CAMP Signaling Modulates General Anesthetics-induced Amnesia And Sleep Disorder | Posted on:2014-06-21 | Degree:Doctor | Type:Dissertation | Country:China | Candidate:H Zhang | Full Text:PDF | GTID:1264330398466945 | Subject:Anesthesia | Abstract/Summary: | PDF Full Text Request | Background:Cyclic adenosine monophosphate (cAMP, cyclic AMP or3’-5’-cyclic adenosinemonophosphate) is an intracellular second messenger of G-protein coupled receptor(GPCR) signaling. cAMP is synthesized from ATP by adenylyl cyclase (AC) which isactivated by stimulatory G (Gs)-protein-coupled receptors and inhibited by inhibitory G(Gi)-protein-coupled receptors. It’s decomposition into AMP relies on thephosphodiesterase (PDE). In the central nervous system, cAMP regulates the followingthree main pathways: the protein kinase A (PKA)-CREB (cAMP response element-bindingprotein) pathway, the cyclic nucleotide-gated channels (CNG channels, especially thehyperpolarization-activated CGN channels, HCN channels) pathway and exchangeproteins activated by cAMP (Epac) pathway. GPCR/G protein/cAMP signaling is found toparticipate in the actions of both intravenous anesthetics (for example propofol) andinhaled anesthetics (for example isoflurane and sevoflurane). We intend to investigate therole of cAMP in general anesthetics-induced amnesia and sleep disorder in the currentstudy.Section1: Rescue of cAMP/CREB signaling reversed spatial memory retentionimpairments induced by subanesthetic dose of propofolObjective:The intravenous anesthetic propofol causes episodic memory impairments independent ofsedation and unconsciousness in human. Episodic memory is the human-unique memory ofautobiographical events (what) which occurs in specified time (when) and place (where)and is mixed with emotion and other contextual knowledge (context). The non-cued MorrisWater Maze (MWM) is a hippocampus dependent “episodic-like memory” training taskthat gives information on “what-where” elements. We hypothesized that propofol causedepisodic-like spatial memory retention but not acquisition impairments in rats. Theimpaired memory consolidation was accompanied with reduced hippocampalcAMP/CREB signaling. Furthermore, rescuing cAMP/CREB signaling using selectivephosphodiesterase-4inhibitor rolipram could reverse propofol-induced amnesia andcAMP/CREB signaling inhibition. Methods:Male Sprague-Dawley rats were randomized into four groups: vehicle control (C);propofol (P,25mg/kg, intraperitoneal); rolipram (R) and rolipram+propofol (R+P,pretreatment of rolipram25minutes before propofol,0.3mg/kg, intraperitoneal). Sedationand motor coordination were evaluated5,15and25minutes after propofol injection toresist the possibility that inefficient learning and memory after propofol injection duringthe non-Cued MWM was due to sedation and sedation-caused motor incoordination.MWM spatial navigation training (memory acquisition) and probe test (memory retention)were performed5minutes and24hours after propofol injection. Visible cued MWMtraining was simultaneously performed to exclude non-spatial effects. Hippocampal CREBsignaling including cAMP levels; ERK1/2, CaMKII and CREB phosphorylation;CaMKIV, BDNF, c-Fos and Arc protein expression were detected5minutes,50minutesand24hours after propofol administration.Result:Rolipram did not change propofol-induced anesthetic/sedative states. Both propofol androlipram did not impair motor skills evaluated by accelerated rotarod tests. No differencewas found on the latency to the platform during the visible MWM. Propofol impairedspatial memory retention but not acquisition in the non-cued MWM. Rolipram alone didnot change non-cued MWM learning and memory consolidation. Pretreatment withrolipram reversed propofol-induced impairments of spatial memory retention andsuppression on cAMP levels, CaMKII and CREB phosphorylation, BDNF and Arcprotein expression.Conclusion:Propofol caused spatial memory retention impairments but not acquisition inabilitypossibly by inhibiting cAMP/CREB signaling. Section2: RGS/Gαi2/cAMP signaling modulated volatile anesthesia-induced sleepdisruptionsObjective:Postoperative sleep disorders are commonly seen in almost every patient. The changes insleep architecture and circadian rhythms substantially influence surgery effects, causemore complications and are connected with sudden death. Different from intravenousanesthesia, sleep is disrupted after volatile anesthesia with a rebound in REM sleep. Theunderlying mechanisms remain elusive and a better understanding of the relationshipbetween sleep and anesthesia might be useful to help investigate new strategies to improvesleep and facilitate the recovery of surgical patients. Volatile anesthetics but notintravenous anesthetics act on metabotropic, G-protein coupled receptor (GPCR) signaling.GPCR ligands such as acetylcholine, adenosine, serotonin and histamine; GPCRs; effectors(for example cAMP and Gβγ signaling) and regulators all play a role in the benefcial andadverse effects of volatile anesthetics. Regulators of G protein signaling (RGS) proteinsare negative regulators of GPCR signaling and have been shown to modulate the inductionand emergence from isoflurane anesthesia. Specifically, RGS/Gαi2signaling was found tomodulate isoflurane-induced loss of consciousness. The current study further tested thehypothesis that RGS/Gαi2/cAMP signaling modulated normal sleep and disrupted sleepafter isoflurane and sevoflurane anesthesia.Methods:Wild-type (WT), heterozygous (+/GS) and homozygous (GS/GS) mice with a geneticablation of RGS action at Gαi2were subjected to electroencephalographic andelectromyographic recordings:1) under ad libitum sleep;2) after3-hour isoflurane (1.3%in pure oxygen) exposure;3) after3-hour sevoflurane (2.8%in pure oxygen) anesthesia.The analogous mutation (Gly184to Ser) prevented the GTPase accelerating protein (GAP)activity of all RGS proteins targeting Gαi2, thus downstream Gαi2/cAMP and Gβγ signalingwas enhanced and lasted longer. Sleep architecture (%state; mean episode duration andepisode numbers) and power spectra were collected and analyzed as a function of bothgenotypes and conditions for each time period. Results:The homozygous RGS-insensitive (GS/GS) mice showed less wakefulness time (-11.85%)and more NREM sleep time (+13.95%) at baseline compared to the wild-type mice. Thenumbers of NREM sleep and wakefulness episodes were increased and mean episodedurations of NREM sleep and wakefulness were decreased in the GS/GS mice. The GS/GSmice also showed abnormal circadian distribution of sleep and wakefulness. Increasedwakefulness and NREM sleep delta power and decreased REM sleep theta power wereobserved in the GS/GS mice compared to that in the wild-type and+/GS mice. Isofluraneand sevoflurane caused prolonged disruptions of wakefulness, NREM sleep and REMsleep in the wild-type mice. REM sleep changes persisted for more than18.5hours afteranesthesia in the wild-type mice. NREM sleep delta power was also decreased by volatileanesthesia in the wild-type mice. Complete silencing of RGS/Gαi2interaction resulted inless changes in sleep architecture and no changes in power spectra after anesthesia.Recovery of sleep/wake cycle was faster in the GS/GS mice than the wild-type mice.Conclusions:RGS/Gαi2interface regulates sleep amount, sleep consolidation and circadian timing ofsleep. Sleep disruptions after volatile anesthesia partially depend on the inhibition of Gαi2signaling by RGS proteins. | Keywords/Search Tags: | cAMP, rolipram, general anesthetics, amnesia, sleep disorder, RGSproteins | PDF Full Text Request | Related items |
| |
|