eCite Digital Repository

Profiling the effects of repetitive morphine administration on motor behavior in rats


Paul, AK and Gueven, N and Dietis, N, Profiling the effects of repetitive morphine administration on motor behavior in rats, Molecules, 26, (4) pp. 1-14. ISSN 1420-3049 (2021) [Refereed Article]


Copyright Statement

Copyright 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// 4.0/).

DOI: doi:10.3390/molecules26144355


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.

Item Details

Item Type:Refereed Article
Keywords:morphine dosing, behavior, locomotor activity, tolerance
Research Division:Biomedical and Clinical Sciences
Research Group:Pharmacology and pharmaceutical sciences
Research Field:Basic pharmacology
Objective Division:Health
Objective Group:Public health (excl. specific population health)
Objective Field:Behaviour and health
UTAS Author:Paul, AK (Dr Alok Paul)
UTAS Author:Gueven, N (Dr Nuri Guven)
ID Code:147581
Year Published:2021
Web of Science® Times Cited:10
Deposited By:Pharmacy
Deposited On:2021-11-09
Last Modified:2021-12-16
Downloads:10 View Download Statistics

Repository Staff Only: item control page