Modulation of delta opioid-evoked hypothermia in rats by WAY 100635 and fluoxetine.

Delta opioid receptor and 5-hydroxytryptamine (5-HT) interactions in rats were investigated using the endpoint of hypothermia. The intraperitoneal (i.p.) administration of SNC-80, a delta opioid agonist (35 mg/kg, i.p.), produced a significant hypothermia. For combined administration, SNC-80-evoked hypothermia was (1) abolished by pre-treatment with naltrindole (5 mg/kg, i.p.); (2) attenuated by pre-treatment with WAY 100635 (1 mg/kg, s.c.), a 5-HT1A antagonist; and (3) enhanced by pre-treatment with non-hypothermic doses of fluoxetine (2.5, 5 and 10 mg/kg, i.p.). The present data reveal that 5-HT1A receptor activation mediates a significant proportion of the hypothermic response to delta opioid receptor activation and that a 5-HT uptake blockade potentiates delta receptor-induced hypothermia.