Characterization of the tyraminergic system in the central nervous system of the locust,Locusta migratoria migratoides (original) (raw)
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Tyramine: From octopamine precursor to neuroactive chemical in insects
General and Comparative Endocrinology, 2009
It is well acknowledged that tyramine acts as the biosynthetic intermediate precursor for octopamine. This fact has biased the interpretation of biological effects of tyramine towards an artifact of it being a partial agonist on octopamine receptors. Over recent years there has been an accumulation of evidence to show that tyramine is in fact a neuroactive chemical in its own right, with diverse physiological/behavioral roles. In addition, tyramine plays a unique role in a non-neuronal tissue, namely the Malpighian tubules. This review examines this evidence, taking into account the criteria that need to be satisfied in order to claim neuroactive chemical status. Thus, the evidence points to tyramine being synthesized by, and present in, neurons; capable of being released from neurons; removed by high affinity plasma membrane transporters; acting upon specific tyramine receptors; and producing physiological/behavioral effects that can be blocked by antagonists. This composite evidence is strong, although the final proof still awaits analysis on a uniquely identifiable tyraminergic neuron as has been possible with octopamine.
Journal of Insect Physiology, 1993
Tyrosine hydroxylase-like immunoreactivity and serotonin-like immunoreactivity of the subesophageal ganglion of the locust, Locustu mipzroria, reveals several pairs of cells. One pair of tyrosine hydroxylase-like positive cells (SNl) and one pair of serotonin-like positive cells (SN2) both project through nerve 7b to the salivary glands, where they branch extensively over the acini. Individual acinl receive innervation from both SNl and SN2. Co-localization of immunoreactivity was never observed. Neurons that stain positively for tyrosine hydroxylase-like immunoreactivity are considered to be catecholaminergic since tyrosine hydroxylase is the first and rate limiting enzyme in the pathway for the production of catecholamines.
Brain Research, 1976
have shown that catecholamines occur in insect nervous tissue, with dopamine as the predominant compound. Murdock et al. 22 and Emson et al. 9 have reported that homogenates of locust nerve ganglia contain aromatic amino acid decarboxylase, but no detailed study has been carried out on the enzymes catalysing the biosynthesis of catecholamines in insect nervous tissue. This report describes a study on the metabolism of L-[14C]tyrosine, [14C]tyramine and L-[14C]3,4-dihydroxyphenylalanine (L-DOPA) by cerebral and thoracic ganglia of the desert locust, Schistocerca gregaria. Cerebral, meso-and metathoracic ganglia were dissected from adult desert locust S. gregaria (Larujon Locust Suppliers, c/o Welsh Mountain Zoo, Colwyn Bay, N. Wales), as much of the tracheal system as possible removed, and the intact ganglia rinsed thoroughly in locust saline a0. Intact ganglia were incubated at 37 °C in locust saline (100 td, pH 6.8) containing 0.5 #Ci of either L-[U-14C]tyrosine (405 mCi/mmole), [2-14C]tyramine hydrochloride (20-40 mCi/mmole) or e-[2-14C]3,4-dihydroxyphenylalanine (20-40 mCi/mmole) supplied by the Radiochemical Centre, Amersham, Bucks., England. After 2 h incubation, ganglia (either 3 cerebral or 3 meso-plus 3 metathoracic) were homogenized in 50/A incubation medium, in microhomogenization tubes z4, and proteins precipitated by adding an equal volume of acetone-0.1 N HC1 (9:1, v/v) and cooling to-20 °C for 30 rain. Precipitated protein was removed by centrifugation in a haematocrit centrifuge, the supernatant dried down in vacuo and the residue taken up in acetone-0.1 N HCI (9:1, v/v; 10/A). Aliquots were chromatographed in two dimensions, on 10 cm × 10 cm Silica Gel G plastic backed sheets (Camlab, Cambridge, England), using the solvent systems shown in Fig. 1. Where appropriate, 1 /zg of the standards, indicated in Fig. 1, were co-chromatographed with tissue extract to help identify radioactive metabolites. Standards were detected with diazotized sulphanilic acid 2s and radioactive compounds located by autoradiography, using Kodirex X-ray film (KD54T) for 4-7 days. Radioactive spots were scraped off the chromatograms, dispersed in a stable emulsion formed by adding water (1 ml) to toluene-Triton X-100 (2:1, v/v; 3 ml) containing PPO (0.5 g/l) and POPOP (0.1 g/l) as scintillant, and the radioactivity was determined by liquid scintillation counting. Data are expressed as
Journal of Comparative Neurology, 2013
The central complex is a group of modular neuropils in the insect brain with a key role in visual memory, spatial orientation, and motor control. In desert locusts the neurochemical organization of the central complex has been investigated in detail, including the distribution of dopamine‐, serotonin‐, and histamine‐immunoreactive neurons. In the present study we identified neurons immunoreactive with antisera against octopamine, tyramine, and the enzymes required for their synthesis, tyrosine decarboxylase (TDC) and tyramine β‐hydroxylase (TBH). Octopamine‐ and tyramine immunostaining in the central complex differed strikingly. In each brain hemisphere tyramine immunostaining was found in four neurons innervating the noduli, 12–15 tangential neurons of the protocerebral bridge, and about 17 neurons that supplied the anterior lip region and parts of the central body. In contrast, octopamine immunostaining was present in two bilateral pairs of ascending fibers innervating the upper d...
Dopaminergic control of foregut contractions in Locusta migratoria
Journal of Insect Physiology, 2008
Tyrosine hydroxylase-like immunoreactivity is present in cell bodies and processes in the brain and optic lobes of Locusta migratoria, with processes projecting along the frontal connectives to form a neuropile within the frontal ganglion. Immunoreactive cell bodies and processes are also evident in the hypocerebral and ventricular ganglia with processes extending over the foregut. Tyrosine hydroxylase is the rate-limiting enzyme in dopamine biosynthesis, and high-performance liquid chromatography coupled to electrochemical detection was used to confirm the presence of dopamine in the innervation to the foregut. Spontaneous foregut contractions are under the control of the ventricular ganglia and are absent when these ganglia are removed. Dopamine leads to an inhibition of both the amplitude and frequency of phasic contractions of the foregut that are produced when the ventricular ganglia are left attached. Dopamine has direct effects on the foregut muscle in the absence of the ventricular ganglia, inhibiting a proctolin-induced contraction in a dose-dependent manner.
The Effect of Octopamine on the Locust Stomatogastric Nervous System
Frontiers in Physiology, 2012
Octopamine (OA) is a prominent neuromodulator of invertebrate nervous systems, influencing multiple physiological processes. Among its many roles in insects are the initiation and maintenance of various rhythmic behaviors. Here, the neuromodulatory effects of OA on the components of the locust stomatogastric nervous system were studied, and one putative source of OA modulation of the system was identified. Bath application of OA was found to abolish the endogenous rhythmic output of the fully isolated frontal ganglion (FG), while stimulating motor activity of the fully isolated hypocerebral ganglion (HG). OA also induced rhythmic movements in a foregut preparation with intact HG innervation. Complex dose-dependent effects of OA on interconnected FG-HG preparations were seen: 10 −5 M OA accelerated the rhythmic activity of both the HG and FG in a synchronized manner, while 10 −4 M OA decreased both rhythms. Intracellular stimulation of an identified octopaminergic dorsal unpaired median neuron in the subesophageal ganglion was found to exert a similar effect on the FG motor output as that of OA application. Our findings suggest a mechanism of regulation of insect gut patterns and feeding-related behavior during stress and times of high energy demand.
Journal of Insect Physiology, 1988
The storage lobe of the locust corpus cardiacurn consists primarily of neurosecretory cell axons and terminals and serves as a neurohaemal organ for the release of several neuropeptides. Biogenic amines have previously been identified in the storage lobe of the adult corpus cardiacum, and interest in the functional roles of these amines has arisen due to their modulatory actions on numerous physiological processes in insects. It has been suggested that these compounds may be released from the storage lobe as neurohormones, however an alternative possibility is that they serve as neurotransmitters or neuromodulators which act at sites within the corpus cardiacum proper. The present studies were undertaken to determine if specific amine receptor-adenylate cyclases exist in the storage lobe. Octopamine increases the CAMP content of intact cells in the storage lobes of adult and Sth-instar locusts. Forskolin and 5-HT also enhance CAMP levels in the storage lobe however additivity experiments suggest that 5-HT may be interacting with octopamine binding sites. Dopamine is a poor agonist and norepinephrine has no effect on CAMP content. In adult storage lobes octopamine acts on receptors that have pharmacological similarities to octopamine receptors of identified octopaminergic systems. There thus appears to be an octopamine receptor-adenylate cyclase complex in this tissue. These results suggest that octopamine may be involved in regulating some aspect of neurosecretion in the storage lobe of the locust corpus cardiacum. In addition, significantly higher levels of cGMP were found in the storage lobe compared to those reported for the neighbouring glandular lobe, indicating a possible functional role for this cyclic nucleotide.
Brain Research, 1973
In this study, the locust cerebral ganglion was shown to contain intraneuronal dopamine and noradrenaline, with a predominance of dopamine. The neuropil structures contained mostly one of these catecholamines, but a possible mixed intraneuronal appearance could not be excluded. 5-Hydroxytryptamine-containing cell bodies were found in the optical lobe. After incubation with nialamide, a group of cell bodies in the pars intercerebralis exhibited a fluorescence with an excitation maximum typical for 5-hydroxytryptamine but with an atypical emission maximum. This fluorescence might have come from a mixture of two amines, from precursors or metabolites of 5-hydroxytryptamine, or from an additional presence of accumulated catecholamines. Chemical analysis confirmed the presence of dopamine, noradrenaline and 5-hydroxytryptamine.