A loss of hippocampal perineuronal nets produces deficits in dopamine system function: relevance to the positive symptoms of schizophrenia.

2.2 MB·English

by  Shah, A

Citation:TranslPsychiatry(2013)3,e215;doi:10.1038/tp.2012.145
&2013MacmillanPublishersLimited Allrightsreserved 2158-3188/13
www.nature.com/tp
A loss of hippocampal perineuronal nets produces
deficits in dopamine system function: relevance to the
positive symptoms of schizophrenia
AShahandDJLodge
Deficits in parvalbumin containing interneurons are a consistent observation in animal models and schizophrenia patients.
These neurons are surrounded by chondroitin sulfate proteoglycans, forming perineuronal nets, thought to support the high
firing frequencies observed in these neurons. A loss of perineuronal nets has been observed post mortem in human
schizophrenia patients, however, whether this contributes to the symptoms of schizophrenia is not known. Here we directly
examinetheeffectsofchondroitinaseABCdegradationofventralhippocampal(vHipp)perineuronalnets,anddemonstratethat
thisresultsinanenhancedhippocampalactivityandsignificantincreaseindopamineneuronpopulationactivity.Inaddition,
chondroitinase-treatedratsdisplayanaugmentedlocomotorresponsetoamphetamine,consistentwiththeenhancedresponse
to psychomotor stimulants observed in schizophrenia patients. Taken together, these data demonstrate that a loss of vHipp
perineuronalnetsissufficient,inandofitself,toinduceaberranthippocampalanddopaminesystemfunctionconsistentwith
thatobservedinrodentmodelsandschizophreniapatients.
TranslationalPsychiatry(2013)3,e215;doi:10.1038/tp.2012.145;publishedonline15January2013
Introduction imaging studies in schizophrenia patients that demonstrate
increasesinbaselinehippocampalactivitythatarecorrelated
Schizophrenia is a disease affecting up to 1% of the
withpositivesymptomseverity.23–25
population.1 Whereas the exact etiology of schizophrenia is
An increase in hippocampal activity, particularly in ventral
notcurrentlyknown,analterationinGABAergicfunctionisa
subfields, is able to augment dopamine system function,
consistentobservationinbothanimalmodelsaswellaspost-
known to be associated with the positive symptoms of
mortem studies in schizophrenia patients.2–8 Specifically,
schizophrenia.Specifically,activationofthevHipphasbeen
post-mortem studies have demonstrated a reduction in
demonstratedtoincreasethenumberofspontaneouslyactive
cortical glutamic acid decarboxylase;9–11 an upregulation of dopamine neurons in the ventral tegmental area (VTA)26–28
post-synaptic GABA-A receptors12,13 and a decrease in
andthisiscorrelatedwithincreasesindopamineeffluxinthe
GABA uptake sites14–16 in schizophrenia patients. There is nucleusaccumbens.27,29,30Furthermore,wehavepreviously
increasing evidence that deficits in GABAergic transmission
demonstrated that the pathological increase in dopamine
are demonstrated to occur within specific classes of GABA
system function, observed in the MAM-rodent model of
ergicinterneurons, with considerable attentionbeing paidto
schizophrenia, is directly attributable to aberrant ventral
those containing the calcium binding protein parvalbumin.3 hippocampal activity.22 Thus, MAM-treated rats display an
Indeed, a decrease in parvalbumin expression has been increase in dopamine neuron population activity and an
reportedinadiversevarietyofanimalmodels,includingthe augmentedlocomotorresponsetoamphetamineadministra-
methylazoxymethanol(MAM),5,17neonatalventralhippocam- tion, both of which can be normalized by tetrodotoxin
pal lesion6 and phencyclidine models,7,8,18 and has been inactivation of the vHipp.22 This has led us to posit that the
consistently demonstrated in schizophrenia patients, post positivesymptomsofschizophrenia,knowntobeassociated
mortem.10,19,20Althoughnotconclusivelydemonstrated,this withaugmenteddopaminetransmission,maybesecondaryto
decreaseinparvalbuminexpressionislikelyattributableto,or a pathological increase in ventral hippocampal activity.31
resultsin,aberrantinterneuronfunctionleadingtoattenuated Furthermore, this increase in hippocampal activity may be
perisomatic inhibition and an augmented pyramidal neuron attributabletoadecreasedfunctionofperisomatictargeting,
activity.Indeed,wehavepreviouslydemonstratedthatMAM- parvalbuminpositiveinterneurons.
treatedrats(forreviewseeLodgeetal.21)displayadecrease Parvalbumin containing interneurons in the cortex and
in hippocampal parvalbumin positive neurons, deficits in hippocampus are encapsulated by chondroitin sulfate pro-
evoked gamma oscillatory activity and an increase in teoglycans forming an extracellular matrix known as a
hippocampal neuronal activity.5,22 This is consistent with perineuronalnet(Figure1).Althoughperineuronalnetswere
DepartmentofPharmacologyandCenterforBiomedicalNeuroscience,UniversityofTexasHealthScienceCenter,SanAntonio,TX,USA
Correspondence:DrDJLodge,DepartmentofPharmacologyandCenterforBiomedicalNeuroscience,UniversityofTexasHealthScienceCenter,7703FloydCurl
Drive,MC7764,SanAntonio,TX78229,USA.
E-mail:[email protected]
Keywords:chondroitinase;dopamine;parvalbumin;perineuronalnet;schizophrenia;ventralhippocampus
Received6September2012;revised16November2012;accepted24November2012
Hippocampalperineuronalnetsandschizophrenia
AShahandDJLodge
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Figure1 Perineuronalnetssurroundparvalbuminpositiveinterneuronsthroughouttheventralhippocampus.Photomicrographsatincreasinglevelsofmagnification(from
toptobottom)demonstratethedistributionofparvalbuminpositiveinterneurons(red)andperineuronalnets(green)throughouttheventralregionsofthehippocampus.The
mergedimages(c,fandi)demonstratethatasignificantnumberofparvalbumin-containingneuronsareenvelopedbyperineuronalnets,asdeterminedbylectinlabeling.
describedbyGolgioveracenturyago,relativelylittleisknown (1mlkg(cid:2)1, i.p.). Male pups were weaned on day 21 and
about their function.32 Recent work has suggested that housedingroupsof2–3withlittermatesuntiladulthood(48
perineuronal nets act to stabilize synapses,33 support weeks), at which time they were used for neurochemical
synapticplasticity34,35andregulatethemotilityofextracellular studies.
ions.36,37 Given that perineuronal nets appear to envelop
Kv3.1b expressing neurons,37 it has been suggested that Westernblot. AdultMAMandsaline-treatedrats(n¼5per
these structures likely support the high firing frequencies of group: 300–450g) were anaesthetized with sodium pento-
fast-spikinginterneurons.Interestingly,alossofperineuronal barbital (120mgkg(cid:2)1, i.p.) and rapidly decapitated. The
nets has been recently reported throughout the medial ventralhippocampuswasdissectedoniceandhomogenized
temporal lobe of postmortem schizophrenia patients.38,39 in disruption buffer (50mM Tris, 150mM NaCl, pH 7.4)
Wesuggestthatalossofperineuronalnetsmaycontributeto containing a protease inhibitor cocktail (Sigma-Aldrich, St
theaberranthippocampalactivityandsubsequentdopamine Louis,MO,USA:P8340).Theperineuronalnetfractionwas
hyperfunction associated with the positive symptoms of isolated essentially as described previously.41 Specifically,
schizophrenia. Here we examine whether a loss of vHipp homogenates were centrifuged at 14000r.p.m. for 10min
perineuronal nets is sufficient, in and of itself, to produce and the pellet resuspended in disruption buffer containing
physiological and behavioral deficits associated with the 0.5%TritonX-100.Thehomogenatewascentrifugedandthe
positivesymptomsofschizophrenia. pellet resuspended in 200ml incubation buffer (0.1M Tris,
0.03M sodium acetate, pH 8.0) containing 0.1U of chon-
droitinase ABC and incubated at 371C for 2.5h. The
Materialsandmethods
homogenate was centrifuged and the supernatant analyzed
All experiments were performed in accordance with the as a purified perineuronal net fraction. Given that the initial
guidelines outlined in the USPHS Guide for the Care and washesareunlikelytoreleasechondroitinsulfateproteogly-
Use of Laboratory Animals, and were approved by the cans from perineuronal nets,41 the proteins examined
InstitutionalAnimalCareandUseCommitteeoftheUniversity following chondroitinase ABC digestion should be those
ofTexasHealthScienceCenter,SanAntonio. associated with perineuronal nets; indeed we obtained
dramatically different results when analyzing chondroitin
Animals. MAM acetate treatments were performed as sulfate proteoglycans from the cytosolic fractions (data not
described previously.40 In brief, timed pregnant female shown).
Sprague–DawleyratswereadministeredMAM(25mgkg(cid:2)1, Proteinswereseparatedona4–20%gradientgel(Bio-Rad,
i.p.) on GD17. Control rats received injections of saline Hercules, CA, USA) and transferred to polyvinyl difluoride
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membranes. Membranes were blocked and incubated with were also incubated with rabbit antiparvalbumin 1:1000
eithermouseantineurocan1:100(DSHB,IowaCity,IA,USA: (Abcam: AB11427)) followed by antirabbit-AlexaFluor 594
1F6-s),mouseantiphosphacan1:100(DSHB:3F8-s),mouse (1:1000for1hatroomtemperature).SectionsofvHippfrom
antibrevican 1:1000 (BD Biosystems, San Jose, CA, USA: each rat were visualized to confirm the loss of perineuronal
610894) or mouse antiGAPDH 1:1000 (Abcam, Cambridge, netsinchondroitinaseABC-treatedrats.
MA, USA: ab9484), followed by HRP-antimouse 1:5000.
Membranes were treated with an ECL substrate (Pierce, Analysis. Electrophysiological analysis of dopamine and
Rockford,IL,USA)andopposedtofilmpriortoscanningand
vHipp neuron activity was performed using commercially
quantificationwithImageJ.
available computer software (LabChart v7.1). Locomotor
activitywasanalyzedwithActivityMonitor(MedAssociates),
Chondroitinasetreatment. Allsurvivalsurgicalprocedures
whereas western blots films were scanned on an Epson
were performed under general anesthesia in a semi-sterile
PerfectionV700andopticaldensitymeasuredusingImageJ.
environment.Briefly,maleSprague–Dawleyrats(250–350g) Immunohistochemistry was examined on an Axio Lab.A1
were pretreated with atropine (0.1mgkg(cid:2)1, i.p.), anesthe- Fluorescence Microscope and images taken with an
tizedwithsodiumpentobarbital(60mgkg(cid:2)1,i.p.)andplaced attached AxioCam ICc1 digital camera. All data are
inastereotaxicapparatus.ChondroitinaseABCfromProteus represented as the mean±standard error of the mean
vulgaris (0.05Uml(cid:2)1) or penicillinase from Bacillus cereus (s.e.m.) unless otherwise stated. All statistics were calcu-
(0.05Uml(cid:2)1) were backfilled into a glass micropipette and latedusingSigmaPlot (SystatSoftware, Chicago,IL,USA).
pressure injected (0.75ml) bilaterally into the ventral hippo-
campus(A/P(cid:2)5.3,M/L±5.2,D/V(cid:2)7.5mm).Thepipettewas
Materials. MAM acetate was purchased from Midwest
removed, the wound sutured, the rat removed from the
Research Institute (Kansas City, MO, USA). The mono-
stereotaxicframeandmonitoredcloselyuntilconscious.Rats
cloncalantibodiesantineurocan(1F6-s)andantiphosphacan
were housed for at least a week before subsequent
(3F8-s), developed by RU Margolis and RK Margolis, were
experiments.
obtained from the Developmental Studies Hybridoma Bank.
Theanti-brevicanantibody(610894)waspurchasedfromBD
Extracellular recordings. Extracellular recordings were
Biosciences, whereas the antiparvalbumin (ab11427) and
performed as described previously.22 In brief, rats (300–
antiGAPDH (ab9484) antibodies were purchased from
450g) were anaesthetized with chloral hydrate
ABCAM. The HRP-anti-mouse, AlexaFluor 596-conjugated
(400mgkg(cid:2)1, i.p.) and placed in a stereotaxic apparatus.
anti-rabbit, AlexaFluor 488-conjugated to streptavidin and
Glass extracellular microelectrodes were lowered into the
ProLongGoldantifademountantwereobtainedfromInvitro-
VTA (n¼14–16 rats per group: A/P (cid:2)5.3, M/L þ0.6mm
gen (Grand Island, NY, USA). The Laemmli Sample Buffer,
from bregma and from (cid:2)6.5 to (cid:2)9.0mm ventral of brain
Mini-Protean gels and polyvinyl difluoride membranes were
surface) or ventral hippocampus (n¼7rats per group: A/P
from Bio-rad. Sodium pentobarbital, atropine, protease inhi-
(cid:2)5.3, M/L þ5.2mm from bregma and from (cid:2)5.0 to
bitor cocktail (P8340), amphetamine, chondroitinase ABC
(cid:2)8.5mm ventral of brain surface). Spontaneously active
fromProteusvulgaris,PenicillinasefromBacilluscereusand
dopamine neurons were identified with open filter settings
lectin from Wisteria floribunda were purchased from Sigma.
(low pass: 30Hz, high pass: 30kHz) using previously
Allotherchemicalsandreagentswereofeitheranalyticalor
established electrophysiological criteria,42 whereas putative
laboratory grade,andpurchasedfromstandardsuppliers.
pyramidal neurons were defined as those with firing
frequencieso2Hzasreportedpreviously.43,44
Results
Locomotoranalysis. Chondroitinase-orPenicillinase-trea-
tedrats(n¼16–18pergroup:300–450g)wereplacedinan Western blot. A loss of perineuronal nets has been
open field arena (Med Associates, St Albans, VT, USA), described, post mortem, in schizophrenia patients.38,39 To
wherespontaneouslocomotoractivityintheX–Yplanewas examine whether this is also observed in rodent models of
determined for 45min by beam breaks and recorded with thedisease,weexaminedtheabundanceofperineuronalnet
Open Field Activity Software (Med Associates). Rats were proteins throughout the vHipp of the MAM model of
then injected with amphetamine (0.5mgkg(cid:2)1, i.p.) and schizophrenia. MAM-treated rats demonstrated a significant
locomotoractivityrecordedforanadditional90min. decrease in the levels of the vHipp perineuronal net
chondroitin sulfate proteoglycans, Brevican (SAL:
Histochemistry. Anesthetizedratswereperfusedtranscar- 2.857±0.662 c.f. MAM: 0.833±0.104; Po0.05 Two-way
dially with saline followed by formaldehyde and their brains ANOVA, Holm–Sidak t¼3.989, n¼5 rats per group in
removed,postfixed/cryopreservedfor24h.Coronalsections duplicate) and Phosphacan (SAL: 2.020±0.518 c.f. MAM:
of the ventral hippocampus were used to detect expression 0.670±0.084; Po0.05 Two-way ANOVA, Holm–Sidak
ofperineurnalnets.Asubsetofbrainswerealsoprocessed t¼2.661,n¼5ratspergroupinduplicate),butnotNeurocan
for parvalbumin immunohistochemistry. Briefly, sections (SAL: 1.102±0.195 c.f. MAM: 0.665±0.101; P40.05),
were blocked (2% normal goat serum for 30min) followed whencomparedtocontrol, saline-treatedrats(Figure2).
byincubationwithlectinfromWisteriafloribunda(4mgml(cid:2)1)
andvisualizationbyAlexaFluor488 conjugatedtostreptavi- In vivo electrophysiology. To confirm that a decrease in
din(1:500for1hatroomtemperature).Asubsetofsections perineuronal nets results in aberrant vHipp activity, as
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reportedintheMAMmodel,weperformedinvivorecordings hippocampal activity, presumably due to a decrease in
from putative vHipp pyramidal neurons. Specifically, chon- fast-spikinginterneuronfunction.
droitinase-treated rats displayed a significantly greater GiventhatanaugmentedvHippactivityhasbeendemon-
average firing rate of putative pyramidal neurons when strated to increase dopamine system function,22,28,45 we
compared to rats receiving intra-vHipp penicillinase (Penn: recordedtheactivityofthepopulationofspontaneouslyactive
0.74±0.09Hz c.f. Chase: 0.99±0.07Hz; Po0.05 Rank dopamineneuronsthroughouttheVTAofchondroitinase-and
Sum Test, n¼41–63 cells per group). These data suggest penicillinase-treated rats. Interestingly, the chondroitinase-
that a loss of perineuronal nets is sufficient to augment induced loss of hippocampal perineuronal netsresulted in a
significant increase in the number of spontaneously activity
dopamine neurons observed per electrode track (Penn:
0.92±0.11cells per track c.f. Chase: 1.73±0.13cells per
track;Po0.05Studentst-testt¼(cid:2)4.739n¼14–16ratsper
group)withoutsignificantlyalteringaveragefiringrateorburst
firing(Figure3),similartopreviousobservationsintheMAM
model.22
Amphetamine-induced hyperlocomotion. We have pre-
viously demonstrated that increases in dopamine neuron
activity, secondary to augmented vHipp activity, result in a
behavioral hyperactivity to low doses of psychomotor
stimulants.22,45 Here we demonstrate that rats treated with
intra-vHipp chondroitinase ABC display a significantly
increased locomotor response to amphetamine when com-
pared to penicillinase-treated rats (Two-way ANOVA;
F ¼40.845: n¼16–18 rats per group; Figure 4),
(Treatment)
demonstrating that a loss of hippocampal perineuronal nets
results in behavioral alterations consistent with those
observed in rodent models as well as in schizophrenia
patients.46,47
Figure2 MAM-treatedratsdisplaydecreasesinthelevelsofthechondroitin
sulfateproteoglycansassociatedwithvHippperineuronalnets.Representativefilms Discussion
demonstratingtheabundanceofthreechondroitinsulfateproteoglycans,brevican,
Here we demonstrate that a loss of ventral hippocampal
neurocanandphosphacanaredepictedin(a),whereasthequantitationofthese
dataarepresentedin(b).wrepresentssignificantdifferencefromsaline-treatedrats, perineuronal nets is sufficient to augment hippocampal
Two-way ANOVA followed by Holm–Sidak post-hoc, n¼5 rats per group in activity and increase dopamine system function. Moreover,
duplicate. this is correlated with an enhanced behavioral response to
Figure3 EnzymaticdegradationofvHippperineuronalnetsaugmentsdopamineandhippocampalactivity.vHippchondroitinaseABCtreatmentresultedinaselective
increaseindopamineneuronpopulationactivity(a),withnosignificanteffectonaveragefiringrate(b),orburstfiring(c)whencomparedtocontrol,penicillinase-treated,rats.
ThedegradationofperineuronalnetsresultedinanincreaseintheaveragefiringrateofpurportedpyramidalneuronsthroughoutthevHipp(dande).wrepresentssignificant
differencefrompenicillinase-treatedrats,Studentst-test(RankSumTestifdatafailednormalitytest),n¼14–16ratspergroupforA,n¼88–125cellspergroupforbandc
andn¼41–63cellspergroupfor(dande).
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structure of the perineuronal net.49 Indeed, qualitative
examination of the vHipp following chondroitinase ABC
demonstrated a striking decrease in lectin staining to
perineuronal nets (Figure 5). In contrast, the administration
ofpenicillinase,fromBacilluscereus,didnotappeartoalter
the distribution of perineuronal nets (Figure 5), and was
thereforeusedasacontrol.
It has been suggested that perineuronal nets support the
highfiringfrequenciesoffast-spiking,parvalbumin-containing
interneurons. Given that these are perisomatic targeting
interneurons, a loss of function would be anticipated to
increase pyramidal activity. Indeed, here we demonstrate a
significantlygreaterfiringrateofputativepyramidalneurons
throughout the ventral hippocampus of chondroitinase-
treatedrats,whencomparedtopenicillinase-treatedcontrols.
Figure 4 Enzymatic degradation of vHipp perineuronal nets results in an
Interestingly,thisincreaseinhippocampalfunctionisqualita-
enhanced locomotor response to amphetamine. vHipp chondroitinase ABC
tively similar to that observed in the MAM model,22 and is
treatment did not appear to alter spontaneous locomotor activity in a novel
environment; however, a significant increase in the locomotor response to consistentwithhumanimagingdatademonstratingaugmen-
amphetamine (administered at the dashed line) was observed in rats with ted hippocampal activity in schizophrenia patients.23–25 It
perineuronal net degradation. wrepresents a mean effect of treatment, whereas shouldbenotedthathippocampalculturestreatedinvitrowith
*indicatessignificantdifferencebetweenchondroitinaseABCandpenicillinasein chondroitinaseABCdonotdisplayalteredelectrophysiologi-
pairwisemultiplecomparisonsacrosstime;Two-wayANOVA,followedbyHolm–
cal parameters including resistance, capacitance, resting
Sidakpost-hoc,n¼16–18ratspergroup).
membranepotential,norweretheamplitudeorhalfwidthof
action potentials of interneurons altered.50 Thus, the results
amphetamine,amarkerofpositivesymptomsofschizophre- observed in the current study likely reflect alterations in
nia.46,47 Given that a loss of perineuronal nets has been interneuron function that are either a consequence of the
reportedthroughoutthemedialtemporallobeofpost-mortem treatment regimen(thatis,oneinjectionwithanimalstested
schizophrenia patients,38 we suggest that alterations in 41 week later c.f. 48h of direct exposure in vitro) or,
extracellular matrix proteins may have a significant role in alternatively, may require the normal patterns of afferent
thepathophysiologyofschizophrenia. inputobservedintheintactbrain.Indeed,thegeneticdeletion
Asdetailedabove,adecreasedexpressionofperineuronal of tenascin, an integral component of the perineuronal net,
nets has been reported throughout the temporal lobe38 of resultsinadecreaseinperisomaticinhibitionandenhanced
post-mortem schizophrenia patients. Here we demonstrate excitatorysynaptictransmissionofpyramidalneuronsofthe
thattheMAM-rodentmodeldemonstratessignificantlylower hippocampus,51consistentwiththedatapresentedhere.
levels of the perineuronal net proteins, brevican and phos- We have previously demonstrated that the hippocampus
phacan, throughout the ventral hippocampus. It should be can regulate dopamine system function via a multi-synaptic
noted that MAM-treated rats also display reductions in pathway including the nucleus accumbens and ventral
parvalbumin-containing interneurons;5 thus, whether the pallidum (for review see Lodge et al.31).Moreover, we posit
decreasedexpressionofperineuronalnetproteinsreflectsa that the aberrant vHipp activity may actually be a primary
loss of parvalbumin neurons, or vice versa, is not currently pathologyunderlyingthepositivesymptomsofschizophrenia.
known.Interestingly,theseobservedalterationsinphospha- For this reason, we examined whether the chondroitinase-
can expression are consistent with genetic association induced increase in hippocampal activity was sufficient to
studies demonstrating that PTPRZ1, the gene encoding augment dopamine neuron activity in the VTA. Indeed,
phosphacan,mayinfluencethesusceptibilityforschizophre- chondroitinase-treated rats displayed a significantly greater
nia.48Thus,thedecreasedexpressionofphosphacanfurther number of spontaneously active VTA dopamine neurons
supportsthevalidityoftheMAMmodel,asitappearstomimic whencomparedtopenicillinase-treatedcontrols.Thenumber
phosphacan abnormalities in schizophrenia patients, albeit ofdopamineneuronsfiringspontaneouslyisthoughttoreflect
viaadifferentmechanism. the gain of the dopamine system whereby the functionally
Given that we have previously demonstrated that MAM- relevant,phasicsignalcanbeamplifiedordampenedbased
treated rats display augmented vHipp activity that underlies on environmental context and novelty.28 Thus, a sustained
thedopaminehyperfunctionandbehavioralhyperresponsivity increase in the number of spontaneously active dopamine
to psychomotor stimulants,22 we investigated whether a neuronswouldartificiallyascribehighsaliencetoeventsthat
decreaseinvHippperineuronalnetswassufficienttoinduce are not typically salient, and may contribute to the positive
aberrant hippocampal and dopamine system function, symptoms of schizophrenia.31 An increase in dopamine
thought to underlie the positive symptoms of the schizo- neuronpopulationactivityhasbeenpreviouslysuggestedto
phrenia. Perineuronal nets throughout the vHipp were underlietheaugmentedresponsetopsychomotorstimulants
enzymatically degraded, in a region specific manner, by the observed in animal models,22,40,52 as well as schizophrenia
administrationofchondroitinaseABCfromProteusvulgaris. patients.46,47 This can be examined in rodent models by
Chondroitinase ABC degrades glycosaminoglycans, includ- investigating the locomotor response to a low dose of
ing chondroitin sulfate and hyaluronan, disrupting the amphetamine.22,45,53 Indeed, we now demonstrate that
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Figure5 Intra-vHippadministrationofchondroitinaseABC(b,dandf),butnotpenicillinase(a,cande),resultsinasignificantdecreaseinlectinstainingtoperineuronal
netsthroughoutthevHipp.Photomicrographsdemonstratetheextentofperineuronalnetdegradation,indicatedbytheredcirclein(b).ChondroitinaseABCresultedina
regionspecificreductionofperineuronalnetsobservedinthevHipp(dashedboxinaandb—magnifiedincandd)butnotinmoredorsalregionsofthecortex(solidboxina
andb—magnifiedineandf).Penicillinase-treatedratsdisplaynumerousperineuronalnets(indicatedbyarrows)throughoutboththevHipp(c)andcortex(e).
chondroitinase-treated rats display a significantly greater Studies Hybridoma Bank developed under the auspices of the NICHD
locomotor response to amphetamine administration when and maintained by the University of Iowa Department of Biology, Iowa City,
comparedtopenicillinase-treatedrats.Takentogether,these IA,USA.
data demonstrate that a loss of hippocampal perineuronal
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