Role of noradrenaline in levodopa reversal of reserpine akinesia

Brain Research, 77 (1974) 521-525

521

© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands

Role of noradrenaline in levodopa reversal of reserpine akinesia

C. D. MARSDEN, A. DOLPHIN, R. C. DUVOISIN*, P. J E N N E R AND D. TARSY**

University Department of Neurology, Institute of Psychiatry and King's College Hospital Medical School, Denmark Hill, London SE5 (Great Britain) (Accepted May 30th, 1974)

It has been suggested that the Parkinsonian syndrome of tremor, rigidity, akinesia and postural deformity should be termed 'the striatal dopamine deficiency syndrome'16. All cases, whether due to Parkinson's disease (idiopathic paralysis agitans), post-encephalitic Parkinsonism, or drugs such as reserpine, phenothiazines or butyrophenones, are associated with 'actual or functional deficiency of dopamine in the striatum'16. The dramatic response of Parkinsonism, excluding the drug-induced syndrome, to levodopa therapy is attributed to replenishment of striatal dopamine stores. Although only a small increase in brain noradrenaline synthesis has been demonstrated following administration of levodopa to normal animals 1,1°, there is evidence that levodopa increases locomotor activity of normal animals by stimulation of both dopaminergic and noradrenergic receptors in the brain 8,17,19,21. It is possible that noradrenaline formation is in part responsible for the efficacy of levodopa treatment of Parkinson's disease. Historically, reversal of the locomotor effects of reserpine by levodopa6 gave rise to the concepts of dopamine deficiency and levodopa therapy in Parkinson's disease. Moreover, reserpine not only causes marked depletion of brain monoamines, but it is also one of many drugs known to produce parkinsonian syndromes in some patients. In the present study, we have investigated the possibility that the reversal by levodopa of the akinetic-rigid syndrome produced by reserpine depends upon changes in noradrenaline as well as dopamine levels. The capacity of various drugs to inhibit the reversal of reserpine-induced akinesia in mice (white 'P' or Swiss 'S' strain, 18-24 g) by levodopa has been studied. Locomotor activity was recorded initially as the number of mice out of batches of 10 that walked out of a demarcated area (10 cm × 8 cm) within 15 sec of being placed in the centrO s. Normal mice walked briskly out of the area within the time limit while 3 h after reserpine only 10 ~ of animals did so. In other experiments locomotor activity * Permanent address : Department of Neurology, Mount Sinai School of Medicine, New York, N.Y., U.S.A. ** Permanent address: Department of Neurology, Boston University School of Medicine, and Boston Veterans Administration Hospital, Boston, Mass., U.S.A.

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SHORT COMMUNICATIONS 100

.-~

80

~

"

L-DOPA

-~_ ~ 60-

~

4o PBZ + L-DOPA 20

FLA-63 + L-DOPA o

•

~

'l' '~ '~ Reserpine Saline L- DOPA or PBZ ~FLA-63

"

,i

o

Time

(h.)

Fig. l. Effect of FLA-63 and phenoxybenzamine on the levodopa reversal of reserpine akinesia. Locomotor activity was measured at hourly intervals as the number of animals out of a batch of 10 that walked out of a defined area within a time limit (see text). Seven to sixteen batches were used for each experiment and the mean percentage of animals per batch that walked out of the area within the limit is shown (± 1 S.E.M.). Reserpine (4 mg/kg) was administered at the time 0; saline, FLA-63 (bis-(4-methyl-l-homopiperazinyl thiocarbonyl) disulphide) (25 mg/kg)or phenoxybenzamine (20 mg/kg) was administered 1 h later, and levedopa (500 mg/kg) was administered 1 h afterwards. All drugs were administered i.p. in saline or suspended in 1 ~ methocel in a volume of 0.5 ml or less. was measured using groups o f 3 mice in 2 sets o f Animex activity meters ( L K F F a r a d Electronics). L e v o d o p a rapidly and completely reversed the akinesia p r o d u c e d by prior reserpine treatment as previously described 6. The immobile, rigid animal soon began to pace the cage, run, climb, gnaw and fight. The peak o f the response was reached about 1-1.5 h after the administration o f levodopa and disappeared after about 4 h (Figs. 1 and 2). Prior treatment with FLA-63, in a dose k n o w n to inhibit the enzyme dopamine/3-hydroxylase 8, responsible for the conversion o f dopamine into noradrenaline, considerably reduced the levodopa reversal o f reserpine-induced akinesia (Figs. 1 and 2; Table I). A similar effect was seen when FLA-63 was administered orally in a dose o f 15 mg/kg. There was some spontaneous m o v e m e n t in the first h o u r following levodopa administration in animals pretreated with FLA-63. This early and transient effect was apparent in the results o f recording l c o m o t o r activity with the Animex counter (Fig. 2); FLA-63 reduced the m a x i m u m l o c o m o t o r response to levodopa by a b o u t 40 ~ and shortened its duration. This early activity, however, was unlike that seen in reserpinised animals treated with levodopa alone. The latter animals characteristically paced the cage, climbed the bars and fought amongst themselves. Reserpinised animals treated with F L A - 6 3 and levodopa tended to sniff, twitch or j u m p and showed an exaggerated response to auditory and tactile stimuli. In previous studies 1,8 pretreatment with FLA-63 has also caused a qualitative change in the response o f reserpinised rats to levodopa. Pretreatment with phenoxybenzamine, in a dose k n o w n to block spinal noradrenaline receptors2, a also reduced the levodopa reversal o f reserpine-induced akinesia

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SHORT COMMUNICATIONS 1400. "2 1200. o \ 1000. e) o

800'

E 600. 400, 200'

Saline or eBz or FLA-63

0 '7' L-DOPA Dlus MK-486

1

2

3

4 Time (h.)

Fig. 2. Effect of FLA-63 and phenoxybenzamine on the levodopa reversal of reserpine akinesia. Locomotor activity was measured over 10 rain intervals for 6 h by Animex counters. The mean number of counts/10 rain interval is shown for 5 batches of animals for each experiment ( ± 1 S.E.M.). Reserpine (10 mg/kg) was administered 16-24 h before recording. Saline, FLA-63 (25 mg/kg) or phenoxybenzamine (20 mg/kg) was administered 1 h after recording commenced and levodopa (200 mg/kg) plus MK 486 (L~-methyldopahydrazine) (25 mg/kg), a selective peripheral dopa decarboxylase inhibitor, was administered 1 h later.

as measured by both techniques (Figs. 1 and 2; Table I). As in the case of FLA-63, levodopa administered after phenoxybenzamine caused a small increase in motor activity (Fig. 2) but again this was not the normal levodopa response. The behaviour during this period was limited to sporadic twitching or jumping (as described in And6n2). Chlorpromazine and haloperidol, in doses known to block both central dopamine and noradrenaline receptors2, 3 also reduced the levodopa effect (Table I), chlorpromazine more so than haloperidol. Pimozide, which is believed to primarily block dopamine receptors in the brain 3 had no effect on the levodopa response (Table I). These results suggest that noradrenaline formed from levodopa may play a role in causing reversal of reserpine akinesia. A drug that inhibits dopamine/3-hydroxylase activity (FLA-63), and a drug that blocks noradrenaline receptors (phenoxybenzamine), both reduced the effect of levodopa. Since reserpine interferes with the uptake and storage of dopamine in presynaptic storage granules, the site of dopamine /3hydroxylase, it interferes with the conversion of exogenous levodopa to noradrenaline 13. However, synthesis of noradrenaline continues to take place in the presence of reserpine 14 and levodopa has been reported to significantly increase whole-brain noradrenaline levels in reserpinised rats 1. FLA-63 and phenoxybenzamine are not thought to interfere with the formation of dopamine from levodopa, nor are they believed to block dopamine receptors. From these results it seems possible that the levodopa reversal of reserpine akinesia may require the formation of noradrenaline as well as dopamine. The residual motor effects of levodopa after FLA-63 or phenoxybenzamine pretreatment may

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TABLE I EFFECT OF LEVODOPAALONECOMPAREDWITH THE EFFECTOF LEVODOPAAFTERPRETREATMENTWITH FLA-63, PHENOXYBENZAMINE~CHLORPROMAZ1NE~HALOPERIDOL,AND PIMOZIDEON RESERPINEAKINESIA Drugs* administered

Dose (mglkg)

No. of batches

Mean % reversalof reserpine reversal* * ( ± 1 S.E.M.)

Significance of differencefrom levodopa result

Levodopa alone Levodopa plus FLA-63 Levodopa plus phenoxybenzamine Levodopa plus chlorpromazine Levodopa plus haloperidol Levodopa plus pimozide

500 500 25 500 20 500 5.0 500 1.0 500 1.0

16 7

73.9 ± 2.7 15.5 ± 4.0

-P < 0.001

8

16.3 ± 4.2

P < 0.001

11

22.8 ± 7.3

P < 0.001

11

42.1 ± 6.5

P < 0.001

8

80.6 ± 4.8

P > 0.05

* All drugs, except pimozide, were administered as indicated in the legend to Fig. 1. Pimozide was given 1 h after reserpine but 4 h before levodopa. ** Measured 1 h after levodopa administration as indicated in the legend to Fig. 1.

represent the action o f d o p a m i n e alone, b u t they were n o t d r a m a t i c a n d d i d n o t p r o d u c e a r e s t o r a t i o n o f n o r m a l m o t o r behaviour. A n d 6 n et al. 5 have also c o n c l u d e d f r o m o t h e r experiments, t h a t s t i m u l a t i o n o f n o r a d r e n e r g i c receptors is i m p o r t a n t for m o t o r activity in reserpine-treated animals. T h e y f o u n d t h a t the ability o f a p o m o r p h i n e to reverse reserpine akinesia was increased some t w o - f o l d b y c o n c u r r e n t a d m i n i s t r a t i o n o f clonidine, which is believed to stimulate central n o r a d r e n e r g i c receptors selectively4. Clonidine by itself h a d no effect, a n d so c o n c u r r e n t d o p a m i n e r g i c a n d n o r a d r e n e r g i c s t i m u l a t i o n a p p e a r e d essential f o r successful reversal o f reserpine akinesia. These results suggest t h a t the efficacy o f l e v o d o p a in P a r k i n s o n i s m m a y be due, n o t only to the f o r m a t i o n o f d o p a m i n e , b u t to the f o r m a t i o n o f n o r a d r e n a l i n e as well. W h i l e the m a i n p a t h o l o g i c a l change in P a r k i n s o n ' s disease is d e g e n e r a t i o n o f the substantia nigra, o t h e r p i g m e n t e d b r a i n stem nuclei are also affected including the locus coeruleus 15, a m a j o r source o f ascending n o r a d r e n e r g i c fibres to the cerebrum, dienc e p h a l o n a n d cerebellum lz. Indeed, n o t only is d o p a m i n e deficient in the P a r k i n s o n i a n brain, b u t n o r a d r e n a l i n e is r e d u c e d to some 50 ~ o f n o r m a l levels in the h y p o t h a l a mus, s u b s t a n t i a n i g r a a n d i n f e r i o r h e a d o f the c a u d a t e nucleus 9,11,z°. However, there have been o n l y a few studies on b r a i n n o r a d r e n a l i n e in P a r k i n s o n ' s disease a n d the results are n o t conclusive. C e r e b r o s p i n a l fluid levels o f 3 - m e t h o x y - 4 - h y d r o x y p h e n y l ethylene glycol ( M H P E G ) , a m a j o r cerebral m e t a b o l i t e o f n o r a d r e n a l i n e , in P a r k i n son's disease have shown no difference f r o m n o r m a l 7. F u r t h e r studies are r e q u i r e d to investigate the possibility t h a t the m o t o r disability o f P a r k i n s o n ' s disease is due to

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c o m b i n e d deficiency o f cerebral d o p a m i n e and n o r a d r e n a l i n e , and that l e v o d o p a m a y be a successful r e p l a c e m e n t t h e r a p y f o r both. This w o r k was s u p p o r t e d by the M e d i c a l R e s e a r c h Council. O n e o f us (D.T.) wishes to t h a n k the C o m m i t t e e to C o m b a t H u n t i n g t o n ' s Disease an d the W e l l c o m e Trust.

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