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.Insomnia is the most common sleep problem and affects approximately one third of the adult American population 1 . Patients with insomnia are generally subdivided into three categories: sleep onset insomnia, sleep maintenance insomnia and terminal insomnia (early-morning awakening coupled with an inability to return to sleep) 2 . The biological basis for these insomnia classifications remains unknown. Nonetheless, a single class of drugs, agonistic modulators of GABA A receptors, effectively ameliorates these diverse symptoms 2,3 . GABA A receptors are a family of pentameric ligand-gated Cl -channels 4 and are a major source of inhibitory currents throughout the CNS 5,6 . These receptors are also an important target for pharmacologic treatment of many other neurological disorders in addition to sleep 7 .The fruit fly Drosophila melanogaster is an ideal model for dissecting the relationships between molecules and behaviors, as well as between different sleep states 8,9 . As in mammals, it has been shown that the sleep-like state of Drosophila is associated with reduced sensory responsiveness and reduced brain activity 10,11 , and is subject to both circadian and homeostatic regulation 12,13 . Researchers have also identified a number of genes 14,15 , Notably, the mutation that causes the insecticide resistance phenotype (A302S) 20 specifically decreases the rate of RDL desensitization with little or no effect on other channel properties 23 . As a consequence, the mutant receptor has a longer single channel open duration and, therefore, increased channel current, at least under certain conditions (see below). Because of these characteristics, and because this mutation does not have obvious effects on health or viability, we decided to establish the importance of GABAergic transmission to sleep in flies and to examine the effects of the Rdl mutation.Interestingly, flies with this mutant GABA A receptor subunit slept more, primarily because of decreased sleep lat...

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Insect acetylcholinesterase is the target site for organophosphorus and carbamate insecticides and point mutations in the Ace gene are associated with resistance in Drosophila melanogaster and Musca domestica. However, little is known of the genetic regulation of insect Ace genes. Here we report the isolation of four different cDNAs from an Aedes Ace locus and identification of the gene promoter. Northern analysis reveals two large (>10 kb) transcripts and one smaller transcript of 4 kb. The region containing the initiation of transcription was localized by sequencing the two 5' most cDNAs and by 5' RACE. The transcription start point was subsequently identified by primer extension and is flanked by a perfect arthropod initiator consensus sequence. The promoter lacks a TATA box but contains several matches to other consensus sequences for eukaryotic transcription factors. In common with the Drosophila Ace gene, there are also multiple potential initiators of translation (ATGs) upstream of the main open reading frame. The structure of the 5' leader and promoter is compared to that found in other insect and vertebrate Ace genes and the possibility that this locus is homologous to one of two Ace loci described in another mosquito, Culex pipiens, is discussed.