Abstract
The transcription factor ΔFosB is increased in the brain after repeated exposure to several forms of stimuli. The nucleus accumbens (NAc), an area of the brain involved in rewarding behavior, is a site of major ΔFosB activity after exposure to chronic stimuli, including, but not limited to, drugs of abuse, stress, wheel running, sucrose consumption, and sex. The medial preoptic area (MPOA) is an area important for sexual and parental behavior. The immediate-early gene product c-Fos is observed in the medial preoptic nucleus (MPN) after initial sexual experience, and to a greater degree after multiple experiences. c-Fos is also found in the MPOA after parental behavior (i.e. retrieving pups), as is FosB, the full-length transcript of which ΔFosB is a truncated form. ΔFosB has recently been found to be increased in the NAc after multiple sexual experiences; however, FosB and ΔFosB have not been investigated in the MPOA after any amount of sexual experience. For this thesis, we used immunohistochemistry (IHC) to investigate FosB/ΔFosB activation in the MPOA of male rats that were given various amounts of sexual experience, including fifteen, one, and zero sessions. Two groups received fifteen sessions; one group received their last experience one week before sacrifice, whereas the second group received their last experience the day before sacrifice. We found the number of FosB/ΔFosB-immunoreactive cells is increased significantly in the MPN of males given one experience, compared to naïve males and the experienced group receiving their last experience one week before sacrifice; those given long-term sexual experience (up until the day before) were not significantly different from any of the other 3 groups. Western immunblotting was used to determine the molecular identity of the protein being expressed in IHC. It appears that ΔFosB, at 35-37kDa, is expressed in the MPOA after the first sexual experience. Based on these results, it is postulated that ΔFosB in the MPOA may be important for the priming of sensory and/or motor integration in the MPOA with the initial sexual experience of male rats.
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