NEONATAL TESTOSTERONE EXPOSURE INFLUENCES NEUROCHEMISTRY OF NONOPIOIDSWIM STRESS-INDUCED ANALGESIA IN ADULT MICE

The effects of neonatal hormone manipulations on swim stress-induced a nalgesia (SSIA) magnitude and neurochemical quality were examined in S wiss-Webster mice of both sexes. Previous research has indicated that non-opioid SSIA mechanisms in adult Swiss-Webster mice are sexually di morphic. Male mice exhibit non-opioid SSIA following a 3-min swim in c old (15 degrees C) water that is antagonized by the non-competitive NM DA antagonist MK-801 (dizocilpine; 0.075 mg/kg), whereas female mice d o not display NMDA-mediated analgesia in the presence of estrogen. Sin ce male and female mice show equipotent magnitudes of SSIA, it was con cluded that female mice display a neurochemically distinct, estrogen-d ependent SSIA mechanism specific to their gender. In the present study , female mice exposed to testosterone during the neonatal period displ ay NMDA-mediated analgesia even in the presence of estrogen in adultho od. Thus, expression of the female-specific, estrogen-dependent SSIA m echanism previously described may be dependent on the absence of testo sterone during early ontogeny.