Intracisternal and intraperitoneal administration of morphine attenuates mechanical allodynia following compression of the trigeminal ganglion in rats.
OBJECTIVE
To investigate the effects of morphine on mechanical allodynia following compression of the trigeminal ganglion in the rat.


METHODS
Experiments were carried out on male Sprague-Dawley rats weighing between 250 and 260 g. For compression, a 4% agar solution (8 microL) was injected into the trigeminal ganglion. In the control group, rats were sham operated without agar injections. The authors evaluated the effects of intraperitoneal or intracisternal administration of morphine on mechanical allodynia evoked by air-puff stimulation of the vibrissa pad area 14 days following compression of the trigeminal ganglion.


RESULTS
Mechanical allodynia was established within 3 days and lasted beyond postoperative day 24. Intraperitoneal administration of morphine (2 or 5 mg/kg) significantly blocked mechanical allodynia ipsilateral to the compression of the trigeminal ganglion. Intraperitoneal administration of morphine also inhibited mechanical allodynia on the contralateral side. Moreover, intracisternal administration of morphine (5 microg) strongly suppressed both ipsilateral and contralateral mechanical allodynia. The antiallodynic effects of morphine were blocked by pretreatment with naloxone, an opioid receptor antagonist.


CONCLUSIONS
These results suggest that the application of a high dose of morphine may be of great benefit in treating trigeminal neuralgia-like nociception.
Le
Min K
MK
Department of Physiology, Korea University College of Medicine, Seoul, Korea.
Shin
Hea J
HJ
Yang
Gwi Y
GY
Yoon
Young W
YW
Han
Seong K
SK
Bae
Yong C
YC
Ahn
Dong K
DK
D000818:Animals; D002946:Cisterna Magna; D005157:Facial Pain / Q000188:drug therapy*; D007267:Injections; D007274:Injections, Intraperitoneal; D008297:Male; D009020:Morphine / Q000008:administration & dosage* / Q000037:antagonists & inhibitors; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000008:administration & dosage*; D009408:Nerve Compression Syndromes / Q000188:drug therapy*; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012668:Trigeminal Ganglion / Q000503:physiopathology*; D014277:Trigeminal Neuralgia / Q000188:drug therapy; D014738:Vibrissae
D009292:Narcotic Antagonists; D009294:Narcotics; D009270:Naloxone; D009020:Morphine