Effects of 14-methoxymetopon, a potent opioid agonist, on the responses to the tail electric stimulation test and plus-maze activity in male rats: neuroendocrine correlates.
We have studied the effects of 14-methoxymetopon (HS 198), a potent opioid agonist, on the responses to the tail electric stimulation test and plus-maze activity of adult male rats. The prototype mu agonist morphine was used as the drug of reference. Besides we addressed the effects of HS 198 on the serum corticosterone levels and on serotonergic systems of discrete brain regions. Both drugs were administered subcutaneously. Morphine (5 mg/kg) and HS 198 (30 microg/kg) induced a similar effect on the nociceptive test, with both drugs significantly increasing the threshold for the vocalization afterdischarge, which is related to the emotional component of pain. In the plus-maze, morphine (5 mg/kg) and HS 198 (20 and 30 microg/kg) induced similar increases in the percentages of entries and time in the open arms, two parameters related to the anxiety state of the animals. The results indicate that HS 198 is far more potent than morphine in reducing the emotive/affective component of pain and in inducing an anxiolytic effect. HS 198 (30 microg/kg) also induced parallel increases in the serum corticosterone levels and the hypothalamic serotonin content. A possible correlation between the anxiolytic action of the drug and its effect on the hypothalamic serotonergic system is suggested.
Urigüen
Leyre
L
Departamento de Biología Animal II, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain.
Fernández
Beatriz
B
Romero
Eva Maria
EM
De Pedro
Nuria
N
Delgado
Maria Jesús
MJ
Guaza
Carmen
C
Schmidhammer
Helmut
H
Viveros
Maria Paz
MP
D000818:Animals; D001007:Anxiety / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D003345:Corticosterone / Q000097:blood / Q000378:metabolism; D004558:Electric Stimulation; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D009020:Morphine / Q000494:pharmacology; D009022:Morphine Derivatives / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D009434:Neural Pathways / Q000187:drug effects* / Q000378:metabolism; D010146:Pain / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D010147:Pain Measurement / Q000187:drug effects; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D014828:Vocalization, Animal / Q000187:drug effects / Q000502:physiology
D009022:Morphine Derivatives; D009294:Narcotics; C081949:14-methoxymetopon; D012701:Serotonin; D009020:Morphine; D003345:Corticosterone