RESUMO
Adrenergic signaling profoundly modulates animal behavior. For example, the invertebrate counterpart of norepinephrine, octopamine, and its biological precursor and functional antagonist, tyramine, adjust motor behavior to different nutritional states. In Drosophila larvae, food deprivation increases locomotor speed via octopamine-mediated structural plasticity of neuromuscular synapses, whereas tyramine reduces locomotor speed, but the underlying cellular and molecular mechanisms remain unknown. We show that tyramine is released into the CNS to reduce motoneuron intrinsic excitability and responses to excitatory cholinergic input, both by tyraminehonoka receptor activation and by downstream decrease of L-type calcium current. This central effect of tyramine on motoneurons is required for the adaptive reduction of locomotor activity after feeding. Similarly, peripheral octopamine action on motoneurons has been reported to be required for increasing locomotion upon starvation. We further show that the level of tyramine-ß-hydroxylase (TBH), the enzyme that converts tyramine into octopamine in aminergic neurons, is increased by food deprivation, thus selecting between antagonistic amine actions on motoneurons. Therefore, octopamine and tyramine provide global but distinctly different mechanisms to regulate motoneuron excitability and behavioral plasticity, and their antagonistic actions are balanced within a dynamic range by nutritional effects on TBH.
Assuntos
Oxigenases de Função Mista/genética , Neurônios Motores/metabolismo , Octopamina/genética , Receptores de Amina Biogênica/genética , Tiramina/metabolismo , Animais , Comportamento Animal/fisiologia , Canais de Cálcio Tipo L/genética , Canais de Cálcio Tipo L/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/fisiologia , Privação de Alimentos/fisiologia , Larva/metabolismo , Larva/fisiologia , Locomoção/genética , Locomoção/fisiologia , Oxigenases de Função Mista/metabolismo , Neurônios Motores/fisiologia , Estado Nutricional/genética , Estado Nutricional/fisiologia , Octopamina/metabolismo , Receptores de Amina Biogênica/metabolismo , Sinapses/metabolismo , Sinapses/fisiologiaRESUMO
Division of labor is a defining characteristic of social insects and fundamental to their ecological success. Many of the numerous tasks essential for the survival of the colony must be performed at a specific location. Consequently, spatial organization is an integral aspect of division of labor. The mechanisms organizing the spatial distribution of workers, separating inside and outside workers without central control, is an essential, but so far neglected aspect of division of labor. In this study, we investigate the behavioral mechanisms governing the spatial distribution of individual workers and its physiological underpinning in the ant Myrmica rubra. By investigating worker personalities we uncover position-associated behavioral syndromes. This context-independent and temporally stable set of correlated behaviors (positive association between movements and attraction towards light) could promote the basic separation between inside (brood tenders) and outside workers (foragers). These position-associated behavior syndromes are coupled with a high probability to perform tasks, located at the defined position, and a characteristic cuticular hydrocarbon profile. We discuss the potentially physiological causes for the observed behavioral syndromes and highlight how the study of animal personalities can provide new insights for the study of division of labor and self-organized processes in general.
