Modulatory effects on Drosophila larva hearts: room temperature, acute and chronic cold stress

Abstract

Ectothermic animals are susceptible to temperature changes such as cold shock with seasons. To survive through a cold shock or season, ectotherms have developed unique strategies. Our interest is focusing on the modulation of physiological functions during cold shock and prolonged cold exposure in the fruit fly. We use Drosophila melanogaster as a model system to investigate cardiac function in response to modulators (5-HT-serotonin, Ach-acetylcholine, OA-octopamine, DA-dopamine and a cocktail of modulators) in acute cold shock and chronic cold shock conditions. Semi-intact larvae are used to provide direct access to the modulators of known concentration in a defined saline. The results show that 10 µM 5HT is the only modulator which maintains heart rate for larva raised at 21 °C and then exposed to acute cold shock (10 °C). The modulators 1 µM OA, 10 µM 5HT, 1 mM Ach, 10 µM Ach and a cocktail of modulators (at 10 µM) increased the heart rate significantly in larvae which were cold conditioned (10 °C for 10 days). HPLC analysis indicated both OA and 5-HT decreased in chronic cold conditioning. The larvae maintain heart function in the cold which may be contributed by low circulating levels of modulators. The larval heart responds better to 5-HT, OA, and Ach in conditioned cold than for acute cold, suggesting some acclimation to cold.

Role of the Insect Neuroendocrine System in the Response to Cold Stress

“…Based on these results, similar dependencies may also be observed in insects. This supposition is partially confirmed by the results of Zhu et al (2016) in a study on the D. melanogaster heart. The authors demonstrated a strong excitatory effect of biogenic amines on the larval heart during cold exposure but only in the case of 5-HT.…”

“…However, as suggested by Zhu et al (2016), different modes of action of OA at different temperatures may be related to the activation of different subunits of the G protein-coupled receptor. The Gαq subunit, whose activation evokes a positive chronotropic effect, is most likely suppressed, but Gαi-coupled receptors are activated, which may lead to the opposite effect of OA on insect heart during cold stress (Zhu et al, 2016). Generally, biogenic amines may be needed to maintain heart functioning during chronic exposure to cold.…”

“…Generally, biogenic amines may be needed to maintain heart functioning during chronic exposure to cold. This is essential for circulating nutrients/cryoprotectants and immune function, which undoubtedly influence insect survival during exposure to cold (Zhu et al, 2016).…”

Physiological Changes as a Measure of Crustacean Welfare under Different Standardized Stunning Techniques: Cooling and Electroshock

“…However, one needs to be cautious in relating changes in the compounds in the hemolymph to one condition such as exercise, environment, or stunning procedure, as these compounds can vary with a molt cycle, circadian cycle, gravid status, social dominance, and health of the animals [ 15 , 16 , 40 , 41 , 42 ]. Even insects show changes in levels of biogenic amines with environmental stressors and/or exercise [ 43 , 44 , 45 ]. In cold (10 °C) exposed Drosophila melanogaster both serotonin and octopamine concentrations decreased in the hemolymph [ 46 ].…”

A new method to characterize function of theDrosophilaheart by means of optical flow

“…In contrast to its success as a genetic model system, the minuteness of Drosophila challenges the methods used to quantify performance of its tubular heart. Various approaches have been employed that include manual counting of heart vessel contractions (Zhu et al, 2016), electrophysiological recordings of muscle potential (Johnson et al, 1998) and sophisticated optical methods (Klassen et al, 2017;Wasserthal, 2007;Wolf et al, 2006). A resilient compromise between instrumental costs on the one hand and the richness in detail of the data on the other hand has been the semiautomatic optical heartbeat analysis (SOHA) developed by Fink and Ocorr, which determines functional parameters of the fly tubular heart from high-speed digital video film (Cammarato et al, 2015;Fink et al, 2009).…”