Adipokinetic hormone (AKH), energy budget and their effect on feeding and gustatory processes of foraging honey bees.

The adipokinetic hormone (AKH) of insects is considered an equivalent of the mammalian hormone glucagon as it induces fast mobilization of carbohydrates and lipids from the fat body upon starvation. Yet, in foraging honey bees, which lack fat body storage for carbohydrates, it was suggested that AKH may have lost its original function. Here we manipulated the energy budget of bee foragers to determine the effect of AKH on appetitive responses. As AKH participates in a cascade leading to acceptance of unpalatable substances in starved Drosophila, we also assessed its effect on foragers presented with sucrose solution spiked with salicin. Starved and partially-fed bees were topically exposed with different doses of AKH to determine if this hormone modifies food ingestion and sucrose responsiveness. We found a significant effect of the energy budget (i.e. starved vs. partially-fed) on the decision to ingest or respond to both pure sucrose solution and sucrose solution spiked with salicin, but no effect of AKH per se. These results are consistent with a loss of function of AKH in honey bee foragers, in accordance with a social life that implies storing energy resources in the hive, in amounts that exceed individual needs.

Antidepressant and antinociceptive activities in animal models and in vitro assessment of the anti-thyroid activity of bis(DL-pyroglutamate)magnesium complex.

BACKGROUND: Magnesium is an essential element related with biochemistry of the brain and different types of depression have been associated with its deficiency. METHODS: The structure of a novel magnesium bis(DL-pyroglutamate) (Mg(DL-pGlu)2) was elucidated by X-ray crystallography. Wistar rats were used in the in vivo experiments. The antidepressant-like effect was assessed by the forced swim test (FST) and the antinociceptive activity was evaluated using hot plate test. In both, non-specific effects were evaluated by the open field test. Anti-thyroid activity was examined using Lang's method. Albumin binding behavior was evaluated by 3D fluorescence spectroscopy. RESULTS: For the Mg(DL-pGlu)2 complex (30 mg/kg), the FST test on Wistar rats revealed a decrease of 22% in the immobility time and an increment of 106% in the swimming time. The compound alters neither the locomotor activity nor the body weight after chronic administration. At the same dose, it showed antinociceptive activity, increasing the response latency. It blocks iodination reactions generating a charge transfer complex with iodine hence indicating anti-thyroid activity (Kc = 45366.5 ±â€¯29 M-1). Albumin 3D fluorescence spectroscopy experiments showed intensity increase of peak A and decrease of peak B. CONCLUSIONS: The results showed that the new compound produced a lowering of the immobility time and an increment of the swimming ability of the rats. The compound is able to increase the response latency in 70.0%, to capture iodine (anti-thyroid activity) and to interact with albumin through covalent type of interaction of the free NH groups.

Assessment of neuropeptide binding sites and the impact of biostable kinin and CAP2b analogue treatment on aphid (Myzus persicae and Macrosiphum rosae) stress tolerance.

BACKGROUND: Neuropeptides are regulators of critical life processes in insects and, due to their high specificity, represent potential targets in the development of greener insecticidal agents. Fundamental to this drive is understanding neuroendocrine pathways that control key physiological processes in pest insects and the screening of potential analogues. The current study investigated neuropeptide binding sites of kinin and CAPA (CAPA-1) in the aphids Myzus persicae and Macrosiphum rosae and the effect of biostable analogues on aphid fitness under conditions of desiccation, starvation and thermal (cold) stress. RESULTS: M. persicae and M. rosae displayed identical patterns of neuropeptide receptor mapping along the gut, with the gut musculature representing the main target for kinin and CAPA-1 action. While kinin receptor binding was observed in the brain and VNC of M. persicae, this was not observed in M. rosae. Furthermore, no CAPA-1 receptor binding was observed in the brain and VNC of either species. CAP2b/PK analogues (with CAPA receptor cross-activity) were most effective in reducing aphid fitness under conditions of desiccation and starvation stress, particularly analogues 1895 (2Abf-Suc-FGPRLa) and 2129 (2Abf-Suc-ATPRIa), which expedited aphid mortality. All analogues, with the exception of 2139-Ac, were efficient at reducing aphid survival under cold stress, although were equivalent in the strength of their effect. CONCLUSION: In demonstrating the effects of analogues belonging to the CAP2b neuropeptide family and key analogue structures that reduce aphid fitness under stress conditions, this research will feed into the development of second generation analogues and ultimately the development of neuropeptidomimetic-based insecticidal agents. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Assessment of the role of TRH in the release of [3H]-dopamine from rat nucleus accumbens-lateral septum slices.

We have studied [3H]-dopamine ([3H]-DA) release from rat nucleus accumbens lateral septum slices in response to various paradigms aimed at increasing endogenous or exogenous thyrotropin releasing hormone (TRH) concentrations in the extracellular space. High KCl concentrations significantly enhanced [3H]-DA release by fourfold. TRH (10(-4) or 5 x 10(-4) M) did not affect [3H]-DA release. The release of [3H]-DA was not stimulated by TRH either in the presence of N-1-carboxy-2-phenylethyl (N(im)benzyl)-histidyl-beta naphthylamide, a specific pyroglutamyl peptidase II inhibitor, or that of specific inhibitors of prolyl endopeptidase and pyroglutamyl peptidase I. None of the peptidase inhibitors modified the [3H]-DA release by themselves. These results suggest that the TRH stimulation of [3H]-DA release in vitro observed in previous studies is not due to peptide inactivation but may be due to a nonspecific effect. TRH enhancement of DA release in nucleus accumbens in vivo may not be the result of a direct effect of TRH on DA terminals.