Brain neuropeptides: Tachykinins, neuropeptide Y, neurotensin and vasoactive intestinal polypeptide in the rat brain: Modifications by ECT and indomethacin

BRAIN NEUROFE~IDES: TACHYKININS, NEUROFEP~DB Y, I~STINAL NEUROTENSIN AND VASOA~IVE POLYPEPTIDE IN THE RAT BRAIN: MODIFICATIONS BY ECT AND INDOMETHACIN

ELVAR THEODORSSON1, ALEKSANDER A. MATR$2 and CARINA STENFOR$

Karolinska Institute, Departments of lClinica1 Chemistry, Karolinska Hospital, and 2Psychiatry, St G&an Hospital, Stockholm, Sweden.

(Final form, October 1989)

Abstract Theodorsson, Elvar, Aleksander A. Math&. and Carina Stenfors: Brain neuropeptides: Tachykinins, Neuropeptide Y, Neurotensin and Vasoactive Intestinal Polypeptide in the rat brain: Modifications by ECT and Indomethacin. Proq. Neuro-Psychopharmacol.L Biol. Psychiat. 199O,J&:387407 1. The effects of electroconvulsive treatment (ECT) and indomethacin on brain regional and right-left hemispheric dfstributlon of tachykinins (TK), neuropeptide Y (NPY), neurotensin (NT) and vasoactive intestinal polypeptide (VIP) were studied in the rat. 2. Differences in peptide concentration between brain regions (frontal cortex, striatum, occipital cortex, hippocampus and hypothalamus) were found for all five peptides measured (all P values less than 0.001). 3. Furthermore, concentration differences between the hemispheres were found for SP, NKA and VIP (P < 0.001, PC 0.001 and P < 0.005, respectively), but not for NT and NPY. Peptide concentrations were generally higher in the right than the left hemisphere: e.g., SP levels in the frontal cortex, striatum, occipital cortex and hippocampus were 194, 390, 335 and 136 percent higher, respectively, in the right compared to the left hemisphere. The results are consistent with other findings of right-left distribution of some neurotransmitters.

brain

asymmetries

in

4. One ECT had no detectable effects on concentrations of SP, NKA, NT or

VIP. However, the mean concentration of NPY was higher in all regions (except the striatum) and both hemispheres (P = 0.004). 5. In the rats pretreated with indomethacin, levels of SP, NKA and NT were decreased (P < 0.001, P < 0.001 and P--O.039 respectively), whereas the concentrations of VIP and NPY were not affected. For SP and NKA the decrease was apparent in all brain regions and both in the right and left hemispheres. For NT, the effect was more prominent in the left than in the right hemisphere.

387

E.Thoodorsson

388

3(: VW rd

Nzur%e%n,

et al.

Electroconvulsive treatment Indomethacin Neuropeptide Y, Tachykinins, Vasoactive I&estinal polypeitide.

Abbreviations: acetylcholine (ACh), adrenaline (A), dopamine (DA), electroconvulsive treatment (ECT), neurokinin A (NKA), neuropeptide Y (NPY), neurotensin (NT), noradrenaline (NA), prostaglandin (PG), prostaglandin E (pGB)* serotonin (5-HT), substance P (SP), vasoactive intestinal polypeptide (VIP).

The number of putative neurotransmitters in the brain is continuously increasing, and many neuropeptides have been added to the list in the past two decades. Neuropeptides are frequently present in the same neNe cells as other neuropeptides or monoamine neurotransmitters. Thus, to mention a few examples, neurotensin (NT) co-exists with dopamine (DA) and adrenaline (A), substance P (SP) with serotonin (5-HT), neuropeptide Y (NPY) with noradrenaline (NA) and vasoactive intestinal polypeptide (VIP) with acetylcholine (ACh) (WcCann.and Weiner 1987, Shimada et al. 1988, Iiijkfelt al. 1987, Lindefors 1987, Kanazawa et al. 1984). A variety of interactions - such as increase/decrease in release, changes in binding, effects on turnover, etc - between neuropeptfdes and neurotransmitters have been reported (Lindefors 1987, Khorram et al. 1988, Wahlestedt et al. 1987, McCann and Weiner 1987, Teledgy 1987, Mitsushio et al. 1988). The possible role of neuropeptides in the etiology and pathogenesis of major mental disorders is the object of many investigations (Berrettini et al. 1987, Bissette et al. 1986, Rimdn et al. 1984, 3egoU et al. 1988, Widerlov et al. 1982, 1988). WOreOVer, drugs effective in treatment of schizophreniaand depressive disorder have been shown to affect the regional concentrations of a number of neuropeptides (Brodin et al. 1987, Mitsushio et al. 1988, Lindefors 1987, Hong et al. 1982). Several brain functions are associated predominantly with one brain region or with one of the hemispheres. As a corollary, certain CNS disorders are also presumed to be, at least in part, localized to a certain brain region or lataralized. Thus in major depression the deficit is hypothesized to be primarily associated with the right brain hemisphere and, conversely, in schizophrenic disorders predominantly left hemisphere dysfunction has been suggested (Bryden 1982, Otto et al. 1987). In view of the preceding and the demonstrated CNS lateralization in the content of some neurotransmitters and fatty acids (Ginobili et

Modifications

of brain neuropeptides

389

al. 1986, Glick et al. 1982, Oke et al. 1980, Pediconi et al. 1984, Reynolds 1983), we investigated concentrations of neuropeptides in the right and left hemispheres and right and left parts of certain brain regions. Electroconvulsive treatment (ECT) is generally considered the most efficient therapy of major depression. While its mechanism of action remains unknown, a multitude of neurotransmitters, hormones and arachidonic acid derivatives changes have been demonstrated (Lerer et al. 1984, Malitz 6r Sackeim 1986). Since effects of ECT on the regional concentration of neuropeptides have not been explored, the tissue concentration of brain tachykinins (SP and neurokinin A (NKA)), NPY, NT and VIP following ECT were investigated. Previous studies have shown an interaction between peptides, neurohormones and arachidonic acid metabolites in the nervous system (Piomelli et al. 1987, Ojeda et al. 1981, Hartung et al. 1988, Canonico et al. 1985, Shimatzu et al. 1983, Schaad et al. 1987). Furthermore, following ECT there is an increase in prostaglandins (PG) in animal brain as well as in plasma PGE metabolite in humans (Bazan 8 Birkle 1985, Berchtold-Kanz et al. 1981, Mathe et al. 1987). The authors, therefore, investigated the effects of ECT and indomethacin, a PG synthesis inhibitor, on regional concentrations of neuropeptides in the brain. Methods

Animals Male Sprague-Dawley rats (ALAB Sollentuna, Sweden) weighing 200-220 g were used. They were housed 6 to a cage at a constant room temperature (21+l°C) with free access to water and standard rat chow, and with a 12 h light-dark cycle. Test Drocedures The rats were randomly divided into four groups receiving following treatments: (1) n = 13, vehicle (0.2 mL B.C.) 2 hours prior to one transauricular ECT (15OV, 50H2, 20ms stimuli for 1 set using a Grass S44 stimulator), (2) n = 6, vehicle (0.2 mL B.C.) 2 hours prior to one sham ECT, (3) n = 6, indomethacin (3 mg/kg, 0.2 mL, s.c.) 2 hours prior to

E. Theodorsson el al.

390

ECT, and (4) n = 4, indomethacin (3 mq/kq, 0.2 mL, s.c.) 2 hours prior to sham ECT. The current-deliveringelectrode was placed in random order either on the right or left ear. Three minutes after ECT or sham ECT the rats were decapitated, the brains were quickly removed on dry ice and dissected according to the method of Glowinsky and Iversen (1965) into frontal striatum, cortex, occipital cortex, hippocampus and hypothalamus. Immediately after dissection, each region was divided into right and left half. All regions were weighed and stored at -8OOC. Extraction of tlrssuesgmules The samples were cut into small pieces in the frozen state, boiled for 10 min in 1 mol/L acetic acid and homogenized. After centrifuqation, the supernatants were lyophilized and stored at -2OOC before analysis. Radioimnunoassav The tissue concentrations of SP, NKA, NPY, NT and VIP were analyzed by competitive radioimmunoassays:Antiserum SP2 (Brodin et al. 1986) reacts with SP and SP sulfoxide but not with other tachykinins. Antiserum K12 (Theodorsson-Norheimet al. 198533)reacts with NKA, NKA(3-lo), NKA(IlO), neurokinin B (NKB), neuropeptide K (NPK) and with an eledoisin-like peptide but not with SP . Antiserum Nl (Theodorsson-Norheim et al. 1985b) reacts with the mid-portion of NPY but not with fragments of NPY. Antiserum Ii (Theodorsson-Norheim and Rose11 1983) reacts with the Cterminus of NT. Antiserum VIP2 raised against porcine VIP does not crossreact with qastrin, pancreatic polypeptide, qlucaqon, neuropeptide Y or neurotensin (unpublished). Statistical analvsh The mean and one standard deviation are used as measures of central tendency and variation, respectively, throughout the study. Percent changes in concentrations represent changes in mean concentrations. Descriptive statistical analysis was performed as described earlier (Theodorsson 1988). Analyses of variance and covariance were performed using SYSTAT version 4.0 (Wilkinson 1988). The effects of ECT and indomethacin, as well as regional and right/left differences were estimated, using the concentration of peptides aa a dependent variable. Furthermore, interactions between all these factors were tested. P values less than 0.05 were considered significant.

Modi~~ations

of brain ~lc~lrop~pti[les

Results

peaion&&&&rences

and mation

of Peotide Concentrations

Significant differences in peptide concentration between the brain regions were found for all peptides studied (P values c O.OOl)(Table 1,2). The concentrations of SP and NKA were highest in the striatum and lowest in the hippocampus (Fig. 1,2). The concentrations of NT were also highest in the striatum, but in contrast to SP and NKA they were similar in hippocampus and striatum (Fig. 3). As opposed to SP, NKA and NT, the concentrations of VIP were highest in the frontal and occipital cortex and lowest in the striatum and hippocampus (Fig. 5). Lastly, concentrations of NPY were statistically different between the brain regions examined, although the distribution - compared to other peptides - was rather even (Fig. 4). Overall concentration differences between the hemispheres were found for SP, NKA and VIP (P values < 0.001, 0.001 and 0.005, respectively), whereas no significant differences were found for NT and NPY, (Table 1‘21. Significant region - right/left interaction was fOUnd for SP, NKA, NPY and VIP (P values c 0.001, 0.01, 0.001 and 0.01, respectively). Peptide concentrations were in most cases higher in the right hemisphere than in the left. Within the specific regions the right/left differences were most pronounced in atriaturnand frontal and occipital cortex for SP and NKA, and in frontal cortex and hippocampus for VIP. For NPY, the right-left difference was found in frontal and occipital cortex. Thus the concentrations of SP in the frontal cortex, striatum, occipital cortex and hippocampus were 194%, 3909, 335% and 136% higher, respectively, in the right hemisphere than in the left. The corresponding figures for NKA were Y2%, 128%, 105% and 109%, and for VIP 20%, 125%, 27% and 231%. While for SP, NKA, and VIP higher right than left peptide concentrations were found, the opposite, that is higher left than right concentration was demonstrated for NPY.

E. Theodorsson et al.

392

Table 1 Analysis of Variance and Covariance for Substance P, Neurokinin A and Neurotensin SUDSTANCRP SOURCE

SUM-OF-SQUARES

ECT INDC RF#G R-L ECT*INW ECT*REG ECT*R-L INDG*REG INDG*R-L RRG*R-L

0.861 4931.586 6270.194 3607.949 4.191 31.959 20.070 4189.984 2424.314 5528.701

ERROR

64191.553

DF

MEAN-SQUARE

1 1 3 1 1 3 1 3 1 3

0.861 4931.586 2090.065 3607.949 4.191 10.653 20.070 1396.661 2424.314 1842.900

227

SUM-OF-SQUARES

DF

ECT INDO REG R-L ECT*INDtY ECT*REG ECT*R-L INDC*REG INDO*R-L RRG*R-L

7.417 10674.385 13010.682 4079.309 28.527 34.690 559.647 9305.157 851.472 3854.721

1 1 3 1 1 3 1 3 1 3

ERROR

71362.048

227

SOURCE ECT INDC REG R-L INDO*RRG INDG*R-L RRG*R-L ERROR

SUM-OF-SQUARES DF 0.129 30.401 274.464 0.473 11.863 4.345 9.859

1 1 3 1 3 1 3

1659.400

235

P

0.003 17.440 7.391 12.75 0.015 0.038 0.071 4.939 8.573 6,517

0.956 < 0.001 < 0.001 < 0.001 0.903 0.990 0.790 0.002 0.004 < 0.001

282.782

NEUROXININ

SOURCE

F-RATIO

A

MEAN-SQUARE

7.417 10674.385 4336.894 4079.309 28.527 11.563 559.647 3101.719 851.472 1284.907

F-RATIO 0.024 33.955 13.795 12.976 0.091 0.037 1.780 9.866 2.709 4.087

P 0.878 < 0.001 c 0.001 < 0.001 0.764 0.991 0.183 < 0.001 0.101 0.007

314.370

MEAN-SQUARE

0.129 30.401 91.488 0.473 3.954 4.345 3.286

F-RATIO

P

0.018 0.892 4.305 0.039 12.956 < 0.001 0.067 0.796 0.560 0.642 0.615 0.434 0.465 0.707

7.061

ECT denotes the contribution of electroconvulsive treatment: INDO denotes the contribution of indomethacin; RRG denotes different brain regions; R-L of the right and left hemispheres. The effect of interactions between the different factors is depicted with an *. P is the probability estimate.

Modifications

393

of brain ncuropeptidcs

Table 2 Analysis

of Variance and Covariance for Neuropeptide Intestinal Polypeptide.

NEUROPEPTIDE SOURCE

SUM-OF-SQUARES

DF

Y

MFAN-SQUARE

40.689

ECT INDD REG R-L ECT*INW ECT*RFG ECT*R-L INDG*REG INDG*R-L RRG*R-L

4.157 114.491 0.089 18.824 2.643 3.250 29.139 87.562 309.995

ERROR

1092.140

SUM-OF-SQUARES

ECT INDO REG R-L ECT*INDO ECT*REG ECT*R-L INDO*REG INDC*R-L RRG*R-L

110.954 2.529 90118.443 2242.593 45.431 718.937 2.882 1622.788 681.682 2981.801

ERROR

62074.796

* The effect

F-RATIO

40.689

4.157 38.164 0.089 18.824 0.881 3.250 9.713 87.562 103.332

3 227

DF

8.457 0.004 0.864 0.354 7.932 < 0.001 0.018 0.892 3.912 0.049 0.183 0.908 0.676 0.412 2.019 0.112 18.200 < 0.001 21.477 < 0.001

WLYPEPTIDE

MEAN-SQUARE

1 1 3 1 1 3 1 3 1 3

110.954 2.529 30039.481 2242.593 45.431 239.646 2.882 540.929 681.682 993.934

225

275.888

of interactions

P

4.811

VASOAC?FIVR INTESTINAL

SOURCE

Y and Vasoactive

between

F-RATIO

P

0.402 0.527 0.009 0.924 108.883 < 0.001 8.129 0.005 0.165 0.685 0.869 0.458 0.010 0.919 1.961 0.121 2.471 0.117 3.603 0.014

the different

factors.

E.T~eadorsson et&.

394

120

251

VEHICLE c7

HDOYEIHWN

RIGHT

c3

amlEFT

RIGHT

mm

7 I

z

40

I

is 5

20 0

-l

?ZZ SW FRONT

ECT StUM STR

ECT SHAM ECT SW GCCIP HIPPOC

0 ECT SIMM ECT SIMM ECT SHAM Et.3 SK& FRONT @$TR OCCIP HIPPOC

Fig 1. Concentration of immunoreactivesubstance P (pmol/g) in the right and left frontal cortex, striatum, occipital cortex and hippocampus in rats receiving a single electroconvulsivetreatment (ECT) or sham ECT. All animals were pretreated with either indomethacin or vehicle.

VEHICLE Cl RIGHT

7100 5 E 8o <

mlm

60

1 40

9 z

2o 0 EC&T&d

ECT SHAM ECT SHAll ECT SHAM HIPPOC STR GCciP

EC3Sl&Al

ECT SW STR

ECT SIUM OCCIP

ECT SW HIPPOC

Fig 2. Concentration of immunoreactiveneurokinin A (pmol/g) in different regions of the brain in rats receiving a single ECT or sham ECT. All animals were pretreated with either indomethaoinor vehicle

Modifications

of brain ncuropcptides

25

25

p20

s20

Ti 515 V 3 10

2 515 V 7 10 I

I

395

!s5

t5 0

IXX SHAM ECT SHAM EC1 SHAM ECT SHAM FRONT

SIR

OcclP

HIPPOC

0 ECT SHAM ECT SW4 FRONT

STR

ECT SNM4 ECT SW OcC!P HIPPOC

Fig 3. Concentration of immunoreactiveneurotensin (pmol/g) in the right and left frontal cortex, striatum, occipital cortex and hippocampus in rats receiving a single electroconvulsivetreatment (ECT) or sham ECT. All animals were pretreated with either indomethacfn or vehicle.

ECT SHAU EtiT S& FRONT Sm

OGCIP

HIPPOC

ECT SHAM ECT SHAM ECT SH& FRONT SlR OCCIP

HIPPOC

Fig 4. Concentration of immunoreactiveneuropeptide Y (pmol/g) in different regions of the brain in rats receiving a single ECT or sham ECT. All animals were pretreated with either indomethacin or vehicle

E.Thcodorsson

39fi

et al,

Effectsof One transauricular ECT, did not change the regional concentrations of SP, NIZA,VIP or NT, regardless of whether the rats were pretreated with vehicle or indomethacin (Figs. 1,2,3,5). However, the concentration of NPY was higher in the ECT rats by 24.5% and 6.5% in the right and left frontal cortex, 5.5% and 3.8% in the right and left occipital cortex, and 11.0% and 12.9% in the right and left hippocampus, respectively, indicating a significant increase of the NPY concentrations in response to ECT (P = 0.004). In the hypothalamus, no effects of ECT were found for any of the peptides studied (Table 3., Fig. 6.). Effects of Indomethachn In the rats pretreated with indomethacin, levels of SP, NKA and NT were decreased (P values < 0.001, 0.001 and 0.05, respectively) (Table 1, Figs. 1,2,3), whereas no significaht effects were found on the concentration of VIP and NPY (Table 2, Figs. 4,5) except in the hypothalamus where the NPY concentrations were lower in the rats pretreated with indomethacin (P = 0.017, Fig. 6, Table 2). For SP and NKA the decrease was apparent in all brain regions and in both the right and left hemispheres. For NT, the effect was more prominent in the left than in the right brain, in particular in striatum and hippocampus. Further comparison to the vehicle pretreated animals showed that in the indomethacin pretreated rats the SP concentrations were 61% and 57% lower in the right and left frontal cortex, respectively, and 87% and 64% in the right and left striatum. The concentrations of NKA were 56% and 74% lower in the right and left frontal cortex and 77% and 84% lower in the right and left striatum. Significant interactions were observed between indomethacin and right/left hemispheres for SP and NXA. With regard to SP, the most pronounced lowering by indomethacin was obtained in the striatum, followed by frontal and occipital cortex. The smallest effect was seen in the hippocampus. Moreover, decrements were larger in right compared to the left hemisphere. Similar interactions were obtained for NKA (Table 1, Figs. 1,2). No indomethacin-brain region interaction was observed for NT, NPY and VIP. In vehicle pretreated animals the concentrations of NT were 87% and 3.2%higher in the left striatum and hippocampus compared to the right counterparts. In indomethacin pretreated animals, however, NT

Modifications of brain neuropeptides

397

concentrations were 532 and 15% lower in the left compared to the right striatum and hippocampus. Thus indomethacin reversed the right-left concentration differences for RT in the striatum and hippocampus (Fig. 3). In the hypothalamus, significant decreases of SP, NRA, NT and NPY were found, while the concentrations of VIP did not change (Table 3., Fig. 6). Table 3 Analysis of Variance and Covariance for Substance P, Neurokinin A, Neurotensin, Neuropeptide Y and Vasoactive Intestinal Polypeptide in the Hypothalamus. ANALYSIS OF VARIANCE Substance P: SOURCE SUM-OF-SQUARES DF ECU! 139.991 1 INDD 27302.507 1 ECT*INDC 19.965 1 ERROR 93019.737 26

MEAN-SQUARE F-RATIO 139.991 0.039 27302.507 7.631 0.006 19.965 3577.682

P 0.845 0.010 0.941

Neurokinin A: SOURCE SUM-OF-SQUARES DF ECT 71.251 1 INDC 35952.395 1 ECT*INDC 26.508 1 ERROR 83048.284 26

MEAN-SQUARE F-RATIO 0.022 71.251 35952.395 11.256 0.008 26.508 3194.165

P 0.882 0.002 0.928

Neurotensin: SOURCE SUM-OF-SQUARES DF ECT 26.050 1 INDC 1160.674 1 ECT*INW 22.402 1 ERROR 4484.826 26

MEAN-SQUARE F-RATIO 26.050 0.151 1160.674 6.729 22.402 0.130 172.493

P 0.701 0.015 0.721

Neuropeptide Y: SOURCE SUM-OF-SQUARES DF MEAN-SQUARE F-RATIO ECT 0.710 1 0.710 0.015 INDD 299.740 1 299.740 6.455 ECT*INDD 41.705 1 41.705 0.898 ERROR 1253.758 27 46.435

P 0.902 0.017 0.352

Vasoactive Intestinal Polypeptide: SOURCE SUM-OF-SQUARES DF MEAN-SQUARE F-RATIO ECT 0.148 1 0.148 0.074 INDC 1.075 1 1.075 0.535 ECT*INDC 3.615 1 3.615 1.801 ERROR 52.192 26 2.007

P 0.788 0.471 0.191

ECT denotes the contribution of electroconvulsive treatment and INDO of indomethacin. The effect of interaction between ECT and INDC is depicted with an l . P is the probability estimate.

398

E. Theodorsson el al.

120

120

y100

FlOO

‘iiE

80

zE

80

* 7 I

60

2 7

60

40

5

20

I 5

0

ECTSW FRONT

20 0

ECTSWM ECTW m

4o

OCCIP

ECT SHAM HIPPOC

ECT SW FRONT

.

.

.

.

5. Concentration of immunoreactivevasoactive intestinal polypeptide (pmol/g) in the right and left frontal cortex, striatum, occipital cortex and hippocampus in rats receiving a single electroconvulsive treatment (ECT) or sham ECT. All animals were pretreated with either indomethacin or vehicle.

Fig

200

a

1A

I

a

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8

Lh!l

150

B ,100

’ so

4

,

ECT SHAM ECT SIMM ECT SW ql? OCCIP HIPPOC

EcTstwEcTsw ltmmmkm-

Fig 6. Concentration of immunoreactivesubstance P, neurokinin A, neurotensin, neuropeptide Y and vasoactive intestinal polypeptide (pmol/g) in the hypothalamus of rats receiving single electroconvulsivetreatment (ECT) or sham ECT. All animals were pretreated with either indomethacin or vehicle. For further explanation of statistics see the text and Table 3.

Modifications

of brain neuropeptidcs

Discussion Tgchvkinim Large differences in

rat

were

in peptide concentrations between the brain regions

found

for

all

peptides

studied.

established that the distribution of neuropeptides the CNS

(Arai 8 Emson

1986, Beal et al.

Previous

work

has

is uneven throughout

1987, Xanazawa

et al.

1984,

Lindefors 1987, Pernow 1983). NXA, a recently discovered member of the tachykinin family, has a similar distribution to SP in the mammalian CNS (Xanazawa et results,

al.

our

Interestingly,

1984,

Brodin

data

show

a

SP

and NXA

et

al.

marked followed

each

highest concentrations were measured The

levels were

there was

lower

a marked

differences were

in the

frontal

tachykinin

other

quite

and occipital interaction.

(a) between brain regions;

between the right and left parts, and

with

these

distribution.

closely

and

the

the hypothalamus and striatum.

in

region-right/left

found

1986). In agreement

regional

cortex.

Thus,

Moreover,

concentration

(b) within a region,

(c) within a hemisphere,

concen-

tration differences between the regions were different in the right and left hemispheres.

Such a regional distribution

with the hypothesis that tachykinins are of perhaps those pertaining influences

DA release

antipsychotic

drugs

seems to be consistent

relevance in CNS functions,

to affect and sensory input. Findings that SP

and metabolism affect

and that both antidepressive

tachykinins

in

specific

brain

and

regions

(Lindefors 1987, Bong et al. 1982, Mitsushio et al 1988, Brodin et al. 1987) also appear to be supportive of such an assumption. Xeurotensin Neurotensin

like tachykinins,

is also widely

distributed

in the CNS

(HBkfelt et al. 1987, Uhl and Snyder 1976). However, significant differences in regional distribution of NT and tachykinins were shown in our study; NT was found in high concentrations also in the hippocampus. rat hypothalamus 1988).

This

implicated

NT

is of

and SP coexist interest

in schizophrenic

since

in single neurons

(Shimada et al.

hippocampus .and amygdala

disorder.

Moreover,

In

NT. interacts

have with

been DA,

lower NT in CSF of schizophrenic patients has been reported, and, it has been suggested that NT is an endogenous antipsychotic

(Widerlov et al.

1982, Rimon et al. 1984, Nemeroff 1980, Nemeroff et al. 1983).

Neuropeptide Y is present in highest concentration in the brain stem, the basal ganglia, the hypothalamus and several limbic areas (Beal et al. 1987, Card and Moore 1988). The highest concentrations of NPY were found in striatum and a region-right/left interaction in frontal and occipital cortex was demonstrated. As opposed to tachykinins, the levels were higher in the left than in the right cortex. In view of noradrenaline's probable involvement in depressive disorders, co-existence of noradrenaline and NPY, and NPYs regional distribution, it is conceivable that vicissitudes in NPY may play a role in normal expression of affect as well as in depression. Vasoactive Intest-

Polvoeotid8

VIP is co-localized with ACh, has an effect on cerebral blood flow and metabolism, modulates hypothalamic influence on release of pituitary hormones and excites the central neurons (Said 1986, Teledgy 1987, Eckenstein and Baughman 1984, Phillis et al. 1978). VIP is widely distributed in the CNS (Sims et al. 1980, Said 1986, Jegou et al. 1988). In human, the highest levels were found in the frontal cortex (Jegou et al. 1988). Our results are in general agreement with those previously reported: several times higher concentrations were found in the frontal and occipital cortex compared to striatum, hippocampus and hypothalamus. In addition, a marked region-right/left interaction was demonstrated. VIP contents in right parts of striatum and hippocampus was higher than in the left parts, thereby also demonstrating a different relative distribution in the right and left hemispheres. The regional distribution of VIP stands thus in contrast to that of SP, NRA and NPY and is not at variance with its reported functions in the CNS. Riaht/reft

~emisDheric

ZadWance

in

Concentrations

A right/left hemispheric imbalance was demonstrated for SP, NRA and VIP but not for NT and NPY. Peptide concentrations were usually higher in the right hemisphere than in the left. These results are in agreement with the findings that some neurotransmitters,e.g. DA, NA and ACh, as well as fatty acids are unevenly distributed between the right and left brain hemispheres (Oke et al 1980, Ginobili et al 1986, Pediconi et al 1984, Reynolds 1983, Glick et al 1980). This lateralization of neurotransmitter distribution and hypothesized changes in their function may

Modifications

of brain ueuropcptidcs

401

perhaps constitute partial basis for the linkage of certain brain functions, and probably some disease states, to one hemisphere. In parallel, our findings of the right/left SP, NXA and VIP imbalance appear to be consistent with the possibility that also neuropeptides play a part in CNS functions and that distinct peptide changes are of significance in pathogenesis of some CNS disorders.

In contrast to marked changes in monoamine neurotransmitters and hormones following a single ECT (Lsrer et al. 1984, Malitz and Sackheim 1986) no effect on the concentrations of SP, NXA, NT or VIP were found. However, NPY levels were elevated: the largest change was measured in the hippocampus. NPY affects release of hypothalamic and pituitary hormones (Xhoramm et al. 1988, Wahlestedt et al. 1987) and in behavioral experiments, NPY suppresses rat activtty and increases food intake (Heilig et al. 1988, Xalra et al. 1988). In the periphery, NPY can stimulate prostaglandin synthesis (Mohy and Malik 1988). These properties of NPY are of interest in view of certain similarities to the effects of ECT. Moreover, NPY co-exists with monoamines and lower CSF levels in depression were demonstrated by some, though not all, investigators (Berrettini et al. 1987, Widerltivet al. 1988). On the basis of these observations it is possible to speculate that changes in neuropeptides such as NPY may, in part, account for the beneficial effects of ECT in depression. Time course and repeated ECT studies are being conducted in an attempt to clarify this issue. ufects of Indomethacb An interaction between neuropeptides and prostaglandin E (PGE) in the brain has been established (Tojo et al. 1986, Shimatzu et al. 1983, Hartung et al. 1988, Piomelli et al. 1987, Schaad et el. 1987). In other experiments, a marked increase in metabolic products of arachidonic acid in rat brain in response to ECT has been demonstrated (Berchtold-Xanzet al. 1981, Bazan and Birkle 1985, Mathe et al. 1987). Moreover, ECT affects the catecholamines and existence of a catecholamine - PG interrelationship has been repeatedly shown. We, therefore, studied effects of indomethacin, an inhibitor of cyclooxygenase, on neuropeptides in the brain. Indomethacin reduced the concentration of tachykinins, had a smaller effect on NT and NPY, and apparently did not influence VIP. As far as the indomethacin-right/leftbrain interaction, a more pronounced

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SP decrease was found in the right compared to the left hemisphere, the largest effects were registered in the right striatum, frontal and occipital cortex. Effects of indomethacin on NKA were similar to those on SP, implying that they are specific for the tachykinin family of neuropeptides. Although we did not measure eicosanoids in the same samples, indomethacin dose and modus of application make it likely that the action was exerted via changes in the synthesis of eicosanoids. Our results thus raise the possibility of the existence of a tachykinineicosanoid interrelationship in the CNS. Studies with other inhibitors of eicosanoid synthesis are currently in progress.

Conclusion Three main findings are presented in this paper: (1) a right/left hemispheric imbalance was demonstrated in SP, NIZAand VIP concentrations but not in NT and NPY concentrations; (2) ECT treatment increased the concentration of NPY, especially in the hippocampus region: and (3) pretreatment with indomethacin decreased the tissue concentrations of tachykinins. These findings support the hypothesis that neuropeptides play a part in the physiology and pathophysiology of the central nervous system, and indicate that drug and electroconvulsive treatments selectively affect neuropeptide concentrations in the brain.

Acknowledaements Supported by the Swedish Medical Research Council (7464), the Swedish Cancer Research Fund (2313), the Swedish Society for Medical Sciences, Karolinska Institute Research Funds, the Soderstrdm-Konigska Foundation and C. Groschinskys Fund.

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Inquiries and reprint requests should be addressed to: Dr. Elvar Theodorsson Department of Clinical Chemistry Karolinska Hospital S-104 01 Stockholm Sweden