Naunyn-Schmiedeberg's
Naunyn-Schmiedeberg's Arch. Pharmacol. 297, 8 5 1 - $52 (1977)
Archivesof
Pharmacology
9 by Springer-Verlag1977
Endogenous Ligands of Opiate Receptors HANSJORG TESCHEMACHER Max-Planck-lnstitut f/ir Psychiatrie, Abteilung Neuropharmakologie, Kraepelinstrasse 2, D-8000 Mtinchen 40,
Federal Republic of Germany
SUMMARY. F r o m b r a i n and from p i t u i t a r y tissue of v e r t e b r a t e s several p e p t i d e s w i t h m o l e c u l a r w e i g h t s b e t w e e n 500 and 3500 d a l t o n s - h a v e b e e n isolated, w h i c h b e h a v e like o p i a t e s in o p i a t e r e c e p t o r b i n d i n g assays, in i s o l a t e d tissue preparations and in the intact animal. KEY WORDS: endogenous opiates
Endorphins - enkephalin peptides - neurohormones -
The d e t e c t i o n of o p i a t e r e c e p t o r s in the nervous tissue of v e r t e b r a t e s (see H~llt, this symposium) was the starting p o i n t for a m o s t i n t e n s i v e search for the endogenous ligands of these receptors. In fact, several groups s u c c e e d e d independ e n t l y in i s o l a t i n g s u b s t a n c e s w i t h o p i a t e - l i k e p r o p e r t i e s from v a r i o u s m a m m a l i a n tissues. Hughes (1975) r e p o r t e d about a m a t e r i a l e x t r a c t e d f r o m b r a i n tissue of several species, w h i c h b e h a v e d like an o p i a t e in i s o l a t e d p r e p a r a t i o n s of the g u i n e a pig i l e u m m y e n t e r i c p l e x u s / l o n g i t u d i n a l m u s c l e and the mouse vas deferens. T e r e n i u s and W a h l s t r 6 m (1975) and P a s t e r n a k et al. (1975) d e m o n s t r a t e d the b i n d i n g of c o m p o u n d s o c c u r i n g in c e r t a i n e x t r a c t s from m a m m a l i a n brain to o p i a t e r e c e p t o r s in vitro. In extracts f r o m b o v i n e p i t u i t a r y tissue a n o t h e r m a t e r i a l was d e t e c t e d w h i c h binds to o p i a t e receptors and b e h a v e s like an o p i a t e in the isolated tissue Dremarations mentioned above (Teschemacher et al., 1975). S t r u c t u r a l i d e n t i f i c a t i o n of these commounds, t e r m e d e n d o r p h i n s by Eric Simon (Goldstein, 1976), was to follow soon. Hughes et al. (1975) i d e n t i f i e d the o p i a t e - l i k e b e h a v i n g p r i n c i p l e in pig brain extracts i s o l a t e d by Hughes (1975): It c o n s i s t e d of two p e n t a p e p t i d e s (methio n i n e - e n k e p h a l i n and l e u c i n e - e n k e p h a l i n ; fig. q). R e c e n t l y another, m u c h larger n e n t i d e (C-fragment of ~-lipotropin, fig. l) was found in p o r C i n e brain tissue (Bradbury er al., 1976). In addition, there are other e n d o r p h i n s in b r a i n tissue w h i c h have not yet been i d e n t i f i e d
(Goldstein, 1976; Gunne et al., 1976). F r o m p o r c i n e p o s t e r i o r p i t u i t a r y lobe/ h y p o t h a l a m u s fragments (Lazarus et al., 1976) three m e D t i d e s w i t h o p i a t e - l i k e prop e r t i e s have b e e n i s o l a t e d and i d e n t i f i e d (a-, D- and y - e n d o r p h i n , see fig. l). The amino acid s e q u e n c e s of m e t h i o n i n e - e n k e p h a l i n as well as of a-, ~- and y - e n d o r phin w e r e r e c o g n i z e d to r e p r e s e n t parts of the s e q u e n c e of the p i t u i t a r y h o r m o n e 5-1ipotropin. C - f r a g m e n t (Li and Chung, 1976; B r a d b u r y et al., 1976) and C ' - f r a g m e n t (Bradbury et al., 1976) of ~-lipotropin (see fig. l), i s o l a t e d from pituitary tissue of several species, b e h a v e d like opiates, too; the C - f r a g m e n t was found to be i d e n t i c a l w i t h 5-endorphin. However, there are, in addition, other e n d o r p h i n s in the p i t u i t a r y w i t h p r o p e r ties o b v i o u s l y d i f f e r i n g from those of the ~ - l i p o t r o p i n series (Goldstein, 1976). All e n d o r p h i n s so far found b e h a v e d like o p i a t e s in the i s o l a t e d tissue prep a r a t i o n s m e n t i o n e d above and in o p i a t e r e c e p t o r b i n d i n g assays. These p r o p e r t i e s had b e e n used to c h a r a c t e r i s e these compounds as e n d o r p h i n s during i s o l a t i o n procedures. In addition, central effects v e r y similar to those of o p i a t e s have been r e c e n t l y o b s e r v e d after a d m i n i s t r a tion of e n d o r p h i n s in vivo. However, whereas ~-endorphin induced pronounced and long lasting effects (Loh et al., 1976; B r a d b u r y et al., 1976), v e r y w e a k and t r a n s i e n t effects w e r e o b s e r v e d after a d m i n i s t r a t i o n of the e n k e p h a l i n s (Belluzzi et al., 1976). Strong a n a l g e s i a and other effects as o b s e r v e d w i t h o p i a t e s (Teschemacher et al., 1976) as w e l l as cross t o l e r a n c e and d e p e n d e n c e l i a b i l i t y (Bl~sig and Herz, 1976) w e r e o b s e r v e d after i n t r a v e n t r i c u l a r i n j e c t i o n in rats of a p a r t i a l l y i d e n t i f i e d p e p t i d e cons i s t i n g of about 30 amino a c i d r e s i d u e s (Kromer et al., 1976). Thus, it is e v i d e n t that the e n d o r p h i n s m i m i c k the o p i a t e s in most respects. It is not yet clear w h e t h e r the endorphins so far i s o l a t e d and i d e n t i f i e d are, in fact, r e l e a s e d in any s i t u a t i o n or
S 52 H-TYR-GLY-GLY-PHE-MET-OH
METHIONINE-ENKEPHALIN
H-TYR-GLY-GLY-PHE-LEU-OH
LEUCINE
-ENKEPHALIN
H-I TYR-OLY-GLY-PHE-MET - J ~-
-THR- SER-GLU-LYS- SER76 -OLN- THR-PRO-LEU-VAL-
I"HR-
J
- LEU-PHE-LYS-ASN-ALA-I
~(
i
ENDORPHIN
C-FRAGMENT OF ~-LIPOTROPIN
LE-
[I L E] 87 -VAL-LYS-ASN-ALA-H IS91
- L y $ - LYS-GLY-GLN*OH
Fig. I. Amino acid sequences of endorphins isolated from various tissues of vertebrates. Above the sequence of the enkephalins. Beneath, the sequences of endorphins representing N-terminal fragments of the sequence of ~-lipotropin, residues 61 to 91. Figures: positions of residues in the $-lipotropin sequence. Residue 83: porcine: valin; ovine: isoleucin, a-endorphin: res. 61-76; ~endorphin
Naunyn-Schmiedeberg's Arch. Pharmacol. 297, 8 5 1 - $52 (1977)
Archivesof
Pharmacology
9 by Springer-Verlag1977
Endogenous Ligands of Opiate Receptors HANSJORG TESCHEMACHER Max-Planck-lnstitut f/ir Psychiatrie, Abteilung Neuropharmakologie, Kraepelinstrasse 2, D-8000 Mtinchen 40,
Federal Republic of Germany
SUMMARY. F r o m b r a i n and from p i t u i t a r y tissue of v e r t e b r a t e s several p e p t i d e s w i t h m o l e c u l a r w e i g h t s b e t w e e n 500 and 3500 d a l t o n s - h a v e b e e n isolated, w h i c h b e h a v e like o p i a t e s in o p i a t e r e c e p t o r b i n d i n g assays, in i s o l a t e d tissue preparations and in the intact animal. KEY WORDS: endogenous opiates
Endorphins - enkephalin peptides - neurohormones -
The d e t e c t i o n of o p i a t e r e c e p t o r s in the nervous tissue of v e r t e b r a t e s (see H~llt, this symposium) was the starting p o i n t for a m o s t i n t e n s i v e search for the endogenous ligands of these receptors. In fact, several groups s u c c e e d e d independ e n t l y in i s o l a t i n g s u b s t a n c e s w i t h o p i a t e - l i k e p r o p e r t i e s from v a r i o u s m a m m a l i a n tissues. Hughes (1975) r e p o r t e d about a m a t e r i a l e x t r a c t e d f r o m b r a i n tissue of several species, w h i c h b e h a v e d like an o p i a t e in i s o l a t e d p r e p a r a t i o n s of the g u i n e a pig i l e u m m y e n t e r i c p l e x u s / l o n g i t u d i n a l m u s c l e and the mouse vas deferens. T e r e n i u s and W a h l s t r 6 m (1975) and P a s t e r n a k et al. (1975) d e m o n s t r a t e d the b i n d i n g of c o m p o u n d s o c c u r i n g in c e r t a i n e x t r a c t s from m a m m a l i a n brain to o p i a t e r e c e p t o r s in vitro. In extracts f r o m b o v i n e p i t u i t a r y tissue a n o t h e r m a t e r i a l was d e t e c t e d w h i c h binds to o p i a t e receptors and b e h a v e s like an o p i a t e in the isolated tissue Dremarations mentioned above (Teschemacher et al., 1975). S t r u c t u r a l i d e n t i f i c a t i o n of these commounds, t e r m e d e n d o r p h i n s by Eric Simon (Goldstein, 1976), was to follow soon. Hughes et al. (1975) i d e n t i f i e d the o p i a t e - l i k e b e h a v i n g p r i n c i p l e in pig brain extracts i s o l a t e d by Hughes (1975): It c o n s i s t e d of two p e n t a p e p t i d e s (methio n i n e - e n k e p h a l i n and l e u c i n e - e n k e p h a l i n ; fig. q). R e c e n t l y another, m u c h larger n e n t i d e (C-fragment of ~-lipotropin, fig. l) was found in p o r C i n e brain tissue (Bradbury er al., 1976). In addition, there are other e n d o r p h i n s in b r a i n tissue w h i c h have not yet been i d e n t i f i e d
(Goldstein, 1976; Gunne et al., 1976). F r o m p o r c i n e p o s t e r i o r p i t u i t a r y lobe/ h y p o t h a l a m u s fragments (Lazarus et al., 1976) three m e D t i d e s w i t h o p i a t e - l i k e prop e r t i e s have b e e n i s o l a t e d and i d e n t i f i e d (a-, D- and y - e n d o r p h i n , see fig. l). The amino acid s e q u e n c e s of m e t h i o n i n e - e n k e p h a l i n as well as of a-, ~- and y - e n d o r phin w e r e r e c o g n i z e d to r e p r e s e n t parts of the s e q u e n c e of the p i t u i t a r y h o r m o n e 5-1ipotropin. C - f r a g m e n t (Li and Chung, 1976; B r a d b u r y et al., 1976) and C ' - f r a g m e n t (Bradbury et al., 1976) of ~-lipotropin (see fig. l), i s o l a t e d from pituitary tissue of several species, b e h a v e d like opiates, too; the C - f r a g m e n t was found to be i d e n t i c a l w i t h 5-endorphin. However, there are, in addition, other e n d o r p h i n s in the p i t u i t a r y w i t h p r o p e r ties o b v i o u s l y d i f f e r i n g from those of the ~ - l i p o t r o p i n series (Goldstein, 1976). All e n d o r p h i n s so far found b e h a v e d like o p i a t e s in the i s o l a t e d tissue prep a r a t i o n s m e n t i o n e d above and in o p i a t e r e c e p t o r b i n d i n g assays. These p r o p e r t i e s had b e e n used to c h a r a c t e r i s e these compounds as e n d o r p h i n s during i s o l a t i o n procedures. In addition, central effects v e r y similar to those of o p i a t e s have been r e c e n t l y o b s e r v e d after a d m i n i s t r a tion of e n d o r p h i n s in vivo. However, whereas ~-endorphin induced pronounced and long lasting effects (Loh et al., 1976; B r a d b u r y et al., 1976), v e r y w e a k and t r a n s i e n t effects w e r e o b s e r v e d after a d m i n i s t r a t i o n of the e n k e p h a l i n s (Belluzzi et al., 1976). Strong a n a l g e s i a and other effects as o b s e r v e d w i t h o p i a t e s (Teschemacher et al., 1976) as w e l l as cross t o l e r a n c e and d e p e n d e n c e l i a b i l i t y (Bl~sig and Herz, 1976) w e r e o b s e r v e d after i n t r a v e n t r i c u l a r i n j e c t i o n in rats of a p a r t i a l l y i d e n t i f i e d p e p t i d e cons i s t i n g of about 30 amino a c i d r e s i d u e s (Kromer et al., 1976). Thus, it is e v i d e n t that the e n d o r p h i n s m i m i c k the o p i a t e s in most respects. It is not yet clear w h e t h e r the endorphins so far i s o l a t e d and i d e n t i f i e d are, in fact, r e l e a s e d in any s i t u a t i o n or
S 52 H-TYR-GLY-GLY-PHE-MET-OH
METHIONINE-ENKEPHALIN
H-TYR-GLY-GLY-PHE-LEU-OH
LEUCINE
-ENKEPHALIN
H-I TYR-OLY-GLY-PHE-MET - J ~-
-THR- SER-GLU-LYS- SER76 -OLN- THR-PRO-LEU-VAL-
I"HR-
J
- LEU-PHE-LYS-ASN-ALA-I
~(
i
ENDORPHIN
C-FRAGMENT OF ~-LIPOTROPIN
LE-
[I L E] 87 -VAL-LYS-ASN-ALA-H IS91
- L y $ - LYS-GLY-GLN*OH
Fig. I. Amino acid sequences of endorphins isolated from various tissues of vertebrates. Above the sequence of the enkephalins. Beneath, the sequences of endorphins representing N-terminal fragments of the sequence of ~-lipotropin, residues 61 to 91. Figures: positions of residues in the $-lipotropin sequence. Residue 83: porcine: valin; ovine: isoleucin, a-endorphin: res. 61-76; ~endorphin
