Neuroscience Research, 4 (1987) 249-254 Elsevier Scientific Publishers Ireland Ltd.

NSR00168

Regular stripe-like activation and suppression of metabolic activity in the cerebellar cortex following

apomorphine administration to haloperidol-pretreated rats

Shinichi H o s o k a w a , S h i z u k o Tegosh i and M o t o h i r o K a t o

Department of Neurophysiology, Neurological Institute. Faculty of Medicine. Kyushu University, Fukuoka (JapatO

(Received 4 April 1986; Revised version received 7 August 1986; Accepted 8 August 1986)

Key words:Apomorphine; Haloperidol; [14C]deoxygiucose method; Local cerebral glucose utilization; Cerebellum; Stripe-like pattern; Parasagittal "microzone"

Alteration of the pattern of metabolic activity in the cerebellar cortex, as produced by apomorphine in rats given chronic pretreatment with haloperidol was studied by means of the [t4C]deoxyglucose method. Apomorphine induced a regular stripe-like activation and suppression of metabolic activity in the caudal paravermal area of the cerebellar hemisphere and in the caudal vermis of the cerebeUar cortex. This stripe-like pattern, oriented perpendicularly to the cerebellar fissure, suggests the functional organization of the cerebellar cortex in a direction which is parallel to the longitudinal axis of folia.

The columnar organization, as a functional unit of the cerebral cortex, has been well studied, not only electrophysiologically 4 and neuroanatomically 9 but also by metabolic

studies using the [ '4C]deoxyglucose method t~ However, the functional unit in the cerebellar cortex has not been fully established yet. Recently, it has been shown that a parasagittal, zonal functional unit "microzone" exists within the cerebellar cortex i'2"6.7.

In this paper, we report a regular stripe-like activation and suppression of metabolic activity, which oriented perpendicularly to the cerebellar fissure, and which was produced by a dopaminergic agonist, apomorphine, in rats given chronic pretreatment

with a dopaminergic receptor blocker, haloperidol. These changes in the pattern of

Correspondence: S. Hosokawa, Department of Neurophysiology, Neurological Institute, Faculty of Medicine, Kyushu University 60, Higashi.ku, Fukuoka 812, Japan.

25O

m~tahobc activity in the cereballar cortex suggest the functional organization of the eerebellar cortex in a direction which is parallel to the longitudinal axis of folia.

Ten female Sprague-Dawley albino rats, weighing 270-325 g, were used: 5 for the experimental group, and the other 5 for die control group, In the experimental group, the effects of apomorplfin~ were investigated after wkhdrawal from chronic p~- treatment with a dop~inergic receptor blocker, baloperidol. Chm~ie pretreat meat wit h halopeddoI ([ mg/kg/day) was giwn r for 4 weeks by means of a sub- cutan~usly implanted osulodc pump (Alzet 2ML4; Alan, Pale Alto, CA) After 5 days withdrawal o f haloperidol, apomorphine hydrochlorlde ( 1,5 nlg/kg, bY.) was given 5 rain before rim local cerebral glucose ufibzmion (LCGU) study. Comml ~imals r~eived a alndlar volume of isotonic ~aline instead of apomorphi~e,

Details oflpe method of LCGU determination are as reportediZ. In brief, the animals were deprived of food for at least [0 h prior to the sutdy. LCGU determinafion was conducted with the ~imal fully alert and restrained with a loos~fitting east placed around the lower abdomen, pelvis and legs, A bolus of 2-deoxy-D-l-[14C]glueose ({~aC]DG) (125/zCi/kg) (Amersham, 59 mCi/nmol) was injected through a catheter pinned in the femoral vein. Arterial blood sampl~ were collected al sp~iftc times via the l~moral artery catheter into heparinized tubes. Forty-five minutes after the [14C]DG injection, the animals were decapitated, the brains immediately removed and then processed for autoradiographs. ~l]le ~neentrafion of I'C ia a given brain structure was d~ived fronl its optical density and those of standard disc plates in which the eo~ee~- tt'afto~ of "C had been calibrated. LCGU were calculated from file brain eoncemr a~ion of '4C and the plasma concentrations of [14C]DG and glucose, according Io the equation developed by Sokoloff et ab 12. Even though the administration of apomor- phine after withdrawal from chronic pretreatment with haloperidol led to widespread LCGU chan~es in the ext rapyramidal and other systems, we report here ov3y the effects in the eerebefi~ cortex and r~la~ed strueture~. Selected s~rions co~espondlng to the autorediogr aphs, were stained with Cresyl violet.

Administration of apomorphine (1.5 mg/kg~ Lv.) caused remarkable hehavioral changes characterized by stereotypie behaviors including sniffing, repetitive movements ofl~ead and limbs, licking and gnawing, and a increased locomotor activity. Widldrawal from chronic pretreatment with haloperidol ~sulted in increased responses to apomor- phine, in temls of ine~ased locomomr acfi'Aty.

There was a dlscemible differ~ce in the pattern of the autoradiographs of the eerebell~ cortex between the experimental and control groups (Fig. 1). In the cerebellum oftpe eomrols, 3 layers could be cle~ly distinguished, which w~e p~allel to the c~ebell~ fissure. The layers were, from the surface inward, the mol~ular layer, tile granular layer, ~nd the white matter. The gr~ular layer showed the highest density, indicating the highest LCGU ~ o n g l~e 3layers, In the experimental group given aponlorpldne after withdrawal from chronic haloperidol pretreatmenh the caudal paravcrmal area of ce~bell~ hemisphere showed a stripe-like activation and ~pp~ssion, with regul~ inte~,als. The d i~ l ion of stripes was practically per-

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Fig. 1. Autoradiographs (A, B, C, D) and Cresyl violet-stained sections (E, F) in rats of control (A, B) and experimental (C, D, E, F) groups, in the autoradiographs ofcontrol, the caudal vermis (A) and hemisphere (B) of the cerebellum showed the 3 layers which were in parallel to the cerebellar fissure. The layers are, from the surface inward, the molecular layer, the granular layer, and the white matter. In the experimental group administered apomorphine after withdrawal from chronic haloperidol pretreatment, the caudal part of the eerebellar vermis (C) and the caudal paravermal area of the cerebellar hemisphere (D) showed a stripe-like activation and suppression with regular interval of 3.50-450 ~m. The direction of stripc.s was practically perpendicular to the cerebellar fissure. The histological sections (E, F), which correspond to C

and D, respectively, showed no histological difference between the activated and suppressed stripes.

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pendieul~ to the cerebzll~ ,assure. Tile stripes involvpd both molecular and granular layers, but were limited to within one to,aule. The width or the activated stripes was 372 + 161~m (mean + S,E,~vL) (n = 16), ~ d that of the suppressed stripes was 359 .+_ 24 a m QI - 10). These strip~,ake patterns were evident in 3 of 5 rats in the experiment ~1 group. The strlpedLke pattern was also observed in the caudal vennis in 5/5 rats in the experimental group. The width of the activated stripes in the verm[s was 428 • t2 im~ 01 = 17), ~nd that of suppressed stripes was 367 • 15 Enl (n - 17). The 3 layers observed in the eonu'ol group were not visible in tl~e region with the strlpe-llke pattern. Then was no di~ernible ,ais~ologieal difference in terms of the number of heWn or gled cells between the part with the activated stripes and that of the suppressed stripes in the ,aistalogical section, corresponding to the autoradiograp,as (Fig, I E and F). An,synced punclme ~eas with ~ i~egular distribution and a rather weak activation of more wide-speeed areas were obs~ved in other parts of the ce~bellar cortex.

The alternating coIumn~ pattern ofacPvated and suppressed metabolic activity was also observed in the ce~bral cortex, mainly localized in the sensory-motor area. The width of activated eotumns was 365 + 10 (u ~ l,a), The columnar pattern was not observed in either prefrontal, cingulate, posterior p~ie t al, temporal or occipital areas

The quantitative analysis of LCG U demonstrated that the averaged rates of LCGU in the cerebegar cortex were si~i,aeanay high~ in tile experim~tal group, compared with the controls. The LCGU increases in the activated stripes in the eerebell~ hemisphere mad vermis were particularly large, whereas, the values in the suppressed stripes in the cerebdtar hemisphere showed a significant decrease (P < ,a.,aS), compared with the values of the controls (Tablel). The sensory-motor cerebral cortex (layers IV, VI) and inferior olive also showed significant LCGU increases, in Ihe experimental group~ TheinFerlor olive sbowed the increase as a whole, and any regionut difi~renee in LCGU in that structure was not evident, The pontiac nudal and cerebeHar nuclei s,aowed no rigal,ae~t LCGU changes, in the experimental group,

This study clearly demonstrated that aponlorphine induces a we0-organized strip~ like activation and suppression of tile ~letabogc activity in the caudal p a ~ v e ~ d a~a of the cereballnr ,aemisphe~, and the caudal vermis of the cerebe,aar cortex ofra ls given chronic pretreatment with haloperidol. This stripe-like pattern, which was oriented perpendicularly to the cereballar fissure, together with the e o l ~ n ~ activation in the sensory-motor cerebralcortex, suggests a funelional organization of the cerebell~ cortex in a direction which is parallel to the longitudinal 8xis of foils. The mee,aanlsm of the genesis of regular intervals betw~n stripes is unknown. However, recent neurt,~latomi- eat and el~trop,ayalologieal studies have shown that a p~asagit~l , Iongi~ud,a~al "micro- zone" with a width of about 200 ~lm may represent a functional un,a of the cereballar cortex l.~.7. Moreover, it has b~n shown that the climbing fibre inpu~ to o~e mlerozone is in,aiblted by stimulation e r a ne~e that projects to an adjoining mierozone ~, Such physiological mechanisms might be re lev~t in the genesis o f the stripes with regular inle~als. Each of these ~tripes may possibly represent one or some "mierozonegr demonstrated in et~trop,ayslnlogleal 1~ and neuro~atomical ~'7 studies.

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TABLE I

LOCAL CEREBRAL GLUCOSE UTILIZATION IN THE CEREBRO-CEREBELLAR SYSTEM OF RATS, ADMINISTERED A?OMORPHINE (1.5 mg/kg, i.v.) AFTER WITHDRAWAL FROM CHRONIC PRETREATMENT WITH HALOPERIDOL (1 mg/kg/day FOR 4 WEEKS)

Values represent mean + S.E.M. of LCGU values (pmol/100 g/rain) averaged between the two sides.

(nOntr5~l ~xp_e~ment

Cerebral cortex Sensory-motor area

Layer IV 121 _+. 4 186 + 16'* Layer VI I01 3 130 + 11"

Pontinc nucleus 77 + 13 88 + 4

Inferior olive 102 + 9 132 + 8*

Cerebellar cortex Hemisphere

Activated stripes 69 + 6 133 + 12'* Suppressed stripes 69 6 53 3*

Vermis Activated stripes 103 + 5 217 + 30** Suppressed stripes 103 5 85 7

Cerebellar nucleus 133 + 12 137 + 16

The effects of the dopaminergic agonist, apomorphine, on local cerebral glucose utilization have been examined extensively 5'8'1 t. Punctate areas of increased L C G U in the cerebellar hemisphere aad columnar activation in the posterior vermis following apomorphine administration have been previously reported by McCulloch et al. ~ 1. However, they did not describe the direction of the columns in the vermis, the regularity ofintervals, and the width of the columns. They did not describe the "stripe-like pattern" in the cerebellar hemisphere. Moreover, they did not discuss the significance of the pattern of the L C G U changes in the cerebellum. In the present study, a stripe-like activation and suppression with regular intervals, of 350-450/~m, which was oriented perpendicularly to the cerebellar fissure, was observed in the caudal paravermal area of the cerebellar hemisphere as well as in the caudal vermis. Rather irregular punctate increased areas were also observed in other areas of the cerebellar hemisphere. The L C G U changes in the eerebellar cortex produced by apomorphine in rats given chronic pretreatment with haloperidol seems to be enhanced and more organized (unpublished observation).

The following two possibilities have to be considered concerning the mechanism of L C G U changes by apomorphine in the cerebellar cortex where few dopaminergic

receptors are present : one is t ranssynapt ic functional changes mediated by the changes

in structures which contain dopaminergic receptors, such as the striatumS; and the o ther

is secondary functional changes caused by the increased moto r activity induced by

apomorphine . The latter seems more likely, since the L C G U change in the cerebellar

cortex, as p roduced by apomorphine , was abolished in para lyzed animals (unpublished

observat ion) .

ACKNOWLEDG EM ENTS

This s tudy was suppor ted in par t by grants f rom the J a p a r e s e Minis t ry o f Educat ion ,

Science and Culture (Gran t Nos. 58106003 and 59770555). We thank M. Yoneda and

K. H a t a n a k a for technical assistance, M. O h a r a (Kyushu Universi ty) for commen t s on

the manuscr ipt .

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