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PubMed1985

Octopamine receptors in the molluscan aortic bulb: effects of clozapine and chlordimeform.

The presence of specific, stereo-selective octopamine receptors has been demonstrated in the non-spontaneously beating accessory ventricle (aortic bulb) of the clam Tapes watlingi. Analogues of octopamine with a single chloro group in either the para or meta positions of the benzene ring were 10 times less potent than octopamine in their agonist activity. In low concentrations (less than 200 microM), phentolamine, chlordimeform and clozapine were octopamine antagonists. In high concentrations (greater than 200 microM), clozapine, clonidine and chlordimeform induced changes in aortic tone similar to that produced by p-octopamine. This activity may result from the chloro-substituted phenamidine skeleton in both clozapine and chlordimeform.

Action Potentials↗
PubMedDate not supplied

Acanthocheilonema viteae: octopamine and its physiological role.

Octopamine acts as an important neurotransmitter and neuromodulator in arthropods, mollusks, and nematodes. In mammals, however, no definite function for this amine has yet been described. By virtue of this difference in the neurophysiological requirement of the mammalian host and nematodes, octopamine offers good opportunity for exploring this area deeply with a view to identify a unique target for filarial chemotherapy. Results of the present study indicated that Acanthocheilonema viteae, the rodent filarial parasite, utilized tyrosine as a precursor for producing octopamine and some other biogenic amines. Octopamine exhibited specific saturable binding with the membrane prepared from the anterior portion of the filariid. This amine induced concentration dependent increase in the membrane potential which possibly caused tonic paralysis of the filariid. The rate of micro filarial release by the female worms also declined in the presence of this amine. The study thus provided preliminary evidences for the presence of an octopamine neurotransmitter system and also about some of the roles it plays in A. viteae.

Animals↗
PubMed2006

Octopamine and tyramine influence the behavioral profile of locomotor activity in the honey bee (Apis mellifera).

The biogenic amines octopamine and tyramine are believed to play a number of important roles in the behavior of invertebrates including the regulation of motor function. To investigate the role of octopamine and tyramine in locomotor behavior in honey bees, subjects were injected with a range of concentrations of octopamine, tyramine, mianserin or yohimbine. Continuous observation of freely moving worker bees was used to examine the effects of these treatments on the amount of time honey bees spent engaged in different locomotor behaviors such as walking, grooming, fanning and flying. All treatments produced significant shifts in behavior. Decreases in time spent walking and increases in grooming or stopped behavior were observed for every drug. However, the pattern of the shift depended on drug, time after injection and concentration. Flying behavior was differentially affected with increases in flying seen in octopamine treated bees, whereas those receiving tyramine showed a decrease in flying. Taken together, these data provide evidence that octopamine and tyramine modulate motor function in the honey bee perhaps via interaction with central pattern generators or through effects on sensory perception.

Animals↗
PubMed1997

Octopamine-containing neurons in the alimentary tract of the earthworm (Eisenia fetida).

Octopamine-containing nerve cells have been demonstrated in the enteric plexus of the earthworm (Eisenia fetida), applying immunocytochemistry and HPLC assay. A few octopamine-immunoreactive neurons occurred in the fore- and hindgut, whereas their number in the midgut was considerably greater. Octopamine levels detected by HPLC correlated with the distribution of octopamine-containing nerve cells. A regulatory role for these intrinsic octopaminergic neurons is suggested in the enteric plexus in the earthworm alimentary tract. This is the first report on the occurrence of octopamine-containing nerve cells in the peripheral nervous system of an invertebrate.

Animals↗
PubMed1975

Urinary and serum octopamine in patients with portal-systemic encephalopathy.

Urinary excretion and serum concentrations of octopamine were studied in seventeen controls, thirty-three patients with portal-systemic encephalopathy, and thirteen patients with liver disease without encephalopathy. No differences were detected between control subjects and patients without encephalopathy. Urinary excretion and serum concentrations of octopamine were significantly higher in patients with encephalopathy compared with those without encephalopathy. The presence and grade of portal-systemic encephalopathy seemed to correlate more closely with the serum-octopamine concentrations than with urinary octopamine excretion. It is postulated that octopamine may be involved in the pathogenesis of portal-systemic encephalopathy.

Adolescent↗
PubMed1977

The role of the false neurotransmitter octopamine in the hypotension of fulminant hepatic failure.

1. An investigation was carried out into the mechanism of unexplained hypotension in patients with fulminant hepatic failure. The cardiac output and peripheral resistance were compared in normotensive and hypotensive patients. In addition, the serum concentration of the false neurotransmitter octopamine and the pressor response to noradrenaline, and to the indirectly acting sympathomimetic agent tyramine, were measured in hypotensive and normotensive patients with fulminant hepatic failure and in healthy subjects. 2. The cardiac output and the peripheral resistance were decreased in the hypotensive patients, and their mean heart rate was slower than in the normotensive patients. Although the serum octopamine concentration was significantly elevated in the patients compared with the control subjects, the highest octopamine concentrations were unexpectedly found in the normotensive patients and a significant positive correlation could be demonstrated between the resting blood pressure and the serum octopamine concentration. The pressor response to tyramine and noradrenaline were similar in the hypotensive patients, the normotensive patients and control subjects. 3. These results suggest that neither increased serum concentrations of the false neurotransmitter octopamine, nor end-organ insensitivity to released noradrenaline are responsible for the hypotension. A more likely explanation is toxic depression of the vasomotor centre. The opening of peripheral arteriovenous shunts, possibly as a result of endotoxaemia, might be an additional factor.

Cardiac Output↗
PubMed1997

Cloning and expression of a complementary DNA encoding a molluscan octopamine receptor that couples to chloride channels in HEK293 cells.

A cDNA encoding a G-protein-coupled receptor was cloned from the central nervous system of the pond snail Lymnaea stagnalis. The predicted amino acid sequence of this cDNA most closely resembles the Drosophila tyramine/octopamine receptor, the Locusta tyramine receptor, and an octopamine receptor (Lym oa1) that we recently cloned from Lymnaea. After stable expression of the cDNA in HEK293 cells, we found that [3H]rauwolscine binds with high affinity to the receptor (KD = 6.2.10(-9) M). Octopamine appears to be the most potent naturally occurring agonist to displace the [3H]rauwolscine binding (Ki = 3.0.10(-7) M). Therefore, the receptor is considered to be an octopamine receptor and is consequently designated Lym oa2. The novel receptor shares little pharmacological resemblance with Lym oa1, indicating that the two receptors represent different octopamine receptor subfamilies. Octopaminergic stimulation of Lym oa2 does not induce changes in intracellular concentrations of cAMP or inositol phosphates. However, electrophysiological experiments indicate that octopamine is able to activate a voltage-independent Cl- current in HEK293 cells stably expressing Lym oa2. Although opening of this chloride channel most probably does not require the activation of either protein kinase A or C, it can be blocked by inhibition of protein phosphorylation.

Amino Acid Sequence↗
PubMed2003

Octopaminergic agonists for the cockroach neuronal octopamine receptor.

The compounds 1-(2,6-diethylphenyl)imidazolidine-2-thione and 2-(2,6-diethylphenyl)imidazolidine showed the almost same activity as octopamine in stimulating adenylate cyclase of cockroach thoracic nervous system among 70 octopamine agonists, suggesting that only these compounds are full octopamine agonists and other compounds are partial octopamine agonists. The quantitative structure-activity relationship of a set of 22 octopamine agonists against receptor 2 in cockroach nervous tissue, was analyzed using receptor surface modeling. Three-dimensional energetics descriptors were calculated from receptor surface model/ligand interaction and these three-dimensional descriptors were used in quantitative structure-activity relationship analysis. A receptor surface model was generated using some subset of the most active structures and the results provided useful information in the characterization and differentiation of octopaminergic receptor.

Adenylyl Cyclases↗
PubMed1988

Identification and function of octopamine and tyramine conjugates in the Limulus visual system.

Major metabolites of octopamine and tyramine in the Limulus nervous system are identified here as gamma-glutamyl octopamine and gamma-glutamyl tyramine. We show that these conjugates are normal products of amine metabolism in Limulus, and that they are normally present in octopamine-rich Limulus tissues. The synthesis of these conjugates is not restricted to nervous tissue, but the highest activity of gamma-glutamyl amine synthetase was measured in the CNS. Our interest in these molecules stems from our previous observations which showed that they were synthesized and stored in, and released from, the efferent fibers to Limulus eyes which modulate the sensitivity of the eyes to light. Here we provide direct evidence for the release of the conjugates from Limulus eyes in response to depolarization, and that gamma-glutamyl octopamine can increase the sensitivity of the lateral eye to light. Our observations lend support to the hypothesis that gamma-glutamyl octopamine may serve as an intercellular messenger in the Limulus visual system.

Animals↗
PubMed1987

Beta-adrenergic activities of octopamine and synephrine stereoisomers on guinea-pig atria and trachea.

The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on beta 1- and beta 2-adrenoceptors in guinea-pig atria and trachea have been compared with that of noradrenaline. The rank order of potency of the (-)-forms on beta 1-adrenoceptors was noradrenaline greater than m-synephrine greater than m-octopamine = p-octopamine greater than p-synephrine. m-Synephrine was 100-fold, m- and p-octopamine about 6000-fold, and p-synephrine about 40,000-fold less active than noradrenaline. The (+)-forms were 1-2 orders of magnitude less active than their (-)-counterparts. The four (-)-compounds were more than four orders of magnitude less active than noradrenaline on beta 2-adrenoceptors, and the (+)-forms had no detectable activity in concentrations as high as 10(-4) M. If m- and p-octopamine are co-released with noradrenaline in amounts proportional to their concentration, their activities at these structures are too low to be physiologically significant.

Adrenergic beta-Agonists↗
PubMed1984

The role of cyclic nucleotides and calcium in the mediation of the modulatory effects of octopamine on locust skeletal muscle.

The role of cyclic AMP and calcium in the mediation of the effects of octopamine has been investigated in the extensor tibiae muscle of the hind leg of the locust. Elevation of cyclic AMP levels in the preparation by means of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), by means of the diterpene adenylate cyclase activator, forskolin, and by means of cyclic nucleotide analogues mimics the post-synaptic effects of octopamine application at different frequencies of neuronal stimulation. These conditions also mimic the presynaptic effects of octopamine on spontaneous release of transmitter from the slow motoneurone. The effects of octopamine on the preparation are calcium sensitive, with the maximal sensitivity occurring between 0.5 and 4.0 mM-external calcium. The results are discussed in terms of the role of cyclic AMP and calcium in the mediation of the effects of octopamine.

1-Methyl-3-isobutylxanthine↗
PubMed1993

The effects of p-octopamine on salivary flow rates and protein secretion by rat submandibular glands.

The effects of p-octopamine injected i.v. and i.p on salivary flow rates and proteins secreted by the submandibular glands of rats were studied with and without various types of autonomic blockers at different doses, and with two enzyme inhibitors. The salivary flow rates and the amounts of protein secreted progressively increased with increasing doses injected both i.v. and i.p., whereas they were dramatically reduced with almost all autonomic blockers and disulfiram, a dopamine-beta-hydroxylase inhibitor. Salivation was completely abolished in response to p-octopamine in combination with metoprolol or phenoxybenzamine at high doses, and simultaneous injections of prazosin and propranolol. The concentration of protein in submandibular saliva in response to p-octopamine injected i.v. and i.p. was not dose-dependent and significantly increased with all of the alpha-blockers except yohimbine, and with atropine and disulfiram. The protease activity was dose-dependent but was reduced significantly with alpha-blockers except yohimbine and with two enzyme inhibitors. The alpha-type of protein was secreted in response to p-octopamine injected i.v. and i.p. at all doses except with the lowest dose i.p., which caused the beta-type to be secreted. The alpha-type was completely replaced by the beta-type with all alpha-blockers at all doses, except with yohimbine, but no change was observed with various types of beta-blockers, yohimbine, atropine, and two enzyme inhibitors. Thus, p-octopamine could stimulate both the alpha- and beta-adrenoceptors in the submandibular glands of rats.

Adrenergic alpha-Antagonists↗
PubMed2000

Octopamine mimics the effects of parasitism on the foregut of the tobacco hornworm Manduca sexta.

The parasitic braconid wasp Cotesia congregata lays its eggs inside the body of the larval stage of its host, the moth Manduca sexta. The Cotesia congregata larvae develop within the hemocoel of their host until their third instar, when they emerge and spin cocoons and pupate on the outer surface of the caterpillar. From this time until their death approximately 2 weeks later, the Manduca sexta larvae show striking behavioral changes that include dramatic declines in spontaneous activity and in the time spent feeding. Coincident with these behavioral changes, it is known that octopamine titers in the hemolymph of the host become elevated by approximately 6.5-fold. Octopamine is an important modulator of neural function and behavior in insects, so we examined hosts for neural correlates to the behavioral changes that occur at parasite emergence. We found that, in addition to the changes reported earlier, after parasite emergence (post-emergence), Manduca sexta larvae also showed marked deficits in their ability to ingest food because of a disruption in the function of the frontal ganglion that results in a significant slowing or the absence of peristaltic activity in the foregut. This effect could be produced in unparasitized fifth-instar larvae by application of blood from post-emergence parasitized larvae or of 10(-6)mol l(-1)d,l-octopamine (approximately the level in the hemolymph of post-emergence larvae). In contrast, blood from parasitized larvae before their parasites emerge or from unparasitized fifth-instar larvae typically had no effect on foregut activity. The effects of either post-emergence parasitized blood or 10(-6)mol l(-1) octopamine could be blocked by the octopamine antagonists phentolamine (at 10(-5)mol l(-1)) or mianserin (at 10(-7)mol l(-1)).

Animals↗
PubMed2001

Oscillations of the transepithelial potential of moth olfactory sensilla are influenced by octopamine and serotonin.

The biogenic amine octopamine is known to enhance the sensitivity of male moths to their species-specific pheromones in flight-tunnel experiments. This sensitization of pheromone-guided upwind flight is at least partly due to octopamine-dependent increases in the peak nerve impulse frequency of the pheromone response of olfactory receptor neurons. It is not known, however, whether octopamine exerts its effects directly on the electrical properties of the olfactory receptor neurons or indirectly, via modulation of the accessory cells of the sensillum. In extracellular tip recordings of pheromone-dependent trichoid sensilla on the antennae of male Manduca sexta moths, we investigated the effects of octopamine and serotonin on the transepithelial potential, which is generated by the activity of V-ATPases in sensillar accessory cells. In addition, the action potential activity of unstimulated olfactory receptor neurons was examined in the presence of biogenic amines. Under constant environmental conditions, the transepithelial potential oscillated regularly with periods of 2-8 min and with a 1-25mV peak-to-peak amplitude over periods of several hours. These oscillatory intervals were interrupted by periods of relatively stable transepithelial potential, correlated with flight activity by the moth. Octopamine reduced the amplitude of the transepithelial potential oscillation and decreased the resistance of the sensillum preparation in a dose-dependent manner. Serotonin altered the waveform of the transepithelial potential, but did not change the resistance of the preparation. Thus, both amines affect the accessory cells, but have different targets in the regulation of the transepithelial potential. Neither amine significantly influenced the spontaneous action potential activity of the olfactory receptor neurons.

Action Potentials↗
PubMed1992

[Effect of octopamine on arterial pressure and renal function in the normal rat].

Octopamine is a beta hydroxylated phenylethanolamine which accumulates in patients with chronic liver damage. A pathogenic role of octopamine in hemodynamic and systemic alterations of advanced liver failure was investigated in normal awake rats. An infusion of octopamine (220 ug/kg/min) was associated with an increase in mean arterial pressure, urinary volume, urinary Na and K output and their filtration fractions. Glomerular filtration rate and renal plasma flow were not affected. A sudden and marked decrease in mean blood pressure and diuresis was observed after stopping octopamine infusion. Findings during the infusion differ from those observed in the hepatorenal syndrome, although the post infusion period was characterized by hypotension and oliguria. Octopamine behaves as a vasoconstrictor and may interfere with the action of physiologic neurotransmitters.

Animals↗
PubMed1994

A LOCUST OCTOPAMINE-IMMUNOREACTIVE DORSAL UNPAIRED MEDIAN NEURONE FORMING TERMINAL NETWORKS ON SYMPATHETIC NERVES

In insects, octopamine is present in neurohaemal regions of the thoracic sympathetic nervous system, but its cellular source is unknown. We describe a dorsal unpaired median neurone (DUM1b) in the locust metathoracic ganglion that forms a meshwork of varicose, presumably neurohaemal, endings on the surfaces of sympathetic nerves. Other targets include several ventral longitudinal muscles, the spiracle closer muscle, tissue remnants of degenerated nymphal muscles and the salivary glands. Using an established antiserum, DUM1b is shown to be octopamine-immunoreactive, and its target muscles to be covered with octopamine-immunoreactive varicosities. Octopamine influences one of these muscles in essentially the same way that another well-described octopaminergic neurone, DUMEti, modulates the extensor tibiae muscle of the hind leg. We propose that DUM1b is an octopaminergic modulator of muscle contractions and may also influence numerous other body functions by releasing octopamine as a hormone from sympathetic neurohaemal areas.

Journal Article↗
PubMed2005

Octopamine-immunoreactive neurons in the brain and subesophageal ganglion of the hawkmoth Manduca sexta.

Octopamine is a neuroactive monoamine that functions as a neurohormone, a neuromodulator, and a neurotransmitter in many invertebrate nervous systems, but little is known about the distribution of octopamine in the brain. We therefore used a monoclonal antibody to study the distribution of octopamine-like immunoreactivity in the brain of the hawkmoth Manduca sexta. Immunoreactive processes were observed in many regions of the brain, with the distinct exception of the upper division of the central body. We focused our analysis on nine ventral unpaired median (VUM) neurons with cell bodies in the labial neuromere of the subesophageal ganglion. Seven of these neurons projected caudally through the ventral nerve cord. Two neurons projected rostrally into the brain (supraesophageal ganglion), and one of these was a bilateral neuron that sent projections to the gamma-lobe of the mushroom body and the lateral protocerebrum. Octopamine-immunoreactive processes from one or more cells originating in the subesophageal ganglion also form direct connections between the antennal lobes and the calyces of the mushroom bodies.

Animals↗
PubMed2006

Comparison of octopamine-like immunoreactivity in the brains of the fruit fly and blow fly.

A serum raised against conjugated octopamine reveals structurally comparable systems of perikarya and arborizations in protocerebral neuropils of two species of Diptera, Drosophila melanogaster and Phaenicia sericata; the latter is used extensively for electrophysiological studies of the optic lobes and their central projections. Clusters of cell bodies in the brain as well as midline perikarya provide octopamine-like immunoreactive processes to the optic lobes, circumscribed regions of the protocerebrum and the central complex, particularly the protocerebral bridge, fan-shaped body, and ellipsoid body. Ventral unpaired median somata provide immunoreactive processes within the subesophageal ganglion and tritocerebrum. Ascending neurites from these cells also supply the antennal lobe glomeruli, regions of the lateral protocerebrum, the mushroom body calyces, and the lobula complex. The mushroom body's gamma lobes contain immunoreactive processes that originate from processes that arborize in the protocerebrum. The present observations are discussed with respect to similarities and differences between two species of Diptera, one of which has neurons large enough for intracellular penetrations. The results are also discussed with respect to recent studies on octopamine-immunoreactive organization in honey bees and cockroaches and the suggested roles of octopamine in sensory processing, learning, and memory.

Animals↗