Effect of octopamine

Central actions of octopamine. There is no doubt that, at the present time, more detail is known about the peripheral effects of octopamine than its central effects. This is almost certainly due to the amenability of peripheral preparations to experimentation. Table... 

This, coupled to the fact that phosphodiesterase inhibitors can cause glowing and potentiate the effects of octopamine (see 85), indicates that the initiation of the normal adult firefly flash is mediated through an elevation of cyclic AMP levels secondarily to the activation of an octopamine-sensitive adenylate cyclase. 

Stimulation of the two identified octopaminergic neurons which project to the lateral oviducts also results in an elevation in cyclic AMP. The major physiological effects of octopamine (reduction in amplitude of neurally-evoked contractions and inhibition of myogenic contractions) are induced by agents which artificially elevate cyclic AMP levels (IBMX, forskolin, dibutyryl cylic AMP). 

An octopamine-sensitive adenylate cyclase is not the only means by which octopamine may exert its effects. Whilst DUMETi and octopamine modulate the amplitude and rate of relaxation of twitch tension in the extensor tibiae muscle of locusts via cyclic AMP, their effects upon the myogenic rhythm are mediated via a different route (86) Thus, elevated cyclic AMP does not induce a decrease in the frequency of myogenic rhythm as does octopamine, and the effects of octopamine are not potentiated by IBMX. In fact the mode of action of octopamine in reducing the frequency of myogenic contractions remains unknown. 

Price DN, Berry MS (2006) Comparison of effects of octopamine and insecticidal essential oils on activity in the nerve cord, foiegut and dmsal unpaired median neurons of cockroaches. J Insect Physiol 52 309-319... 

A direct effect of vasoactive amines on the organism which are not degraded in GI tracts due to the lack of mono- and diaminooxidase (MAO and DAO) or their blockade by medicines or alcohol. This group of amines includes tyramine (in Cheddar, emmental, roquefort cheeses, pickled fish, and walnuts), phenylethylamine (in chocolate), serotonin (in bananas), octopamine (in lemons), and histamine (in fermented foods, e.g., blue cheeses, but also in strawberries, tomatoes, wines, and in mackerel that have not been stored properly [scombrotoxin illness]). 

Table II. Potency of Octopamine and DCDM in the Crayfish Behavioral Assay and the Effect of Selected Octopaminergic Antagonists on their Action.

General Functions of Octopamine in Arthropods. The actions of OA in invertebrates therefore are multiple and probably involve both central and peripheral sites. Moreover, as pointed out previously, many of the known actions of OA are comparable to those of NE and E in the vertebrate central and sympathetic nervous systems. These multiple effects are concerned with arousal and stress responses, increasing the responsiveness to outside stimuli, and alerting the resting animal and priming it for action and movement. It is interesting, though inconclusive, in this context to note that ants... 

NMR studies have been carried out on Schiff bases derived from pyridoxal phosphate and amino acids, since they have been proposed as intermediates in many important biological reactions such as transamination, decarboxylation, etc.90 The pK.d values of a series of Schiff bases derived from pyridoxal phosphate and a-amino adds, most of which are fluorinated (Figure 11), have been derived from H and19F titration curves.91 The imine N atom was found to be more basic and more sensitive to the electron-withdrawing effect of fluorine than the pyridine N atom. Pyridoxal and its phosphate derivative are shown in Figure 12a. The Schiff base formation by condensation of both with octopamine (Figure 12b) in water or methanol solution was studied by 13C NMR. The enolimine form is favoured in methanol, while the ketoamine form predominates in water.92... 

Millard, B. J., Tippett, R. A., Couch, M. W., and Williams, C. M. (1977). Evidence for the lack of a carrier effect in the solvent extraction and determination of octopamine by gas chromatography-mass spectrometry. Biomed. Mass Spectrom. 4, 381-384. 

Reserpine. As mentioned earlier, the Rauwolfia alkaloid reserpine is noted for its ability to deplete aromatic biogenic amines in nervous tissue of mammals and insects. One of the more remarkable effects of reserpine in humans is to render individuals indifferent to environmental stimuli. Reserpine appears to have a similar effect on insects, although information is still relatively scanty. In the cockroach, Periplaneta americana, reserpine at 50 vg/g causes strong and long-lasting depletion of the aromatic biogenic amines dopamine, octopamine, and 5-hydroxytryptamine (24). Numerous authors have noted that reserpine has tranquilizing effects on insects, e.g., the ant Formica rufa (30) and . americana (24,31). 

FIGURE 7.3 Effect of l-ethyl-3-methylimidazolium tertafluoroborate concentrations on retention factors (k ) of basic compounds. Symbols = octopamine o = synephrine = tyramine. (From Tang, F. et al. J. Chromatogr. A. 2006,1125,182-188. With permission from Elsevier Science.)... 

Endogenous biogenic amines in the brain include catecholamines [NE (noradrenaline, NA), dopamine (DA), epinephrine (adrenaline)] 5-HT, histamine, and the so-called trace amines (P-phenylethylamine, tyramine, tryptamine, and octopamine). These amines have in common a arylalkylamine stmcture, and all have been implicated in the etiology of one or more psychiatric disorders and/or in therapeutic and/or adverse effects of drugs used to treat such disorders. In this review on depression, the focus in the case of biogenic amines will be on 5-HT, NE, and DA, although epinephrine and histamine and trace amines have also been implicated (see the section on Other Antidepressant Approaches and Targets ). 

Vanderlinden C, Mallefet J. Synergic effects of tryptamine and octopamine on ophiuroid luminescence (Echinodermata). In press J Exp Biol 2004. 

Because of our earlier observations that octopamine might be a neurotransmitter in insects but not vertebrates, several years ago we carried out an experiment to determine whether large doses of exogenous octopamine might exert detrimental behavioral effects in insects, analogous to what might happen if a vertebrate received an overdose of adrenalin or amphetamine. As a control, we decided to compare the activity of octopamine (chemically para-octopamine) with a positional isomer, meta-octopamine, which we found had little activity on insect adenylate cyclase (17). 

Figure 1. Antifeeding effects of para-octopamine versus meta-octopamine (a positional isomer with little activity as an agonist of insect adenylate cyclase), when sprayed on tomato leaves which were then fed to first instar Manduca sexta larvae.

TABLE I. Effects of Phenyliminoimidazolidines (NC-5 and NC-7), Octopamine (OCT), and a Formamidine (DDCDM) on Activating Adenylate Cyclase in Three Insect Species... 

Table VIII gives the effects on levels of dopamine and its precursor DOPA after exposure of bulb mites in vials precoated with chlordimeform. Chlordimeform resulted in an initial increase in levels of dopamine and DOPA after 24 hours, DOPA levels still were increased, but there was a significant decrease in levels of dopamine (23). In other studies (22), it was shown that whole homogenates of bulb mites rapidly metabolized PEA, but were appreciably less active against tryptamine, 5-hydroxytryptamine, and dopamine. Moreover, no deamination of octopamine was detected (Table IX). PEA metabolism by bulb mite homogenates was inhibited...

The stimulation of the octopaminergic nervous system of invertebrates is a proven strategy for the control of important pest species. This has been achieved in the past by the use of octopamine receptor agonists such as formamidine and imidazoline derivatives. However, other potential strategies to achieve this end include the inhibition of cyclic nucleotide phosphodiesterase, inhibition of the neural reuptake of octopamine, and inhibition of octopamine N-acetyltransferase. Using the American cockroach nervous system, formamidines were found to inhibit both the uptake and acetylation of octopamine, but not with a potency comparable to their effect on octopamine receptors. The tricyclic antidepressant, desipramine, and the benzylamine, xylamine, were the most active inhibitors of these octopamine removal systems. The pharmacological profiles for uptake and N-acetylation appear to be quite similar, but differ from that of the adenylate cyclase-linked octopamine receptor. 

Effects of Drugs on the Uptake of Octopamine. Several drugs were tested for their effects on both components (Na-dependent and Na-independent) of uptake. The final concentration of IcH ]-octopamine (2 uM) was chosen so that about 50% of the uptake was Na-dependent and 50% was Na-independent. Based on the study of Evans (21) t the former fraction, which is readily saturable and shows a high affinity for OA, probably relates to one or more specific uptake systems, while the Na-independent fraction is not readily saturable, shows a low affinity for OA and may relate to its absorption onto the perineurium. Drugs were assayed on both fractions at 0.1 mM. No significant 020%) inhibition of the Na-independent fraction was seen with any compound. However, several of these agents proved to be effective inhibitors of Na-dependent uptake (Table III). 

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