunoreactive. The cross-reactivity ratios established in the competition experiments allowed the specificity of the immune response to be defined. In each case, it was found to be high. The results suggest that the antibodies of L-DOPA and DA antisera recognize preferentially the catechol moiety, whereas for the anti-NA and anti-OA antibodies, the lateral chain is important.

Animals↗
PubMed1985

The brain octopamine and phenylethanolamine content in rats in thioacetamide-induced hepatogenic encephalopathy.

The brain octopamine (OA) and phenylethanolamine (PhEA) content was determined in rats subjected to repeated intraperitoneal administrations of thioacetamide (TAA) known to produce different stages of hepatogenic encephalopathy (HE). A more than 2.5-fold increase of OA and a 2-fold increase of PhEA was observed after prolonged (3 times) administration of TAA, coinciding with impaired ammonia detoxication in brain and with the onset of pathophysiological changes typical for HE. Only insignificant changes in the content of the amines were observed in the early stages of the experiment as well as in the recovery period. The results are consistent with the "false neurotransmitter" hypothesis of Fischer and Baldessarini, assuming the participation of OA and PhEA in the pathogenesis of HE.

2-Hydroxyphenethylamine↗
PubMed1982

Octopamine mediated relaxation of maintained and catch tension in locust skeletal muscle.

1. The modulatory actions of an identified octopaminergic neurone (DUMETi) that projects to the extensor-tibiae muscle of the locust hind leg depend upon the frequency of stimulation of the slow motoneurone (SETi) to this muscle. 2. At low frequencies of SETi stimulation (1Hz and below) the predominant modulatory effects are increases in the amplitude and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), the reduction of maintained tension becomes considerably more important. 3. Both octopamine application and DUMETi stimulation reduce the amount of catch tension displayed by the extensor muscle when SETi is fired in a variety of different stimulus patterns. The extensor-tibiae muscle is itself 'pattern sensitive' since is shows a 'positive spacing effect' when SETi is stimulated at an average frequency of 1 Hz. 4. It is suggested that a primary function of DUMETi is to change the response of the muscle from one that favours maintenance of posture to one that favours rapid changes in joint position or force, such as might occur during locomotion.

Animals↗
PubMed2005

Tyramine and octopamine: ruling behavior and metabolism.

Octopamine (OA) and tyramine (TA) are the invertebrate counterparts of the vertebrate adrenergic transmitters. They are decarboxylation products of the amino acid tyrosine, with TA as the biological precursor of OA. Nevertheless, both compounds are independent neurotransmitters that act through G protein-coupled receptors. OA modulates a plethora of behaviors and peripheral and sense organs, enabling the insect to respond correctly to external stimuli. Because these two phenolamines are the only biogenic amines whose physiological significance is presumably restricted to invertebrates, pharmacologists have focused their attention on the corresponding receptors, which are still believed to represent promising targets for new insecticides. Recent progress made on all levels of OA and TA research has enabled researchers to understand better the molecular events underlying the control of complex behaviors.

Animals↗
PubMed1983

Modulation of synaptic transmission and excitation-contraction coupling in the opener muscle of the crayfish, Astacus leptodactylus, by 5-hydroxytryptamine and octopamine.

The modulatory actions of 5-hydroxytryptamine (5-HT) and octopamine (OA) were investigated in the opener nerve-muscle preparation of the crayfish, Astacus leptodactylus. Membrane resistance and resting potential were unaltered by 5-HT and OA at concentrations up to 2.5 X 10(-5) M; but EPSP-amplitudes were increased, up to 3-fold by OA and up to 18-fold by 5-HT. The lowest effective concentration was 2.5 X 10(-9) M; a maximal effect was produced at 2.5 X 10(-6) M. The effect was reversible only after prolonged washing. The enhancement of EPSPs by 5-HT or OA is due to an increased amplitude of the synaptic current; the current duration is not altered. The facilitation ratio (ratio of amplitudes of a pair of EPSPs) is not significantly affected by 5-HT or OA despite the often enormous increase of the absolute EPSP-amplitudes. The modulatory action also affects the excitation-contraction (e-c) coupling process: the effectiveness of e-c coupling was increased 7.4-fold by 5-HT (2.5 X 10(-6) M) and 18.7-fold by OA (5 X 10(-6) M). The threshold potential of e-c coupling was not affected.

Animals↗
PubMed2002

Fictive locomotion induced by octopamine in the earthworm.

We investigated the function of octopamine (OA) as a motor pattern inducer in the earthworm Eisenia fetida. We used semi-intact preparations, consisting of 20 sequential segmental ganglia of the ventral nerve cord (VNC) together with the body wall from the middle of the animal. Bath-application of 10(-4) mol l(-1) OA to the semi-intact preparation induced phasic muscle contractions, which are consistent with crawling. In the isolated VNC, OA induced bursts of motor neuron activity in the first lateral nerves. Burst frequency increased with OA concentration, with a large increase in activity observed in the range 10(-6)-10(-4) mol l(-1). At 10(-4) mol l(-1), the coefficient of variation of burst periods (BPs) was smaller than that seen upon application of OA at other concentrations, which is indicative of rhythmic bursts. These rhythmic bursts propagated along the VNC from the anterior to posterior, with a propagation velocity ranging from 60 to 110 mm s(-1). This velocity is consistent with the propagation velocity of muscle contraction during crawling behavior in the intact earthworm. From these results, we conclude that fictive crawling motor patterns are observed at 10(-4) mol l(-1) OA, and that OA can induce rhythmic bursts in the isolated VNC of the earthworm.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Multiple sites of associative odor learning as revealed by local brain microinjections of octopamine in honeybees.

In a classical conditioning procedure, honeybees associate an odor with sucrose resulting in the capacity of the odor to evoke an appetitive response, the extension of the proboscis (PER). Here, we study the effects of pairing an odor with injections of octopamine (OA) as a substitute for sucrose into three putative brain sites of odor/sucrose convergence. OA injected into the mushroom body (MB) calyces or the antennal lobe but not the lateral protocerebral lobe produces a lasting, pairing-specific enhancement of PER. During pairings, OA injected into the MB calyces results in an additional pairing-specific effect, because it does not lead to an acquisition but a consolidation after conditioning. These results suggest that the neuromodulator OA has the capacity of inducing associative learning in an insect brain. Moreover, they suggest the antennal lobes and the calyces as at least partially independent sites of associating odors that may contribute differently to learning and memory consolidation.

Animals↗
PubMed2000

The octopamine-containing buccal neurons are a new group of feeding interneurons in the pond snail Lymnaea stagnalis.

In the pond snail, Lymnaea stagnalis, the paired buccal ganglia contain 3 octopamine-immunoreactive neurons, which have previously been shown to be part of the feeding network. All 3 OC cells are electrically coupled together and interact with all the known buccal feeding motoneurons, as well as with all the modulatory and central pattern generating interneurons in the buccal ganglia. N1 (protraction) phase neurons: Motoneurons firing in this phase of the feeding cycle receive either single excitatory (depolarising) synaptic inputs (B1, B6 neurons) or a biphasic response (hyperpolarisation followed by depolarisation) (B5, B7 motoneurons). Protraction phase feeding interneurons (SO, N1L, NIM) also receive this biphasic synaptic input after OC stimulation. All of protraction phase interneurons inhibit the OC neurons. N2 (retraction) phase neurons: These motoneurons (B2, B3, B9, B10) and N2 interneurons are hyperpolarised by OC stimulation. N2 interneurons have a variable (probably polysynaptic) effect on the activity of the OC neurons. N3 (swallowing) phase: OC neurons are strongly electrically coupled to both N3 phase (B4, B4cluster, B8) motoneurons and to the N3p interneurons. In case of the interneuronal connection (OC<->N3) the electrical synapse is supplemented by reciprocal chemical inhibition. However, the synaptic connections formed by the OC neurons or N3p interneurons to the other members of the feeding network are not identical. CGC: The cerebral, serotonergic CGC neurons excite the OC cells, but the OC neurons have no effect on the CGC activity. In addition to direct synaptic effects, the OC neurons also evoke long-lasting changes in the activity of feeding neurons. In a silent preparation, OC stimulation may start the feeding pattern, but when fictive feeding is already occurring, OC stimulation decreases the rate of the fictive feeding. Our results suggest that the octopaminergic OC neurons form a sub-population of N3 phase feeding interneurons, different from the previously identified N3p and N3t interneurons. The long-lasting effects of OC neurons suggest that they straddle the boundary between central pattern generator and modulatory neurons.

Animals↗
PubMed1979

[Effects of octopamine on pulmonary circulation of the pig].

The perfusion of octopamine in pig produces an increase of cardiac output with decrease of pulmonary vascular resistances. The changes in lung circulation depend by a direct action of this drug on nervous control of vascular walls because when the pulmonary shunt increase the effect is not correlated to changes a pattern of breathing.

Animals↗
PubMed1983

Comparison of central actions of intraventricularly administered octopamine, phenylethylamine and adrenaline in rats.

The paper reviews and summarizes the results obtained in a series of experimental papers on the central action of octopamine (OCT), phenylethylamine (PEA) and adrenaline (ADR) on the central nervous system. The mechanism of amines' central action is related to stimulation of noradrenergic and dopaminergic systems. The central effect of OCT and PEA seems to be related to the interaction with specific binding sites.

Animals↗
PubMedDate not supplied

[Antidepressive effects of 3 endogenous monoamines: psychopharmacologic profiles of noradrenaline, octopamine and phenethylamine].

Norepinephrine (NE), octopamine (OA) and phenethylamine (PEA) are easily destroyed by M.A.O. but we could show, even injected intraperitoneally that they are active upon tests used generally to reveal an "antidepressant" effect. This effect is especially studied by using antagonism of apomorphine, reserpine, oxotremorine-induced hypothermia. The psychopharmacological spectra of NE and OA are close to the one of salbutamol and the observed effects correspond to alpha- and beta-adrenergic stimulations. The PEA spectrum is similar to the one of amphetamine and the observed effects correspond to adrenergic stimulations and to a dopaminergic stimulation. The mechanisms involved in the tests realized to show an "antidepressant" effect could reflect an activity not only through endogeneous NA but also possibly through endogeneous OA and PEA.

Animals↗
PubMed1981

The effect of intraventricular phenylethylamine and octopamine on the central effects of tremorine and pilocarpine and the acetylcholine level in the rat brain.

Phenylethylamine (PEA, 50 and 100 microgram ivc) and octopamine (OCT, 50 and 250 microgram ivc) potentiated the tremorine (10 mg/kg ip) induced hypothermia in the rat. This effect was partially antagonized by atropine (10 mg/kg ip). PEA and OCT significantly prolonged the duration of pilocarpine (100 mg/kg iv) induced catalepsy in rats. PEA (100 microgram ivc) and OCT (250 microgram ivc) depressed the acetylcholine (ACh) level in the cerebral cortex and striatum but did not affect it in the hippocampus. In addition, these amines enhanced the synthesis of ACh in the cerebral cortex, and PEA also in the rat striatum.

Acetylcholine↗
PubMed1982

The effect of intracerebroventricularly administered octopamine, phenylethylamine and epinephrine on the central serotonergic system of the rat.

Octopamine (OCT, 50-250 micrograms) and epinephrine (EPI, 10-100 micrograms) given intracerebroventricularly (icvtr) antagonized the head twitch response induced in the rat by 5-hydroxytryptophan or 5-methoxytryptamine, and hyperthermia induced by quipazine in rats kept at high ambient temperature. Phenylethylamine [PEA, 10-100 micrograms] did not change the action of serotonergic stimulants. OCT, PEA and EPI significantly depressed the cerebral level of serotonin [5-HT], and OCT also reduced the concentration of 5-hydroxyindoleacetic acid. OCT depressed, while EPI slightly accelerated the 5-HT turnover rate; PEA practically did not affect the turnover. The results indicate that OCT and EPI given icvtr to rats antagonize the central serotonergic system.

5-Hydroxytryptophan↗