Changes in total and free tryptophan levels in serum following acute morphine administration in arthritic rats.
In 'arthritic' rats a decrease in total tryptophan and an increase in free tryptophan levels was observed in serum after morphine administration (10 mg kg, s.c.). These changes were maximum within 15 and 30 min after injection. A decrease in total and an increase in free tryptophan levels in serum were observed 30 min after naloxone administration (1 mg/kg, i.m.). An increase in tryptophan and 5-hydroxyindoleacetic acid levels was also observed in the brain after morphine and naloxone. These observations suggest that the rise in 5-hydroxytryptamine synthesis provoked by morphine may be partly related to an increase in the availability of tryptophan from blood. However, the analgesia induced by the opiate appears unlikely to be directly related to this effect.
Weil-Fugazza
J
J
Unité de Recherches de Neurophysiologie Pharmacologique de l'INSERM (U. 161), 2 rue d'Alésia, 75014 Paris, France.
Godefroy
F
F
Coudert
D
D
Besson
J M
JM