Potentiation of apomorphine and d-amphetamine effects by naloxone

Life Sciences, Vol. 28, pp. 629-634 Printed in the U.S.A.

POTENTIATION

OF APOMORPHINE

P.M. Adams,

Pergamon Press

AND D-AMPHETAMINE

EFFECTS

BY NALOXONE

R. Beauchamp and C. Alston

Department of Psychiatry and Behavioral Sciences and Pharmacology and Toxicology University of Texas Medical Branch Galveston, Texas 77550 (Received in final form November

24, 1980)

Su~nar~ The effects of naloxone, an opiate antagonist, on the stereotypic behavior and locomotor activity induced by apomorphine and d-amphetamine were studied. Groups of adult male Sprague-Dawley rats were first tested for stereotypy and locomotor activity after apomorphine (0.0 - 2.0 mg/kg) or d-amphetamine (0.0 - 10.0 mg/kg). Groups were subsequently tested with saline or naloxone (1.0 4.0 mg/kg) plus the previously used dosaqe of apomorphine or d-amphetamine. Naloxone alone did not produce stereotypy, but did significantly reduce locomotor activity. Naloxone potentiated apomorphine and d-amphetamine induced stereotypy. Apomorphineinduced activity was increased by naloxone, but d-amphetamineinduce@ activity at 2.5 mg/kg was reduced. The results are compatible with the suggestion that naloxone may potentiate both apomorphine and d-amphetamine by inhibiting an opiate receptor mechanism which normally interacts with catecholamine neuronal action. Previous research on the opiate receptor a~tagonist, naloxone, has shown that this drug reduced locomotor activity (13; 2; 9; I) in a number species. Holtzman (10) found naloxone did not alter the response rate of selfstimulation through implanted electrodes but that naloxone reduced the normally observed increase in response rate induced by d-amphetamine. This suggested a relationship between the opiate receptor and catecholamine neuronal function felt to be important for self-stimulation responding. Subsequent reports on the interaction of naloxone with other behaviors associated with d-amphetamine supported the concept of a functional link between the opiate receptors and catecholamines, particularly dopamine (12). Seaal et al (13) found naloxone (0.5 - 10 mg/kg) blocked the amphetamineinduced increase in crossover activity. Naloxone alone blocked crossover activity at these dosages. This reduction in activity persisted for up to one hour following administration of the drug. Stereotypy, a behavior induced by dopamine agonists such as apomorphine, is altered by naloxone. Cox et al (4) reported that naloxone at 1.0 mg/kg would block apomorphine-induced stereotypy. Previously, Henderson and West~aemper (8) reported a similar antagonism by naloxone. These results were consistent with the suggestion of Harris et al (7) that naloxone may potentiate presynaptic inhibition of dopamine release. 0024-3205/81/060629-06502.00/0 Copyright (c) 1981 Pergamon Press Ltd.

630

Naloxone

and D o p a m i n e A g o n i s t s

Vol.

28, No.

6, 1981

Dettmar et al (5) found naloxone a n t a g o n i z e d the ipsilateral rotation induced by a m p e h t a m i n e in rats lesioned u n i l a t e r a l l y in the substantia nigra. Diamond and Borison (6) also found a high dose of naloxone (40 mg/kg) reduced the a m p h e t a m i n e - i n d u c e d ipsilatera! rotation. However, the effects of L-Dopa were increased by naloxome. T h e y found m e t - e n k e p h a l i n increased a m p h e t a m i n e induced ipsilateral rotati0n but d e c r e a s e d a p o m o r p h i n e - i n d u c e d c o n t r a l a t e r a l rotation. The a p o m o r p h i n e - i n d u c e d rotation is c o m m o n l y thought to represent a p o s t - s y n a p t i c dopamine r e c e p t o r s u p e r s e n s i t i v i t y that results from the d e n e r v a t i o n following d e g e n e r a t i o n of the s u b s t a n t i a n i g r a - c a u d a t e projection. Diamond and Boris0n propose~ that n a l o x o n e p o t e n t i a t e d the effects of d o p a m i n e r g i c agents h a v i n g p o s t - s y n a p t i c action and a n t a g o n i z e d p r e s y n a p t i c action. In order to better c h a r a c t e r i z e the dose of naloxone that is e f f e c t i v e in a l t e r i n g a p o m o r p h i n e and a m p h e t a m i n e p r o d u c e d b e h a v i o r s the p r e s e n t study analyzed s t e r e o t y p y and locomotor activity. A range of doses of a p o m o r p h i n e and d - a m p h e t a m i n e was selected in order t~ m a x i m i z e the l i k e l i h o o d of o b s e r v i n g p o t e n t i a t i o n and/or i n h i b i t i o n by n a l o x o n e for each b e h a v i o r a l measure. Methods

and M a t e r i a l s

Sub~ect_~s: The subjects were 40 adult S p r a g u e - D a w l e y r a n d o m - b r e d male rats d e r i v e d from Texas Inbred L a b o r a t o r y stock. The animals weighed 190 - 250 g, were group housed, and m a i n t a i n e d on ad lib food and water t h r o u g h o u t the study. The c o l o n y room lighting was r e g u l a t e d on a 12 hour l i g h t - d a r k cycle, and the room t e m p e r a t u r e m a i n t a i n e d at 22 + I ° C.

Apparatus: S t e r e o t y p y ratings were done in pairs of a n i m a l s regardless of drug t r e a t m e n t in a P l e x i g l a s chamber (26 x 25 x 21 cm) housed inside of a I m square animal cubicle e q u i p p e d with a l-way mirror. The chamber c o n t a i n e d a qrid floor made of stainless steel rods. All ratings were made through the lw a y m i r r o r and used the Kelly et al (11) criteria on a 0 - 6 scale. I ~ c o m o t o r a c t i v i t y was m e a s u r e d in two horizontal, dough-nut shaped a c t i v i t y chambers. Each chamber was 91 cm in c i r c u m f e r e n c e with an 8 cm wide alley. There were 4 m i c r o s w i t c h - c o n n e c t e d p l a t e s e q u a l l y spaced on the floor of the chamber. The m i c r o s w i t c h e s were c o n n e c t e d to counters to a u t o m a t i c a l l y r e c o r d the number of plate crosses. Each chamber was e n c l o s e d in a soundinsulated cubicle with low i l l u m i n a t i o n . Procedure: The animals were r a n d o m l y a s s i g n e d to various drug t r e a t m e n t groups. All i n j e c t i o n s and b e h a v i o r a l m e a s u r e m e n t s were m a d e b e t w e e n 0900 and 1400 hours in the light phase of the l i g h t - d a r k cycle. All injections were made s u b c u t a n e o u s l y in the thoracic region of the body. No injection was m a d e within 6 days of a p r e v i o u s treatment. After injection, the animals were i m m e d i a t e l y p l a c e d in pairs in the P l e x i g l a s c h a m b e r for assessing stereotypy. Patings of s t e r e o t y p y were made b l i n d by two o b s e r v e r s independently. O b s e r v a t i o n a l rating for I minute was made at 10, 20, and 30 minutes following a drug injection. The animals were then r e m o v e d and p l a c e d i n d i v i d u a l l y in the a c t i v i t y chambers. L o c o m o t o r a c t i v i t y was r e c o r d e d at the end of 40, 50 and 60 minutes post-injection.

Groups of 5 animals were given a p o m o r p h i n e (0.5, 1.0 or 2.0 mg/kg) da m p h e t a m i n e sulfate (2.5, 5.0 or 10.0 mg/kg) or saline (0.1 m l / i n j e c t i o n ) . These groups of a n i m a l s s u b s e q u e n t l y r e c e i v e d the same apomorphine, a m p h e t a m i n e

Vol.

28, No.

6, 1981

Naloxone

and Dopamine

Agonists

631

or saline treatment plus a dosage of naloxone (1.0, 2.0 or 4.0 mg/kg). The order of the nalo~one dosage treatment was counterbalanced to control for possible sequence effects of treatment. The nalo×one injection preceded the apomor~]ine, d-amphetamine or saline injection by one minute. Results Stereotypy: Naloxone alone did not produce stereotypy at the dosage lev@Is tested in the present study. This was found regardless of the time followi~g injection that the stereotypy was assessdd (Figure I and 2). ~poldorphine induced a dosage-related increase in stere'otypy intensi~y (Figure I). An analysis of variance for apomorphine dosage ~ffects across 10 minute observation intervals was significant (F=33.4, 3,48 dr, p < .01). Naloxone at all doses p o t e n t i a t e d the a p o m o r p h i n e - i n d u c e d stereotypy at 0.5 mg/kg and prolonge d the intensity of the stereotypy at the level normally observed at higher doses of apomorphine (p < .05).

_

10 MINUTES

20 MINUTES

30 MINUTES

4

2

~, uJ

~---~ O---o

Ol

I

I

I

0 . 0 0.5 1.0 2.0

I

1

I

I

0 . 0 0.5 1.0 2.0

APOMORPHINE Fig. Potentiation

!

Sahne (:3 1.0 m g / k g Naloxone 2 0 m g / k g Naloxone 4 0 m g / k 9 Naloxone

O

I

I

I

0 . 0 0 . 5 1.0 2.0

(mg/kg)

I

of apomorphine-indu(-ed

stereotypy

by naloxone.

D-amphetamine-induced stereotypy was dosage related (F=128.3, 3,48 df, p < .001). The intensity at a given dosage was also related to the time from injection (F=8.6, 2,48 df, p < .01). D-amphetamine-induced stereotypy was p o t e n t i a t e d by" naloxone (p < .05) as shown in Figure 2. This was most apparent at the 2.5 mg/kg d-mmphetamine dosage where naloxone potentiated the intensity of the stereotypy to a level approaching that seen with 5.0 or 10.0 mg/kg dosages.

632

Naloxone and Dopamine Agonists

(3 Z

:

~4~:3O UJ R" UJ 2 I--(/3 Z I.

,<

5U4

30 MINUTES

20 MINUTES

10 M I N U T E S

6-

Vol. 28, No. 6, 1981

0"

:E

: Sllline 11.0mll/kg hl41~=m~ ~---Zl 2.0 .~/1~ Nal~me,e o - - - 0 4.0 .,~/Iql Nale0mne

/ f I

' 10.0 Ol'O 2 . 5 0i 0 2.5 5,0 0-025 i 5.010.0 ' D-AMPHETAMINE (mg/kg) Fig. Potentiation

I T 5.0 10.0

2

of d-amphetamine-induced

stereotypy by naloxone.

Locomotor Activity: Naloxone alone produced a significant decrease in activity (Figure 3) at each of the assessment intervals (F=4.0, 3,48 df, p < .05). Apomorphine alone produced a dose-related increase in locomotor activity (F=3.37, 3,48 df, p < .05). Nalo×one potentiated apomorphine-induced activity at 2.0 mg/kg at each ten minute interval. This potentiation was significantly related to the dose of naloxone (p < .05).

--

o

30o 280

~ SALINE 1.0 mg/kg NALOXONE '~---& 2 0 mg/kg NALOXONE O - - O 4 0 mg/kg NALOXONE

40 MINUTES

260

I I le'

240

/I

220

II iI iI #1

200 180

50 MINUTES

~)

t

l

? #

I I

!

I i

It

f

I

140 120

60 MINUTES

I /

II

f

100 8O 60 4O 20 i 0.0

1 0.5

[ 1,0

l 2.0

O0

0.5

1.0

2.0

0.0

0.5

1.0

2,0

APOMORPHINE (mg/kg)

Fig. Potentiation

of apomorphine-induced

3 locomotor

activity by nalo×one.

Vol.

28, No. 6, 1981

Naloxone and Dopamine Agonists

Amphetamine at 2.5 mg/kg produced a significant increase in locomotor activity which persisted across all three intervals (F=16.5, 1,24 dr, p < .01). Naloxone produced a dose-related inhibition of this amphetamineinduced increase in activity (F=3.28, 3,48 dr, p < .05) regardless of the post-injection interval measured. Naloxone also produced significantly lower activity levels at 5.0 mg/kg (F=7.99, 3, 48 p < .01) of d-amphetamine but only at the 40 minute interval.

SALINE 1 0 rng/kg NALOXONE /,---a. 2 0 mg/kg NALOXONE o - - - o 4 0 mg/kg NALOXONE 260

40 MINUTES

50 MINUTES

60 MINUTES

240

~ 2c~ ,~

18() 160

140 120

~

so so

/

40

2o

,/o

',,~.-*

~ I

i

00

25

J

i

5 0 100

i

,

r

i

i

i

,

,

00

25

50

100

00

25

50

100

D-AMPHETAMINE ( m g / k g )

Fig. 4 Inhibition of the d-amphetamine

effects on locomotor

activity by nalo~one.

Discussion If there are presynaptic opiate receptors that act to inhibit the release of dopamine and possibly norepinephrine then inhibiting these receptors with naloxone would in effect enhance the action of d-amphetamine in producing behavioral stereotypy through increased release of transmitter. The result would be a shift in the dose-response curve for inducing intense stereotypic behavior and, therefore, likely prolong the effects of a given dosage. Likewise, the effects of d-amphetamine on locomotor activity would be shifted to be more like that observed at higher dosages (i.e., less activity). This action of naloKone would e~plain the effects observed by Holtzman et al (9). Increased release of transmitter at the receptor site would likely facilitate the effects of agonist action on the receptors, requiring less of the agonist to produce a significant effect on behavior. It also would potentiate the effects at the higher dosage levels both with respect to intensity and duration. A shift in the dose-response curve for apomorphineinduced stereotypy by naloxone could account in part for the observations of Diamond and Borison (6). Diamond and Borison suggested that naloxone worked through post-synaptic mechanisms by inhibiting an enkephalinergic interneuron that inhibits the activation of dopamine receptors. The disinhibition produced by naloxone would explain the increased response to apomorphineinduced stereotypy and locomotor activity. It is less clear how the effects of naloxone act to facilitate the d-amphetamine effects observed in the present study. A post-synaptic disinhibition might account in part for the

633

634

N a l o x o n e and D o p a m i n e

Agonists

Vol.

28, No.

6, 1981

i n c r e a s e d s t e r e o t y p y observed. The e f f e c t s of n a l o × o n e on d - a m p h e t a m i n e i n d u c e d l o c o m o t o r a c t i v i t y may r e f l e c t this i n c r e a s e d s t e r e o t y p y and shift in the d o s e - r e s p o n s e curve due to p o s t - s y n a p t i c a c t i v a t i o n of dopamine receptors. However, Diamond and B o r i s o n p r e d i c t e d that naloxone w o u l d reduce p r e s y n a p t i c - a c t i n g agents like a m p h e t a m i n e . W h i l e the r e d u c e d effect of 2.5 m g / k g of d - a m p h e t a m i n e on a c t i v i t y with naloxone could be i n t e r p r e t e d as s u p p o r t for their hypothesis, either m e c h a n i s m would be c o m p a t i b l e with the o b s e r v e d effect of a m p h e t a m i n e on locomotor a c t i v i t y at 2.5 mg/kg. In addition to the p o s s i b l e role of p r e - s y n a p t i c and p o s t - s y n a p t i c opiate receptors m e d i a t i n g d o p a m i n e r g i c function there is the d i s t i n c t i o n b e t w e e n n i g r a - s t r i a t a l and e x t r a s t r i a t a l d o p a m i n e r g i c function (3; 11). While the s t r i a t u m is c o m m o n l y linked to stereotypy, the control of locomotor a c t i v i t y appears less specific. It is less clear how the i n t e r a c t i o n of opiate receptors and dopamine r e c e p t o r s in these d i f f e r e n t a n a t o m i c a l p a t h w a y s relates to s t e r e o t y p y and locomotor activity. However, the earlier reports of Dettmar et al (5) and Segal et al (13) together with the postulation of a d i s t i n c t i o n in the p r e - s y n a p t i c and the p o s t - s y n a p t i c i n t e r a c t i o n of opiate receptors with d o p a m i n e r g i c n e u r o t r a n s m i s s i o n suggest that furthec ~esearch on the i n v o l v e m e n t of opiate receptors in the d o p a m i n e r g i c m e d i a t i o n of these b e h a v i o r s is required. Acknowledgements This work was s u p p o r t e d Pysch[atry, 5T02MH06034

in part by funds - 24.

from U n d e r g r a d u a t e

Training

Grant in

References I. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

S. AMIR, M. S O L O M O N and S. AMIT, Neuropharm. 18 171-173 (1979). A. A R N S T E N and D. SEGAL, Life Scio 25 1035-1042 (1979). B. C O S T A L L and R. NAYLOR, Psychopharm. 41 57-64 (1975). B. COX, M. ARY and P. LOMAX, J. Pharm. Exp. Ther. 196 637-641 (1976). P. DETTMAR, A. CCWAN and D. WALTER, Neuropharm. 17 1041-1044 (1978). B. D I A M O N D and R. BORISON, N e u r o l o g y 28 1085-1088 (1978). R. HARRIS, D. SNELL, H. LOH and E. WAY, Proc. W e s t Pharmacol. 19 448-451 (1976). G. H E N D E R S O N and R. W E S T K A E M P E R , Proc. W e s t Pharmacol. 18 204-207 (1975). S. HOLTZMAN, J. Phar. Exp. Ther. 189 51-59 (1974). S. HOLTZMAN, P s y c h o p h a r m . 46 223-227 (1976). P. KELLY, P. S E V I O U R and S. IVERSEN, Brain Res. 94 507-522 (1975). H. LAL, Life Sci. 17 483-495 (1975). D. SEGAL, R. BROWNE, A. ARNSTEN, D. DERRINGTON, F. BLOOM, R. G U I L L E M I N and N. LING, In: E n d o r p h i n s in Mental Health Research. Ed. by E. Usdin, W. B u n n e y and N. Kline (1979).