Increased Volatile Anesthetic Requirement in Short-sleeping Drosophila  Mutants

Abstract

Background Anesthesia and sleep share physiological and behavioral similarities. The anesthetic requirement of the recently identified Drosophila mutant minisleeper and other Drosophila mutants was investigated. Methods Sleep and wakefulness were determined by measuring activity of individual wild-type and mutant flies. Based on the response of the flies at different concentrations of the volatile anesthetics isoflurane and sevoflurane, concentration-response curves were generated and EC50 values were calculated. Results The average amount of daily sleep in wild-type Drosophila (n=64) was 965 ±15 minutes and 1022 ± 29 in na[har38] p>0.05; n=32) (mean ± SEM, all p compared to wild-type and other shaker alleles). Shmns flies slept 584 ±13 minutes (n=64, p<0.01), Sh102 412 ± 22 minutes (n=32, p<0.01) and Sh120 782 ± 25 minutes (n=32, p<0.01). The EC50 values for isoflurane were 0.706 (95% confidence interval 0.649 to 0.764, n=661) and for sevoflurane 1.298 (1.180 to 1.416, n=522) in wild-type Drosophila, 1.599 (1.527 to 1.671, n=308) and 2.329 (2.177 to 2.482, n=282) in Sh102, 1.306 (1.212 to 1.400, n=393) and 2.013 (1.868 to 2.158, n=550) in Shmns, 0.957 (0.860 to 1.054, n=297) and 1.619 (1.508 to 1.731, n=386) in Sh120, and 0.6154 (0.581 to 0.649, n=360; p<0.05) and 0.9339 (0.823 to 1.041, n= 274) in na[har38], respectively (all p<0.01). Conclusions A single-gene mutation in Drosophila that causes an extreme reduction in daily sleep is responsible for a significant increase in the requirement of volatile anesthetics. This suggests that a single gene mutation affects both sleep behavior and anesthesia and sedation.

Shaker-Related Potassium Channels in the Central Medial Nucleus of the Thalamus Are Important Molecular Targets for Arousal Suppression by Volatile General Anesthetics

“…We discovered that blocking the mammalian homologues of Shaker channels in the CMT, but not in the nearby nuclei, of lightly anesthetized rats by the ShK toxin restored "consciousness," as evidenced by an arousal response, strongly supporting the idea that ShK-sensitive Shaker-related K ϩ channels in the CMT are involved in regulating the arousal state and controlling levels of consciousness. These data are consistent with previously demonstrated altered sensitivity to inhalational anesthetics and/or disrupted sleep cycles in Drosophila melanogaster strains containing mutant Shaker K ϩ channels (Kaplan and Trout, 1969;Tinklenberg et al, 1991;Walcourt et al, 2001;Cirelli et al, 2005;Weber et al, 2009).…”

“…ShK, a potent blocker of Kv1 channels, reverses sevoflurane-induced anesthesia in rodents Since Kv1 channels in the rodent brain are primarily heterotetramers containing Kv1.1, Kv1.3, Kv1.4, and Kv1.6 subunits (Turrigiano et al, 1996;Koch et al, 1997;Coleman et al, 1999;Kupper et al, 2002;Trimmer and Rhodes, 2004;Gazula et al, 2010;Pongs and Schwarz, 2010;Ramirez-Navarro et al, 2011), we examined the effect of ShK, a peptide inhibitor of Kv1.1, Kv1.3, and Kv1.6 channels with picomolar potency (Castañeda et al, 1995), in rats anesthetized with the inhalational anesthetic sevoflurane. Rats were continually exposed to a dose of sevoflurane (1.3 Ϯ 0.05% atm) well past the point required to lose the righting reflex as an index of loss of consciousness.…”

“…Of these, Kv1.4 is a rapidly inactivating A-type channel, while the others are delayed rectifiers. Neuronal Kv1 channels coassemble with each other and with auxiliary ␤ subunits forming homomultimers or heteromultimers with diverse biophysical properties (Turrigiano et al, 1996;Koch et al, 1997;Coleman et al, 1999;Kupper et al, 2002;Trimmer and Rhodes, 2004;Gazula et al, 2010;Pongs and Schwarz, 2010;Ramirez-Navarro et al, 2011). In this study, we directly tested the effects of anesthetics on heterologously expressed homomeric Kv1.1, Kv1.2, Kv1.3, Kv1.4, and Kv1.5 channels.…”

“…Given the importance of Kv1 channels for fine-tuning and regulation of neuronal firing rate and pattern (Wang et al, 1993(Wang et al, , 1994Gazula et al, 2010), and the ability of sevoflurane to activate Kv1.2 and Kv1.5 channels (Barber et al, 2012), it is compelling to hypothesize that these channels in the CMT might be essential molecular targets for anesthetics. It had been reported earlier that microinfusion into the CMT nucleus of specific antibodies against Kv1.2 channels, mammalian homologues of Shaker and an important component of neuronal excitability in thalamocortical neurons (Lambe and Aghajanian, 2001), restores "consciousness" (measured as righting reflex) in anesthetized rats even in the maintained presence of the anesthetic (Alkire et al, 2009) supporting the role of Kv1.2 channels in general anesthesia.…”

“…Furthermore, the intralaminar and midline thalamic nuclei, including central medial thalamic (CMT) nucleus, are known to be a nonspecific arousal system (Van der Werf et al, 2002). The firing of thalamocortical neurons is regulated by several ion channels, including Kv1-, Kv3-, and Kv4-family channels (Wang et al, 1994;Kasten et al, 2007;Kanyshkova et al, 2011), although the exact role of Kv1 channels in these nuclei has not been defined.…”