INVOLVEMENT OF CENTRAL SEROTONERGIC PATHWAYS IN ANALGESIA ELICITED BYSALMON-CALCITONIN IN THE MOUSE

The contribution of central serotonergic pathways to the analgesic act ivity induced by salmon calcitonin in the writhing test was investigat ed. Salmon calcitonin was administered to mice after lesioning of the ascending and descending serotonergic pathways by means of i.p. admini stration of p-chloroamphetamine (40 mg/kg, for 2 days) or p-chlorophen ylalanine (300 mg/kg, for 3 days). The analgesic effect induced by sal mon calcitonin at the doses of 10 and 20 IU/kg was not evident in mice previously treated with p-chloroamphetamine or p-chlorophenylalanine. However, the analgesic effect of salmon calcitonin 40 IU/kg was not s ignificantly modified by p-chloroamphetamine or p-chlorophenylalanine pretreatment. Salmon calcitonin did not alter the depletion of 5-hydro xytryptamine (5-HT) and 5-hydroxyindoleacetic acid after p-chloroamphe tamine or p-chlorophenylalanine administration. Similarly, this hormon e did not change the NSD 1015-induced accumulation of 5-hydroxytryptop han or the tranylcypromine-induced accumulation of 5-HT. These results indicate that although salmon calcitonin does not influence the synth esis and metabolism of 5-HT, it does require the integrity of the sero tonergic system in order to cause analgesia.