Influence of mouse genotype on responses of central biogenic amines to alcohol intoxication and aging

Alcohol, Vol. 3, pp. 345-350, 1986. ¢ Ankho International Inc. Printed in the U.S.A.

0741-8329/86 $3.00 + .00

Influence of Mouse Genotype on Responses of Central Biogenic Amines to Alcohol Intoxication and Aging F. BESNARD, E. KEMPF, G. FUHRMANN, J~ K E M P F *

A N D A. E B E L 1

Centre de Neurochimie du C N R S , 5 rue Blaise Pascal, 67084 Strasbourg Cedex, France *Institut de Chimie Biologique, Facuh~ de MOdecine, 11 rue H u m a n n , 67085 Strasbourg Cedex, France R e c e i v e d 3 S e p t e m b e r 1985 BESNARD, F., E. KEMPF, G. FUHRMANN, J. KEMPF AND A. EBEL. Influence of mouse genotype on responses of central biogenie amines to alcohol intoxication and aging. ALCOHOL 3(6) 345-350, 1986.--Dopamine and serotonin responses to various periods of alcohol treatment have been followed in striatum and hippocampus of two inbred strains of mice and related to the effect of aging. A striking strain dependency was noted for chronic alcohol effects and also for senescence. For both neurotransmitters studied the C57B1 strain loses tolerance to prolonged alcohol injury earlier than the Balb/c strain. This loss of tolerance accompanying aging may be indicative of more widespread changes in CNS adaptability in this strain. The unequal capacity to adapt also appears to depend on the nervous structure and the neurotransmitter considered. Alcohol and aging induced changes are not identical. In a given mouse strain, significant effects of either drug or aging induced disturbances are noted. A similar molecular process could operate in both aging and alcohol abuse, but the neurochemical effect might depend on the nervous structure or neurotransmitter involved. Such a phenomenon may be the basis of differences in behavioral changes observed in alcoholics. Dopamine Serotonin Inbred mouse strains

Chronic alcohol intoxication

Aging

STRONG interindividual differences exist in drug induced behavioral changes in man. Also in animals, strain dependent differences in reactivity to drugs are evident. After an acute ethanol treatment we previously noted that reactions of central cholinergic and aminergic neurotransmission differ markedly in two inbred strains of mice [3,7]. Prominent differences in these neurotransmitter activities were noted particularly in the nigrostriatai and septohippocampal pathways. We proposed that these changes could be in part involved in motor incoordination (disturbances in neurotransmitter interactions in striatum) and memory impairment (hippocampus), well known after acute ethanol intoxication. Chronic ethanol exposure also affects behavior differently. In alcoholics, again memory deficit and/or motor impairment have been recorded [1] and point to functional changes in neurotransmission in basal ganglia and the limbic system. These neurotransmitter reactivities in response to long term alcohol exposure are obviously the result of primary, secondary and adaptive reactions to alcohol injury. Also age related changes have to be considered in these long term experiments as they can modify responsiveness to alcohol [6,11]. We recently noted such phenomena for striatal and hippocampal cholinergic response to long term alcohol exposure in mice [6]. As cholinergic activity is in close relationship with

Striatum

Hippocampus

dopamine and serotonin neurotransmission in striatum and hippocampus [12], we were interested in the present report to see (l) to what extent long term alcohol exposure could disturb dopamine and serotonin neurotransmission, (2) if genetically determined differences in this neurotransmitter reactivity could be revealed and (3) to what extent chronic alcohol induced disturbances should differ from specific effects of aging processes. To investigate these different points we studied, in striatum and hippocampus, effects of various periods of chronic alcohol exposure on dopamine and serotonin neurotransmission in two inbred strains of mice, C57B1 and Balb/c. METHOD

Animals Female mice of the C57B1/60RL and Balb/c O R L strains were obtained from the Centre d'Elevage du CNRS (Orl6ans La Source, France) and group-housed under controlled light and temperature conditions with unlimited access to standard rodent pellets and liquids. Animals were compared at 7, 19 or 27 months. Senescent mice with pathological affections (i.e., tumors, respiratory infections . . . . ) were excluded from the study. All experiments were started after exposure to light for 3 to 4 hours.

1Requests for reprints should be addressed to Dr. A. Ebel, Centre de Neurochimie du CNRS, 5, rue Blaise Pascal, 67084 Strasbourg Cedex, France.

345

B E S N A R D ET AL.

346 DOPAC C57

1

ng/g

0

0

DOPA

Balb

0

C57

Balb

ng/g

~

1000

500

HVA

2000,

.~ 5

1000,

7 19 27

0

T " 3M~

7 19 27

7 months 19 27 old

FIG. 1. Effects of chronic alcohol treatment on levels of dopamine metabolites, DOPAC and HVA in the striatum of C57B1 and Balb/c mice. The animals were killed after 5, 17 and 25 months alcohol exposure. At these times they were respectively 7, 19 and 27 months old. Values are expressed as ng/g wet weight. The height of each column is the mean of 10 experiments -+S.E. • control mice, [] ethanol treated mice. ~ - p < 0 . 0 1 versus controls of the same age. Ap<0.05, A~o<0.01 versus controls of 7 months.

0

•

7 months 19 27old

FIG. 2. Effects of chronic alcohol treatment on striatal DOPA and 3MT levels in C57B1 and Balb/c mice (see Fig. 1). For DOPA measurements, NSD 1015 (100 mg/kg IP) was administered 30 min before death. • control mice, [] ethanol treated mice. ,A-p<0.05, *~-p<0.01 vs. controls of the same age. ~ko<0.05, &&o<0.01 vs. controls of 7 months.

TABLE 1

Experimental T h e a n i m a l s w e r e d i v i d e d into e x p e r i m e n t a l a n d c o n t r o l g r o u p s . A d m i n i s t r a t i o n o f alcohol to m i c e o f t h e experim e n t a l g r o u p b e g a n w h e n a n i m a l s w e r e t w o m o n t h s old. T h e y w e r e a l l o w e d to d r i n k o n l y a n a q u e o u s s o l u t i o n o f e t h a n o l (15%, v/v). T h e a v e r a g e daily alcohol c o n s u m p t i o n w a s a b o u t 8.5 g/kg. All a n i m a l s w e r e fed a b a l a n c e d diet w h i c h w a s supplied ad lib. T h e b o d y w e i g h t o f e t h a n o l t r e a t e d mice g e n e r a l l y did n o t significantly differ from matched water treated controls.

STRAIN COMPARISON OF C H R O N I C E T H A N O L ADMINISTRATION E F F E C T S ON D O P A M I N E A N D S E R O T O N I N L E V E L S IN STRIATUM

Time of Ethanol Treatment

C57 Balb

control ethanol control ethanol

Sample Preparation A n i m a l s w e r e sacrificed by d e c a p i t a t i o n , the b r a i n s excised a n d i m m e d i a t e l y chilled. D i s s e c t i o n w a s p e r f o r m e d o n a n ice-cooled glass plate. B l o o d e t h a n o l levels w e r e d e t e r m i n e d using t h e B o e h r i n g e r A l c o h o l U . V . Test.

Drugs D O P A a n d 5 H T P levels w e r e m e a s u r e d a f t e r inhibition o f the a r o m a t i c a m i n o acid d e c a r b o x y l a s e b y N S D 1015 (m-hyd r o x y b e n z y l h y d r a z i n e HC1, Aldrich); this d r u g w a s a d m i n i s t e r e d i n t r a p e r i t o n e a l l y at a d o s e of 100 mg/kg, 30 m i n b e f o r e sacrifice. Pargyline h y d r o c h l o r i d e (Sigma) 75 mg/kg a l o n e o r in c o m b i n a t i o n w i t h t r o p o l o n e (Aldrich) 100 mg/kg w a s diss o l v e d in saline a n d i n j e c t e d i n t r a p e r i t o n e a l l y .

Biochemical Assays S e p a r a t e g r o u p s o f a n i m a l s w e r e u s e d for m e a s u r e m e n t s

C57 Balb

control ethanol control ethanol

5 Months

17 Months

25 Months

DA (ng/g)

DA (ng/g)

DA (ng/g)

13590 _+ 208* 13383 _+ 200 11716 -+ 410 12465 _+ 477

13249 --- 464 13753 _+ 514 11645 -+ 288 11285 - 359

12194 _+ 460 12513 + 203 10912 +_ 525 10181 _+ 459

5HT (ng/g)

5HT (ng/g)

5HT (ng/g)

604 582 500 504

_+ _+ _+ _+

36 15 14 13

566 589 448 497

-+ _+ _+ _+

18 16 19 15

524 596 421 437

-+ _+ +_

22 26 20 16

*Mean of 10 experiments -+ S.E. Results are expressed as ng/g wet weight.

of DA and 5HT metabolites and measurements of DOPA and 5 H T P a f t e r d e c a r b o x y l a s e inhibition. Dopamine (DA), 3-4-dihydroxyphenylacetic acid ( D O P A C ) , h o m o v a n i l l i c acid ( H V A ) , 3 - m e t h o x y - t y r a m i n e (3MT), 3 - 4 - d i h y d r o x y p h e n y l a l a n i n e ( D O P A ) a n d s e r o t o n i n (5HT), 5-hydroxyindolacetic acid (5HIAA) and 5hydroxytryptophan (5HTP) were determined simultaneously using a reverse phase chromatography procedure coupled with an electrochemical detector (LCEC).

B1OGENIC AMINES IN ALCOHOL AND AGING

C57

5HTP

ng/g~ I i C57

5HIAA

ng/g 1°°°I

347

Balb

Balb

20O

100

7

19

27

7

19 27 months old

FIG. 3. Effects of chronic alcohol treatment on 5HIAA levels in the striatum of C57B1 and Balb/c mice (see Fig. 1). • control mice, [] ethanol treated mice. "~rp<0.01 vs. controls of the same age. &Ap<0.01 vs. controls of 7 months.

On the day of analysis, frozen samples of striatum or hippocampus were weighed and homogenized in HCIO4 0.1 N containing Na-metabisulfite 6 mM and EDTA 1 mM. The homogenates were centrifuged at 10,000 g for 20 min at 4°C. Aliquots of the supernatants were transferred into the LCEC system with a Wisp automatic injector (Waters). The LCEC system consisted of a Bioanalytical systems LC4 amperometric detector with a glassy carbon working electrode and a pump (Waters). The potential was set at 800 mV (vs. Ag-AgCI reference electrode). The column, a Bondapack phenyl column (10/~m particle size, 300x 3.1 mm i.d.) was purchased from Waters Assoc. The flow rate was 1.4 ml/min, and the sensitivity was set at 5 nA/V (1 volt full scale). The mobile phase consisted of 3% methanol in 0.1 M Na-phosphate buffer pH 2.5, Na ~ EDTA 0.1 mM, and l-octane sulfonic acid Na salt (BDH) 2 mM, 3,4-dihydroxyhydrocinnamic acid (Aldrich) was used as internal standard. Results were analyzed by three-factor analysis of variance (ANOVA), the factors being: strain (two levels: C57B1, Balb/c), treatment (two levels: control and alcohol), age (three levels: 7 months, 19 months and 27 months). Further analysis for individual between-group comparisons were carried out with post hoc tests (Duncan multiple range test). RESULTS

The effects of long term exposure to alcohol on DA and 5HT neurotransmission were followed in 5, 17 and 25 months alcohol treated mice and in aged controls. The means of the morning blood ethanol levels in animals consuming ethanol were found to be 1.09-+0.23 in C57B1 mice and 0.97___0.27 in Balb/c mice.

lnterstrain Comparison of" the EaCfect o f Ethanol on the Content o f Dopamine and its Metabo/ites DOPAC, HVA and 3MT in Striatum The results are summarized in Table 1, and Figs. 1 and 2. Ethanol intoxication and aging processes produce no changes in DA levels in the two strains. There is an overall

7

19

27

7

19 27 months o~d

FIG. 4. Effects of chronic alcohol treatment on striatal 5HTP levels in the C57B1 and Balb/c mice. All mice were injected with NSD 1015 (100 mg/kg IP) 30 min before killing. • control mice, [] ethanol treated mice. ~rp<0.05, "~'kp<0.01 vs. control mice of the same age.

TABLE 2 STRAIN COMPARISON OF CHRONIC ALCOHOL ADMINISTRATION EFFECTS ON SEROTONIN LEVELS IN HIPPOCAMPUS

Time of Ethanol Treatment 5 Months 5HT (ng/g) C57 Balb

control ethanol control ethanol

580 _ 543 ± 496 ± 468 ±

20* 18 21 22

17 Months 5HT (ng/g)

25 Months 5HT (ng/g)

588 ± 11 573 ± 18 450 _+ 29 473 _+ 27

582 _ 22 622 ___30 424 ± 21 462 ± 9

*Mean of l0 experiments _+ S.E. Results are expressed as ng/g wet weight.

increase in DOPAC and HVA levels with alcohol treatment, DOPAC: F(1,97)=38.4, p<0.01; HVA: F(1,97)=32.3, p<0.01, with a significant interaction between alcohol treatment and strain, F(1,97)= 4.15, p <0.05. When compared to same strain aged mice, alcohol increases DOPAC and HVA only in Balb/c mice. For DOPAC significant differences are noted in 5 and 17 months alcohol treated Balb/c mice (/9<0.01); for HVA in 17 and 25 months treated mice (p<0.01) (Fig. l). With aging there is an overall reduction in DOPAC and HVA content, DOPAC: F(2,97)16.7, p<0.01; HVA: F(2,97)--36.9, p<0.01, with no significant interaction between age and strain. When compared to young mice, DOPAC declines significantly (p<0.05) in 27 months old mice in both strains. HVA decreased in 19 and 27 months old mice in both strains (p<0.01) (Fig. 1). In contrast to DOPAC and HVA there is an overall decrease in 3MT levels with alcohol treatment, F(1,97)= 13.9, p<0.01, and with aging processes, F(2,97)=11.06, p<0.01, with a significant interaction between alcohol, age and strain, F(2,97)=5.79, p<0.01. When compared to same strain aged mice a significant decrease is noted in 5 months alcohol treated Balb/c mice (p<0.05) and in 25 months

B E S N A R D ET AI..

348

5HTP

ng/g 5HIAA

ng/g

600

]

C5:

•

Balb

1OOO[

C57 i, - -"f_ ,

.

Balb &

*

400 200

~t

5 O O ~ 7

19

27

7

19

at

27

months old FIG. 5. Effects of chronic alcohol treatment on 5HIAA levels in the hippocampus of C57Bl and Balb/c mice (see Fig. I). • control mice, [] ethanol treated mice. ,k,p<0.01 vs. controls of the same age. A~ko<0.01 vs. controls of 7 months.

7

19

There is no overall effect in DOPA accumulation levels with alcohol treatment, but a significant interaction between alcohol and strain, F(1,78)= 12.4, p<0.01. When compared to same aged mice, alcohol increases DOPA in 5 months (p<0.01) and 25 months treated (p<0.05) Balb/c. In C57BI mice alcohol decreases DOPA in 25 months alcohol treated mice (p<0.01) (Fig. 2).

lnterstrain Comparison of the Effect of Ethanol on the Content ~f 5HT and its Metabolite 5HIAA in Striatum The results are summarized in Table 1 and Fig. 3. Ethanol produces no changes in 5HT levels in the two strains (Table I). There is an overall increase in 5HIAA contents with alcohol treatment, F(1,97)=7.48, p<0.01, with a significant interaction between alcohol treatment and strain, F(1,97)= 10.29, p<0.01. When compared to same aged mice, alcohol increases 5HIAA levels in 17 months and 25 months alcohol treated Balb/c mice (p<0.01) (Fig. 3). With aging processes there is an overall reduction in 5HIAA levels, F(2,97)=5.51, p<0.01, with a significant interaction between age and strain, F(2,97)=10.83, p<0.01. When compared to young mice 5HIAA significantly decline in 19 and 27 months old C57B1 mice (p<0.01) (Fig. 3).

lnterstrain Comparison of the Effect of Ethanol on 5HTP After Inhibition of Aromatic Amino Acid Decarboxylase in Striatum There is no overall effect in 5HTP accumulation levels with alcohol treatment, but a significant interaction between alcohol, age and strain, F(2,77)=4.81, p<0.01. When compared to same aged mice there is an increase in 5HTP in 5 months alcohol treated C57B1 (p<0.01) and Balb/c (/9<0.05) mice, but a decrease in 25 months treated C57B1 mice (p<0.01) (Fig. 4).

7

old

19 27 months

FIG. 6. Effects of chronic alcohol treatment on 5HTP levels in the hippocampus of C57B1 and Balb/c mice (see Fig. 1). All mice were injected with NSD 1015 (100 mg/kg IP) 30 min before killing. • control mice, [] ethanol treated mice. *p<0.05, *~rp<0.01 vs. controls of the same age. Ap<0.05, AAKo<0.01 vs. controls of 7 months.

treated C57Bl mice (p<0.01). When compared to young mice, a significant decrease is noted only in 27 months old Balb/c mice (p<0.01) (Fig. 2).

Interstrain Comparison of the Effect of Ethanol on DOPA After Inhibition of DOPA Decarboxylase in Striatum

27

TABLE 3 STRAIN COMPARISON O F C H R O N I C A L C O H O L ADMINISTRATION E F F E C T S ON T H E E F F L U X OF T H E M E T A B O L I T E S F R O M STRIATUM AND H I P P O C A M P U S

Striatum DOPAC k (hr q

HVA k (hr -1)

Hippocamus 5H1AA k (hr 1)

5HIAA k thr ~i

C57 (12) control C57(14) ethanol

0.22 +- 0.08*

1.35 ± 0.08 0.53 _+ 0.12 0.68 _+ 0.07

0.21 +_0.1

1.41 ±0.07 0.51 _+0.08 0.74_+0.05

Balb(12) control Balb (14) ethanol

0.17+_0.08

1.46±0.09

0.29 +_ 0.07

1.41 +_ 0.07 0.41 +_ 0.08 0.63 +_ 0.04

0.36_+0.11

0.65+_0.08

(n) is the number of experiments. *Mean of (n) experiments _+ S.D.

lnterstrain Comparison of the Effect of Ethanol on the Content of 5HT and its Metabolite 5H1AA in Hippocampus The results are summarized in Table 2 and Fig. 5. Ethanol intoxication and aging processes produce no changes in 5HT levels in the two strains (Table 2). There is an overall increase in 5HIAA levels with alcohol treatment, F(1,102)=5.65, p<0.05, and a significant interaction between alcohol and strain, F(I, 102)= 17.2, p <0.01. When compared to same aged mice alcohol increases 5HIAA in 17 and 25 months alcohol treated Balb/c mice (p<0.01) (Fig. 5). With aging processes there is no overall effect in 5HIAA levels, but a significant interaction between age and strain, F(2,102)=13,3, p<0.01. When compared to young mice 5HIAA decline in 19 and 27 months old C57B1 mice (p<0.01) (Fig. 5).

B I O G E N I C A M I N E S IN A L C O H O L A N D A G I N G

Interstrain Comparison of the Effect of Ethanol on 5HTP After Inhibition of Aromatic Amino Acid Decarboxylase in Hippocampus Ethanol intoxication produces an overall decrease in 5HTP accumulation levels, F(1,84)=5.08, p < 0 . 0 5 , with a significant interaction between alcohol and strain, F(1,84)=5.8, p<0.05. When compared to same aged mice alcohol decreases 5HTP levels in 17 months (p<0.05) and in 25 months (p<0.01) C57B1 alcohol treated mice (Fig. 6). With aging processes there is no overall effect in 5HTP levels, but a significant interaction between alcohol, age and strain, F(2,84)=8.02, p<0.01. When compared to young mice 5HTP levels increase in 19 and 27 months old C57BI mice (p<0.05) (Fig. 6).

Effect of Chronic Ethanol on Decline of Acidic Metabolites After MAO and COMT Inhibition in Striatum and Hippocampus To investigate whether chronic alcohol administration had an effect on the disappearance of DOPAC, H V A and 5HIAA, 17 months alcohol intoxicated mice were given pargyline + tropolone 30 and 60 min before sacrifice. The fractional rate constant (k) for the disappearance of metabolites was calculated from the exponential decline during MAO and COMT inhibition, k is a measure of the effiux of metabolites from brain and is calculated from the expression k=0.693/tl~. No differences were found either in DOPAC, HVA and 5HIAA decline in striatum or in 5HIAA in hippocampus of the two strains (Table 3). DISCUSSION

Chronic alcohol treatment apparently modifies central biogenic neurotransmission differently in C57BI and Balb/c mice. With regard to striatal dopamine neurotransmission, Balb/c mice react after chronic alcohol treatment in the same paradoxical way that we noted after acute alcohol treatment [7]: a significant decrease in 3MT, an index of DA release, is associated with an increase in DOPA, a useful indicator of DA synthesis. Increased synthesis of DA can be the result of a loss of inhibitory control on DA synthesis, after an alcohol induced decrease in DA release. This particular pattern of DA activity may mean that the initial activation of DA neurons induced by acute ethanol [7] remains during the early period (5 months) of chronic alcohol exposure. If ethanol treatment is continued, the dopaminergic neurotransmission develops a relative tolerance to the effect of the drug (3MT and DOPA levels regain normal values). In C57B1 mice tolerance to the drug appears to be achieved more rapidly than in Balb/c mice, since at 5 months treatment, 3MT levels approach control values and DOPA is not significantly changed. However, the C57B1 strain loses tolerance earlier than the Balb/c, as reflected by the striking reduction of 3MT levels, we noted, with no compensatory increase of DA synthesis (Fig. 2). This loss of tolerance, as animals age, is of particular interest as it may be indicative, in C57B1 mice, of age induced changes in CNS adaptability. In the Balb/c strain, after 5 months alcohol exposure DOPAC and HVA follow the DOPA increment. The question arises as to why, when alcohol treatment is pursued, both DOPAC and H V A levels are still elevated whereas DOPA and 3MT return to normal values. Alcohol, through its impact on neuronal membranes [2], may alter the efflux of these metabolites from the brain and, therefore, be the cause of the observed DOPAC and HVA increment. To test this

349 proposal we followed the decline of acidic metabolites after MAO and COMT inhibition. But we could not find any alcohol induced differences in this transport. A satisfactory explanation for the effects of chronic alcohol on striatal DOPAC and HVA is not available at present. Strain dependency in reaction to chronic alcohol treatment is also noted for serotonin turnover. Once more the C57B1 mice seem to lose their ability to adapt to prolonged alcohol injury earlier than Balb/c: a strong decrease in serotoninergic activity is observed in striatum and hippocampus after 25 months alcohol exposure in C57B1, whereas the Balb/c mice remain tolerant, as far as can be ascertained from the unchanged 5HTP levels. In addition, 5HT metabolite levels (5HIAA) appear again preferentially altered in this strain. As for striatal DOPAC and HVA, disturbed efflux of this metabolite cannot account for this phenomenon. Also structure dependent differences have been shown, as displayed by unchanged serotonin synthesis in hippocampus and serotonin alterations in striatum in Balb/c mice. These observations provide further arguments that variations in regional neurotransmitter reactivity to the drug (1) may be secondary to the resulting imbalance in neurotransmitter interactions, interactions which, in turn, are structure dependent, and (2) may be due to primary differences in the genetic mechanisms controlling the expression of certain neurotransmitter systems. Acute (4,5 g/kg single dose by intubation) [7] and chronic alcohol intoxication do not induce similar changes on biogenic amine neurotransmission. The immediate alterations in neurotransmitter activities in acute treatment [7] first can persist throughout chronic exposure, and then animals progressively adapt to the drug. Having developed tolerance, the biological systems suddenly can lose their capacity to adapt. One factor that has clearly been shown to affect adaptative mechanisms is genetic. A second factor could be the strain dependent unequal reactivity to aging processes. So striatal dopaminergic mechanisms of the Balb/c strain are significantly disturbed by senescence (decreased DA turnover and DA release) whereas C57B1 mice appear unaffected. A second example is provided by serotonin neurotransmission in hippocampus where only C57B1 mice react to aging by increased serotonin synthesis. Finally again structure dependency is noted in response to aging as shown in C57B1 mice, by increased serotonin turnover in hippocampus and not in striatum. The basis of the strain and structure dependent differences we noted may be due to many causes. Genotypic variations in density of nerve terminals and receptors may be one of them [4, 5, 14]; the native level of a given neurotransmitter activity another possibility. Effects of ethanol on neuronal membranes and their consequences on neurotransmission should also be considered [2, 8-10]. In conclusion our findings afford the following comments: (1) alterations induced by chronic alcohol consumption on biogenic amines differ in degree according to the duration of alcohol exposure, (2) comparison between genetically homogeneous mice strains show strain specific alcohol induced changes in striatal and hippocampal DA and 5HT metabolism, (3) alcohol and aging induced alterations in biogenic amine levels are not similar; the latter exhibiting also a striking strain dependency, and (4) in a given strain, both drug and aging induced disturbances appear structure dependent and related to the type of neurotransmitter considered.

350

BESNARD ET AL.

T h e s e p r o b a b l e g e n e linked d i f f e r e n c e s m a y indicate t h a t the o b s e r v e d n e u r o t r a n s m i t t e r pecularities c o u l d be the basis o f strain specific b e h a v i o r a l reactivity to alcohol, a n d m a y be i n v o l v e d in specific b e h a v i o r a l e x p r e s s i o n s .

S u c h a p h e n o m e n o n m a y b e o n t h e basis o f interindividual b e h a v i o r a l d i f f e r e n c e s in m a n a n d explain w h y some alcoholics are affected by K o r s a k o f f d i s e a s e s a n d o t h e r s by strong motor impairments.

ACKNOWLEDGEMENTS Work was supported by a grant from IREB, Paris, France. The authors thank Ms. C. Schleef, E. Scherrer and Mr. J. L. Toussaint for their excellent technical assistance. They wish to thank Ms. F. Herth and S. Ott for typing the manuscript. They are very grateful to Dr. K. Langley for stylistic assistance and his kindly help for rewriting the manuscript.

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