Page - 84 - in Advances in Neuroimmunology

BrainSci. 2016,6, 25 Keywords: restraint stress; chronicethanolwithdrawal; cytokinemRNAs;CRF;alcohol;CP154,526 1. Introduction Acutewithdrawal fromchronicethanol (WCE)exposure isassociatedwith increasedanxiety-like behavior [1–3]. Breeseetal. [4]also foundinathree-withdrawalprotocol thatstresssubstitutedfor the initial twowithdrawalssuchthatwithdrawal fromasinglefive-daycycleofchronicethanol induced anxiety. Subsequently, Breese et al. [5] found that the anxiety-like response to restraint stresswas facilitatedwhen thestresswasappliedafterWCE—afinding inagreementwithother reports that stressafterWCEcanenhancenegativeeffects [6,7]. Breeseetal. [8]andKnappetal. [9]alsoreportedthatadministrationof lipopolysaccharide (LPS) oracytokine into thebrainsubstitutedfor the initial intermittentethanolexposuresappliedprior to asingleCEexposure to inducenegativeeffects. This latteroutcomewascomparable to thechange observedwithpriorexposure tostress [4,5]orafterWCE[2,3,10].Morerecently,Whitmanetal. [9] reportedthatWCEincreasedcytokinemRNAsinthecortex—acytokine immuneresponse thatwas not related to infection [11–13]. Whitmanet al. [9] also observed increases inmRNAs for toll-like receptor4 (TLR4)andHighMobilityGroupBox1Protein (HMGB1)whichserveasanendogenous systemthatactivatesneuroimmunefunction[11,12,14–16]. TheinductionofcytokinemRNAsincreases afterWCEwasblockedbyaCRF1receptor (CRF1R)antagonist [9]—afindingpossibly linking the cytokinemRNAchanges toCRFinvolvement in theanxiety-likebehavior thataccompaniesWCEand stress [3–5]. Variousstudieshave linkedstress to increases incytokinemRNAsinvariousbrainsites [17–25]. Collectively, these reports provided new information about the effects of various stressors (social stress/defeat, footshockortailshock,restraint, forcedswim,glucose/insulinchallenge,orcoldstress) onneuroimmunemRNAresponsesof thehypothalamus,hippocampus,cerebellum,posteriorcortex, andnucleusof thesolitarytract.Relatedly,workfromourgrouphadshownthatrestraintstresscould substitute for the initial repeated exposures to chronic alcohol to induce anegative emotional state followingafuturewithdrawalas inferredfromanxiety-likebehavior, (e.g., [4]). Toexplore thepotential relevance of stress effects on neuroimmune responses in a chronic ethanol andwithdrawalmodel, Breeseetal. [8]administeredLPSorapro-inflammatorycytokine intobraintosubstitute for the initial intermittentethanolwithdrawalsormildstresstoinduceanxiety-likebehaviorfollowingasingleethanol withdrawal thatotherwisewouldbeincapableofelicitinganxiety[4,5].Missingfromthisstrategywas an assessment ofwhether the restraint stress itself inducedneuroimmune changes consistentwith functionaleffectsonbehavior. Thus,akeynewcomponentof thecurrentstudieswastoassesswhether stress,whichbyitselfhasbeenshowninsomestudies to increasebraincytokines (e.g., [18,20,21,26]), producedchangescomparable to those triggeredbyWCE.Additionally, comparisonsweremadeof cytokinemRNAindifferentbrainregionsafter stressorWCE.Finally, tocomplementearlier studies withWCEandcortical cytokines, thepresentstudyexploredwhetheracorticotrophin-releasingfactor receptor antagonistwouldattenuate stress-inducedcytokines in the cortex. This lineof inquiry is pertinent tounderstandingtherelativeoverlapofneuroimmuneeffectsof stressandtheWCEmodel inrelationtoalcoholabuse,drugaddiction,andseveralpsychiatricdisorders (see [6–8,27–35]). 2.MaterialsandMethods 2.1.Animals Adult male Sprague–Dawley (S–D) rats or Wistar Rats (Charles-River, Raleigh, NC, USA) weighing180–200guponarrivalweregrouphousedandfedRMH3000ratchow(TestDiets,Richmond, IN, USA) for 2–3 days prior to study to acclimate them to the new environment (temperatures 70–72˝F;humidity40%–60%;andlight/darkcycle12h:12hwith lights from7:00a.m. to7:00p.m.). 84