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Dopamine D-1 and D-2 receptor agonists and antagonists and neuropeptide-induced excessive grooming
European Journal of Pharmacology, 173 (1989) 227- 231
227
Elsevier EJP 20520 Short communication
Dopamine D-1 and D-2 receptor agonists and antagonists and neuropeptide-induced excessive grooming T j e e r d B. V a n W i m e r s m a G r e i d a n u s , C a r l a Maigret, M a r i e k e T o r n , E r n s t R o n n e r , S a c h a V a n der K r a c h t , N i c J.A. V a n der W e e a n d D i r k H . G . V e r s t e e g Rudolf Magnus Institute, Vondellaan 6, 3521 GD Utrecht, The Netherlands
Received 10 October 1989, accepted 24 October 1989
The administration of the dopamine D-1 receptor antagonist, SCH 23390, but not of the dopamine D-2 receptor antagonist, sulpiride, suppressed the excessive grooming induced by a new environment or by various neuropeptides. In addition, administration of the dopamine D-1 agonist, SK & F 38393, induced excessive grooming but that of the dopamine D-2 agonist, quinpirole, did not. It is suggested that dopamine D-1 rather than D-2 receptor stimulation is an important mechanism underlying novelty-induced as well as neuropeptide-induced excessive grooming. Grooming behavior; Neuropeptides; SCH 23390; Sulpiride; SK& F 38393; Quinpirole
1. Introduction
It has been shown that excessive grooming induced by the i.c.v, administration of ACTH, /~-endorphin, bombesin, T R H , substance P or somatostatin was suppressed following s.c. pretreatment with the dopamine receptor antagonist, haloperidol (Van Wimersma Greidanus et al., 1987; 1988a,b; Van Wimersma Greidanus and Maigret, 1988). In contrast, the total grooming scores for the excessive grooming induced by the somatostatin analog, SMS 201-995 (Sandostatin), were not reduced by haloperidol; pretreatment with this receptor antagonist only resulted in a shift in the pattern of the excessive grooming i n d u c e d b y S a n d o s t a t i n (Van W i m e r s m a Greidanus et al., 1987). Based on these and other data it was suggested that the role of dopaminergic
Correspondence to: T.B. Van Wimersma Greidanus, Rudolf Magnus Institute, VondeUaan 6, 3521 GD Utrecht, The Netherlands.
systems can be regarded as general modulation of grooming behavior (Van Wimersma Greidanus et al., 1988b). Haloperidol is known to be a dopamine D-2 receptor antagonist (Hyttel, 1983). In view of this and other findings, most of the behavioral actions of dopaminergic and neuroleptic drugs were believed to be mediated via dopamine D-2 receptors (Molloy and Waddington, 1984), while the status of D-1 dopamine sites as behaviorally significant receptors received little attention. It is only recently, as more selective dopamine D-1 and D-2 receptor agonists and antagonists have become available, that the significance of the dopamine receptor subtypes has been investigated in more detail (Murray and Waddington, 1989). We nowe examined the effect of the dopamine D-1 receptor antagonist, SCH 23390 (Hyttel, 1983) and of the dopamine D-2 receptor antagonist, sulpiride, on excessive grooming induced by various neuropeptides. The results show that dopamine D-1 receptors, but not D-2 receptors, are involved in neuropeptide-induced grooming in the rat.
0014-2999/89/$03.50 © 1989 Elsevier Science Publishers B.V. (Biomedical Division)
228 2. Materials and methods
The rats used were males of an inbred Wistar strain (TNO, Zeist, The Netherlands) and weighed approximately 150 g. The brain ventricular system was cannulated for i.c.v, injection of the peptides by placing a polyethylene cannula in the right lateral ventricle (Brakkee et al., 1979). This operation was performed under H y p n o r m ® (5.0 mg fluanison and 0.2 mg fentanyl per 0.5 m l / k g s.c.; D u p h a r BV, A m s t e r d a m , The Netherlands) anesthesia. The animals were allowed 5 days to recover from the surgery and were single-caged under standard light-dark conditions (light on 07:00 a,m., off 07:00 p.m.) with food and water available ad libitum. The rats were allocated randomly to different treatment groups and received 2 t~l i.c.v, injections. Each animal was used only once. Peptides were injected i.c.v, in the following doses: A C T H (Organon BV, Oss, The Netherlands): 1 #g; /~-endorphin (Organon BV, Oss, The Netherlands): 100 /~g; bombesin (B 610, UCB, The Hague, The Netherlands): 30 ng; T R H (Organon BV, Oss, The Netherlands): 2/~g; substance P ( B a c h e m F e i n c h e m i k a l i e n A G , Bubendorf, Switzerland): 100 ng; somatostatin (Aminopan ~, B150, UCB, Breda, The Netherlands): 1 /~g; SMS 201-995 (Sandostatin ®, Sandoz, Basel, Switzerland): 50 ng. SCH 23390 (Schering Co.., Bloomfield, N J, USA; 0.05 m g / k g s.c.) was given as pretreatment 20 rain prior to peptide administration. Pretreatment with sulpiride (Delagrange, Paris, France; 2 ~g i.c.v.) was performed 10 min prior to peptide administration. The i.c.v, route was chosen for this latter drug since it was known from the results of preliminary experiments that systemic administration of sulpiride does not result in significant effects, probably due to poor penetration into the brain (Traber et al., 1982). Additional experiments were done with the dopamine D-1 and D-2 receptor agonists administered s.c. in graded doses, 1, 3 and 10 m g / k g ( S K & F 38393, purchased from Research Biochemicals Inc., Matick, MA, USA) or of 0.2, 1.0 and 3.0 m g / k g (quinpirole, gift from Lilly Research Labs, Indianapolis, IN, USA). Grooming was tested according to Gispen and Isaacson (1981). Briefly, the rats were placed in
Perspex observation boxes (26 × 10 × 13 cm) immediately after the i.c.v, injection of the peptides or after s.c. administration of the agonists or placebo. Scoring of grooming frequencies was started 10 min later with a 15 s sampling for a period of 50 rain, resulting in a theoretical maximal grooming score (T) of 200. The following elements of grooming were scored: head washing (H), body grooming (B), paw licking (P), anogenital grooming + tail licking (A), scratching (S). The results are expressed as means ( ± S . E . M . ) grooming score per treatment group for 50 rain. The analysis of variance (ANOVA) in combination with a supplemental t-test was used for statistical evaluation of the data.
3. Results
Excessive grooming was induced by all peptides. Pretreatment with SCH 23390 (0.05 m g / k g s.c.) resulted in a marked reduction of total grooming in placebo-treated rats (novelty-induced grooming) as well as in rats treated with the various neuropeptides (table 1). The reduction by SCH 23390 was more pronounced for the excessive grooming induced by B-endorphin, substance P, T R H or somatostatin than for grooming induced by ACTH, bombesin or SMS 201-995. Moreover, it appeared that the dopamine D-1 receptor antagonist suppressed or reduced all or at least most of the various elements of grooming behavior with the exception of the excessive grooming induced by SMS 201-995. In this latter case only the element, head washing, was significantly reduced. Results from preliminary experiments showed that pretreatment with sulpiride (0.05 m g / k g ) s.c. 20 and 40 min prior to A C T H or placebo administration did not suppress grooming. Even a dose of 50 m g / k g (s.c.) administered 20 min prior to A C T H or placebo did not result in a significant decrease in grooming scores. Only an excessive amount, 20 /~g, i.c.v, injected 10 rain prior to ACTH, bombesin or placebo induced a small but significant reduction in the scores for some grooming elements (data not shown). The i.c.v, administration of sulpiride (2 /~g) did not affect grooming
229 TABLE 1 Influence of SCH 23390 (0.05 m g / k g s.c., 20 min prior to peptide administration) on grooming scores displayed by rats treated with placebo (saline, SAL) or with various neuropeptides. The data are m e a n s ± S.E.M. of behavioural counts for n = 6-11 animals per group. H: head washing; B: body grooming; A: ano-genital grooming; P: paw licking; S: scratching; T: total grooming score; fiE: fl-endorphin. Treatment
Grooming scores
H
B
A
P
S
T
SAL SCH23390 flE, 100ng SCH+flE
6.1±1.4 1.4±0.3 a 13.7±1.9 a 6.2±1.2 b
11.9±1.9 1.7±0.6 a 28.2±2.9 " 7.6±1.7 b
3.7±0.9 0.6±0.2 a 12.5±3.4 ~ 3.7±1.1 b
9.4±2.8 1.9±0.5 a 22.3±4.1 a 4.6±1.2 b
2.9± 0.8 0 32.7± 7.6 ~ 4.2± 2.8 b
34.0± 5.6± 109.3± 26.2±
5.4 0.7 a 5.8 a 5.9 b
SAL SCH23390 SubstanceP, 100ng SCH+substanceP
9.0±1.5 3.1±0.5 a 10.8±1.3 1.7±0.6 b
13.8±2.3 2.7±0.6 a 17.5±2.5 3.1±1.5 b
4.0±1.4 0.9±0.3 a 11.4±1.4 ~ 0.6±0.3 b
9.3±1.9 1.0±0.2 a 11.9±1.7 2.1±0.7 b
2.8± 0.5 0.1± 0.1 a 14.3± 5.7 ~ 0
39.0± 7.9± 65.6± 7.6±
3.8 1.0 a 6.5 a 2.6 b
SAL SCH23390 TRH, 2 # g SCH+TRH
10.2±3.2 3.2±1.2 a 13.7±2.5 2.9±0.7 b
10.5±1.9 3.2±1.8 a 14.7±1.3 3.8±0.2 b
4.0±1.0 1.5±0.7 a 2.3±0.7 0.4±0.2 b
10.3±2.3 0.5±0.2 a 21.9±2.6 ~ 2.3±0.5 b
1.2± 0.5 0.2± 0.2 41.4±11.6 ~ 1.6± 0.9 b
36.2± 8.5± 93.4± 11.0±
5.9 2.8 a 9.9 " 1.9 b
SAL SCH23390 Somatostatin, l ~ g SCH+somatostatin
9.5±1.6 2.5±0.8 ~ 9.4±2.4 3.8±0.8 b
12.0±1.5 2.0±0.8 a 18.0±3.0 3.5±1.1 b
4.8±1.9 0.5±0.5 a 8.0±2.5 1.3±0.6 b
6.0±0.9 1.7±0.6 a 15.3±2.4 ~ 1.5±0.5 b
3.8± 0.2± 21.4± 0.4±
1.1 0.2 ~ 4.7 a 0.4 b
36.2± 6.8± 72.1± 10.4±
4.2 2.0 a 6.3 a 2.5 b
SAL SCH233~ SMS201.995,50ng SCH+SMS
7.3±1.2 2.6±0.5 ~ 37.1±9.0 a 19.6±2.5 b
11.3±2.6 3.3±0.6 a 9.1±3.2 5.5±0.7
4.2±1.1 1.1±0.4 a 2.0±0.6 1.4±0.4
8.5±1.6 1.6±0.4 a 11.4±1.8 10.1±2.4
3.2± 1.1 0 46.1± 8.1 a 38.0± 7.8
34.5± 8.6± 105.9± 74.6±
5.2 1.3 a 9.3 ~ 9.6 b
SAL SCH23390 ACTH, I ~ g SCH+ACTH
8.8±2.2 3.6±1.0 a 24.8±3.2 a 14.3±0.8 b
9.8±2.3 2.8±1.5 a 25.7±6.4 a 10.5±2.9 ~
5.2±1.2 0.6±0.4 a 13.7±4.8 3.5±1.6 b
9.6±1.3 3.2±1.7 a 50.2±5.7 " 21.5±2.5 b
1.0± 0.6 0 7.0± 3.2 a 0
9.2±1.3 2.0±0.9 ~ 8.4±1.0 9.2±0.9
11.8±3.0 2.0±1.4 ~ 11.4±1.4 6.4±0.7 b
4.4±2.0 0 ±0 11.2±2.1 a 4.2±0.9 b
7.8±1.2 4.4±0.9 a 26.7±2.7 a 18.5±2.0 ~
SAL SCH23390 Bombesin, 30ng SCH+bombesin
1.2± 0.2± 75.4± 33.9±
0.6 0.2 6.8 a 6.7 b
34.4± 4.5 10.2± 3.6 ~ 121.3±18.9 a 49.8± 5.5 b 34.4± 8.6± 132.9± 72.2±
4.9 1.9 a 7.7 a 9.0 b
a p ~< 0.05 vs. SAL; b p ~< 0.05 vs. peptide.
behavior
e i t h e r in p lacebo-treated
rats or in rats
treated with any of the neuropeptides. cant
effect on
only
seen
one
of the various
occasionally
D-2 antagonist
A signifi-
elements
following
this
was
dopamine
( t a b l e 2).
Administration SK&F
38393,
quinpirole,
but
not
an
increase
in
anogenital
grooming.
Scratching
w a s n o t a f f e c t e d a t all. T h e t o t a l g r o o m i n g
scores
d i d n o t e x c e e d 60, e v e n f o l l o w i n g a d m i n i s t r a t i o n of the highest dose.
of the dopamine
agonist,
washing and paw licking, and to a lesser extent to
of
induced
the
D-1
agonist,
dopamine
excessive
D-2
grooming
4. D i s c u s s i o n
(data not shown). The excessive grooming induced by SK&F
38393 appeared
i n c r e a s e in the f r e q uencies
to be due mainly to an of the elements,
head
The present D-1
receptor
results showed antagonist,
SCH
that the dopamine 23390,
suppresses
230 TABLE 2
Influence of sulpiride (2 /~g i.c.v., 10 min prior to peptide administration), on grooming scores of rats treated with placebo (saline, SAL) or with different neuropeptides. The data are means_+ S.E.M. of behavioural counts for n = 6-11 animals per group. See title to table 1 for further abbreviations. Treatment
SAL Sulpiride flE, 1 0 0 n g Sulpiride+flE
Grooming scores H
B
A
P
S
8.5_+1.6 9.2 _+3.0 13.1_+1.2 a 13.0_+2.2
14.7_+2.3 10.8 _+2.3 25.4+2.4 a 26.8_+4.2
4.2_+1.3 4.8 _+1.8 10.6_+0.9 ~ 13.3_+2.0
7.7_+2.2 11.4 _+2.8 20.4_+3.3 a 30.7_+4.5
2.0+_ 1.2 _+ 37.3-+ 22.2_+
0.7 0.6 6.3 a 5.4
T 37.0+_ 37.4 _+ 106.9_+ 106.0_+
5.1 7.5 5.5 ~ 6.9
SAL Sulpiride TRH, 1/~g Sulpiride+TRH
6.1 _+0.6 4.2-+1.0 5.8-+0.8 6.5-+1.9
10.0 _+1.0 7.6-+2.0 8.9-+2.0 9.2-+1.5
6.8 _+ 1.8 5.4_+1.1 2.2_+0.5 a 5.5_+1.3
9.7 _+ 1.6 7.0-+0.7 15.6+2.7 a 17,2-+2.2
6.9 + 3.3_+ 35.6-+ 21.7-+
1.4 1.0 a 7.4 a 5.4 b
39.5 + 27.5_+ 68.0-+ 60.8-+
3.7 2.9 a 8.3 a 6.7
SAL Sulpiride Substance P, 100 ng Sulpiride+subst. P
7.8-+1.5 5.3_+0.7 7.9_+ 1.0 6.4_+0.5
8.2_+2.2 11.0_+1.0 15.9_+1.8 a 15.8_+1.7
5.7-+1.4 4.0_+0.8 7.3_+0.8 7.3_+1.2
11.7-+1.6 13,2_+1.7 19,7_+1.9 a 16,1_+1.1
1.7-+ 2.3_+ 8.3_+ 10.4_+
0.8 0.7 2.5 a 4.1
35.0-+ 35.8_+ 59.1 _+ 55.9_+
4.0 3.3 4.7 a 3.3
SAL Sulpiride Somatostatin, 1/~g Sulp.+somatostatin
7.7_+1.4 6.3_+1.4 12.4_+2.4 6.5_+1.5 b
13.7_+1.6 11.1_+0.7 13.6_+4.3 12.3-+3.0
6.9_+2.0 6.7_+1.4 5.9_+1.3 6.3_+2.0
6,3_+0.9 10,7_+1.7 17,3_+3.4 a 14,6_+2.5
1.9_+ 3.0_+ 22.7_+ 34.6_+
0.7 hl 7.5 ~ 5.8 b
36.4_+ 37.9_+ 71.9_+ 74.3-+
3.2 1.2 6.2 a 6.2
SAL Sulpiride SMS 201.995, 50 ng Sulpiride+SMS
6.5_+1.3 6.1-+0.9 14.8-+2.0 a 22.7_+3.8
8.0_+1.6 9.3-+1.8 4.5_+0.8 6.6_+1.0
4.3_+1.1 5.6_+1.0 2.9_+0.9 3.8_+1.1
4.7_+0.6 5.6_+0.9 11.2+_2.3 a 20.3_+4.2 b
5.7_+ 1.6 3.5_+ 1.1 66.8-+13.7 a 74.3-+ 7.6
29.2-+ 3.2 30.1 + 3.7 100.2_+16.4 ~ 127.4_+ 7.0
SAL Sulpiride ACTH, 1/xg Sulpiride + ACT H
10.4-+1.5 8.6 -+ 1.8 32.3_+4.6 a 35.2 -+ 3.9
11.8+_2.1 8.6 -+ 2.0 43.5_+5.2 a 45.2 _+4.3
4.2-+1.2 5.2 -+ 2.0 9.0_+3.8 9.3 _+2.2
6.2-+2.1 7.0 _+1.9 51.3+_5.4 a 52.0 _+6.0
0.4_+ 2.0 _+ 7.0-+ 12.7 -+
33.0+_ 31.4 -+ 143.0-+ 154.3 -+
SAL Sulpiride Bombesin, 30 ng Sulp. + bombesin
5.7_+1.6 7.4 _+ 1.2 13.8_+2.4 a 13.0_+2.7
14.0_+1.8 9.0 _+2.3 20.3-+3.4 16.0_+2.8
5.3_+0.7 4.9 -+ 1.0 10.8-+2.1 a 9.3_+2.1
8.7-+1.0 8.9 _+1.8 18.0+_3.1 a 9.3_+1.5 b
3.2-+ 0.6 1.9 _+ 0.9 59.8-+ 14.0 a 80.5_+17.7
0.2 1.0 4.3 ~ 4.0
5.5 6.6 9.9 a 5.9
36.8+ 1.8 32.0 _+ 6.6 122.8_+13.8 ~ 128.2_+13.8
a p ~ 0.05 vs. SAL; b p ~ 0.05 vs. peptide.
novelty-induced as well as neuropeptide-induced excessive grooming whereas the dopamine D-2 receptor antagonist, sulpiride, does not affect grooming. This latter observation confirms earlier findings by Traber et al. (1982) who reported the ineffectiveness of even high doses of sulpiride on ACTH-induced excessive grooming. Moreover, the dopamine D-1 receptor agonist, SK&F 38393, but not the dopamine D-2 receptor agonist, quinpirole, induced grooming. These findings confirm previous findings by Waddington and coworkers who found a behavioral effect of SK&F 38393 and in
particular reported a dose-dependent increase of sniffing, locomotion and grooming and the induction of a characteristic syndrome of intense grooming in well-habituated animals (Molloy and Waddington, 1984; Murray and Waddington, 1989). A complex functional interaction between D-1 and D-2 dopamine receptors has been suggested to be involved in unconditioned behaviors associated with postsynaptic activity of dopamine agonists (Braun and Chase, 1986) and, more particularly, a cooperative form of functional interaction between D-1 and D-2 systems has been sug-
231 gested to regulate grooming behavior (Murray and Waddington, 1989). C o n c e r n i n g the excessive grooming induced by a new environment or by various neuropeptides, the present data suggest strongly that stimulation of dopamine D-1 rather t h a n D - 2 r e c e p t o r s is a n i m p o r t a n t m e c h a n i s m u n d e r l y i n g t h e i n d u c t i o n o f n o v e l t y - i n d u c e d exc e s s i v e g r o o m i n g as well as n e u r o p e p t i d e - i n d u c e d excessive grooming and support the view that e x c e s s i v e s c r a t c h i n g is n o t p r i m a r i l y m e d i a t e d b y dopamine receptors.
References Brakkee, J.H., V.M. Wiegant and W.H. Gispen, 1979, A simple technique for rapid implantation of a permanent cannula into the rat brain ventricular system, Lab. Animal Sci. 29, 78. Braun, A.R. and T.N. Chase, 1986, Obligatory D - l / D - 2 receptor interaction in the generation of dopamine agonist-related behaviors, European J. Pharmacol. 131,301. Gispen, W.H. and R.L. Isaacson, 1981, ACTH-induced excessive grooming in the rat, Pharmacol. Ther. 12, 209. Hyttel, J., 1983, SCH 23390 - The first selective dopamine D-1 antagonist, European J. Pharmacol. 91, 153.
Molloy, A.G. and J.U Waddington, 1984, Dopaminergic behaviour stereospecifically promoted by the D 1 agonist R-SK & F 38393 and selectively blocked by the D l antagonist SCH 23390, Psychopharmacology 82, 409. Murray, A.M. and J.L. Waddington, 1989, The induction of grooming and vacuous chewing by a series of selective D-1 dopamine receptor agonists; two directions of D-I:D-2 interaction, European J. Pharmacol. 160, 377. Traber, J., H.R. Klein and W.H. Gispen, 1982, Actions of antidepressant and neuroleptic drugs on ACTH- and novelty-induced behavior in the rat, European J. Pharmacol. 80, 407. Van Wimersma Greidanus, Tj.B. and C. Maigret, 1988, Grooming behavior induced by substance P, European J. Pharmacol. 154, 217. Van Wimersma Greidanus, Tj.B., C. Maigret and B. Krechting, 1987, Excessive grooming induced by somatostatin or its analog SMS 201-995, European J. Pharmacol. 144, 277. Van Wimersma Greidanus, Tj.B., C. Maigret, G.J.E. Rinkel, P. Metzger, M. Panis, F.E.M. Van Zinnicq Bergmann, P,J.I.M. Poelman and D.L. Colbern, 1988a, Some characteristics of TRH-induced grooming behavior in rats, Peptides 9, 283. Van Wimersma Greidanus, Tj.B., F. Van de Brug, L.M. De Bruijckere, P.H.M.A. Pabst, R.W. Ruesink, R.L.E. Hulshof, B.N.M. Van Berckel, S.M. Arissen, E.J.P. De Koning and D.K. Donker, 1988b, Comparison of bombesin-, ACTH-, and fl-endorphin-induced grooming. Antagonism by haloperidol, naloxone, and neurotensin, Ann. N.Y. Acad. Sci. 525, 219.
227
Elsevier EJP 20520 Short communication
Dopamine D-1 and D-2 receptor agonists and antagonists and neuropeptide-induced excessive grooming T j e e r d B. V a n W i m e r s m a G r e i d a n u s , C a r l a Maigret, M a r i e k e T o r n , E r n s t R o n n e r , S a c h a V a n der K r a c h t , N i c J.A. V a n der W e e a n d D i r k H . G . V e r s t e e g Rudolf Magnus Institute, Vondellaan 6, 3521 GD Utrecht, The Netherlands
Received 10 October 1989, accepted 24 October 1989
The administration of the dopamine D-1 receptor antagonist, SCH 23390, but not of the dopamine D-2 receptor antagonist, sulpiride, suppressed the excessive grooming induced by a new environment or by various neuropeptides. In addition, administration of the dopamine D-1 agonist, SK & F 38393, induced excessive grooming but that of the dopamine D-2 agonist, quinpirole, did not. It is suggested that dopamine D-1 rather than D-2 receptor stimulation is an important mechanism underlying novelty-induced as well as neuropeptide-induced excessive grooming. Grooming behavior; Neuropeptides; SCH 23390; Sulpiride; SK& F 38393; Quinpirole
1. Introduction
It has been shown that excessive grooming induced by the i.c.v, administration of ACTH, /~-endorphin, bombesin, T R H , substance P or somatostatin was suppressed following s.c. pretreatment with the dopamine receptor antagonist, haloperidol (Van Wimersma Greidanus et al., 1987; 1988a,b; Van Wimersma Greidanus and Maigret, 1988). In contrast, the total grooming scores for the excessive grooming induced by the somatostatin analog, SMS 201-995 (Sandostatin), were not reduced by haloperidol; pretreatment with this receptor antagonist only resulted in a shift in the pattern of the excessive grooming i n d u c e d b y S a n d o s t a t i n (Van W i m e r s m a Greidanus et al., 1987). Based on these and other data it was suggested that the role of dopaminergic
Correspondence to: T.B. Van Wimersma Greidanus, Rudolf Magnus Institute, VondeUaan 6, 3521 GD Utrecht, The Netherlands.
systems can be regarded as general modulation of grooming behavior (Van Wimersma Greidanus et al., 1988b). Haloperidol is known to be a dopamine D-2 receptor antagonist (Hyttel, 1983). In view of this and other findings, most of the behavioral actions of dopaminergic and neuroleptic drugs were believed to be mediated via dopamine D-2 receptors (Molloy and Waddington, 1984), while the status of D-1 dopamine sites as behaviorally significant receptors received little attention. It is only recently, as more selective dopamine D-1 and D-2 receptor agonists and antagonists have become available, that the significance of the dopamine receptor subtypes has been investigated in more detail (Murray and Waddington, 1989). We nowe examined the effect of the dopamine D-1 receptor antagonist, SCH 23390 (Hyttel, 1983) and of the dopamine D-2 receptor antagonist, sulpiride, on excessive grooming induced by various neuropeptides. The results show that dopamine D-1 receptors, but not D-2 receptors, are involved in neuropeptide-induced grooming in the rat.
0014-2999/89/$03.50 © 1989 Elsevier Science Publishers B.V. (Biomedical Division)
228 2. Materials and methods
The rats used were males of an inbred Wistar strain (TNO, Zeist, The Netherlands) and weighed approximately 150 g. The brain ventricular system was cannulated for i.c.v, injection of the peptides by placing a polyethylene cannula in the right lateral ventricle (Brakkee et al., 1979). This operation was performed under H y p n o r m ® (5.0 mg fluanison and 0.2 mg fentanyl per 0.5 m l / k g s.c.; D u p h a r BV, A m s t e r d a m , The Netherlands) anesthesia. The animals were allowed 5 days to recover from the surgery and were single-caged under standard light-dark conditions (light on 07:00 a,m., off 07:00 p.m.) with food and water available ad libitum. The rats were allocated randomly to different treatment groups and received 2 t~l i.c.v, injections. Each animal was used only once. Peptides were injected i.c.v, in the following doses: A C T H (Organon BV, Oss, The Netherlands): 1 #g; /~-endorphin (Organon BV, Oss, The Netherlands): 100 /~g; bombesin (B 610, UCB, The Hague, The Netherlands): 30 ng; T R H (Organon BV, Oss, The Netherlands): 2/~g; substance P ( B a c h e m F e i n c h e m i k a l i e n A G , Bubendorf, Switzerland): 100 ng; somatostatin (Aminopan ~, B150, UCB, Breda, The Netherlands): 1 /~g; SMS 201-995 (Sandostatin ®, Sandoz, Basel, Switzerland): 50 ng. SCH 23390 (Schering Co.., Bloomfield, N J, USA; 0.05 m g / k g s.c.) was given as pretreatment 20 rain prior to peptide administration. Pretreatment with sulpiride (Delagrange, Paris, France; 2 ~g i.c.v.) was performed 10 min prior to peptide administration. The i.c.v, route was chosen for this latter drug since it was known from the results of preliminary experiments that systemic administration of sulpiride does not result in significant effects, probably due to poor penetration into the brain (Traber et al., 1982). Additional experiments were done with the dopamine D-1 and D-2 receptor agonists administered s.c. in graded doses, 1, 3 and 10 m g / k g ( S K & F 38393, purchased from Research Biochemicals Inc., Matick, MA, USA) or of 0.2, 1.0 and 3.0 m g / k g (quinpirole, gift from Lilly Research Labs, Indianapolis, IN, USA). Grooming was tested according to Gispen and Isaacson (1981). Briefly, the rats were placed in
Perspex observation boxes (26 × 10 × 13 cm) immediately after the i.c.v, injection of the peptides or after s.c. administration of the agonists or placebo. Scoring of grooming frequencies was started 10 min later with a 15 s sampling for a period of 50 rain, resulting in a theoretical maximal grooming score (T) of 200. The following elements of grooming were scored: head washing (H), body grooming (B), paw licking (P), anogenital grooming + tail licking (A), scratching (S). The results are expressed as means ( ± S . E . M . ) grooming score per treatment group for 50 rain. The analysis of variance (ANOVA) in combination with a supplemental t-test was used for statistical evaluation of the data.
3. Results
Excessive grooming was induced by all peptides. Pretreatment with SCH 23390 (0.05 m g / k g s.c.) resulted in a marked reduction of total grooming in placebo-treated rats (novelty-induced grooming) as well as in rats treated with the various neuropeptides (table 1). The reduction by SCH 23390 was more pronounced for the excessive grooming induced by B-endorphin, substance P, T R H or somatostatin than for grooming induced by ACTH, bombesin or SMS 201-995. Moreover, it appeared that the dopamine D-1 receptor antagonist suppressed or reduced all or at least most of the various elements of grooming behavior with the exception of the excessive grooming induced by SMS 201-995. In this latter case only the element, head washing, was significantly reduced. Results from preliminary experiments showed that pretreatment with sulpiride (0.05 m g / k g ) s.c. 20 and 40 min prior to A C T H or placebo administration did not suppress grooming. Even a dose of 50 m g / k g (s.c.) administered 20 min prior to A C T H or placebo did not result in a significant decrease in grooming scores. Only an excessive amount, 20 /~g, i.c.v, injected 10 rain prior to ACTH, bombesin or placebo induced a small but significant reduction in the scores for some grooming elements (data not shown). The i.c.v, administration of sulpiride (2 /~g) did not affect grooming
229 TABLE 1 Influence of SCH 23390 (0.05 m g / k g s.c., 20 min prior to peptide administration) on grooming scores displayed by rats treated with placebo (saline, SAL) or with various neuropeptides. The data are m e a n s ± S.E.M. of behavioural counts for n = 6-11 animals per group. H: head washing; B: body grooming; A: ano-genital grooming; P: paw licking; S: scratching; T: total grooming score; fiE: fl-endorphin. Treatment
Grooming scores
H
B
A
P
S
T
SAL SCH23390 flE, 100ng SCH+flE
6.1±1.4 1.4±0.3 a 13.7±1.9 a 6.2±1.2 b
11.9±1.9 1.7±0.6 a 28.2±2.9 " 7.6±1.7 b
3.7±0.9 0.6±0.2 a 12.5±3.4 ~ 3.7±1.1 b
9.4±2.8 1.9±0.5 a 22.3±4.1 a 4.6±1.2 b
2.9± 0.8 0 32.7± 7.6 ~ 4.2± 2.8 b
34.0± 5.6± 109.3± 26.2±
5.4 0.7 a 5.8 a 5.9 b
SAL SCH23390 SubstanceP, 100ng SCH+substanceP
9.0±1.5 3.1±0.5 a 10.8±1.3 1.7±0.6 b
13.8±2.3 2.7±0.6 a 17.5±2.5 3.1±1.5 b
4.0±1.4 0.9±0.3 a 11.4±1.4 ~ 0.6±0.3 b
9.3±1.9 1.0±0.2 a 11.9±1.7 2.1±0.7 b
2.8± 0.5 0.1± 0.1 a 14.3± 5.7 ~ 0
39.0± 7.9± 65.6± 7.6±
3.8 1.0 a 6.5 a 2.6 b
SAL SCH23390 TRH, 2 # g SCH+TRH
10.2±3.2 3.2±1.2 a 13.7±2.5 2.9±0.7 b
10.5±1.9 3.2±1.8 a 14.7±1.3 3.8±0.2 b
4.0±1.0 1.5±0.7 a 2.3±0.7 0.4±0.2 b
10.3±2.3 0.5±0.2 a 21.9±2.6 ~ 2.3±0.5 b
1.2± 0.5 0.2± 0.2 41.4±11.6 ~ 1.6± 0.9 b
36.2± 8.5± 93.4± 11.0±
5.9 2.8 a 9.9 " 1.9 b
SAL SCH23390 Somatostatin, l ~ g SCH+somatostatin
9.5±1.6 2.5±0.8 ~ 9.4±2.4 3.8±0.8 b
12.0±1.5 2.0±0.8 a 18.0±3.0 3.5±1.1 b
4.8±1.9 0.5±0.5 a 8.0±2.5 1.3±0.6 b
6.0±0.9 1.7±0.6 a 15.3±2.4 ~ 1.5±0.5 b
3.8± 0.2± 21.4± 0.4±
1.1 0.2 ~ 4.7 a 0.4 b
36.2± 6.8± 72.1± 10.4±
4.2 2.0 a 6.3 a 2.5 b
SAL SCH233~ SMS201.995,50ng SCH+SMS
7.3±1.2 2.6±0.5 ~ 37.1±9.0 a 19.6±2.5 b
11.3±2.6 3.3±0.6 a 9.1±3.2 5.5±0.7
4.2±1.1 1.1±0.4 a 2.0±0.6 1.4±0.4
8.5±1.6 1.6±0.4 a 11.4±1.8 10.1±2.4
3.2± 1.1 0 46.1± 8.1 a 38.0± 7.8
34.5± 8.6± 105.9± 74.6±
5.2 1.3 a 9.3 ~ 9.6 b
SAL SCH23390 ACTH, I ~ g SCH+ACTH
8.8±2.2 3.6±1.0 a 24.8±3.2 a 14.3±0.8 b
9.8±2.3 2.8±1.5 a 25.7±6.4 a 10.5±2.9 ~
5.2±1.2 0.6±0.4 a 13.7±4.8 3.5±1.6 b
9.6±1.3 3.2±1.7 a 50.2±5.7 " 21.5±2.5 b
1.0± 0.6 0 7.0± 3.2 a 0
9.2±1.3 2.0±0.9 ~ 8.4±1.0 9.2±0.9
11.8±3.0 2.0±1.4 ~ 11.4±1.4 6.4±0.7 b
4.4±2.0 0 ±0 11.2±2.1 a 4.2±0.9 b
7.8±1.2 4.4±0.9 a 26.7±2.7 a 18.5±2.0 ~
SAL SCH23390 Bombesin, 30ng SCH+bombesin
1.2± 0.2± 75.4± 33.9±
0.6 0.2 6.8 a 6.7 b
34.4± 4.5 10.2± 3.6 ~ 121.3±18.9 a 49.8± 5.5 b 34.4± 8.6± 132.9± 72.2±
4.9 1.9 a 7.7 a 9.0 b
a p ~< 0.05 vs. SAL; b p ~< 0.05 vs. peptide.
behavior
e i t h e r in p lacebo-treated
rats or in rats
treated with any of the neuropeptides. cant
effect on
only
seen
one
of the various
occasionally
D-2 antagonist
A signifi-
elements
following
this
was
dopamine
( t a b l e 2).
Administration SK&F
38393,
quinpirole,
but
not
an
increase
in
anogenital
grooming.
Scratching
w a s n o t a f f e c t e d a t all. T h e t o t a l g r o o m i n g
scores
d i d n o t e x c e e d 60, e v e n f o l l o w i n g a d m i n i s t r a t i o n of the highest dose.
of the dopamine
agonist,
washing and paw licking, and to a lesser extent to
of
induced
the
D-1
agonist,
dopamine
excessive
D-2
grooming
4. D i s c u s s i o n
(data not shown). The excessive grooming induced by SK&F
38393 appeared
i n c r e a s e in the f r e q uencies
to be due mainly to an of the elements,
head
The present D-1
receptor
results showed antagonist,
SCH
that the dopamine 23390,
suppresses
230 TABLE 2
Influence of sulpiride (2 /~g i.c.v., 10 min prior to peptide administration), on grooming scores of rats treated with placebo (saline, SAL) or with different neuropeptides. The data are means_+ S.E.M. of behavioural counts for n = 6-11 animals per group. See title to table 1 for further abbreviations. Treatment
SAL Sulpiride flE, 1 0 0 n g Sulpiride+flE
Grooming scores H
B
A
P
S
8.5_+1.6 9.2 _+3.0 13.1_+1.2 a 13.0_+2.2
14.7_+2.3 10.8 _+2.3 25.4+2.4 a 26.8_+4.2
4.2_+1.3 4.8 _+1.8 10.6_+0.9 ~ 13.3_+2.0
7.7_+2.2 11.4 _+2.8 20.4_+3.3 a 30.7_+4.5
2.0+_ 1.2 _+ 37.3-+ 22.2_+
0.7 0.6 6.3 a 5.4
T 37.0+_ 37.4 _+ 106.9_+ 106.0_+
5.1 7.5 5.5 ~ 6.9
SAL Sulpiride TRH, 1/~g Sulpiride+TRH
6.1 _+0.6 4.2-+1.0 5.8-+0.8 6.5-+1.9
10.0 _+1.0 7.6-+2.0 8.9-+2.0 9.2-+1.5
6.8 _+ 1.8 5.4_+1.1 2.2_+0.5 a 5.5_+1.3
9.7 _+ 1.6 7.0-+0.7 15.6+2.7 a 17,2-+2.2
6.9 + 3.3_+ 35.6-+ 21.7-+
1.4 1.0 a 7.4 a 5.4 b
39.5 + 27.5_+ 68.0-+ 60.8-+
3.7 2.9 a 8.3 a 6.7
SAL Sulpiride Substance P, 100 ng Sulpiride+subst. P
7.8-+1.5 5.3_+0.7 7.9_+ 1.0 6.4_+0.5
8.2_+2.2 11.0_+1.0 15.9_+1.8 a 15.8_+1.7
5.7-+1.4 4.0_+0.8 7.3_+0.8 7.3_+1.2
11.7-+1.6 13,2_+1.7 19,7_+1.9 a 16,1_+1.1
1.7-+ 2.3_+ 8.3_+ 10.4_+
0.8 0.7 2.5 a 4.1
35.0-+ 35.8_+ 59.1 _+ 55.9_+
4.0 3.3 4.7 a 3.3
SAL Sulpiride Somatostatin, 1/~g Sulp.+somatostatin
7.7_+1.4 6.3_+1.4 12.4_+2.4 6.5_+1.5 b
13.7_+1.6 11.1_+0.7 13.6_+4.3 12.3-+3.0
6.9_+2.0 6.7_+1.4 5.9_+1.3 6.3_+2.0
6,3_+0.9 10,7_+1.7 17,3_+3.4 a 14,6_+2.5
1.9_+ 3.0_+ 22.7_+ 34.6_+
0.7 hl 7.5 ~ 5.8 b
36.4_+ 37.9_+ 71.9_+ 74.3-+
3.2 1.2 6.2 a 6.2
SAL Sulpiride SMS 201.995, 50 ng Sulpiride+SMS
6.5_+1.3 6.1-+0.9 14.8-+2.0 a 22.7_+3.8
8.0_+1.6 9.3-+1.8 4.5_+0.8 6.6_+1.0
4.3_+1.1 5.6_+1.0 2.9_+0.9 3.8_+1.1
4.7_+0.6 5.6_+0.9 11.2+_2.3 a 20.3_+4.2 b
5.7_+ 1.6 3.5_+ 1.1 66.8-+13.7 a 74.3-+ 7.6
29.2-+ 3.2 30.1 + 3.7 100.2_+16.4 ~ 127.4_+ 7.0
SAL Sulpiride ACTH, 1/xg Sulpiride + ACT H
10.4-+1.5 8.6 -+ 1.8 32.3_+4.6 a 35.2 -+ 3.9
11.8+_2.1 8.6 -+ 2.0 43.5_+5.2 a 45.2 _+4.3
4.2-+1.2 5.2 -+ 2.0 9.0_+3.8 9.3 _+2.2
6.2-+2.1 7.0 _+1.9 51.3+_5.4 a 52.0 _+6.0
0.4_+ 2.0 _+ 7.0-+ 12.7 -+
33.0+_ 31.4 -+ 143.0-+ 154.3 -+
SAL Sulpiride Bombesin, 30 ng Sulp. + bombesin
5.7_+1.6 7.4 _+ 1.2 13.8_+2.4 a 13.0_+2.7
14.0_+1.8 9.0 _+2.3 20.3-+3.4 16.0_+2.8
5.3_+0.7 4.9 -+ 1.0 10.8-+2.1 a 9.3_+2.1
8.7-+1.0 8.9 _+1.8 18.0+_3.1 a 9.3_+1.5 b
3.2-+ 0.6 1.9 _+ 0.9 59.8-+ 14.0 a 80.5_+17.7
0.2 1.0 4.3 ~ 4.0
5.5 6.6 9.9 a 5.9
36.8+ 1.8 32.0 _+ 6.6 122.8_+13.8 ~ 128.2_+13.8
a p ~ 0.05 vs. SAL; b p ~ 0.05 vs. peptide.
novelty-induced as well as neuropeptide-induced excessive grooming whereas the dopamine D-2 receptor antagonist, sulpiride, does not affect grooming. This latter observation confirms earlier findings by Traber et al. (1982) who reported the ineffectiveness of even high doses of sulpiride on ACTH-induced excessive grooming. Moreover, the dopamine D-1 receptor agonist, SK&F 38393, but not the dopamine D-2 receptor agonist, quinpirole, induced grooming. These findings confirm previous findings by Waddington and coworkers who found a behavioral effect of SK&F 38393 and in
particular reported a dose-dependent increase of sniffing, locomotion and grooming and the induction of a characteristic syndrome of intense grooming in well-habituated animals (Molloy and Waddington, 1984; Murray and Waddington, 1989). A complex functional interaction between D-1 and D-2 dopamine receptors has been suggested to be involved in unconditioned behaviors associated with postsynaptic activity of dopamine agonists (Braun and Chase, 1986) and, more particularly, a cooperative form of functional interaction between D-1 and D-2 systems has been sug-
231 gested to regulate grooming behavior (Murray and Waddington, 1989). C o n c e r n i n g the excessive grooming induced by a new environment or by various neuropeptides, the present data suggest strongly that stimulation of dopamine D-1 rather t h a n D - 2 r e c e p t o r s is a n i m p o r t a n t m e c h a n i s m u n d e r l y i n g t h e i n d u c t i o n o f n o v e l t y - i n d u c e d exc e s s i v e g r o o m i n g as well as n e u r o p e p t i d e - i n d u c e d excessive grooming and support the view that e x c e s s i v e s c r a t c h i n g is n o t p r i m a r i l y m e d i a t e d b y dopamine receptors.
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Molloy, A.G. and J.U Waddington, 1984, Dopaminergic behaviour stereospecifically promoted by the D 1 agonist R-SK & F 38393 and selectively blocked by the D l antagonist SCH 23390, Psychopharmacology 82, 409. Murray, A.M. and J.L. Waddington, 1989, The induction of grooming and vacuous chewing by a series of selective D-1 dopamine receptor agonists; two directions of D-I:D-2 interaction, European J. Pharmacol. 160, 377. Traber, J., H.R. Klein and W.H. Gispen, 1982, Actions of antidepressant and neuroleptic drugs on ACTH- and novelty-induced behavior in the rat, European J. Pharmacol. 80, 407. Van Wimersma Greidanus, Tj.B. and C. Maigret, 1988, Grooming behavior induced by substance P, European J. Pharmacol. 154, 217. Van Wimersma Greidanus, Tj.B., C. Maigret and B. Krechting, 1987, Excessive grooming induced by somatostatin or its analog SMS 201-995, European J. Pharmacol. 144, 277. Van Wimersma Greidanus, Tj.B., C. Maigret, G.J.E. Rinkel, P. Metzger, M. Panis, F.E.M. Van Zinnicq Bergmann, P,J.I.M. Poelman and D.L. Colbern, 1988a, Some characteristics of TRH-induced grooming behavior in rats, Peptides 9, 283. Van Wimersma Greidanus, Tj.B., F. Van de Brug, L.M. De Bruijckere, P.H.M.A. Pabst, R.W. Ruesink, R.L.E. Hulshof, B.N.M. Van Berckel, S.M. Arissen, E.J.P. De Koning and D.K. Donker, 1988b, Comparison of bombesin-, ACTH-, and fl-endorphin-induced grooming. Antagonism by haloperidol, naloxone, and neurotensin, Ann. N.Y. Acad. Sci. 525, 219.