Evaluation of the commonly used analgesics in the naked mole-rat (heterocephalus glaber) and the root-rat mole-rat (tachyoryctes splendens) using the hot-plate test
Abstract
The aims of the experiments were to study pain
mechanisms and behaviour in two species of mole-rats, the
naked mole-rat (Heterocepha/us g/aber) and the root-rat
mole-rat (Tachyoryctes sp/endens). Two opioids (pethidine
and codeine), three. non-steroidal anti-inflammatory drugs
(paracetamol, acetylsalicylic acid (ASA) and indomethacin)
and two steroid anti-inflammatory drugs (dexamethasone
and hydrocortisone) were used in this study. The hot-plate
test used in this study was set at a temperature of 600 C.
The two species of mole-rats were kept under controlled
laboratory conditions.
In both species of mole-rats the opiates used
(pethidine: 10, 20 or 30 mg/kg, codeine: 15, 25, 35 or 50
mg/kg) had no antinociceptive effect but instead induced a
dose-dependent reduction in response latency.
Administration of pethidine or codeine also induced
aggressive behaviour and sensorimotor effects in the naked
mole-rat. The change in behaviour was not observed in the
root-rat mole-rat after pethidine administration.
Paracetamol (400 mg/kg) and indomethacin (40 or 50 mg/kg)
caused a significant increase in stepping latency in the
naked mole-rat. Lower doses of these drugs had no
antinociceptive effect. No anti nociceptive effect of either
acetylsalicylic acid (200, 400 or 600 mg/kg),
hydrocortisone (75, 150 or 225 mg/kg) or dexamethasone
(10, 20 or 30 mg/kg) was demonstrated in the study.
It is concluded that the opioid system of the mole-rat
plays no role in the regulation of thermal nociception. In the
naked mole-rat however, the opioid system seems to play an
important role in the regulation of aggressive and motor
behaviour.
Citation
Master of Science (Comparative Mammalian Physiology)Publisher
University of Nairobi Department of Animal Physiology, University of Nairobi,