The differential effect of the anxiolytic agent 8-OH-DPAT during lactationis independent of pup withdrawal and maternal behavior

Injection of the serotonergic agonist, 8-hydroxy-2-(di-n-propylamino-tetral in (8-OH-DPAT) (0.5 mg/kg ip) produced a clear anxiolytic-like effect (as m easured in the burying behavior test), after parturition, which remains unt il day 6 of lactation. Thereafter 8-OH-DPAT completely lacked action. In or der to analyze whether lactation prevented the action of 8-OH-DPAT, dams we re separated from their pups for five consecutive days. The blockade of the anxiolytic effect of 8-OH-DPAT does not disappear by isolation of the moth ers from their offspring or from neighboring pups. Finally, to investigate the possible role of maternal behavior in the blockade of the anxiolytic ef fect of 8-OH-DPAT a third experiment was made in which ovariectomized femal es were rendered maternal by the sensitization procedure. These females res pond normally to the antianxiety actions of 8-OH-DPAT. Results suggest that a long-term clue triggered by lactation, possibly related to prolactin sec retion, interferes with the anxiolytic effect of 8-OH-DPAT. (C) 2000 Elsevi er Science Ltd. All rights reserved.