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At least 127 records · Page 7Linked to original sources
PubMed1983

Presence of octopamine in firefly photomotor neurons.

Various tissues involved in producing luminescence in larval fireflies (Photuris versicolor) were examined for the presence of octopamine. These tissues included the terminal abdominal ganglion (A8) which innervates the paired lantern organs, the cell bodies of the photomotor neurons and the isolated larval lanterns. A previous study has identified the 4 motoneurons arising from A8 which bilaterally innervate the paired larval lanterns through symmetrical axons existing both sides of the ganglion. Individual photomotor neuron somata were isolated, pooled and found to contain about 0.03 pmol/soma giving an effective concentration of 2.8 mM octopamine. Significant amounts of octopamine were also found within the peripheral effector tissue. The presence of octopamine throughout the luminescence-producing pathway further supports the hypothesis that octopamine serves a neurotransmitter function in firefly bioluminescence. In this system, it appears that octopamine serves a more direct role as a neurotransmitter that that postulated for its modulatory and hormonal functions in other arthropod systems. Furthermore, the bioluminescent response of the larval firefly lantern provides a useful dynamic system to study the physiology, pharmacology and biochemistry of octopaminergic transmission.

Animals↗
PubMed1984

Stimulation by octopamine of the sodium efflux in barnacle muscle fibres.

The behaviour of the ouabain-insensitive Na efflux in barnacle muscle fibres towards DL-octopamine has been investigated. It is found that these fibres are quite often sensitive to external application of octopamine. A concentration as low as 10(-9) M is effective. The kinetic results indicate that the stimulatory response develops within 5-10 min of exposure of the fibre to octopamine and is transitory in nature. The response to octopamine is greater in size in the presence of 1-isoamyl-3-isobutylxanthine (IAX) than in the presence of 1-propyl-3-methyl-7-(5-hydroxyhexyl)-xanthine (PMX). But neither IAX nor PMX stops the response from decaying. The response to octopamine is highly dependent on the presence of external Ca2+. The provisional conclusion is that the barnacle muscle fibre may be a useful preparation for studying the hormonal function of octopamine.

1-Methyl-3-isobutylxanthine↗
PubMed2005

Activity modulation in cockroach sensillum: the role of octopamine.

The plasticity of sensory perception is provided partially by modulation of receptor cells. The electrical activity of American cockroach chemoreceptor cells in response to sex pheromone was measured under the influence of octopamine treatment and tracheal anoxia. Both experimental procedures caused decreased electroantennograms but affected spike activity differently: octopamine treatment increased firing rate, whereas anoxia decreased it. Spike frequency under octopamine treatment was elevated in response to pheromone stimulation and at background activity. Experiments with perfusion of isolated antennae showed a direct effect of octopamine on spike activity of pheromone sensilla, and excluded the possibility of indirect effects via octopamine-dependent release of other biologically active substances. The suggested mechanism of octopamine action is receptor cell membrane depolarization.

Animals↗
PubMed1997

Octopamine modulates ionic currents and spiking in dorsal unpaired median (DUM) neurons.

Modulatory effects of octopamine on ionic currents and spiking in isolated cockroach dorsal unpaired median neurons were investigated by means of the chopped voltage-/current-clamp and the patch-clamp technique. Octopamine increased the spiking frequency at concentrations < or = 10 microM and reduced it at > 10 microM. It enhanced a low voltage-activated Ca2+ current at 1 to 100 microM. At concentrations up to 10 microM two components of Ca2+-activated K+ current were potentiated. At > 10 microM octopamine in addition reduced a high voltage-activated Ca2+ current and the Ca2+-activated K+ current. A membrane permeant cAMP-analogue imitated the effects obtained at high octopamine concentration. Octopamine and cAMP in addition reduced a depolarizing resting current at both low and high concentration. Possible mechanisms and physiological significance are discussed for the opposite effects of octopamine observed at low versus high concentrations.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Effects of aging on p- and m-octopamine, catecholamines, and their metabolizing enzymes in the rat.

Functions of octopamine in the mammalian brain are still not well known. An important aspect of this problem is the relationship between octopamines and catecholamines. Previous data have shown that their respective ontogenic evolutions are not parallel. Do the changes in brain related to aging also differentially affect these two groups of molecules? In order to check this point, the brain levels of p- and m-octopamine, p-tyramine, noradrenaline, and dopamine, as well as the activities of metabolizing enzymes, were determined in young adult and aging rats (20-26 months). Unlike catecholamines, there is a drastic decrease of p-octopamine after 20 months of age in the hypothalamus and telencephalon. p-Tyramine levels are also lowered. This change appears to be due to a decrease of the aromatic L-amino acid decarboxylase activity. These data, as those of ontogenic studies, confirm that p-octopamine and catecholamine metabolisms may have some independent steps and, moreover, that p-octopamine may have a role in the normal activity of the brain.

2-Hydroxyphenethylamine↗
PubMed1990

Octopamine uptake and metabolism in the insect nervous system.

Several insect tissues were examined for their ability to take up octopamine in the presence and absence of sodium ions. The cockroach Malpighian tubules, ovary, and ventral nerve cord showed the highest level of sodium-dependent uptake. The adult firefly lantern exhibited substantial sodium-independent uptake. Some of these tissues were also examined for their ability to metabolize octopamine by N-acetylation. Measurable N-acetyltransferase activity was present in the cockroach ventral nerve cord, tobacco hornworm CNS, and firefly light organ. N-Acetylation is proposed to be the major metabolic pathway for octopamine in the cockroach (Periplaneta americana) nervous system. Several classes of compounds, including octopamine receptor agonists, tricyclic antidepressants, amphetamines, chloroethylbenzylamines, and some experimental insecticides, were tested for their ability to inhibit octopamine uptake and metabolism. The sodium-insensitive component of uptake was not inhibited by most compounds tested, but the sodium-sensitive component was strongly inhibited by xylamine, N-ethyl-N-chloroethyl-o-bromobenzylamine, and their aziridinium ions (60-100%). These compounds also effectively inhibited N-acetyl-transferase (IC50 values at or below 1 microM). Other good inhibitors of N-acetyltransferase included desipramine, synephrine, and an experimental insecticide, CGA 132427. Formamidine pesticides had limited effect on both processes, and neither action seems likely to be involved in their octopaminergic actions in vivo. Cocaine was unique in stimulating N-acetyltransferase activity. When inhibition of sodium-sensitive uptake is compared with inhibition of N-acetyltransferase in the cockroach ventral nerve cord, two groups of inhibitors are discernible. Type 1 compounds inhibit uptake without an effect on N-acetyltransferase, whereas type 2 compounds inhibit both processes. These results suggest a functional linkage between the uptake and acetylation of octopamine.

Animals↗
PubMed1976

Octopamine release at two points along lobster nerve trunks.

Nerve cells in the proximal regions of second thoracic roots in lobsters have been injected with the fluorescent dye Procion Yellow. Examination of the roots reveals an elaborate array of cell branches in a superficial layer of the root in the vicinity of the cell bodies. Large varicosities, up to 10 mum in diameter, are seen lined up along fine nerve branches. 2. In these same regions, electron microscopic examination shows the presence of large profiles filled with 0-1-0-2 mum dense cored granules, and having the appearance of nerve endings. These profiles probably correspond to the varicosities seen in the Procion Yellow injections. The dense cored granules within the endings have a crystalline substructure. All the endings are found within 7 mum of the surface of the root and no obvious physiological target tissue exists in their surroundings. Endings have not been traced directly to root cell bodies.However, granules of similar dimensions to those seen in endings are found in cell bodies, axon-hillock regions and numerous axonal profiles in the superficial root regions near cell bodies. The morphological studies suggest that the root neurones have the typical appearance of neurosecretory cells. 3. Octopamine pools in cell body regions of second thoracic roots can be isotopically labelled by incubation with either [3H]tyramine or [3H]-tyrosine. After labelling, pulsing with 100 mM potassium causes an increase in the rate of release of radioactive material. Upon return to normal media background rates of release are re-established. The enhanced efflux has the following properties: (a) repeated pulses of potassium release less radio-active material each time; (b) a prolonged potassium pulse produces first a peak of release, then a decline to a plateau, and the plateau level of release is maintained for the duration of the potassium pulse; (c) release is dependent on the presence of calcium ions in the bathing fluid and 40 mM cobalt prevents release; (d) release is selective for octopamine. With tyrosine as a precursor compound, as much radioactive tyrosine as octopamine is found in tissues after incubation, yet pulsing with potassium causes an enhanced efflux only of octopamine from preparations. 4. Release of octopamine also can be demonstrated from pericardial organs near the ends of lateral branches of the roots and the properties of the release are identical to those seen with cell body regions. 5. Physiological studies, in which root cells are antidromically activated while recording from cell bodies, suggest that the distal endings of at least some of the root cells are at the pericardial organs. 6. The results suggest that root cell neurones are neurosecretory cells capable of releasing octopamine at two points: one near cell bodies, the other at the pericardial organs near the distal ends of the roots...

Animals↗
PubMed1981

Multiple receptor types for octopamine in the locust.

1. Three different pharmacological classes of octopamine receptor mediate the actions of octopamine on the locust extensor-tibiae neuromuscular preparation. A receptor classification scheme is proposed based on the results of detailed studies with agonists and antagonists. 2. Octopamine1 class receptors mediate the slowing of a myogenic rhythm found in a specialized proximal bundle of muscle fibres. Octopamine2A class receptors mediate the increase in amplitude of slow motoneurone twitch tension and octopamine2B class receptors mediate the increase in relaxation rate of twitch tension induced by firing either the fast or the slow motoneurones. 3. Octopamine1 receptors can be distinguished from the 2A and 2B classes since chlorpromazine (and yohimbine) are much better blocking agents than metoclopramide at the former receptors, whereas the converse is true for the latter class. Also clonidine is a more effective agonist than naphazoline for the former receptors and the converse is true for the latter class. 4. Octopamine 2A can be distinguished for octopamine 2B receptors since metoclopramide, mianserin and cyproheptadine show a strong preference for blocking the former class. Also naphazoline is a much better agonist than tolazoline at the former receptors and tolazoline is a much better agonist than clonidine at a latter. 5. The results are discussed in terms of the location of the various classes of octopamine receptors, their possible relationship to vertebrate alpha-adrenoreceptors, and the significance of the results for studies on octopamine receptors in the vertebrate central nervous system.

Animals↗
PubMed1998

Resting membrane properties of locust muscle and their modulation II. Actions of the biogenic amine octopamine.

Ionic currents in the resting membrane of locust jumping muscle and their modulation by the biogenic amine octopamine were investigated using the two-electrode voltage clamp. A Cl- conductance, GCl,H, which slowly activates on hyperpolarization, can be induced by raising the intracellular Cl- concentration via diffusion of Cl- ions from the recording electrode. The instantaneous I-V characteristic of the current, ICl,H, is linear and reverses at the same potential as the gamma-aminobutyric acid (GABA)-mediated Cl- current. Elevation of [Cl-]i increases the maximal steady state GCl,H (Gmax) and shifts the activation curve of GCl,H to more positive potentials. Octopamine enhances GCl,H, mainly by increasing Gmax. Octopamine also lowers the resting K+ conductance (GK,r). It reduces a hyperpolarization-activated component (GK,H) of GK,r, mainly by decreasing Gmax. Octopamine also transiently stimulates the Na+/K+ pump although this effect was not always seen. The effects of octopamine on the Cl- and K+ conductances are mimicked by membrane permeant cyclic nucleotides. The modulation of GK,r, but not that of GCl,H, seems to be mediated by protein kinase A (PKA). PKA seems to be constitutively activated as indicated by the pronounced increase in GK,r induced by a PKA inhibitor, H89. The properties of GCl,H and related Cl- conductances in invertebrate and vertebrate neurons are compared. GCl,H probably supports efflux of Cl- ions accumulating in the fibers during synaptic inhibition. Octopamine's multiple modulation at the level of the muscle cell membrane, in conjunction with previously established effects on synaptic transmission and excitation-contraction coupling, are suited to support strong and rapid muscle contractions.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Antagonistic effects of phentolamine and octopamine on rhythmic motor output of crayfish thoracic ganglia.

Spontaneous rhythmic motor output of crayfish thoracic ganglia consists of bursts of activity in antagonistic leg motor neurons (MNs), alternating with a rather slow cycle period (typically > or = 20 s). The most common pattern (77% of preparations) consists of long coxal promotor bursts, the duration of which was correlated strongly with cycle period, and relatively short remotor bursts independent of cycle period. Octopamine, at a concentration of 2-30 microM reversibly retarded this rhythm, increasing both cycle period and promotor burst duration. Higher concentrations of octopamine inhibited promotor nerve activity and abolished rhythmic bursting. Phentolamine (10-50 microM) had the opposite effect of decreasing cycle period, mainly by decreasing promotor burst duration. Whereas in the presence of octopamine promotor bursts were lengthened and became even more strongly related to cycle period, phentolamine promoted a more symmetrical rhythm with shorter promotor bursts that were less dependent on cycle period. When octopamine was applied in the presence of phentolamine, there was no significant increase in cycle period or burst duration, although high octopamine concentrations (100 microM) were still capable of inhibiting promotor nerve activity. To our knowledge, pharmacological modulation of a spontaneous locomotor rhythm by an amine antagonist (applied by itself) has not been reported previously. The results raise the testable possibility that phentolamine exerts its modulatory effects by acting as an octopamine antagonist in crayfish thoracic ganglia.

Adrenergic alpha-Agonists↗
PubMed2005

Octopamine and experience-dependent modulation of aggression in crickets.

Intraspecific aggression is influenced in numerous animal groups by the previous behavioral experiences of the competitors. The underlying mechanisms are, however, mostly obscure. We present evidence that a form of experience-dependent plasticity of aggression in crickets is mediated by octopamine, the invertebrate counterpart of noradrenaline. In a forced-fight paradigm, the experience of flying maximized the aggressiveness of crickets at their first encounter and accelerated the subsequent recovery of aggressiveness of the normally submissive losers, without enhancing general excitability as evaluated from the animals' startle responses to wind stimulation. This effect is transitory and concurrent with the activation of the octopaminergic system that accompanies flight. Hemocoel injections of the octopamine agonist chlordimeform (CDM) had similar effects on aggression but also enhanced startle responses. Serotonin depletion, achieved using alpha-methyl-tryptophan, enhanced startle responses without influencing aggression, indicating that the effect of CDM on aggression is not attributable to increased general excitation. Contrasting this, aggressiveness was depressed, and the effect of flying was essentially abolished, in crickets depleted of octopamine and dopamine using alpha-methyl-p-tyrosine (AMT). CDM restored aggressiveness in AMT-treated crickets, indicating that their depressed aggressiveness is attributable to octopamine depletion rather than to dopamine depletion or nonspecific defects. Finally, the flight effect was blocked in crickets treated with the octopamine receptor antagonist epinastine, or with the alpha-adrenoceptor and octopamine receptor antagonist phentolamine, but not with the beta-adrenoceptor antagonist propranolol. The idea that activity-specific induction of the octopaminergic system underlies other forms of experience-dependent plasticity of aggressive motivation in insects is discussed.

Adrenergic alpha-Antagonists↗
PubMed1992

Octopamine and phenylethylamine inhibit prolactin secretion both in vivo and in vitro.

Trace amines are a group of biogenic amines that are present in neural tissue in concentrations ranging from 0.1 to 100 ng/g. In the present work, we examined the action of two trace amines, octopamine and phenylethylamine, which are found in the hypothalamus, on pituitary hormone secretion in different experimental situations in vivo and in dispersed anterior pituitary cells. Both octopamine and phenylethylamine decreased high prolactin levels due to swimming or immobilization stress without affecting other adenohypophysial hormones. With regard to the hypoprolactinemic potencies in the immobilization stress model, it was observed that p-tyramine, another trace amine, was as potent as octopamine. Phenylethylamine was the least effective. To evaluate the site of action of the effect described, the three trace amines were tested in dispersed anterior pituitary cell cultures in vitro. Tyramine and octopamine reduced prolactin secretion in a concentration-dependent manner, at concentrations of 10(-8) to 10(-5) M, whereas the hypoprolactinemic effect observed for phenylethylamine was very weak. In pharmacologic experiments, neither octopamine nor phenylethylamine reduced prolactin release when dopaminergic receptors were blocked. This could mean that their hypoprolactinemic action was mediated through the release of dopamine, or it could be a direct action at a dopaminergic receptor. This is the first description of a specific endocrine action both in vivo and in vitro for octopamine and phenylethylamine. Further studies are needed to ascertain the physiologic or pathologic implication of these findings.

Analysis of Variance↗
PubMed1984

Cellular mechanisms for modulation of posture by octopamine and serotonin in the lobster.

Injection of the monoamines octopamine and serotonin into the hemolymph of lobsters causes them to assume opposing static postures: octopamine causes a tonic extension of all extremities, while serotonin induces a tonic flexion. These amines have been shown previously to act as circulating neurohormones and to cause contraction of isolated exoskeletal muscles. The opposing postures elicited by amine injection do not appear to arise from peripheral actions, however, since serotonin and octopamine have similar effects on both flexor and extensor muscles. Instead, the amines are present within the central nervous system where they are probably released synaptically to activate coordinated patterns of tonic motor activity generating the observed postures. These motor patterns have been recorded from abdominal ganglia and involve the synchronized activation and inhibition of multiple excitatory and inhibitory motoneurons innervating the postural flexor and extensor muscles. These effects can be observed in an isolated abdominal ganglion. To begin a search for the cellular targets of amine action within the central nervous system, we recorded from identified postural motoneurons in abdominal ganglia. In two motoneurons that act to produce postural extension, octopamine reduced and serotonin raised the apparent threshold for action potential generation recorded in the somata. The amines do not significantly affect the resting potential or input resistance of the motoneurons measured in the cell bodies. Although the amine effect on motoneuron excitability could be due to actions directly on the motoneurons, our evidence suggests that at least part of the effect results from activation or inhibition of premotor interneurons: (1) an increase in EPSP frequency is observed in the motoneurons during octopamine superfusion, while a small decrease is observed during serotonin superfusion; (2) the amine effects on action potential threshold are abolished by cobalt ion. These results suggest that octopamine and serotonin have dual effects on posture: within the central nervous system, they act specifically to generate coordinated motor patterns for flexion or extension; as circulating neurohormones, they act nonspecifically to enhance the responses of exoskeletal muscles to motoneuronal activation.

Animals↗
PubMed1998

A novel octopamine receptor with preferential expression in Drosophila mushroom bodies.

Octopamine is a neuromodulator that mediates diverse physiological processes in invertebrates. In some insects, such as honeybees and fruit flies, octopamine has been shown to be a major stimulator of adenylyl cyclase and to function in associative learning. To identify an octopamine receptor mediating this function in Drosophila, putative biogenic amine receptors were cloned by a novel procedure using PCR and single-strand conformation polymorphism. One new receptor, octopamine receptor in mushroom bodies (OAMB), was identified as an octopamine receptor because human and Drosophila cell lines expressing OAMB showed increased cAMP and intracellular Ca2+ levels after octopamine application. Immunohistochemical analysis using an antibody made to the receptor revealed highly enriched expression in the mushroom body neuropil and the ellipsoid body of central complex, brain areas known to be crucial for olfactory learning and motor control, respectively. The preferential expression of OAMB in mushroom bodies and its capacity to produce cAMP accumulation suggest an important role in synaptic modulation underlying behavioral plasticity.

Adrenergic Agents↗
PubMed2005

Use of the exogenous Drosophila octopamine receptor gene to study Gq-coupled receptor-mediated responses in mammalian neurons.

Diverse excitatory and inhibitory neuronal responses are mediated via Gq-coupled receptors, but the lack of a systematic comparison of different receptors or neurons has hindered a better understanding of these responses. Such a comparison may be provided by an exogenous receptor that is activated by compounds that have no effect on endogenous receptors. We therefore expressed an invertebrate biogenic amine receptor, the Drosophila octopamine receptor, in rat cortical neurons and compared octopamine receptor-mediated responses with those mediated by the group I metabotropic glutamate receptor, the endogenous Gq-coupled receptor in rat cortical neurons. Stimulation of either receptor did not result in a calcium response in octopamine receptor-expressing neurons, although octopamine preferentially elicited a calcium increase in octopamine receptor-expressing PC12h cells, while enhancing the neuronal depolarization-induced calcium increase and the electrical excitability. The increased excitability was caused by inward currents resulting from a reduction in the leak current, which was voltage-independent and blocked by genistein, a non-selective tyrosine kinase inhibitor. These results show that, in cortical neurons, exogenous octopamine receptor in mushroom bodies activated the same cell signaling pathway as endogenous metabotropic glutamate receptor, suggesting that the diverse neuronal responses mediated by Gq-coupled receptors are due to the properties of different neurons, rather than to the properties of the receptors.

Action Potentials↗
PubMed1996

Developmental expression of the octopamine phenotype in lobsters, Homarus americanus.

We have used immunocytochemical methods to examine the sequence of appearance of octopamine-immunoreactive neurons during development, and to try to correlate that appearance with the emergence of behavioral or physiological capabilities. The first octopamine neurons express their transmitter phenotype at approximately 43% of embryonic development. The last cells show immunostaining at the 3rd larval stage. In the wild, therefore, immunoreactivity in cells appears over a 9-12 month period. In contrast, serotonin-immunoreactive neurons stain early in embryonic development and the last serotonin-immunoreactive cells appear at about the same time the first octopamine-immunoreactive neurons show staining. The pattern of appearance of octopamine-immunoreactive cells is cell type-specific. A pair of brain cells and the descending interneurons stain first. Additional brain cell staining is seen throughout embryonic development. The ascending interneurons appear next, and a general anterior-posterior gradient typifies their emergence over a relatively short portion of embryonic life (E 48-62%). The neurosecretory cell staining appears last, is segment-specific, begins at about 62% development, and continues to the 3rd larval stage. The emergence of immunostaining for amine neurotransmitters within groups of identified neurons at precise times in development may specify possible functional units. With at least one group of cells, this possibility seems plausible: the three pairs of claw octopamine neurosecretory cells show immunostaining as a unit.

Animals↗
PubMed2005

Octopamine-like immunoreactivity in the honey bee and cockroach: comparable organization in the brain and subesophageal ganglion.

A serum raised against octopamine reveals in cockroaches and honey bees structurally comparable systems of perikarya and their extensive yet discrete systems of arborizations in neuropils. Numerous and prominent clusters of lateral cell bodies in the brain as well as many midline perikarya provide octopamine-like immunoreactive processes to circumscribed regions of the subesophageal ganglion, antennal lobe glomeruli, optic neuropils, and neuropils of the protocerebrum. There is dense octopaminergic innervation in the protocerebral bridge and ellipsoid body of the central complex. The antennal lobes are supplied by at least three octopamine-immunoreactive neurons. In contrast, the mushroom bodies show the fewest immunoreactive elements. In Apis a single axon supplies sparse immunoreactive processes to the calyces' basal ring, collar, and lip. A diffuse arrangement of immunoreactive processes invades all zones of the mushroom body calyces in Periplaneta. These processes derive from an ascending axon ascribed to a dorsal unpaired median neuron at the maxillary segment of the subesophageal ganglion. In both taxa octopamine-immunoreactive processes invade only the gamma lobes of the mushroom bodies, omitting their other divisions. The present observations are discussed with respect to possible roles of octopamine in sensory integration and association.

Animals↗
PubMed1992

Octopamine immunoreactive cell populations in the locust thoracic-abdominal nervous system.

We describe octopamine-immunoreactive somata and their projections in the pro- meso-, meta- and pregenital abdominal-ganglia of locusts. Immunoreactive midline somata were identified as dorsal- and ventral- unpaired median (DUM- and VUM-, respectively) neurones due to their: characteristic large size and positions of somata, primary neurites in DUM-tracts giving rise to T-junctions, and bilaterally projecting axons. In the prothoracic ganglion there are most likely 8 such cells; in the meso- and metathoracic, some 20 each; and in each individual pregenital abdominal ganglion, typically 3. All appear to project to peripheral nerves and their numbers correspond to the number of peripherally projecting DUM-cells identified to date in each ganglion. We suggest that probably all peripherally projecting DUM-cells are octopaminergic in the examined ganglia. Presumptive DUM-interneurones are not octopamine-immunoreactive, but, confirming other studies, are shown to label with an antiserum to gamma-amino butyric acid (GABA). Other octopamine-immunoreactive neurones include a pair of midline, prothoracic, anterior medial cells, not necessarily DUM-cells, and a pair of ventral lateral somata in each thoracic- and the first abdominal ganglion. The latter project intersegmentally in ventral tracts. Intersegmentally projecting octopamine-immunoreactive fibers in dorsal tracts probably arise from a prothoracic DUM-cell, which leaves through suboesophageal nerves, or descending suboesophageal DUM-cells. Thus, the octopamine-immunoreactive system of thoracic and pregenital abdominal ganglia in locust comprises all peripherally projecting DUM-cells and a plurisegmental network.

Abdomen↗