Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats
Efficient repetitive clinical use of morphine is limited by its numerous side effects, whereas analgesic tolerance necessitates subsequent increases in morphine dose to achieve adequate levels of analgesia. While many studies focused on analgesic tolerance, the effect of morphine dosing on non-analg...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-07-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/26/14/4355 |
| _version_ | 1827687233262452736 |
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| author | Alok K. Paul Nuri Gueven Nikolas Dietis |
| author_facet | Alok K. Paul Nuri Gueven Nikolas Dietis |
| author_sort | Alok K. Paul |
| collection | DOAJ |
| description | Efficient repetitive clinical use of morphine is limited by its numerous side effects, whereas analgesic tolerance necessitates subsequent increases in morphine dose to achieve adequate levels of analgesia. While many studies focused on analgesic tolerance, the effect of morphine dosing on non-analgesic effects has been overlooked. This study aimed to characterize morphine-induced behavior and the development and progression of morphine-induced behavioral tolerance. Adult male Sprague–Dawley rats were repetitively treated with subcutaneous morphine for 14 days in two dose groups (A: 5 mg/kg/day (b.i.d.) → 10 mg/kg/day; B: 10 mg/kg/day (b.i.d.) → 20 mg/kg/day). Motor behavior was assessed daily (distance traveled, speed, moving time, rearing, rotation) in an open-field arena, before and 30 min post-injections. Antinociception was measured using tail-flick and hot-plate assays. All measured parameters were highly suppressed in both dosing groups on the first treatment day, followed by a gradual manifestation of behavioral tolerance as the treatment progressed. Animals in the high-dose group showed increased locomotor activity after 10 days of morphine treatment. This excitatory phase converted to an inhibition of behavior when a higher morphine dose was introduced. We suggest that the excitatory locomotor effects of repetitive high-dose morphine exposure represent a signature of its behavioral and antinociceptive tolerance. |
| first_indexed | 2024-03-10T09:30:38Z |
| format | Article |
| id | doaj.art-866452073c4347a2a543f3413b3c586f |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T09:30:38Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-866452073c4347a2a543f3413b3c586f2023-11-22T04:32:35ZengMDPI AGMolecules1420-30492021-07-012614435510.3390/molecules26144355Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in RatsAlok K. Paul0Nuri Gueven1Nikolas Dietis2School of Pharmacy and Pharmacology, University of Tasmania, Hobart, TAS 7001, AustraliaSchool of Pharmacy and Pharmacology, University of Tasmania, Hobart, TAS 7001, AustraliaMedical School, University of Cyprus, Nicosia 1678, CyprusEfficient repetitive clinical use of morphine is limited by its numerous side effects, whereas analgesic tolerance necessitates subsequent increases in morphine dose to achieve adequate levels of analgesia. While many studies focused on analgesic tolerance, the effect of morphine dosing on non-analgesic effects has been overlooked. This study aimed to characterize morphine-induced behavior and the development and progression of morphine-induced behavioral tolerance. Adult male Sprague–Dawley rats were repetitively treated with subcutaneous morphine for 14 days in two dose groups (A: 5 mg/kg/day (b.i.d.) → 10 mg/kg/day; B: 10 mg/kg/day (b.i.d.) → 20 mg/kg/day). Motor behavior was assessed daily (distance traveled, speed, moving time, rearing, rotation) in an open-field arena, before and 30 min post-injections. Antinociception was measured using tail-flick and hot-plate assays. All measured parameters were highly suppressed in both dosing groups on the first treatment day, followed by a gradual manifestation of behavioral tolerance as the treatment progressed. Animals in the high-dose group showed increased locomotor activity after 10 days of morphine treatment. This excitatory phase converted to an inhibition of behavior when a higher morphine dose was introduced. We suggest that the excitatory locomotor effects of repetitive high-dose morphine exposure represent a signature of its behavioral and antinociceptive tolerance.https://www.mdpi.com/1420-3049/26/14/4355morphine dosingbehaviorlocomotor activitytolerance |
| spellingShingle | Alok K. Paul Nuri Gueven Nikolas Dietis Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats Molecules morphine dosing behavior locomotor activity tolerance |
| title | Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats |
| title_full | Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats |
| title_fullStr | Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats |
| title_full_unstemmed | Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats |
| title_short | Profiling the Effects of Repetitive Morphine Administration on Motor Behavior in Rats |
| title_sort | profiling the effects of repetitive morphine administration on motor behavior in rats |
| topic | morphine dosing behavior locomotor activity tolerance |
| url | https://www.mdpi.com/1420-3049/26/14/4355 |
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