RESUMO
Many lines of evidence indicate that GABA and GABA(A) receptors make important contributions to human sleep regulation. Pharmacological manipulation of these receptors has differential effects on sleep onset and sleep maintenance insomnia. Here we show that sleep is regulated by GABA in Drosophila and that a mutant GABA(A) receptor, Rdl(A302S), specifically decreases sleep latency. The drug carbamazepine (CBZ) has the opposite effect on sleep; it increases sleep latency as well as decreasing sleep. Behavioral and physiological experiments indicated that Rdl(A302S) mutant flies are resistant to the effects of CBZ on sleep latency and that mutant RDL(A302S) channels are resistant to the effects of CBZ on desensitization, respectively. These results suggest that this biophysical property of the channel, specifically channel desensitization, underlies the regulation of sleep latency in flies. These experiments uncouple the regulation of sleep latency from that of sleep duration and suggest that the kinetics of GABA(A) receptor signaling dictate sleep latency.
Assuntos
Química Encefálica/genética , Encéfalo/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Receptores de GABA-A/metabolismo , Sono/genética , Ácido gama-Aminobutírico/metabolismo , Animais , Anticonvulsivantes/farmacologia , Encéfalo/efeitos dos fármacos , Química Encefálica/efeitos dos fármacos , Carbamazepina/farmacologia , Células Cultivadas , Proteínas de Drosophila/efeitos dos fármacos , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Feminino , Masculino , Mutação/genética , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Tempo de Reação/genética , Receptores de GABA-A/efeitos dos fármacos , Receptores de GABA-A/genética , Sono/efeitos dos fármacos , Fatores de TempoRESUMO
Daily rhythms of physiology and behaviour are precisely timed by an endogenous circadian clock. These include separate bouts of morning and evening activity, characteristic of Drosophila melanogaster and many other taxa, including mammals. Whereas multiple oscillators have long been proposed to orchestrate such complex behavioural programmes, their nature and interplay have remained elusive. By using cell-specific ablation, we show that the timing of morning and evening activity in Drosophila derives from two distinct groups of circadian neurons: morning activity from the ventral lateral neurons that express the neuropeptide PDF, and evening activity from another group of cells, including the dorsal lateral neurons. Although the two oscillators can function autonomously, cell-specific rescue experiments with circadian clock mutants indicate that they are functionally coupled.
Assuntos
Ritmo Circadiano/fisiologia , Drosophila melanogaster/fisiologia , Atividade Motora/fisiologia , Neurônios/fisiologia , Animais , Comportamento Animal/fisiologia , Ritmo Circadiano/genética , Criptocromos , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Proteínas do Olho/metabolismo , Genótipo , Atividade Motora/genética , Neurônios/citologia , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Células Fotorreceptoras de Invertebrados/metabolismo , Receptores Acoplados a Proteínas G , Fatores de TempoRESUMO
Recent studies have identified the Drosophila brain circuits involved in the sleep/wake switch and have pointed to the modulation of neuronal excitability as one of the underlying mechanisms triggering sleep need. In this study we aimed to explore the link between the homeostatic regulation of neuronal excitability and sleep behavior in the circadian circuit. For this purpose, we selected Pumilio (Pum), whose main function is to repress protein translation and has been linked to modulation of neuronal excitability during chronic patterns of altered neuronal activity. Here we explore the effects of Pum on sleep homeostasis in Drosophila melanogaster, which shares most of the major features of mammalian sleep homeostasis. Our evidence indicates that Pum is necessary for sleep rebound and that its effect is more pronounced during chronic sleep deprivation (84 h) than acute deprivation (12 h). Knockdown of pum, results in a reduction of sleep rebound during acute sleep deprivation and the complete abolishment of sleep rebound during chronic sleep deprivation. Based on these findings, we propose that Pum is a critical regulator of sleep homeostasis through neural adaptations triggered during sleep deprivation.
RESUMO
Daily sleep cycles in humans are driven by a complex circuit within which GABAergic sleep-promoting neurons oppose arousal. Drosophila sleep has recently been shown to be controlled by GABA, which acts on unknown cells expressing the Rdl GABAA receptor. We identify here the relevant Rdl-containing cells as PDF-expressing small and large ventral lateral neurons (LNvs) of the circadian clock. LNv activity regulates total sleep as well as the rate of sleep onset; both large and small LNvs are part of the sleep circuit. Flies mutant for pdf or its receptor are hypersomnolent, and PDF acts on the LNvs themselves to control sleep. These features of the Drosophila sleep circuit, GABAergic control of onset and maintenance as well as peptidergic control of arousal, support the idea that features of sleep-circuit architecture as well as the mechanisms governing the behavioral transitions between sleep and wake are conserved between mammals and insects.