Central nervous system octopamine

Figure 2. Distribution of octopamine throughout selected parts of the central nervous system of Schistocerca americana gregaria.

II illustrates some of the possible targets for octopamine within the central nervous system, and indicates that octopamine plays an important physiological role as a transmitter or modulator in this area. In addition, injections of octopamine or its mimics into the haemolymph or ganglia, induces behavioural responses. Honeybees show enhanced responsiveness to light and olfactory stimuli after injection of octopamine into the brain (51.73). Blowflies develop a decreased threshold for the intake of sucrose solutions and also consume more sucrose after the injection of octopamine or related compounds (50), while cockroaches exhibit anorexia (74). 

In view of the ability of the formamidines and imidazolines to upset the behaviour of certain pest species, it seems likely that the central nervous system may well be an important site of action for such compounds, and highlights the need for further, more detailed studies, upon the central actions of octopamine. 

Extensive pharmacological investigations of octopamine receptors have been reported for locust skeletal muscle (87), firefly lantern (8j2, 89), tobacco hornworm central nervous system (88,89),... 

Interest in octopamine receptors has grown with the discovery that a novel group of pesticides, the formamidines, are octopamine agonists (95). Thus chlordimeform (CDM) or demethylchlordimeform (DCDM) are able to activate octopamine receptors in firefly lantern (95,96), tobacco hornworm central nervous system (88), locust skeletal muscle (97), locust oviduct muscle (91,), locust corpora cardiaca (98), locust fat body (99). and cockroach haemocytes (39). 

The biogenic amine octopamine (OA) is widely recognized as an important neuroregulator in many invertebrates. It has been proposed as a neurotransmitter in the firefly light organ, and as a neuromodulator of muscle action and a neurohormone in the locust (J, 2). Octopamine also appears to act on central nervous system (CNS) sites affecting coordinated motor actions (3,4), and has been shown to modulate CNS thresholds for feeding in blowflies (5), and olfaction in honeybees (6). 

The chemical mediators in the central nervous system of insects are far from completely explored, but acetylcholine (ACh) and octopamine (2.35) play important roles. The neurotransmitter at insect ganglia is acetylcholine, but that at the neuromuscular junction is not acetylcholine but L-glutamic acid (Usherwood and Machili, 1968), and for this neurotransmitter, no selective antagonist has yet been found. The receptors for the neurotransmitters are well protected by selectively permeable membranes. 

Lee H.M. and Wyse G.A. 1991. Immunocytochemical localization of octopamine in the central nervous system of Limulus polyphemus A light and electron microscopic study. /. Comp. Neurol. 307 683-694. 

Kononenko NL, Woflenberg H, Pfluger HJ (2009) Tyramine as an independent transmitter and a precursor of octopamine in the Locust central nervous system an immunocy-tochemical study. J Comp Neurol 512 433-452... 

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... 

Octopamine is one of the most abundant biogenic amines found in the insect nervous system. Its ubiquitous presence in nervous systems coupled to its broad range of actions has led to a rapid accumulation of knowledge about this amine, which is considered to be the insect equivalent of epinephrine and norepinephrine. Octopamine has both central and peripheral actions, where it serves as a... 

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