Neurochem. Int. Vol. 20, Suppl.,pp. 135S-139S,1992
0197-0186/92$5.00+0.00 Copyright© 1992PergamonPresspie
Printed in Great Britain. All rightsreserved
NEW CLASSES OF SELECTIVE D-1 DOPAMINE RECEPTOR ANTAGONIST PROVIDE FURTHER EVIDENCE FOR TWO DIRECTIONS OF D-1 :D-2 INTERACTION SIOBHANA. DALY and JOHN L. WADDINGTON* Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, St. Stephen's Green, Dublin 2, Ireland AIm~ract--Initial notions of cooperative/synergistic interactions between D-I and D-2 dopamine receptors have been followed by recent evidence suggesting more complex forms of D-I :D-2 interaction. Each of the new, putative selective13--1antagonists SCH 39166, NO 756 and A-69024 antagonised typical behavioural responses to the selective D-2 agonist RU 24213 and concurrently released atypical behaviour. These data extend new notions of both cooperative/synergistic and oppositional D-I :D-2 interactions in the regulation of typical and atypical behaviours, which may involve further subtypes of D-1 and of D-2 receptor. The notion that D - I and D-2 dopamine (DA) receptor systems show important interactions in the regulation of classical DAergic function has its origin in behavioural studies with the first selective D 1 antagonist, the 1-phenyl-benzazepine SCH 23390 (Molloy and Waddington, 1984; Christensen et al., 1984). Over the subsequent years, there has evolved an increasing recognition of a critical role for the D-1 receptor in a number of behavioural phenomena, often in cooperation with the D-2 receptor, and an associated search for comparable profiles of interaction at others levels of DAergic function (Waddington, 1986; Breese and Creese, 1986); ultimately, this work with SCH 23390 and its l-phenylbenzazepine partial D - I agonist counterpart SK&F 38393 gave rise to the concept of cooperative/synergistic D - I : D - 2 interactions in the regulation of psychomotor behaviour, with apparent correlates in a number of electrophysiological processes (Waddington and O'Boyle, 1987; Arnt, 1987; Clark and White, 1987). While these tenets of cooperative/ synergistic D-1 :D-2 interaction still endure in relation to the regulation of many typical DAergic functions, the most recent studies with SCH 23390 and related agonists have indicated the complexity of how D-1 and D-2 receptor systems interact or play independent roles at multiple levels of DAergic function, including DAergic regulation of non-DAergic processes 0Vaddington and O'Boyle, 1989; Waddington, 1989a); indeed, it should not be forgotten that the first form of D - I : D - 2 interaction was oppositional in nature, whereby D-1 stimulation increases while D-2 stimulation
* Author to whom all correspondence should be addressed.
decreases the activity of adenylyl cyclase (Stoof and Kebabian, 1981). Recently, we described not only (i) the antagonism by R-SK&F 83566 (7-Br-SCH 23390) of typical sniffing and locomotion induced by the selective D-2 agonist LY 163502, in accordance with a permissive role for D - I tone via cooperative/synergistic D - I :D-2 interactions, but also (ii) the contemporaneous release of episodes of atypical limb/body jerking by this drug combination; the latter phenomenon suggested that D-1 tone normally inhibited the expression of this D 2-initiated response (Murray and Waddington, 1989a). On the basis of this profile [and the apparently complementary antagonism of typical grooming and release of atypical vacuous chewing by selective D-2 antagonist pretreatment in animals challenged with the selective D - I agonist SK&F 77434 (3N-allylSK&F 38393); Murray and Waddington, 1989b] we proposed the existence of at least two forms of functionally relevant D - I : D - 2 interaction: one cooperative/synergistic, regulating many typical DAergic behaviours, and one oppositional, regulating particular atypical DAergic responses. However, both the conventional formulation of D-1 :D-2 interaction and this more radical dual typology of interactions have their basis in the action of a single class of D-1 compounds, the l-phenyl benzazepines; in particular, they derive essentially from the use of a single D-1 antagonist, SCH 23390. It is clearly a potentially dangerous exercise to base complex theoretical schemes on studies utilising a single drug or even drug class, but it is only very recently that chemicallydistinct selective D - I antagonists have become available. We give here a preliminary account of studies seeking to extend our previous notions of two
135S
136S
l)opamine 90
directions of D I: D 2 interactions using three such putative drugs in comparison with SCH 23390. CHARACTERISATION OF NEW SELECTIVE D-I ANTAGONISTS
K~ values for displacement of the specific binding of [3H]SCH 23390 to D - l receptors and of [3H]spiperone to D-2 receptors were determined using membranes prepared from the striata of male Sprague-Dawley rats, as previously described (Murray and Waddington, 1989a,b). The investigational compounds studied in comparison with SCH 23390 were: SCH 39166 [ ( - )trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxyN-methyl-5H-benzo[d]naphtho[2, l-b]azepine; Chipkin et al., 1988]; NO 756 [(+)-8-chloro-5-(2,3dihydrobenzofuran-7-yt)-3-methyl-2,3,4,5-tetrahydro -lH-3-benzazepine; Andersen et al., 1988]; A-69024 [l-(2-bromo-4,5-dimethoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-l,2,3,4-tetrahydroisoquinoline; Kerman et al., 1989]. The putative selective D - l antagonist SCH 39166 and NO 756 each showed high affinity, and were more than 1000-fold selective, for the D-1 receptor; these characteristics were similar to those of SCH 23390 (Table 1). A ~ 9 0 2 4 also showed affinity and selectivity for the D-1 receptor, but each characteristic was more than an order of magnitude less than that of SCH 39166 and NO 756.
Table 1. Displacement of [3H]SCH 23390 and of [3H]spiperone from striatal D-1 and D - 2 receptors by investigationa! agents Agent
SCH 23390 SCH 39 ! 66 NO 756 A-69024
K~(nM) D- 1
D-2
D--I/D-2
0.28 0.72 0.18 24.5
1287 998 782 1343
0.0002 0.0007 0.0002 0.018
Data are geometric means of at least 3 separate determinations.
EFFECT O F NEW SELECTIVE D - I ANTAGONISTS ON BEHAVIOURAL R E S P O N S E S T O SELECTIVE D-2 R E C E P T O R STIMULATION
Responses to subcutaneous injection of drugs were assessed in male Sprague-Dawley rats over a ! h period using a rapid time-sampling behavioural check list technique supplemented by a 0-6 point stereotypy rating scale, which generated behavioural counts for each individual behaviour evident and a mean overall stereotypy score for the behaviours displayed: all procedures and analyses were as previously described
(Murray and Waddington, 1989a, b). Challenge with the selective D 2 agonist RU 24213 (15.0 mg/kg) induced a typical response or discontinuous sniffing and locomotion in the absence of compulsive stereotypy, on comparison with vehicleinjected animals (Table 2). A 30 min pretreatment with SCH 23390 (0.01-1.0 mg/kg) produced significant antagonism of these typical responses and ot" low overall scores on the stereotypy scale, on comparison with animals given this dose of RU 24213 after pretreatment with vehicle. Additionally, as these typical responses to RU 24213 were reduced by SCH 23390, there emerged episodes of brief, jerking movements of the limbs or whole body. Both SCH 39166 (0.1 10.0 mg/kg) and NO 756 (0.01 1.0 mg/kg) showed a similar profile of activity, giving significant antagonism of the typical responses to RU 24213 and concurrent release of such atypical jerking behaviour; indeed, so prominent were the jerks released by the higher doses of SCH 39166 that they appeared to exert an activating effect on animals, such that sniffing was noted to re-emerge somewhat in the post-jerk periods. A-69024 (1.0-25.0 mg/kg) also gave significant antagonism of the typical responses to RU 24213 and released jerking, though release of the atypical response was less consistent than with SCH 39166 or NO 756. T H E NATURE OF M U L T I P L E F O R M S OF D-I:D-2 INTERACTION?
The above data extend new notions of more than one form of D - I : D - 2 interaction (Murray and Waddington, 1989a,b: Waddington, 1989a), by indicating thatthese complex profiles of behaviour are not idiosyncratic effects of the 1-phenyl-benzazepine selective D-1 antagonist but are apparent using each of the new, chemically distinct selective D-1 antagonists currently available: SCH 39166 (Chipkin et ai.,1988), NO 756 (Andersen et al,. 1988) and A-69024 (Kerkman e t al., 1989). Consistently, each of these agents not only antagonised typical behavioural responses to a selective D-2 agonist in accordance with established cooperative/synergistic D - l : D - 2 interactions , by reduction of tonic activity through D-1 receptors that is normally necessary for the expression of these D-2stimulated responses; each also resulted in the release of atypical jerking behaviour in response to the D-2 agonist. Such jerking is not evident either after selective stimulation of D-2 receptors alone, or in combination with a selective D 2 antagonist: in this latter situation typical D-2 agonist responses are antagonised but no atypical behaviour emerges to fill
Dopamine90
137S
Table 2. EffectofselectiveD-1 antagonis~ on b e h a ~ o u r a l r e s p o n s e s t o theselecfiveD-2agonist R U 24213 Treatment
mg/kg
Sniffing
Jerking
Stereotypy score
Vehicle R U 24213
-15.0
9.8 4- 2.4 29.34-0.3"
0.0 4- 0.0 0.0 ± 0.0
0.4 4- 0.1 1.9 4-0.P
RU ~213 +SCH233~
15.0 0.01 0.1 1.0
28.04-0.7 22.84-2.8 20.04-2.3** 22.04-1.8"*
0.54-0.3 1.24-0.5 1.94-0.8 2.94-0.8*
1.64-0.1 0.84-0.2** 1.04-0.1"* 0.94-0.1"*
RU24213 +SCH391~
15.0 0.1 1.0 10.0
28.54-0.6 16.34-2.7"* 19.34-2.8"* 20.84-2.4**
0.14-0.1 1.94-0.7" 3.64-0.8** 9.04-2.2**
1.64-0.1 0.74-0.2** 0.74-0.1"* 1.04-0.1"*
RU24213 +NO756
15.0 0.01 0.1 1.0
29.44-0.4 26.54-1.9 16.54-2.4"* 15.94-1.8"*
0.14-0.1 0.44-0.3 5.04-1.5"* 5.6±2.2*
1.74-0.2 1.54-0.2 0.74-0.1"* 0.7±0.1"*
R U 24213 + A-69024
15.0 1.0 5.0 25.0
29.04-0.3 25.84-1.2* 18.5 4- 2.7** 14.14-2.2**
0.0 ± 0.0 1.7 4- 0.8* 3.9 4- 0.7* 2.64-1.0"
1.7±0.1 1.0 4- 0.2* 0.7 4- 0. I** 0.54-0.5**
Means ± SEM of n ~ 6 - 8 animals per group. "p
0197-0186/92$5.00+0.00 Copyright© 1992PergamonPresspie
Printed in Great Britain. All rightsreserved
NEW CLASSES OF SELECTIVE D-1 DOPAMINE RECEPTOR ANTAGONIST PROVIDE FURTHER EVIDENCE FOR TWO DIRECTIONS OF D-1 :D-2 INTERACTION SIOBHANA. DALY and JOHN L. WADDINGTON* Department of Clinical Pharmacology, Royal College of Surgeons in Ireland, St. Stephen's Green, Dublin 2, Ireland AIm~ract--Initial notions of cooperative/synergistic interactions between D-I and D-2 dopamine receptors have been followed by recent evidence suggesting more complex forms of D-I :D-2 interaction. Each of the new, putative selective13--1antagonists SCH 39166, NO 756 and A-69024 antagonised typical behavioural responses to the selective D-2 agonist RU 24213 and concurrently released atypical behaviour. These data extend new notions of both cooperative/synergistic and oppositional D-I :D-2 interactions in the regulation of typical and atypical behaviours, which may involve further subtypes of D-1 and of D-2 receptor. The notion that D - I and D-2 dopamine (DA) receptor systems show important interactions in the regulation of classical DAergic function has its origin in behavioural studies with the first selective D 1 antagonist, the 1-phenyl-benzazepine SCH 23390 (Molloy and Waddington, 1984; Christensen et al., 1984). Over the subsequent years, there has evolved an increasing recognition of a critical role for the D-1 receptor in a number of behavioural phenomena, often in cooperation with the D-2 receptor, and an associated search for comparable profiles of interaction at others levels of DAergic function (Waddington, 1986; Breese and Creese, 1986); ultimately, this work with SCH 23390 and its l-phenylbenzazepine partial D - I agonist counterpart SK&F 38393 gave rise to the concept of cooperative/synergistic D - I : D - 2 interactions in the regulation of psychomotor behaviour, with apparent correlates in a number of electrophysiological processes (Waddington and O'Boyle, 1987; Arnt, 1987; Clark and White, 1987). While these tenets of cooperative/ synergistic D-1 :D-2 interaction still endure in relation to the regulation of many typical DAergic functions, the most recent studies with SCH 23390 and related agonists have indicated the complexity of how D-1 and D-2 receptor systems interact or play independent roles at multiple levels of DAergic function, including DAergic regulation of non-DAergic processes 0Vaddington and O'Boyle, 1989; Waddington, 1989a); indeed, it should not be forgotten that the first form of D - I : D - 2 interaction was oppositional in nature, whereby D-1 stimulation increases while D-2 stimulation
* Author to whom all correspondence should be addressed.
decreases the activity of adenylyl cyclase (Stoof and Kebabian, 1981). Recently, we described not only (i) the antagonism by R-SK&F 83566 (7-Br-SCH 23390) of typical sniffing and locomotion induced by the selective D-2 agonist LY 163502, in accordance with a permissive role for D - I tone via cooperative/synergistic D - I :D-2 interactions, but also (ii) the contemporaneous release of episodes of atypical limb/body jerking by this drug combination; the latter phenomenon suggested that D-1 tone normally inhibited the expression of this D 2-initiated response (Murray and Waddington, 1989a). On the basis of this profile [and the apparently complementary antagonism of typical grooming and release of atypical vacuous chewing by selective D-2 antagonist pretreatment in animals challenged with the selective D - I agonist SK&F 77434 (3N-allylSK&F 38393); Murray and Waddington, 1989b] we proposed the existence of at least two forms of functionally relevant D - I : D - 2 interaction: one cooperative/synergistic, regulating many typical DAergic behaviours, and one oppositional, regulating particular atypical DAergic responses. However, both the conventional formulation of D-1 :D-2 interaction and this more radical dual typology of interactions have their basis in the action of a single class of D-1 compounds, the l-phenyl benzazepines; in particular, they derive essentially from the use of a single D-1 antagonist, SCH 23390. It is clearly a potentially dangerous exercise to base complex theoretical schemes on studies utilising a single drug or even drug class, but it is only very recently that chemicallydistinct selective D - I antagonists have become available. We give here a preliminary account of studies seeking to extend our previous notions of two
135S
136S
l)opamine 90
directions of D I: D 2 interactions using three such putative drugs in comparison with SCH 23390. CHARACTERISATION OF NEW SELECTIVE D-I ANTAGONISTS
K~ values for displacement of the specific binding of [3H]SCH 23390 to D - l receptors and of [3H]spiperone to D-2 receptors were determined using membranes prepared from the striata of male Sprague-Dawley rats, as previously described (Murray and Waddington, 1989a,b). The investigational compounds studied in comparison with SCH 23390 were: SCH 39166 [ ( - )trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxyN-methyl-5H-benzo[d]naphtho[2, l-b]azepine; Chipkin et al., 1988]; NO 756 [(+)-8-chloro-5-(2,3dihydrobenzofuran-7-yt)-3-methyl-2,3,4,5-tetrahydro -lH-3-benzazepine; Andersen et al., 1988]; A-69024 [l-(2-bromo-4,5-dimethoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-l,2,3,4-tetrahydroisoquinoline; Kerman et al., 1989]. The putative selective D - l antagonist SCH 39166 and NO 756 each showed high affinity, and were more than 1000-fold selective, for the D-1 receptor; these characteristics were similar to those of SCH 23390 (Table 1). A ~ 9 0 2 4 also showed affinity and selectivity for the D-1 receptor, but each characteristic was more than an order of magnitude less than that of SCH 39166 and NO 756.
Table 1. Displacement of [3H]SCH 23390 and of [3H]spiperone from striatal D-1 and D - 2 receptors by investigationa! agents Agent
SCH 23390 SCH 39 ! 66 NO 756 A-69024
K~(nM) D- 1
D-2
D--I/D-2
0.28 0.72 0.18 24.5
1287 998 782 1343
0.0002 0.0007 0.0002 0.018
Data are geometric means of at least 3 separate determinations.
EFFECT O F NEW SELECTIVE D - I ANTAGONISTS ON BEHAVIOURAL R E S P O N S E S T O SELECTIVE D-2 R E C E P T O R STIMULATION
Responses to subcutaneous injection of drugs were assessed in male Sprague-Dawley rats over a ! h period using a rapid time-sampling behavioural check list technique supplemented by a 0-6 point stereotypy rating scale, which generated behavioural counts for each individual behaviour evident and a mean overall stereotypy score for the behaviours displayed: all procedures and analyses were as previously described
(Murray and Waddington, 1989a, b). Challenge with the selective D 2 agonist RU 24213 (15.0 mg/kg) induced a typical response or discontinuous sniffing and locomotion in the absence of compulsive stereotypy, on comparison with vehicleinjected animals (Table 2). A 30 min pretreatment with SCH 23390 (0.01-1.0 mg/kg) produced significant antagonism of these typical responses and ot" low overall scores on the stereotypy scale, on comparison with animals given this dose of RU 24213 after pretreatment with vehicle. Additionally, as these typical responses to RU 24213 were reduced by SCH 23390, there emerged episodes of brief, jerking movements of the limbs or whole body. Both SCH 39166 (0.1 10.0 mg/kg) and NO 756 (0.01 1.0 mg/kg) showed a similar profile of activity, giving significant antagonism of the typical responses to RU 24213 and concurrent release of such atypical jerking behaviour; indeed, so prominent were the jerks released by the higher doses of SCH 39166 that they appeared to exert an activating effect on animals, such that sniffing was noted to re-emerge somewhat in the post-jerk periods. A-69024 (1.0-25.0 mg/kg) also gave significant antagonism of the typical responses to RU 24213 and released jerking, though release of the atypical response was less consistent than with SCH 39166 or NO 756. T H E NATURE OF M U L T I P L E F O R M S OF D-I:D-2 INTERACTION?
The above data extend new notions of more than one form of D - I : D - 2 interaction (Murray and Waddington, 1989a,b: Waddington, 1989a), by indicating thatthese complex profiles of behaviour are not idiosyncratic effects of the 1-phenyl-benzazepine selective D-1 antagonist but are apparent using each of the new, chemically distinct selective D-1 antagonists currently available: SCH 39166 (Chipkin et ai.,1988), NO 756 (Andersen et al,. 1988) and A-69024 (Kerkman e t al., 1989). Consistently, each of these agents not only antagonised typical behavioural responses to a selective D-2 agonist in accordance with established cooperative/synergistic D - l : D - 2 interactions , by reduction of tonic activity through D-1 receptors that is normally necessary for the expression of these D-2stimulated responses; each also resulted in the release of atypical jerking behaviour in response to the D-2 agonist. Such jerking is not evident either after selective stimulation of D-2 receptors alone, or in combination with a selective D 2 antagonist: in this latter situation typical D-2 agonist responses are antagonised but no atypical behaviour emerges to fill
Dopamine90
137S
Table 2. EffectofselectiveD-1 antagonis~ on b e h a ~ o u r a l r e s p o n s e s t o theselecfiveD-2agonist R U 24213 Treatment
mg/kg
Sniffing
Jerking
Stereotypy score
Vehicle R U 24213
-15.0
9.8 4- 2.4 29.34-0.3"
0.0 4- 0.0 0.0 ± 0.0
0.4 4- 0.1 1.9 4-0.P
RU ~213 +SCH233~
15.0 0.01 0.1 1.0
28.04-0.7 22.84-2.8 20.04-2.3** 22.04-1.8"*
0.54-0.3 1.24-0.5 1.94-0.8 2.94-0.8*
1.64-0.1 0.84-0.2** 1.04-0.1"* 0.94-0.1"*
RU24213 +SCH391~
15.0 0.1 1.0 10.0
28.54-0.6 16.34-2.7"* 19.34-2.8"* 20.84-2.4**
0.14-0.1 1.94-0.7" 3.64-0.8** 9.04-2.2**
1.64-0.1 0.74-0.2** 0.74-0.1"* 1.04-0.1"*
RU24213 +NO756
15.0 0.01 0.1 1.0
29.44-0.4 26.54-1.9 16.54-2.4"* 15.94-1.8"*
0.14-0.1 0.44-0.3 5.04-1.5"* 5.6±2.2*
1.74-0.2 1.54-0.2 0.74-0.1"* 0.7±0.1"*
R U 24213 + A-69024
15.0 1.0 5.0 25.0
29.04-0.3 25.84-1.2* 18.5 4- 2.7** 14.14-2.2**
0.0 ± 0.0 1.7 4- 0.8* 3.9 4- 0.7* 2.64-1.0"
1.7±0.1 1.0 4- 0.2* 0.7 4- 0. I** 0.54-0.5**
Means ± SEM of n ~ 6 - 8 animals per group. "p
