CHAPTER 2
 IVETHOD S

 Animals

 Ninety male Long-Evans (LE) rats and twelve female LE rats were purchased from

Harlan Co. of Indianapolis, INT. Twenty of the male Long Evans (LE) rats (225-250 g)

were used as unhandled controls. Fifty-eight of the male LE rats (225-250 g) were used

as intruders. Twelve of the male LE rats (300-325 g) were used as residents and the

twelve female LE rats (225-250 g) were used as housing mates for the residents. The

weight ranges indicate weights at the time the rats were purchased. The intruders

weighed 275-325 g and the residents weighed 500-800 g at the time of the experiments.

 Six of the unhandled control rats were used in Experiment la, six were used in

Experiment lb, and eight were used in Experiment 2. Thirty of the intruder rats were

used in Experiment la, twelve were used in Experiment lb, and sixteen were used in

Experiment 2. The resident males and the females were used in multiple experiments.

 The rats were housed in polycarbonate cages (43 x 21.5 x 25.5 cm) with sex-

matched and weight-matched pairings for five to seven days of acclimation to a

12hr/12hr light/dark cycle (lights on at 7:00a.m.). Standard chow (LabDiet 5001) and tap

water were available ad libitum. Temperature and humidity in the housing facility were

controlled to 22.720C & 0.940C and 54.1% + 14.6%, respectively.

 The intruder rats were exposed to social defeat stress and remained pair-housed

throughout the experiment. The control rats were not exposed to social defeat stress and

were pair-housed throughout the experiment. The resident rats were vasectomized,