Stereoisomeric identity of octopamine in the central nervous system of invertebrates

Comparative antiradical activity and molecular Docking/Dynamics analysis of octopamine and norepinephrine: the role of OH groups

Octopamine is a neurotransmitter in invertebrates and a phenol analog of norepinephrine. The crystallographic and spectral (UV-visUV, and NMR) characteristics of octopamine were investigated experimentally and theoretically by applying appropriate level of theory, B3LYP-D3BJ/6-311++G(d,p), which reproduced well the experimental bond lengths and angles. The intramolecular interactions governing the stability of conformers were described by NBO and QTAIM analyses. The antiradical potencies of octopamine and norepinephrine towards DPPH and ABTS⁺ were examined with special emphasis on the preferred mechanism and effect of catechol moiety. Several techniques were used to distinguish Hydrogen Atom Transfer (HAT) and Proton Coupled Electron Transfer (PCET) mechanisms for reaction with DPPH. The calculated rate constants of the reactions with both radicals showed that Sequential Proton Loss Electron Transfer (SPLET) mechanism was dominant both thermodynamically and kinetically, with values of thermodynamic functions and rate constants clearly proving the importance of the second hydroxyl group in structure. The Molecular Docking and afterward Molecular Dynamics calculations of formed complexes between octopamine/norepinephrine with β1- and β2- adrenergic receptors examined in details the interactions that lead to the formation of stable complexes. The number of strong interactions of amino acids with norepinephrine was higher, but the absence of hydroxyl group in octopamine did not lead to a significant change in the type of interactions and stability. The formed complexes showed higher flexibility of amino acids, similar compactness of structure as proteins and increased interatomic distances of the backbone when compared to pure proteins.

Molecular cloning and heterologous expression of an alpha-adrenergic-like octopamine receptor from the silkworm Bombyx mori

A cDNA encoding an octopamine (OA) receptor (BmOAR1) was isolated from the nerve tissue of silkworm (Bombyx mori) larvae. Comparison of amino acid sequences showed that BmOAR1 is highly identical to OA receptors isolated from Periplaneta americana (Pa oa(1)), Apis mellifera (AmOA1), and Drosophila melanogaster (OAMB or DmOA1A). BmOAR1 was stably expressed in HEK-293 cells. OA above 1 microM led to an increase in intracellular cyclic AMP concentration ([cAMP](i)). The synthetic OA-receptor agonist demethylchlordimeform also elevated [cAMP](i) to the same maximal level (approximately 5-fold over the basal level) as that induced by OA. However, other biogenic amines, tyramine and dopamine, and chlordimeform were without effects. The [cAMP](i) level raised by OA was lowered by antagonists; the rank order of antagonist activity was chlorpromazine > mianserin = yohimbine. Cyproheptadine and metoclopramide had little effect. OA above 100 nM induced a transient or sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), depending on the concentration of OA. Sequence homology and functional analysis data indicate that BmOAR1 is an alpha-adrenergic-like OA receptor of B. mori.

Activities of octopamine and synephrine stereoisomers on octopaminergic receptor subtypes in locust skeletal muscle

The activities of the (-) and (+)- forms of p-, m- and o-octopamine and p- and m-synephrine have been compared on the different subtypes of octopamine receptor present in the extensor-tibiae neuromuscular preparation from the locust hindleg. The rank order of potency of the (-)-forms on the OCTOPAMINE2A receptors was p-synephrine greater than p-octopamine greater than m-octopamine greater than o-octopamine greater than m-synephrine whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than m-octopamine. (+)-m-Synephrine and (+)-o-octopamine had no effect on this class of receptor when tested up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE2B receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine whilst the rank order of the (+)-forms was p-octopamine greater than p-synephrine greater than m-octopamine greater than o-octopamine. (+)-m-Synephrine again had no effect up to a concentration of 10(-3) M. The rank order of potency of the (-)-forms on the OCTOPAMINE1 receptors was p-synephrine greater than p-octopamine greater than m-synephrine greater than m-octopamine greater than o-octopamine, whilst the rank order of the (+)-forms was p-synephrine greater than p-octopamine greater than o-octopamine greater than m-synephrine greater than m-octopamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of glycogen phosphorylase activity in fat body of Locusta migratoria and Periplaneta americana

Saline extracts of the corpus cardiacum (CC) of Locusta migratoria activate glycogen phosphorylase in locust fat body. The response of phosphorylase to CC extracts and to synthetic adipokinetic hormone (AKH) suggests that the factor responsible for the activating effect of the CC on phosphorylase is AKH, supplemented to a minor degree with Compound II. Octopamine does not influence fat body phosphorylase activity in locusts, however, it elicits a rapid short-term hyperlipemia. In cockroaches, Periplaneta americana, injection of octopamine results in a strong activation of fat body phosphorylase within 1 min. Cockroach CC extract exerts a more prolonged effect on phosphorylase activity than does octopamine.