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L-Nitroarginine methyl ester attenuates the development of morphine tolerance and dependence in mice
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L-NITROARGININE METHYL ESTER ATTENUATES THE DEVELOPMENT OF MORPHINE TOLERANCE AND DEPENDENCE IN MICE Majeed N, Przewlocka B, Machelska H, and Przewlocki R, Neuropeptide Research Department, Institute of Pharmacology, Krak6w, Poland
ABSTRACT The effect of the nitric oxide (NO) synthase inhibitor L-N° - nitroarginine methyl ester (L-NAME) on the morphine-induced analgesia, as well as on the morphine tolerance and dependence was examined in male albino Swiss mice. Neither acute nor repeated administration of L-NAME affected the morphine analgesia, as measured by a hot plate (HI') and a tail-flick (TF) tests. On the other hand, administration of L-NAME (10 mg/kg i.p.) jointly with morphine prevented the development of tolerance to the analgesic effect of morphine. L-NAME also attenuated the morphine dependence, as assessed by naloxone (2 mg/kg)-precipitated withdrawal. These results indicate that NO may play a crucial role in the development of morphine tolerance and dependence. METHODS Male albino Swiss mice (25-30g) were used in this study. The animals were housed in groups of 10 per cage, and were allowed food and water ad libitum. The analgesic effect was measured by the 'IF and HP tests. TF latencies were assessed using an analgesiameter (the Analgesia Test TF-812 HSE, Germany). In short: three successive determinations were carded out for each mouse, and the mean of those scores was used as a TF latency for the particular animal. A 7-second cut-off was used to minimize tissue damage. The HP was kept at 53°C. A 15-second cutoff was introduced to avoid tissue damage. In the acute experiment, the animals were injected with saline or L-NAME (5 10 mg/kg i.p.), followed by i.p. administration of saline or morphine (10 mg/kg) 30 min later. The TF and HP latencies were measured 30 min after the second injection. To determine the effect of L-NAME on the development of morphine tolerance and dependence, the animals received an i.p. injection of morphine (10 mg/kg) once daily for 7 days. The analgesic response was assessed by the TF and HP latencies 30 rain after the second injection. On day 8, the animals were injected with naloxone (2 mg/kg, i.p.) to precipitate withdrawal. The withdrawal syndrome was assessed by placing each mouse in a glass cylinder and recording the incidence of escape jumps for a period of 15 rain. RESULTS L-NAME (10 mg/kg), given in single or repeated doses, had no significant effect on the pain threshold. The compound failed to alter the HP latency. Repeated injections of L-NAME also failed to alter the HP latency. Similarly, there were no significant effects on the pain threshold, as measured by the TF test following acute or chronic L-NAME administration. In addition, L-NAME given acutely or chronically did not affect the acute morphine analgesia, as measured by the HP and TF tests. Mice injected with morphine (10 mg/kg/day) developed tolerance to its analgesic effect, that effect having almost completely disappeared by day 5 after injection. L-NAME in a dose of 10 mg/kg/day, coadministered with morphine, prevented the development of tolerance to the analgesic effect of morphine (Table I). Pretreatment with L-NAME also attenuated the naloxone-precipitated abstinence syndrome. The mice that received repeated daily injections of saline and morphine showed numerous escape jumps in response to 2 mg/kg naloxone i.p. In contrast, the mice that were treated with L-NAME and morphine made significantly fewer escape jumps.
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Table I. Effect of L-NAME on the development tolerance to the analgesic effect of morphine. Values are expressed as mean +_ S.E.M. tail-flick (TF) and hot plate fliP) latencies (s). Significant differences between L-NAME+morphine and morphine group, p <0.05, Duncan's test. L-NAME control
acute i
I
I chronic
MORPHINE I acute
L-NAME + MORPHINE
chronic
acute
i
chronic i
TF
3.1+0.1
3.2+0.1
3.2+.04
5.8+0.5
3.4+0.2
5.8+0.4
6.1+.3
HP
7.1+0.5
6.9+0.3
7.2+0.3
13+0.4
7.2+0.6
14-t-0.2
12:t:0.5
SUMMARY AND CONCLUSIONS The present results show that repeated administration of the NO synthase inhibitor L-NAME attenuates the development of morphine tolerance (1, present study) and dependence. Recent results suggest that the NO pathway may be involved in some behavioral changes following acute (2) as well as neuronal adaptation after chronic opiate administration. The mechanism by which NO may be involved in this phenomena is not clear. Recently it has been found that the NMDA receptor antagonist MK-801 attenuates the development of opiate tolerance and dependence in rats (3). It has also been observed that some central effects of NMDA are likely to be mediated via activation of the NO synthase, with a subsequent release of NO (4). Therefore the present findings suggest a possibility that L-NAME blocks the NO synthase activity induced, most probably, by activation of the NMDA receptor which, in turn, modulates the effects of morphine. In conclusion, the present results provide evidence that NO may play an important role in the mechanisms of development of the opiate tolerance and dependence. Therefore NO synthase inhibitors may be potentially useful in the clinic, when given in combination with opiates. ACKNOWLEDGEMENT This work was supported by a grant (0535/P2/93/04) obtained from the Committee for Scientific Research (KBN, Warszawa)
REFERENCES 1. Kolesnikov Y.A. Chaim G.P. and Pasternak G.W. (1992) Eur. J. Pharmacol. 221: 399-400. 2. Przewlocki R. Machelska H. Przewlocka B. (1993) Life Sci. 53: PL1-5. 3. Trujillo K.A. and Akil H. (1991) Science 251: 85-87. 4. Bredt D.S. Hwang P.H. and Snyder S.H. (1990) Nature 347: 768-770.
L-NITROARGININE METHYL ESTER ATTENUATES THE DEVELOPMENT OF MORPHINE TOLERANCE AND DEPENDENCE IN MICE Majeed N, Przewlocka B, Machelska H, and Przewlocki R, Neuropeptide Research Department, Institute of Pharmacology, Krak6w, Poland
ABSTRACT The effect of the nitric oxide (NO) synthase inhibitor L-N° - nitroarginine methyl ester (L-NAME) on the morphine-induced analgesia, as well as on the morphine tolerance and dependence was examined in male albino Swiss mice. Neither acute nor repeated administration of L-NAME affected the morphine analgesia, as measured by a hot plate (HI') and a tail-flick (TF) tests. On the other hand, administration of L-NAME (10 mg/kg i.p.) jointly with morphine prevented the development of tolerance to the analgesic effect of morphine. L-NAME also attenuated the morphine dependence, as assessed by naloxone (2 mg/kg)-precipitated withdrawal. These results indicate that NO may play a crucial role in the development of morphine tolerance and dependence. METHODS Male albino Swiss mice (25-30g) were used in this study. The animals were housed in groups of 10 per cage, and were allowed food and water ad libitum. The analgesic effect was measured by the 'IF and HP tests. TF latencies were assessed using an analgesiameter (the Analgesia Test TF-812 HSE, Germany). In short: three successive determinations were carded out for each mouse, and the mean of those scores was used as a TF latency for the particular animal. A 7-second cut-off was used to minimize tissue damage. The HP was kept at 53°C. A 15-second cutoff was introduced to avoid tissue damage. In the acute experiment, the animals were injected with saline or L-NAME (5 10 mg/kg i.p.), followed by i.p. administration of saline or morphine (10 mg/kg) 30 min later. The TF and HP latencies were measured 30 min after the second injection. To determine the effect of L-NAME on the development of morphine tolerance and dependence, the animals received an i.p. injection of morphine (10 mg/kg) once daily for 7 days. The analgesic response was assessed by the TF and HP latencies 30 rain after the second injection. On day 8, the animals were injected with naloxone (2 mg/kg, i.p.) to precipitate withdrawal. The withdrawal syndrome was assessed by placing each mouse in a glass cylinder and recording the incidence of escape jumps for a period of 15 rain. RESULTS L-NAME (10 mg/kg), given in single or repeated doses, had no significant effect on the pain threshold. The compound failed to alter the HP latency. Repeated injections of L-NAME also failed to alter the HP latency. Similarly, there were no significant effects on the pain threshold, as measured by the TF test following acute or chronic L-NAME administration. In addition, L-NAME given acutely or chronically did not affect the acute morphine analgesia, as measured by the HP and TF tests. Mice injected with morphine (10 mg/kg/day) developed tolerance to its analgesic effect, that effect having almost completely disappeared by day 5 after injection. L-NAME in a dose of 10 mg/kg/day, coadministered with morphine, prevented the development of tolerance to the analgesic effect of morphine (Table I). Pretreatment with L-NAME also attenuated the naloxone-precipitated abstinence syndrome. The mice that received repeated daily injections of saline and morphine showed numerous escape jumps in response to 2 mg/kg naloxone i.p. In contrast, the mice that were treated with L-NAME and morphine made significantly fewer escape jumps.
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Table I. Effect of L-NAME on the development tolerance to the analgesic effect of morphine. Values are expressed as mean +_ S.E.M. tail-flick (TF) and hot plate fliP) latencies (s). Significant differences between L-NAME+morphine and morphine group, p <0.05, Duncan's test. L-NAME control
acute i
I
I chronic
MORPHINE I acute
L-NAME + MORPHINE
chronic
acute
i
chronic i
TF
3.1+0.1
3.2+0.1
3.2+.04
5.8+0.5
3.4+0.2
5.8+0.4
6.1+.3
HP
7.1+0.5
6.9+0.3
7.2+0.3
13+0.4
7.2+0.6
14-t-0.2
12:t:0.5
SUMMARY AND CONCLUSIONS The present results show that repeated administration of the NO synthase inhibitor L-NAME attenuates the development of morphine tolerance (1, present study) and dependence. Recent results suggest that the NO pathway may be involved in some behavioral changes following acute (2) as well as neuronal adaptation after chronic opiate administration. The mechanism by which NO may be involved in this phenomena is not clear. Recently it has been found that the NMDA receptor antagonist MK-801 attenuates the development of opiate tolerance and dependence in rats (3). It has also been observed that some central effects of NMDA are likely to be mediated via activation of the NO synthase, with a subsequent release of NO (4). Therefore the present findings suggest a possibility that L-NAME blocks the NO synthase activity induced, most probably, by activation of the NMDA receptor which, in turn, modulates the effects of morphine. In conclusion, the present results provide evidence that NO may play an important role in the mechanisms of development of the opiate tolerance and dependence. Therefore NO synthase inhibitors may be potentially useful in the clinic, when given in combination with opiates. ACKNOWLEDGEMENT This work was supported by a grant (0535/P2/93/04) obtained from the Committee for Scientific Research (KBN, Warszawa)
REFERENCES 1. Kolesnikov Y.A. Chaim G.P. and Pasternak G.W. (1992) Eur. J. Pharmacol. 221: 399-400. 2. Przewlocki R. Machelska H. Przewlocka B. (1993) Life Sci. 53: PL1-5. 3. Trujillo K.A. and Akil H. (1991) Science 251: 85-87. 4. Bredt D.S. Hwang P.H. and Snyder S.H. (1990) Nature 347: 768-770.