[Determination of octopamine using high pressure liquid chromatography and electrochemical detection: studies of the brain of the cricket Locusta migratoria cinerascens].
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Animals↗
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Spider peripheral mechanosensory neurons are directly innervated and modulated by octopaminergic efferents.
Octopamine is a chemical relative of noradrenaline providing analogous neurohumoral control of diverse invertebrate physiological processes. There is also evidence for direct octopaminergic innervation of some insect peripheral tissues. Here, we show that spider peripheral mechanoreceptors are innervated by octopamine-containing efferents. The mechanosensory neurons have octopamine receptors colocalized with synapsin labeling in the efferent fibers. In addition, octopamine enhances the electrical response of the sensory neurons to mechanical stimulation. Spider peripheral mechanosensilla receive extensive efferent innervation. Many efferent fibers in the legs of Cupiennius salei are GABAergic, providing inhibitory control of sensory neurons, but there is also evidence for other neurotransmitters. We used antibody labeling to show that some efferents contain octopamine and that octopamine receptors are concentrated on the axon hillocks and proximal soma regions of all mechanosensory neurons in the spider leg. Synaptic vesicles in efferent neurons were concentrated in similar areas. Octopamine, or its precursor tyramine, increased responses of mechanically stimulated filiform (trichobothria) leg hairs. This effect was blocked by the octopamine antagonist phentolamine. The octopamine-induced modulation was mimicked by 8-Br-cAMP, a cAMP analog, and blocked by Rp-cAMPS, a protein kinase A inhibitor, indicating that spider octopamine receptors activate adenylate cyclase and increase cAMP concentration. Frequency response analysis showed that octopamine increased the sensitivity of the trichobothria neurons over a broad frequency range. Thus, the major effect of octopamine is to increase its overall sensitivity to wind-borne signals from sources such as flying insect prey or predators.
8-Bromo Cyclic Adenosine Monophosphate↗
Effects of deuterium substitution on the chronotropic responses to some sympathomimetic amines in the isolated rat atria.
In spontaneously beating rat atria the potencies for the chronotropic effects of the following deuterated phenylethylamine derivatives were higher than the potencies of the corresponding non-substituted (protio-) amines: alpha,alpha,d2-beta-phenylethylamine; alpha,alpha,beta,beta-d4-p-tyramine; alpha,alpha,beta,beta-d4-m-tyramine; alpha,alpha,beta-d3-p-octopamine. In contrast, alpha,alpha,beta-d3-noradrenaline and alpha,alpha,beta-d3-m-octopamine were equipotent with the corresponding protio-amines. Experiments performed in atria depleted of endogenous noradrenaline by pretreatment with reserpine and in atria exposed to the monoamine oxidase (MAO) inhibitor pargyline indicated: a. p-octopamine had both direct and indirect effects, but the chronotropic responses to p-octopamine in tissues with normal MAO activity depended mostly on the direct action of the amine; deuterium substitution enhanced the indirect component of action of p-octopamine; b. m-octopamine possessed considerable indirect effects while d3-m-octopamine behaved as an amine of direct action. The substitution of deuterium for hydrogens in the alpha-carbon of the alkyl-side chain of phenylethylamines decreases the rate of deamination by MAO. Therefore, the results obtained with all the amines, except for m-octopamine and alpha, alpha,p-d3-m-octopamine, could be interpreted in terms of the direct, indirect or mixed action of those compounds and/or of the influence that MAO activity has on the chronotropic responses to these amines. The results obtained with protio- and deuterio-m-octopamine suggested that deuterium substitution, either at the alpha- or the beta-carbon, can alter some other mechanisms in addition to the enzymatic deamination.
Animals↗
Agonist-specific coupling of a cloned human alpha1A-adrenoceptor to different second messenger pathways.
The agonist-specific coupling properties of the three cloned human alpha(1)-adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and the (+/-)- meta- and (+/-)- para- structural isomers of octopamine as agonists. The alpha(1A)- and the alpha(1B)-adrenoceptor subtypes coupled to both the release of arachidonic acid and to the accumulation of inositol phosphates, whereas the alpha(1D)-adrenoceptor subtype only coupled effectively to the accumulation of inositol phosphates. The rank order of potencies of the three agonists tested was the same for all the three receptor subtypes when coupled to either signalling pathway: noradrenaline > meta-octopamine > para-octopamine. Meta-octopamine was a partial agonist of the alpha(1A)-adrenoceptor subtype when coupled to arachidonic acid release, whereas para-octopamine was a full agonist of this pathway. In contrast, meta-octopamine was a full agonist at the alpha(1B)-adrenoceptor subtype when coupled to arachidonic acid release, whereas para-octopamine was a partial agonist of this pathway. Neither meta-octopamine, nor para-octopamine acted as full agonists when coupling any of the three alpha(1)-adrenoceptor subtypes to the accumulation of inositol phosphates. Para-octopamine was only a weak partial agonist of this pathway for all three receptor subtypes. The results show that the modulation of arachidonic acid release and inositol 1,4,5-trisphosphate production occurs in both a subtype- and agonist-specific manner for the alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptor subtypes. In addition, the alpha(1A)-adrenoceptor exhibits agonist-specific coupling (agonist trafficking) to the different second messenger pathways.
Adrenergic alpha-Agonists↗
Evidence for octopaminergic modulation of an insect visceral muscle.
Two dorsal unpaired median neurons (DUMOV1 and DUMOV2) lying in the posterior region of the VIIth abdominal ganglion of Locusta migratoria have axons which project to the muscles of the oviducts. This study reports the presence of octopamine within isolated DUMOV cell bodies, as well as in the oviducal nerve and innervated oviducal muscle. Individual cell bodies were pooled and found to contain about 0.34 pmol of octopamine per cell body giving an approximate value of 1.27 mM octopamine. Octopamine is concentrated within the area of oviducal muscle which receives DUMOV axons. Pharmacological studies reveal that the amplitude of neurally-evoked contractions of the oviducal muscle is reduced in a dose-dependent manner by octopamine, with threshold lying between 5 X 10(-10) M and 7 X 10(-9) M. The receptors for this response show a specificity for octopamine and synephrine, with an order of potency being octopamine = synephrine greater than metanephrine greater than tyramine greater than dopamine. The presence of octopamine throughout this neural pathway, coupled with the demonstration of octopaminergic modulation of muscular contraction, supports the hypothesis that octopamine serves a physiological role in this visceral system.
Animals↗
Biogenic amines modulate olfactory receptor neurons firing activity in Mamestra brassicae.
The modulatory effects of the biogenic amines octopamine and serotonin on pheromonal receptor neurons of Mamestra brassicae were investigated. The responses to sex pheromone components of two cells types (A and B) in single male long sensilla trichodea were monitored. Cell types A and B do not respond to the same compound. The response of type A to a pulse of the major sex pheromone component increased 5 min after octopamine injection. Responses of type B to other odorants increased after 30 min. In the absence of any pheromone stimulation the background firing activity of type A increased following octopamine injection. This background activity was used to evaluate the kinetics of octopamine and other biogenic amine effects on olfactory receptor neurons. Octopamine increased this background activity in a concentration- and time-dependent manner. Clonidine, an octopamine agonist, was shown to be more powerful in increasing the background activity of olfactory receptor neurons. The effects of octopamine and clonidine were hypothesized to arise from specific receptor activation as chlorpromazine (an octopamine antagonist) was shown to block the effect of octopamine. Serotonin, a known neuromodulator in most animal species, induced a reversible inhibition of spike firing. Altogether, these results indicate that biogenic amines can modulate the sensitivity of olfactory receptor neurons of moths either directly or by an action on adaptation.
Amines↗
Parasitic suppression of feeding in the tobacco hornworm, Manduca sexta: parallels with feeding depression after an immune challenge.
The parasitic wasp, Cotesia congregata, suppresses feeding in its host Manduca sexta. Feeding suppression in the host coincides with the emergence of the wasps through the host's cuticle. During wasp emergence, host hemocyte number declined, suggesting that the host mounts a wound/immune response against the exiting parasitoids and/or resulting tissue damage. Eliciting a different type of immune response by injecting heat-killed Serratia marcescens also resulted in a decline in feeding and a reduction in hemocyte number. Both the emerging wasps and the bacteria induced an increase in hemolymph octopamine concentration and a decrease in foregut peristalsis in M. sexta. The emerging parasitoids produced the largest changes. The source of the additional octopamine appeared to be the host in both cases. S. marcescens was found to contain no detectable amounts of octopamine. The parasitoids had insufficient octopamine to account for the amount found in host hemolymph and they did not secrete octopamine in vitro. One cause for the high concentration of octopamine in parasitized M. sexta was that octopamine was removed from the hemolymph approximately 23 times more slowly after the wasps emerged than prior to wasp emergence. The striking similarity between the effects of parasitoids and bacteria on M. sexta feeding, hemocyte number, hemolymph octopamine concentration, and foregut peristalsis supports the possibility that the immune/wound reaction induced by the emerging wasps could play a role in the suppression of host feeding. These results also support the hypothesis that M. sexta exhibit an immune-activated anorexia.
Animals↗
Taurine-like immunoreactivity in octopaminergic neurones of the cockroach, Periplaneta americana (L.).
Taurine (2-aminoethanesulphonic acid) is reported to interact with the octopaminergic system. The distribution of taurine-like immunoreactivity (-LIR) in relation to octopamine-like immunoreactive dorsal unpaired median (DUM) neurones was investigated with the aim of revealing possible colocalization of these two neuromediators. The specificity of the anti-taurine serum used was demonstrated by dot blot immunoassay and by use of preabsorption controls. There was no crossreactivity with octopamine. The specificity of the octopamine antiserum employed has been described elsewhere. Taurine-LIR could be demonstrated in large dorso-median cells in the suboesophageal and the mesothoracic ganglion as well as in the abdominal ganglia. In addition taurine-LIR is distributed in numerous other regions of the ganglia. A comparison of the immunostaining for taurine and octopamine indicates that several of the taurine-like immunoreactive (-LI) neurones are probably members of the octopamine-immunoreactive DUM cell population. These taurine-LI neurones resemble octopamine-LI DUM cells in soma position and size as well as in the projections of their primary neurites. Colocalization of octopamine-LIR and taurine-LIR within the same neuronal element could be shown by alternate immunostaining of consecutive sections. It is probable that all octopamine-LI DUM neurones also exhibit taurine-LIR, and the possible physiological significance of this coexistence is discussed.
Animals↗
The effect of site-directed mutagenesis of two transmembrane serine residues on agonist-specific coupling of a cloned human alpha2A-adrenoceptor to adenylyl cyclase.
1. The effects of substitution of the Ser200 and Ser204 residues with alanine on the signalling properties of the cloned human alpha2A-adrenoceptor, stably expressed in Chinese hamster ovary (CHO) cell lines, have been investigated using noradrenaline and the structural isomers of octopamine. 2. The Ser-->Ala200 or the Ser-->Ala204 mutant forms of the alpha2A-adrenoceptor, when expressed in cells in the absence of pertussis toxin pretreatment, are two orders of magnitude more sensitive to inhibition of cyclic AMP production by (+/-)-para-octopamine and (+/-)-meta-octopamine, respectively, than cells expressing the wild-type receptor. Binding studies indicate that the effects are not due to an increased agonist affinity for the mutant receptors and that they are likely to be due to agonist-mediated conformational changes in receptor structure. 3. After incubation with pertussis toxin, (+/-)-meta-octopamine (100 microM and above) produced a stimulation of cyclic AMP levels in cells expressing the Ser-->Ala204 mutant form of the alpha2A-adrenoceptor but showed no stimulation in cells expressing the Ser-->Ala200 mutant receptor. Under these conditions (+/-)-para-octopamine did not produce any increases in cyclic AMP production in cells expressing either of the mutant receptor forms or the wild-type receptor. 4. The results emphasise the importance of the Ser200 and Ser204 residues of the alpha2A-adrenoceptor in exerting an inhibitory influence on the ability of (+/-)-para-octopamine and (+/-)-meta-octopamine respectively, to induce a receptor-agonist conformation capable of inhibiting forskolin-stimulation of cyclic AMP levels. 5. It is clear that Ser204 also prevents meta-octopamine from generating a receptor-agonist conformation that can increase cyclic AMP levels, emphasising the importance of this residue in the agonist-specific coupling of this receptor to different second messenger systems.
Adenylate Cyclase Toxin↗
Cyclic AMP mediates serotonin-induced synaptic enhancement of lateral giant interneuron of the crayfish.
The lateral giant (LG)-mediated escape behavior of the crayfish habituates readily on repetitive sensory stimulation. Recent studies suggested that the biogenic amines serotonin and octopamine modulate the time course of recovery and/or re-depression of the LG response after habituation. However, little is known of how serotonin and octopamine effect LG habituation and what second-messenger cascades they may activate. To investigate the effect of biogenic amines on LG habituation, serotonin and octopamine were superfused before presenting repetitive sensory stimulation. Serotonin and octopamine increased the number of stimuli needed to habituate the LG response. Their effects were mimicked by mixed application of a cAMP analogue [8-(4-chlorophenylthio)-cAMP (CPT-cAMP)] and a phosphodiesterase inhibitor [3-isobutyl-1-methylxanthine (IBMX)] but not by a cGMP analogue (8-bromoguanosine 3',5'-cyclic monophosphate). Perfusion of the adenylate cyclase inhibitor (SQ22536) abolished the effect of serotonin but not that of octopamine. To investigate the site of action of each biogenic amines in the neural circuit meditating LG escape, the effect of drugs on directly and indirectly elicited postsynaptic potentials in LG was investigated. Serotonin, octopamine, and a mixture of CPT-cAMP and IBMX increased both the direct and indirect synaptic inputs. Simultaneous application of SQ22536 abolished the effect of serotonin on both inputs but did not block the effect of octopamine. Direct injection of the cAMP analogue (Sp-isomer of adenosine-3',5'-cyclic monophosphorothioate) into LG increased both the direct and indirect inputs to LG. These results indicate that serotonin mediates an increase in cAMP levels in LG, but octopamine acts independently of cAMP and cGMP.
1-Methyl-3-isobutylxanthine↗
Agonistic behaviour and biogenic amines in shore crabs Carcinus maenas.
To investigate the role of certain neurohormones in agonistic behaviour, fights were staged between pairs of size-matched male shore crabs Carcinus maenas, and blood samples were taken immediately after the contests had been resolved. Samples were also taken from these crabs at rest (before and after fighting) and after walking on a treadmill. A control group of crabs also had samples taken on each experimental day. Concentrations of tyramine, dopamine, octopamine, serotonin (5-HT) and norepinephrine were determined in each blood sample using a gas chromatography/mass spectrometry (GC-MS) system. Norepinephrine was not detectable in any of the samples, but the standards were recovered. Tyramine values were not significantly different between the control group and the fought group, so tyramine does not appear to be important in agonistic behaviour. A comparison between the control and fought groups shows that fighting had an effect on the concentrations of octopamine, dopamine and 5-HT, but exercise only had an effect on octopamine levels, which showed a reduction from resting values in both winners and losers. Resting and post-fight concentrations of octopamine, dopamine and 5-HT were higher in winners than in losers. 5-HT concentration increased in the blood of fought crabs from resting values, whereas dopamine concentration decreased. In winners, octopamine concentrations decreased from resting values, but in losers octopamine levels increased from resting concentrations. The escalatory behaviour or intensity of fighting performed by winners and losers was related to dopamine levels but not to those of octopamine or 5-HT. Therefore, there appears to be a link between relative concentrations of these three amines (dopamine, octopamine and 5-HT) and fighting ability; the effects are not simply a result of activity. The better competitors have higher concentrations of these three amines at rest and after fighting.
Agonistic Behavior↗
Octopaminergic modulation of synaptic transmission between an identified sensory afferent and flight motoneuron in the locust.
The role of the biogenic amine octopamine in modulating cholinergic synaptic transmission between the locust forewing stretch receptor neuron (fSR) and the first basalar motoneuron (BA1) was investigated. The amines 5-hydroxytryptamine (5-HT, serotonin) and dopamine were also studied. Bath application of octopamine, 5-HT, and dopamine at concentrations of 10(-4) M reversibly decreased the amplitude of monosynaptic excitatory postsynaptic potentials (EPSPs) evoked in BA1 by electrically stimulating the fSR axon. These effects occurred without any detectable change in either input resistance or membrane potential of BA1. The amines also reversibly decreased the amplitude of responses to acetylcholine (ACh) pressure-applied to the soma of BA1. The muscarinic antagonist scopolamine (10(-6) M) had no significant effect on the octopamine-induced decrease in ACh responses. These observations suggest that these amines potentially could physiologically depress cholinergic transmission between fSR and BA1, at least in part, by altering nicotinic rather than muscarinic cholinergic receptor function. Although the octopaminergic agonists naphazoline and tolazoline both mimicked the actions of octopamine, the receptor responsible for octopamine-mediated modulation could not be characterized since amine receptor antagonists tested on the preparation had complex actions. Confocal immunocytochemistry revealed intense octopamine immunoreactivity in the anterior lateral association center, thus confirming the presence of octopamine in neuropil regions containing fSR/BA1 synapses and therefore supporting a role for this amine in the modulation of synaptic transmission between the fSR and BA1. 5-HT-immunoreactivity, conversely, was concentrated within the ventral association centers; very little staining was observed in the dorsal neuropil regions in which fSR/BA1 synapses are located.
Acetylcholine↗
A comparison of agonist-specific coupling of cloned human alpha(2)-adrenoceptor subtypes.
The agonist-specific coupling properties of the three cloned human alpha(2)-adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and (+/-)-meta-octopamine as agonists. Noradrenaline can couple the receptor to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production in all three receptor subtypes, with the relative strength of the coupling to the pathways varying for each of the receptor subtypes. meta-Octopamine selectively couples the alpha(2A)-adrenoceptor only to the inhibition of forskolin-stimulated cyclic AMP production. However, meta-octopamine couples the alpha(2B)- and alpha(2C)-adrenoceptors to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production. The relative potency of meta-octopamine to noradrenaline varies between the different alpha(2)-adrenoceptor subtypes. The effects of meta-octopamine are around two orders of magnitude less potent than those of noradrenaline on both the alpha(2A)- and alpha(2B)-adrenoceptor subtypes. In contrast, in the case of the alpha(2C)-adrenoceptor, meta-octopamine is only one order of magnitude less potent than noradrenaline in the stimulation of forskolin-stimulated cyclic AMP production and, in addition, is equipotent with noradrenaline in the inhibition of forskolin-stimulated cyclic AMP production and has an increased maximal response. This raises the possibility that meta-octopamine may have physiologically important actions via alpha(2C)-adrenoceptors in vivo. The results show that the modulation of cyclic AMP production occurs in both a subtype- and agonist-specific manner for alpha(2A)-adrenoceptors and in a subtype specific manner for alpha(2B)- and alpha(2C)-adrenoceptors.
Adrenergic alpha-Agonists↗
A modulatory octopaminergic neurone increases cyclic nucleotide levels in locust skeletal muscle.
Octopamine increases the level of cyclic AMP in a dose-dependent way in the locust extensor tibiae neuromuscular preparation. The response peaks after a 10 min exposure and then declines to a plateau. The effect of octopamine is potentiated in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). The levels of cyclic GMP in the muscle were not affected by octopamine. The response is stereospecific for the naturally occurring D(-) isomer of octopamine and is also specific for monophenolic biogenic amines. Studies with a range of synthetic agonists and antagonists reveal that the receptors mediating the response are of the OCTOPAMINE2 class. Forskolin, a diterpene activator of adenylate cyclase activity, increases cyclic AMP but not cyclic GMP levels in the extensor muscle. The response has a prolonged time course and is again potentiated by IBMX. Stimulation of the octopaminergic neurone to the extensor muscle increases the levels of cyclic AMP but not those of cyclic GMP. The response is blocked by phentolamine, an alpha-adrenergic blocking agent that also blocks the effects of octopamine in this preparation. The results are discussed in terms of the parallels between the biochemical and physiological effects of octopamine on this muscle and in terms of the mode of action of the octopamine receptors present.
1-Methyl-3-isobutylxanthine↗
Serotonin regulates repolarization of the C. elegans pharyngeal muscle.
Caenorhabditis elegans feeds by rhythmically contracting its pharynx to ingest bacteria. The rate of pharyngeal contraction is increased by serotonin and suppressed by octopamine. Using an electrophysiological assay, we show that serotonin and octopamine regulate two additional aspects of pharyngeal behavior. Serotonin decreases the duration of the pharyngeal action potential and enhances activity of the pharyngeal M3 motor neurons. Gramine, a competitive serotonin antagonist, and octopamine have effects opposite to those of serotonin: gramine and octopamine increase action potential duration and suppress M3 activity. The effects of serotonin, gramine and octopamine on action potential duration are dependent on the pharyngeal motor neurons MC and M3. When the MC and M3 motor neurons are functionally defective, serotonin and octopamine do not regulate the action potential. Our data suggest that serotonin alters pharyngeal physiology to allow for rapid contraction-relaxation cycles. Reciprocal regulation of pharyngeal behavior by serotonin and octopamine provides a mechanism for adapting to the presence and absence of food, respectively.
Action Potentials↗
Octopaminergic modulation of the membrane currents in the central feeding system of the pond snail Lymnaea stagnalis.
Octopamine is released by the intrinsic OC interneurons in the paired buccal ganglia and serves both as a neurotransmitter and a neuromodulator in the central feeding network of the pond snail Lymnaea stagnalis. The identified B1 buccal motoneuron receives excitatory inputs from the OC interneurons and is more excitable in the presence of 10 microM octopamine in the bath. This modulatory effect of octopamine on the B1 motoneuron was studied using the two electrode voltage clamp method. In normal physiological saline depolarising voltage steps from the holding potential of -80 mV evoke a transient inward current, presumably carried by Na(+) ions. The peak values of this inward current are increased in the presence of 10 microM octopamine in the bath. In contrast, both the transient (IA) and delayed (IK) outward currents are unaffected by octopamine application. Replacing the normal saline with a Na(+)-free bathing solution containing K(+) channel blockers (50 mM TEACl, 4 mM 4AP) revealed the presence of an additional inward current of the B1 neurons, carried by Ca(2+). Octopamine (10 microM) in the bath decreased the amplitudes of this current. These results suggest that the membrane mechanisms which underlie the modulatory effect of octopamine on the B1 motoneuron include selective changes of the Na(+)- and Ca(2+)-channels.
Action Potentials↗
Distribution and action of some putative neurotransmitters in the stomatogastric nervous system of the earthworm, Eisenia fetida (Oligochaeta, Annelida).
The chemical neuroanatomy of the stomatogastric nervous system of the earthworm, Eisenia fetida, has been investigated, using antibodies raised against serotonin, tyrosine hydroxylase, octopamine, GABA, FMRFamide, proctolin, Eisenia tetradecapeptide and neuropeptide Y. Neurons immunoreactive to these antibodies can be observed in the stomatogastric ganglia. The labelled cells comprise altogether 95.4% of the total number of neurons in the ganglion. Immunoreactive projections were followed between stomatogastric individual ganglia as well as towards the enteric plexus. Intrinsic neurons containing the different signal molecules examined are present along the entire length of the enteric plexus, but serotonin immunoreactive perikarya were only found in the hindgut. The density of the different immunoreactive neurons, except the serotonin ones, is highest in the pharyngeal plexus, and the number of labelled neurons decreases along the alimentary canal towards the hindgut. A number of epithelial cells also reveal tyrosine hydroxylase, octopamine, GABA and Eisenia tetradecapeptide immunoreactivity. The action of some putative neurotransmitters, such as dopamine, octopamine, serotonin and proctolin was tested on foregut preparations. Dopamine and octopamine (10(-6)-10(-4) M) have an excitatory effect on the musculature, whereas the effect of serotonin depends on the actual muscle tension. Following precontraction evoked by acetylcholine, serotonin in low concentrations (10(-7)-10(-6) M) causes relaxation, whereas in higher (10(-4) M) concentration it evokes slight contractions. In preparations at basal tone, serotonin (10(-7)-10(-6) M) evokes contractions of the foregut. Atropine strongly inhibits the action of acetylcholine but is ineffective against serotonin, dopamine and octopamine. Similarly, the Na+ channel blocker tetrodotoxin fails to influence the contractile effect of dopamine, octopamine and serotonin. These results suggest that dopamine, octopamine and serotonin act directly on the muscle cells of the alimentary tract. Proctolin do not evoke any significant effect on the foregut.
Animals↗
The effect of biogenic amines and their analogs on carbohydrate metabolism in the fat body of the cockroach Blaberus discoidalis.
Several biogenic amines and their analogs were examined for stimulatory effects on glycogen phosphorylase activity and trehalose biosynthesis in fat body of the cockroach, Blaberus discoidalis. Octopamine and synephrine were the most potent activators of fat body phosphorylase; 10 muM octopamine being nearly as effective as the hypertrehalosemic hormone (HTH). Epinephrine, norepinephrine, and tyramine produced intermediate effects, whereas dopamine, 5-hydroxytryptamine, and melatonin had no effect. The fat body octopamine receptors appeared to be pharmacologically related to vertebrate alpha-adrenergic receptors and belonged to the Octopamine1 class receptor. In contrast to previous reports, synephrine also induced both phosphorylase activation and hypertrehalosemia as effectively as octopamine. Demethylchlordimeform, a formamidine insecticide structurally similar to octopamine, also strongly activated fat body phosphorylase, possibly by interaction with the octopamine receptor.
Amidines↗