The first myriapod genome sequence reveals conservative arthropod gene content and genome organisation in the centipede Strigamia maritima.

Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history.

GPCR-mediated rapid, non-genomic actions of steroids: comparisons between DmDopEcR and GPER1 (GPR30).

Steroid hormones classically mediate their actions by binding to intracellular receptor proteins that migrate to the nucleus and act as transcription factors to change gene expression. However, evidence is now accumulating for rapid, non-genomic effects of steroids. There is considerable controversy over the mechanisms underlying such effects. In a number of cases evidence has been presented for the direct activation of G-protein coupled receptors (GPCRs) by steroids, either at the plasma membrane, or at intracellular locations. Here, we will focus on the non-genomic actions of ecdysteroids on a Drosophila GPCR, DopEcR (CG18314), which can be activated by both ecdysone and the catecholamine, dopamine. We will also point out parallels between this system and the activation of the vertebrate GPCR, GPER1 (GPR30), which is thought to be activated by 17ß-estradiol. We propose that the cellular localization and signalling properties of both DopEcR and GPER1 may be cell specific and depend upon their interactions with both accessory molecules and signalling pathways.

A comparison of the signalling properties of two tyramine receptors from Drosophila.

In invertebrates, the phenolamines, tyramine and octopamine, mediate many functional roles usually associated with the catecholamines, noradrenaline and adrenaline, in vertebrates. The α- and ß-adrenergic classes of insect octopamine receptor are better activated by octopamine than tyramine. Similarly, the Tyramine 1 subgroup of receptors (or Octopamine/Tyramine receptors) are better activated by tyramine than octopamine. However, recently, a new Tyramine 2 subgroup of receptors was identified, which appears to be activated highly preferentially by tyramine. We examined immunocytochemically the ability of CG7431, the founding member of this subgroup from Drosophila melanogaster, to be internalized in transfected Chinese hamster ovary (CHO) cells by different agonists. It was only internalized after activation by tyramine. Conversely, the structurally related receptor, CG16766, was internalized by a number of biogenic amines, including octopamine, dopamine, noradrenaline, adrenaline, which also were able to elevate cyclic AMP levels. Studies with synthetic agonists and antagonists confirm that CG16766 has a different pharmacological profile to that of CG7431. Species orthologues of CG16766 were only found in Drosophila species, whereas orthologues of CG7431 could be identified in the genomes of a number of insect species. We propose that CG16766 represents a new group of tyramine receptors, which we have designated the Tyramine 3 receptors.

Identification and characterization of a novel amphioxus dopamine D-like receptor.

Dopamine receptors function to control many aspects of motor control and other forms of behaviour in both vertebrates and invertebrates. They can be divided into two main groups (D(1) and D(2)) based on sequence similarity, ligand affinity and effector coupling. However, little is known about the pharmacology and functionality of dopamine receptors in the deuterostomian invertebrates, such as the cephalochordate amphioxus (Branchiostoma floridae) which has recently been placed as the most basal of all the chordates. A bioinformatic study shows that amphioxus has at least three dopamine D(1)-like receptor sequences. One of these receptors, AmphiD(1)/beta, was found to have high levels of sequence similarity to both vertebrate D(1) receptors and to beta-adrenergic receptors. Here, we report on the cloning of AmphiD(1)/beta from an adult amphioxus cDNA library, and its pharmacological characterization subsequent to its expression in both mammalian cell lines and Xenopus oocytes. It was found that AmphiD(1)/beta has a similar pharmacology to vertebrate D(1) receptors, including responding to benzodiazepine ligands. The pharmacology of the receptor exhibits 'agonist-specific coupling' depending upon the second messenger pathway to which it is linked. Moreover, no pharmacological characteristics were observed to suggest that AmphiD(1)/beta may be an amphioxus orthologue of vertebrate beta-adrenergic receptors.

Aldosterone, STX and amyloid-ß1-42 peptides modulate GPER (GPR30) signalling in an embryonic mouse hippocampal cell line (mHippoE-18).

The GPCR, GPER, mediates many of the rapid, non-genomic actions of 17ß-estradiol in multiple tissues, including the nervous system. Controversially, it has also been suggested to be activated by aldosterone, and by the non-steroidal diphenylacrylamide compound, STX, in some preparations. Here, the ability of the GPER agonist, G-1, and aldosterone in the presence of the mineralocorticoid receptor antagonist, eplerenone, to potentiate forskolin-stimulated cyclic AMP levels in the hippocampal clonal cell line, mHippoE-18, are compared. Both stimulatory effects are blocked by the GPER antagonist G36, by PTX, (suggesting the involvement of Gi/o G proteins), by BAPTA-AM, (suggesting they are calcium sensitive), by wortmannin (suggesting an involvement of PI3Kinase) and by soluble amyloid-ß peptides. STX also stimulates cyclic AMP levels in mHippoE-18 cells and these effects are blocked by G36 and PTX, as well as by amyloid-ß peptides. This suggests that both aldosterone and STX may modulate GPER signalling in mHippoE-18 cells.

Rapid signalling responses via the G protein-coupled estrogen receptor, GPER, in a hippocampal cell line.

The rapid non-genomic actions of 17ß-estradiol in multiple tissues, including the nervous system, may involve the activation of the G-protein-coupled receptor, GPER. Different signalling pathways have been suggested to be activated by GPER in different cell lines and tissues. Controversially, GPER has also been suggested to be activated by the mineralocorticoid aldosterone, and by the non-steroidal diphenylacrylamide compound, STX, in some preparations. Evidence for the ability of the GPER agonist, G-1, and for aldosterone in the presence of the mineralocorticoid receptor antagonist, eplerenone, to potentiate forskolin-stimulated cyclic AMP levels in the hippocampal clonal cell line, mHippoE-18 is reviewed. The effects of both agents are blocked by the GPER antagonist G36, by PTX, (suggesting the involvement of Gi/o G proteins), by BAPTA-AM, (suggesting they are calcium sensitive), by wortmannin (suggesting an involvement of PI3Kinase) and by soluble amyloid-ß peptides. STX also stimulates cyclic AMP levels in mHippoE-18 cells and these effects are blocked by G36 and PTX, as well as by amyloid-ß peptides. This suggests that both aldosterone and STX may be capable of activating GPER in mHippoE-18 cells. Possible molecular mechanisms that may underlie these effects are discussed, together with possible forward directions for research on rapid non-genomic signalling by GPER, emphasising the importance of understanding the spatio-temporal aspects of its signalling in various tissues.

Eleven new putative aminergic G-protein coupled receptors from Amphioxus (Branchiostoma floridae): identification, sequence analysis and phylogenetic relationship.

We have identified eleven novel aminergic-like G-protein coupled receptor (GPCRs) sequences (named AmphiAmR1-11) by searching the genomic trace sequence database for the amphioxus species, Branchiostoma floridae. They share many of the structural motifs that have been used to characterize vertebrate and invertebrate aminergic GPCRs. A preliminary classification of these receptors has been carried out using both BLAST and Hidden Markov Model analyses. The amphioxus genome appears to express a number of D1-like dopamine receptor sequences, including one related to insect dopamine receptors. It also expresses a number of receptors that resemble invertebrate octopamine/tyramine receptors and others that resemble vertebrate alpha-adrenergic receptors. Amphioxus also expresses receptors that resemble vertebrate histamine receptors. Several of the novel receptor sequences have been identified in amphioxus cDNA libraries from a number of tissues.

Behavioral Sensitization to the Disinhibition Effect of Ethanol Requires the Dopamine/Ecdysone Receptor in Drosophila.

Male flies under the influence of ethanol display disinhibited courtship, which is augmented with repeated ethanol exposures. We have previously shown that dopamine is important for this type of ethanol-induced behavioral sensitization but the underlying mechanism is unknown. Here we report that DopEcR, an insect G-protein coupled receptor that binds to dopamine and steroid hormone ecdysone, is a major receptor mediating courtship sensitization. Upon daily ethanol administration, dumb and damb mutant males defective in D1 (dDA1/DopR1) and D5 (DAMB/DopR2) dopamine receptors, respectively, showed normal courtship sensitization; however, the DopEcR-deficient der males exhibited greatly diminished sensitization. der mutant males nevertheless developed normal tolerance to the sedative effect of ethanol, indicating a selective function of DopEcR in chronic ethanol-associated behavioral plasticity. DopEcR plays a physiological role in behavioral sensitization since courtship sensitization in der males was reinstated when DopEcR expression was induced during adulthood but not during development. When examined for the DopEcR's functional site, the der mutant's sensitization phenotype was fully rescued by restored DopEcR expression in the mushroom body (MB) αß and γ neurons. Consistently, we observed DopEcR immunoreactivity in the MB calyx and lobes in the wild-type Canton-S brain, which was barely detectable in the der brain. Behavioral sensitization to the locomotor-stimulant effect has been serving as a model for ethanol abuse and addiction. This is the first report elucidating the mechanism underlying behavioral sensitization to another stimulant effect of ethanol.

Rapid, nongenomic responses to ecdysteroids and catecholamines mediated by a novel Drosophila G-protein-coupled receptor.

Nongenomic response pathways mediate many of the rapid actions of steroid hormones, but the mechanisms underlying such responses remain controversial. In some cases, cell-surface expression of classical nuclear steroid receptors has been suggested to mediate these effects, but, in a few instances, specific G-protein-coupled receptors (GPCRs) have been reported to be responsible. Here, we describe the activation of a novel, neuronally expressed Drosophila GPCR by the insect ecdysteroids ecdysone (E) and 20-hydroxyecdysone (20E). This is the first report of an identified insect GPCR interacting with steroids. The Drosophila melanogaster dopamine/ecdysteroid receptor (DmDopEcR) shows sequence homology with vertebrate beta-adrenergic receptors and is activated by dopamine (DA) to increase cAMP levels and to activate the phosphoinositide 3-kinase pathway. Conversely, E and 20E show high affinity for the receptor in binding studies and can inhibit the effects of DA, as well as coupling the receptor to a rapid activation of the mitogen-activated protein kinase pathway. The receptor may thus represent the Drosophila homolog of the vertebrate "gamma-adrenergic receptors," which are responsible for the modulation of various activities in brain, blood vessels, and pancreas. Thus, DmDopEcR can function as a cell-surface GPCR that may be responsible for some of the rapid, nongenomic actions of ecdysteroids, during both development and signaling in the mature adult nervous system.

Characterisation of Signalling by the Endogenous GPER1 (GPR30) Receptor in an Embryonic Mouse Hippocampal Cell Line (mHippoE-18).

Estrogen can modulate neuronal development and signalling by both genomic and non-genomic pathways. Many of its rapid, non-genomic effects on nervous tissue have been suggested to be mediated via the activation of the estrogen sensitive G-protein coupled receptor (GPER1 or GPR30). There has been much controversy over the cellular location, signalling properties and endogenous activators of GPER1. Here we describe the pharmacology and signalling properties of GPER1 in an immortalized embryonic hippocampal cell line, mHippoE-18. This cell line does not suffer from the inherent problems associated with the study of this receptor in native tissue or the problems associated with heterologously expression in clonal cell lines. In mHippoE-18 cells, 17ß-Estradiol can mediate a dose-dependent rapid potentiation of forskolin-stimulated cyclic AMP levels but does not appear to activate the ERK1/2 pathway. The effect of 17ß-Estradiol can be mimicked by the GPER1 agonist, G1, and also by tamoxifen and ICI 182,780 which activate GPER1 in a variety of other preparations. The response is not mimicked by the application of the classical estrogen receptor agonists, PPT, (an ERα agonist) or DPN, (an ERß agonist), further suggesting that this effect of 17ß-Estradiol is mediated through the activation of GPER1. However, after exposure of the cells to the GPER1 specific antagonists, G15 and G36, the stimulatory effects of the above agonists are replaced by dose-dependent inhibitions of forskolin-stimulated cyclic AMP levels. This inhibitory effect is mimicked by aldosterone in a dose-dependent way even in the absence of the GPER1 antagonists. The results are discussed in terms of possible "Biased Antagonism" whereby the antagonists change the conformation of the receptor resulting in changes in the agonist induced coupling of the receptor to different second messenger pathways.

Insect octopamine receptors: a new classification scheme based on studies of cloned Drosophila G-protein coupled receptors.

Insect octopamine receptors are G-protein coupled receptors. They can be coupled to second messenger pathways to mediate either increases or decreases in intracellular cyclic AMP levels or the generation of intracellular calcium signals. Insect octopamine receptors were originally classified on the basis of second messenger changes induced in a variety of intact tissue preparations. Such a classification system is problematic if more than one receptor subtype is present in the same tissue preparation. Recent progress on the cloning and characterization in heterologous cell systems of octopamine receptors from Drosophila and other insects is reviewed. A new classification system for insect octopamine receptors into "alpha-adrenergic-like octopamine receptors (OctalphaRs)", "beta-adrenergic-like octopamine receptors (OctbetaRs)" and "octopamine/tyramine (or tyraminergic) receptors" is proposed based on their similarities in structure and in signalling properties with vertebrate adrenergic receptors. In future studies on the molecular basis of octopamine signalling in individual tissues it will be essential to identify the relative expression levels of the different classes of octopamine receptor present. In addition, it will be essential to identify if co-expression of such receptors in the same cells results in the formation of oligomeric receptors with specific emergent pharmacological and signalling properties.

Site-directed mutagenesis studies on the Drosophila octopamine/tyramine receptor.

The cloned Drosophila octopamine/tyramine receptor can be coupled to second messenger pathways in an agonist-specific fashion by the endogenously occurring biogenic amines, octopamine and tyramine, when expressed in Chinese hamster ovary cells. We have mutated to alanine a range of receptor amino acids that could potentially form hydrogen bonds with the beta-hydroxyl group of octopamine based on homologies with alpha- and beta-adrenergic receptor subtypes. After stable expression of the mutant receptors in CHO cells we have compared the ability of octopamine and tyramine to displace [(3)H]yohimbine binding to membrane fractions from the mutant cell lines with their ability to modulate adenylyl cyclase activity in intact cells. The results suggest that none of the mutated amino acids residues, at least in isolation, are likely to be involved in interactions with the beta-hydroxyl group of the octopamine side chain. It is possible that amino acids not mutated in the present study are somehow involved in this interaction. Alternatively, it is also possible that the beta-hydroxyl group of the octopamine side chain is capable of interacting with more than one of the amino acids mutated in the present study.

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.

Characterisation of AmphiAmR4, an amphioxus (Branchiostoma floridae) α2-adrenergic-like G-protein-coupled receptor.

Little is known about the evolutionary relationship between vertebrate adrenergic receptors and invertebrate octopamine and tyramine receptors. The complexity of the adrenergic signalling system is believed to be an innovation of the vertebrate lineage but the presence of noradrenaline has been reported in some invertebrate species. The cephalochordate, amphioxus (Branchiostoma floridae), is an ideal model organism for studying the evolution of vertebrate GPCRs, given its unique position at the base of the chordate lineage. Here, we describe the pharmacological characterisation and second messenger coupling abilities of AmphiAmR4, which clusters with α2-adrenergic receptors in a phylogenetic tree but also shares a high sequence similarity to invertebrate octopamine/tyramine receptors in both BLAST and Hidden Markov Model analyses. Thus, it was of particular interest to determine if AmphiAmR4 displayed similar functional properties to the vertebrate α2-adrenergic receptors or to invertebrate octopamine or tyramine receptors. When stably expressed in Chinese hamster ovary (CHO) cells, noradrenaline couples the receptor to both the activation of adenylyl cyclase and to the activation of the MAPKinase pathway. Pharmacological studies with a wide range of agonists and antagonists suggest that AmphiAmR4 functions as an α2-adrenergic-like receptor when expressed in CHO cells.

Characterisation of AmphiAmR11, an amphioxus (Branchiostoma floridae) D2-dopamine-like G protein-coupled receptor.

The evolution of the biogenic amine signalling system in vertebrates is unclear. However, insights can be obtained from studying the structures and signalling properties of biogenic amine receptors from the protochordate, amphioxus, which is an invertebrate species that exists at the base of the chordate lineage. Here we describe the signalling properties of AmphiAmR11, an amphioxus (Branchiostoma floridae) G protein-coupled receptor which has structural similarities to vertebrate α2-adrenergic receptors but which functionally acts as a D2 dopamine-like receptor when expressed in Chinese hamster ovary -K1 cells. AmphiAmR11 inhibits forskolin-stimulated cyclic AMP levels with tyramine, phenylethylamine and dopamine being the most potent agonists. AmphiAmR11 also increases mitogen-activated protein kinase activity and calcium mobilisation, and in both pathways, dopamine was found to be more potent than tyramine. Thus, differences in the relative effectiveness of various agonists in the different second messenger assay systems suggest that the receptor displays agonist-specific coupling (biased agonism) whereby different agonists stabilize different conformations of the receptor which lead to the enhancement of one signalling pathway over another. The present study provides insights into the evolution of α2-adrenergic receptor signalling and support the hypothesis that α2-adrenergic receptors evolved from D2-dopamine receptors. The AmphiAmR11 receptor may represent a transition state between D2-dopamine receptors and α2-adrenergic receptors.

A characterization of the Manduca sexta serotonin receptors in the context of olfactory neuromodulation.

Neuromodulation, the alteration of individual neuron response properties, has dramatic consequences for neural network function and is a phenomenon observed across all brain regions and taxa. However, the mechanisms underlying neuromodulation are made complex by the diversity of neuromodulatory receptors expressed within a neural network. In this study we begin to examine the receptor basis for serotonergic neuromodulation in the antennal lobe of Manduca sexta. To this end we cloned all four known insect serotonin receptor types from Manduca (the Ms5HTRs). We used phylogenetic analyses to classify the Ms5HTRs and to establish their relationships to other insect serotonin receptors, other insect amine receptors and the vertebrate serotonin receptors. Pharmacological assays demonstrated that each Ms5HTR was selective for serotonin over other endogenous amines and that serotonin had a similar potency at all four Ms5HTRs. The pharmacological assays also identified several agonists and antagonists of the different Ms5HTRs. Finally, we found that the Ms5HT1A receptor was expressed in a subpopulation of GABAergic local interneurons suggesting that the Ms5HTRs are likely expressed heterogeneously within the antennal lobe based on functional neuronal subtype.

Amphioxus expresses both vertebrate-type and invertebrate-type dopamine D(1) receptors.

The cephalochordate amphioxus (Branchiostoma floridae) has recently been placed as the most basal of all the chordates, which makes it an ideal organism for studying the molecular basis of the evolutionary transition from invertebrates to vertebrates. The biogenic amine, dopamine regulates many aspects of motor control in both vertebrates and invertebrates, and in both cases, its receptors can be divided into two main groups (D1 and D2) based on sequence similarity, ligand affinity and effector coupling. A bioinformatic study shows that amphioxus has at least three dopamine D1-like receptor sequences. We have recently characterized one of these receptors, AmphiD1/ß, which was found to have high levels of sequence similarity to both vertebrate D1 receptors and to ß-adrenergic receptors, but functionally appeared to be a vertebrate-type dopamine D(1) receptor. Here, we report on the cloning of two further dopamine D(1) receptors (AmphiAmR1 and AmphiAmR2) from adult amphioxus cDNA libraries and their pharmacological characterisation subsequent to their expression in cell lines. AmphiAmR1 shows closer structural similarities to vertebrate D(1)-like receptors but shows some pharmacological similarities to invertebrate "DOP1" dopamine D(1)-like receptors. In contrast, AmphiAmR2 shows closer structural and pharmacological similarities to invertebrate "INDR"-like dopamine D(1)-like receptors.

NMR analysis of Caenorhabditis elegans FLP-18 neuropeptides: implications for NPR-1 activation.

Phe-Met-Arg-Phe-NH2 (FMRFamide)-like peptides (FLPs) are the largest neuropeptide family in animals, particularly invertebrates. FLPs are characterized by a C-N-terminal gradient of decreasing amino acid conservation. Neuropeptide receptor 1 (NPR-1) is a G-protein coupled receptor (GPCR), which has been shown to be a strong regulator of foraging behavior and aggregation responses in Caenorhabditis elegans. Recently, ligands for NPR-1 were identified as neuropeptides coded by the precursor genes flp-18 and flp-21 in C. elegans. The flp-18 gene encodes eight FLPs including DFDGAMPGVLRF-NH2 and EMPGVLRF-NH2. These peptides exhibit considerably different activities on NPR-1, with the longer one showing a lower potency. We have used nuclear magnetic resonance and biological activity to investigate structural features that may explain these activity differences. Our data demonstrate that long-range electrostatic interactions exist between N-terminal aspartates and the C-terminal penultimate arginine as well as N-terminal hydrogen-bonding interactions that form transient loops within DFDGAMPGVLRF-NH2. We hypothesize that these loops, along with peptide charge, diminish the activity of this peptide on NPR-1 relative to that of EMPGVLRF-NH2. These results provide some insight into the large amino acid diversity in FLPs.

Identification and characterization of a novel family of Drosophila beta-adrenergic-like octopamine G-protein coupled receptors.

Insect octopamine receptors carry out many functional roles traditionally associated with vertebrate adrenergic receptors. These include control of carbohydrate metabolism, modulation of muscular tension, modulation of sensory inputs and modulation of memory and learning. The activation of octopamine receptors mediating many of these actions leads to increases in the levels of cyclic AMP. However, to date none of the insect octopamine receptors that have been cloned have been convincingly shown to be capable of directly mediating selective and significant increases in cyclic AMP levels. Here we report on the identification and characterization of a novel, neuronally expressed family of three Drosophila G-protein coupled receptors that are selectively coupled to increases in intracellular cyclic AMP levels by octopamine. This group of receptors, DmOct beta1R (CG6919), DmOct beta2R (CG6989) and DmOct beta3R (CG7078) shows homology to vertebrate beta-adrenergic receptors. When expressed in Chinese hamster ovary cells all three receptors show a strong preference for octopamine over tyramine for the accumulation of cyclic AMP but show unique pharmacological profiles when tested with a range of synthetic agonists and antagonists. Thus, the pharmacological profile of individual insect tissue responses to octopamine might vary with the combination and the degree of expression of the individual octopamine receptors present.

Peripheral neurosecretory cells on the thoracic median nerves of the locust, Schistocerca gregaria.

The distribution of neutral red staining peripheral cell bodies along the nerve trunks of the thoracic median nervous system of the locust, Schistocerca gregaria, is described. Backfilling of the cells with cobalt chloride solution reveals that they are neurones with characteristic axonal processes that terminate in the neurohaemal areas of the median nerve. The neurones react with the dye acridine orange, indicating their neurosecretory nature. This is confirmed by their ultrastructural appearance at the electron microscope level. The distribution and staining properties of the cells are compared with those of peripheral neurones from other insects and the nature of their neurosecretory product is discussed.