BLOCKADE OF THE ANXIOLYTIC ACTION OF 8-OH-DPAT IN LACTATING RATS

The anxiolytic action of 8-OH-DPAT (0.125, 0.5, and 0.75 mg/kg, IP, -1 5 min) was evaluated in ovariectomized and 7-day lactating mother rats . This serotonergic anxiolytic produces a clear reduction in cumulativ e burying behavior and in freezing time (parameters denoting a reducti on in anxiety levels) in ovariectomized subjects. However, in 7-day la ctating mother rats, 8-OH-DPAT lacked its antianxiety effects. Additio nally, as an extra parameter of the animal's emotionality the number o f defecation bolus was registered. A reduction in this parameter in ov ariectomized animals after 8-OH-DPAT (0.5 mg/kg) injection was found. This effect was also blocked in 7-day lactating rats. None of the dose s of the compound tested altered the burying behavior latency (a param eter inversely representing the animal's reactivity). The general ambu latory behavior of ovariectomized subjects was significantly impaired at the highest dose (0.75 mg/kg) of 8-OH-DPAT. Lower doses did not alt er this parameter or the number of times lines are crossed (a paramete r denoting exploratory activity). Discussion is focused on the relatio nship between the activity of the serotonergic system and the secretio n of prolactin in this period. (C) 1998 Elsevier Science Inc.