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Effects of full and partial. Kappa agonists and mu agonists on urine output of normally hydrated rats
Neuropeptides
5:
283-286,
1984
EFFECTS OF FULL AND PARTIAL KAPPA AGONISTS AND MU AGONISTS ON URINE OUTPUT OF NORMALLYRYDRATEDRATS J.
David
Leander
Lilly Research Laboratories Eli Lilly and Company Indianapolis, IN 46285 U.S.A. In rats that have had free access to food and water, full and partial kappa agonists increase urine output within 2 hrs after injection, whereas mu agonists decrease urine output. Partial kappa agonists produce effects Full kappa agonists can be differentiated less than full kappa agonists. into 2 groups on the basis of their 2-hr cumulative urinary output dose-effect curves. Full kappa agonists with mu agonist activities have whereas full kappa agonists without mu inverted U-shaped dose-effect curves, agonist activities have dose-effect curves that show dose-related increasing diuretic effects until plateauing at 10 to 11 mls of urine. Thus the 2-hr dose-effect curve for urine output can classify opioids into at least 4 categories : mu agonist, partial kappa agonist, full kappa agonist with mu agonist activity, and full kappa agonist without mu agonist activity. Opioids generally are classified as acting at three possible receptors Over the years, agonists at mu -- the mu, kappa and delta receptors. receptors have primarily been known as producing antidiuretic (urinary retention) effects. More recently, agonists at kappa receptors have been that is an increase in urinary characterized as producing diuretic effects, Kappa agonists can be grouped into three different output in rats (1,2,3). categories on the basis of the pattern of urinary output at 2 hrs after drug administration in normally hydrated hooded rats (4). One category, which U-50,488 and tifluadom, produces increases includes bremaxocine, proxorphan, in 2-hr cumulative urinary output that are dose related until a plateau of 10 to 15 ml is reached at the higher doses. A second category, which ethylketazocine and MR-2033, produces inverted U-shaped includes ketazocine, dose-effect curves at 2 hrs after injection. That is, there are doses of each drug within the middle of their respective dose-effect curves that produce greater urinary output than larger doses. The third category of kappa agonists are the partial agonists, which include nalorphine, They are characterized by dose-effect butorphanol and oxilorphan (5). curves plateauing at approximately 6 mls of urine at 2 hrs after injection. These partial agonists antagonize the diuretic actions of the full kappa agonist bremazocine and are blocked by relatively high doses (l-10 mg/kg) of naloxone (3,5).
283
The inverted U-shaped curve of ketazocine was interpreted as being due to mu-agonist action of ketazocine at higher doses (2). This conclusion was based on the data in Table 1. Without simultaneous treatment of naloxone, the 1.25 qg/kg dose of ketazocine had a much larger diuretic effect at 2 hrs than the 20 mg/kg dose. The low doses (0.01 and 0.1 mg/kg) of naloxone had no significant effect on the diuretic effect of 1.25 mg/kg of ketazocine, but the higher naloxone doses reduced the diuretic effect. Table 1. Two-hour urine output of normally hydrated hooded rats after either 1.25 or 20 mg/kg of ketazocine and various doses of naloxone. x f S.E.; n=4or5 Naloxone doses
0 mdkg 0.01 0.1 1.0 10.0
1.25 mg/kg
14.6 14.9 12.8 6.0 3.5
?r 1.2 f 1.2 f 1.6 + 0.8 f 0.4
20 mglkg
4.6 7.4 11.1 12.4 10.7
+ 1.0 f 4.4 ?I 1.1 + 2.0 f 0.8
In contrast, the low doses of naloxone increased the diuretic effect of 20 m&kg of ketazocine by presumably antagonizing the mu agonist actions of the larger dose of ketazocine. The mu agonist action of ethylketazocine can be demonstrated also in rats that are water-loaded (3 mls/lOO g of body wgt) simultaneously with drug injection. Table 2 shows that water-loading produces a marked diuretic effect evident at 1 and 2 hr after water-loading. The 5 mg/kg Table 2. Antagonizing the antidiuretic effect of ethylketazocine with p-FNA in water-loaded rats
Treatment
H20 injection 5 mg/kg ethylketazocine p-FNA + ethylketazocine
Cumulative mls of urine 2nd hr 5th hr 1st hr
6.3 + 1.2 0 7.3 f 0.4
1.8 + 1.4 0.9 f 0.2 17.5 f 3.9
9.5 + 1.4 21.8 + 1.8 29.3 + 1.1
dose of ethylketazocine had an antidiuretic action at 1 and 2 hrs after injection and water-loading. This antidiuretic action was completely blocked by pretreating the animals with 20 mg/kg of p-FNA ($-funaltrexamine HCl) (6) 18 hr before the water-loading and administration of ethylketazocine. Note that the ethylketazocine produced a more marked diuretic effect at 5 hrs than water-loading alone, and that the B-FNA pretreatment enhanced that effect. Figure 1 shows that pretreatment with B-FNA also blocks the mu agonist The p-FNA changes the inverted U-shaped effects of higher doses of m-2033. curve of MR-2033 at 2 hrs into a dose-effect curve that eventually plateaus at 10 to 20 mls of urine over the dose range of 0.32 to 20 mglkg. 284
FIRST HOUR
SECOND
THIRD
HOUR
HOUR
18 g
OPRE-B-FNA
16
l
3 6
12-
f
IO-
: 0 d
86
i
4-
d
2-
POST-fl-FNA 20 MO/KG, WHRS
o-
ii 0.02 1
FOURTH
oJ :
,
0.02
0.32
0.32 I
5I 201
HOUR
I
0.02
1
0.32
1
5 20
FIFTH HOUR
1 5 20 mglkg
G oiii-&-G WR-2033
In many replications of the effect of bremazocine in the hooded rats on urinary output, no inverted U-shaped curve has been obtained. Thus it was concluded that bremazocine did not have mu-agonist action, but rather had some weak mu-antagonist action (3). However, when bremazocine was studied in Sprague-Dawley albino rats, bremazocine produced an inverted U-shaped dose-effect curve (data shown in Table 3). Without naloxone, 0.08 mg/kg bremazocine produced a 2-hr diuretic effect of 15.5 mls, whereas 0.32 qg/kg of bremazocine produced less (9.8 mls) of a 2-hr diuretic effect. This decreased diuretic effect of 0.32 qg/kg of bremazocine was eliminated by simultaneous treatment with 1 qg/kg of naloxone. Thus it appears that bremazocine has some demonstrable mu-agonist activity in Sprague-Dawley albino rats but not in hooded rats. Since agonists at the mu-receptor have antidiuretic effects at 2 hrs after injection, the effects of opioids on urinary output at 2 hrs in normally hydrated rats can be used to classify the pharmacological profile of compounds in terms of their activities at mu and kappa receptors in vivo. -Mu agonists have only dose-related antidiuretic effects; full kappa agonists without mu agonist activity have only dose-related diuretic effects plateauing at lo-12 qls; full kappa agonists with mu agonist activity have inverted U-shaped dose-effect curves; and partial kappa agonists have
285
Table 3. Effects of bremazocine alone and in the presence of 1 mg/kg of naloxone on 2-hr urine output of normally hydrated Sprague-Dawley albino rats.
Bremazocine
dose
0 mglkg 0.005 0.02 0.08 0.16 0.32
Alone
1.4 5.8 10.1 15.5 12.0 9.8
(n = 4)
2 +, r r r +
0.4 1.0 0.5 0.5 0.6 1.3
+1 Naloxone
(n = 6)
1.8
f 0.5
3.5 11.6
+- 0.9 + 1.4
16.2
+ 1.6
diuretic effects that plateau at levels of urinary output less than that of To verify that effects of unknown compounds are a full kappa agonists. result of interaction with mu or kappa receptors, the effects should be demonstrated to be blocked by low and high doses, respectively, of naloxone. REFERENCES 1.
Slizgi, G. R. and Ludens, J. H. (1982). Studies on the nature mechanism of the diuretic activity of the opioid analgesic Journal of Pharmacology and Experimental ethylketocyclazocine. Therapeutics 220: 585-591.
2.
Leander, the rat. 89-94.
J. D. (1983). A kappa opioid effect: Increased urination in Journal of Pharmacology and Experimental Therapeutics 224:
3.
Leander, urination. 35-41.
J.
4.
Behavioral effects of agonist and antagonist Leander, J. D. (1984). In: Seiden, L. S. and Balster, R. L. action at kappa opioid receptors. (ea.) Behavioral Pharmacology: The Current Status. Alan R. Liss, New York, in press.
5.
Leander, J. D. (1983). oxilorphan are partial Jouranl of Pharmacology
6.
Ward, S. J., Portoghese, P. S. and Takemori, A. E. (1982). Pharmacological characterization in vivo of the novel opiate Journal of Pharmacology and Experimental S-funaltrexamine (B-FNA). Therapeutics 220: 494-498.
D. (1983). Journal of
and
Further study of kappa opioids on increased Pharmacology and Experimental Therapeutics 227:
Evidence that nalorphine, butorphanol, and European agonists at a K-opioid receptor. 86: 467-470.
286
5:
283-286,
1984
EFFECTS OF FULL AND PARTIAL KAPPA AGONISTS AND MU AGONISTS ON URINE OUTPUT OF NORMALLYRYDRATEDRATS J.
David
Leander
Lilly Research Laboratories Eli Lilly and Company Indianapolis, IN 46285 U.S.A. In rats that have had free access to food and water, full and partial kappa agonists increase urine output within 2 hrs after injection, whereas mu agonists decrease urine output. Partial kappa agonists produce effects Full kappa agonists can be differentiated less than full kappa agonists. into 2 groups on the basis of their 2-hr cumulative urinary output dose-effect curves. Full kappa agonists with mu agonist activities have whereas full kappa agonists without mu inverted U-shaped dose-effect curves, agonist activities have dose-effect curves that show dose-related increasing diuretic effects until plateauing at 10 to 11 mls of urine. Thus the 2-hr dose-effect curve for urine output can classify opioids into at least 4 categories : mu agonist, partial kappa agonist, full kappa agonist with mu agonist activity, and full kappa agonist without mu agonist activity. Opioids generally are classified as acting at three possible receptors Over the years, agonists at mu -- the mu, kappa and delta receptors. receptors have primarily been known as producing antidiuretic (urinary retention) effects. More recently, agonists at kappa receptors have been that is an increase in urinary characterized as producing diuretic effects, Kappa agonists can be grouped into three different output in rats (1,2,3). categories on the basis of the pattern of urinary output at 2 hrs after drug administration in normally hydrated hooded rats (4). One category, which U-50,488 and tifluadom, produces increases includes bremaxocine, proxorphan, in 2-hr cumulative urinary output that are dose related until a plateau of 10 to 15 ml is reached at the higher doses. A second category, which ethylketazocine and MR-2033, produces inverted U-shaped includes ketazocine, dose-effect curves at 2 hrs after injection. That is, there are doses of each drug within the middle of their respective dose-effect curves that produce greater urinary output than larger doses. The third category of kappa agonists are the partial agonists, which include nalorphine, They are characterized by dose-effect butorphanol and oxilorphan (5). curves plateauing at approximately 6 mls of urine at 2 hrs after injection. These partial agonists antagonize the diuretic actions of the full kappa agonist bremazocine and are blocked by relatively high doses (l-10 mg/kg) of naloxone (3,5).
283
The inverted U-shaped curve of ketazocine was interpreted as being due to mu-agonist action of ketazocine at higher doses (2). This conclusion was based on the data in Table 1. Without simultaneous treatment of naloxone, the 1.25 qg/kg dose of ketazocine had a much larger diuretic effect at 2 hrs than the 20 mg/kg dose. The low doses (0.01 and 0.1 mg/kg) of naloxone had no significant effect on the diuretic effect of 1.25 mg/kg of ketazocine, but the higher naloxone doses reduced the diuretic effect. Table 1. Two-hour urine output of normally hydrated hooded rats after either 1.25 or 20 mg/kg of ketazocine and various doses of naloxone. x f S.E.; n=4or5 Naloxone doses
0 mdkg 0.01 0.1 1.0 10.0
1.25 mg/kg
14.6 14.9 12.8 6.0 3.5
?r 1.2 f 1.2 f 1.6 + 0.8 f 0.4
20 mglkg
4.6 7.4 11.1 12.4 10.7
+ 1.0 f 4.4 ?I 1.1 + 2.0 f 0.8
In contrast, the low doses of naloxone increased the diuretic effect of 20 m&kg of ketazocine by presumably antagonizing the mu agonist actions of the larger dose of ketazocine. The mu agonist action of ethylketazocine can be demonstrated also in rats that are water-loaded (3 mls/lOO g of body wgt) simultaneously with drug injection. Table 2 shows that water-loading produces a marked diuretic effect evident at 1 and 2 hr after water-loading. The 5 mg/kg Table 2. Antagonizing the antidiuretic effect of ethylketazocine with p-FNA in water-loaded rats
Treatment
H20 injection 5 mg/kg ethylketazocine p-FNA + ethylketazocine
Cumulative mls of urine 2nd hr 5th hr 1st hr
6.3 + 1.2 0 7.3 f 0.4
1.8 + 1.4 0.9 f 0.2 17.5 f 3.9
9.5 + 1.4 21.8 + 1.8 29.3 + 1.1
dose of ethylketazocine had an antidiuretic action at 1 and 2 hrs after injection and water-loading. This antidiuretic action was completely blocked by pretreating the animals with 20 mg/kg of p-FNA ($-funaltrexamine HCl) (6) 18 hr before the water-loading and administration of ethylketazocine. Note that the ethylketazocine produced a more marked diuretic effect at 5 hrs than water-loading alone, and that the B-FNA pretreatment enhanced that effect. Figure 1 shows that pretreatment with B-FNA also blocks the mu agonist The p-FNA changes the inverted U-shaped effects of higher doses of m-2033. curve of MR-2033 at 2 hrs into a dose-effect curve that eventually plateaus at 10 to 20 mls of urine over the dose range of 0.32 to 20 mglkg. 284
FIRST HOUR
SECOND
THIRD
HOUR
HOUR
18 g
OPRE-B-FNA
16
l
3 6
12-
f
IO-
: 0 d
86
i
4-
d
2-
POST-fl-FNA 20 MO/KG, WHRS
o-
ii 0.02 1
FOURTH
oJ :
,
0.02
0.32
0.32 I
5I 201
HOUR
I
0.02
1
0.32
1
5 20
FIFTH HOUR
1 5 20 mglkg
G oiii-&-G WR-2033
In many replications of the effect of bremazocine in the hooded rats on urinary output, no inverted U-shaped curve has been obtained. Thus it was concluded that bremazocine did not have mu-agonist action, but rather had some weak mu-antagonist action (3). However, when bremazocine was studied in Sprague-Dawley albino rats, bremazocine produced an inverted U-shaped dose-effect curve (data shown in Table 3). Without naloxone, 0.08 mg/kg bremazocine produced a 2-hr diuretic effect of 15.5 mls, whereas 0.32 qg/kg of bremazocine produced less (9.8 mls) of a 2-hr diuretic effect. This decreased diuretic effect of 0.32 qg/kg of bremazocine was eliminated by simultaneous treatment with 1 qg/kg of naloxone. Thus it appears that bremazocine has some demonstrable mu-agonist activity in Sprague-Dawley albino rats but not in hooded rats. Since agonists at the mu-receptor have antidiuretic effects at 2 hrs after injection, the effects of opioids on urinary output at 2 hrs in normally hydrated rats can be used to classify the pharmacological profile of compounds in terms of their activities at mu and kappa receptors in vivo. -Mu agonists have only dose-related antidiuretic effects; full kappa agonists without mu agonist activity have only dose-related diuretic effects plateauing at lo-12 qls; full kappa agonists with mu agonist activity have inverted U-shaped dose-effect curves; and partial kappa agonists have
285
Table 3. Effects of bremazocine alone and in the presence of 1 mg/kg of naloxone on 2-hr urine output of normally hydrated Sprague-Dawley albino rats.
Bremazocine
dose
0 mglkg 0.005 0.02 0.08 0.16 0.32
Alone
1.4 5.8 10.1 15.5 12.0 9.8
(n = 4)
2 +, r r r +
0.4 1.0 0.5 0.5 0.6 1.3
+1 Naloxone
(n = 6)
1.8
f 0.5
3.5 11.6
+- 0.9 + 1.4
16.2
+ 1.6
diuretic effects that plateau at levels of urinary output less than that of To verify that effects of unknown compounds are a full kappa agonists. result of interaction with mu or kappa receptors, the effects should be demonstrated to be blocked by low and high doses, respectively, of naloxone. REFERENCES 1.
Slizgi, G. R. and Ludens, J. H. (1982). Studies on the nature mechanism of the diuretic activity of the opioid analgesic Journal of Pharmacology and Experimental ethylketocyclazocine. Therapeutics 220: 585-591.
2.
Leander, the rat. 89-94.
J. D. (1983). A kappa opioid effect: Increased urination in Journal of Pharmacology and Experimental Therapeutics 224:
3.
Leander, urination. 35-41.
J.
4.
Behavioral effects of agonist and antagonist Leander, J. D. (1984). In: Seiden, L. S. and Balster, R. L. action at kappa opioid receptors. (ea.) Behavioral Pharmacology: The Current Status. Alan R. Liss, New York, in press.
5.
Leander, J. D. (1983). oxilorphan are partial Jouranl of Pharmacology
6.
Ward, S. J., Portoghese, P. S. and Takemori, A. E. (1982). Pharmacological characterization in vivo of the novel opiate Journal of Pharmacology and Experimental S-funaltrexamine (B-FNA). Therapeutics 220: 494-498.
D. (1983). Journal of
and
Further study of kappa opioids on increased Pharmacology and Experimental Therapeutics 227:
Evidence that nalorphine, butorphanol, and European agonists at a K-opioid receptor. 86: 467-470.
286