Figure 1.

Experimental design. A) Stylized diagram of ovarian hormone levels across a 4 day estrous cycle in the rat (based on data from Gorski, 1975). B) Design of experiment #1: Baseline PPI in male and female rats. Two groups of animals were housed in adjacent rooms (5 males and 20 females per room). The rooms were maintained on 12h:12h light/dark cycles with the lights either on (Group 1 rats) or off (Group 2 rats) at 10:00 hrs. Each female rat was tested for PPI a total of 4 times: at 07:00 during D1 and P and at 13:00 hrs during D1 and P. ➀ Represents the time points of testing for rats housed on the light cycle with lights on at 10:00 hrs. ➁ Represents the time points of testing for rats housed on the light cycle with lights off at 10:00 hrs. There was at least a 3 day interval between test sessions. All male rats were tested for PPI a total of 6 times, 3 times at 07:00 hrs and 3 times at 13:00 hrs, with at least a 3 day interval between test sessions (not shown in figure). C) Design of experiment #2: Effect of the NTR antagonist and haloperidol on PPI in female rats. Animals were housed in adjacent rooms (20 females per room) maintained on 12h:12h light/dark cycles with the lights either on (ON) or off (OFF) at 10:00 hrs. All PPI testing was completed at 13:00 hrs. Females in each room were tested either during D1 or P. In the figure, ON-D1, OFF-D1, ON-P or OFF-P represent the time points of testing for each group of animals. Each animal within a group was tested for PPI a total of 4 times. The test sessions consisted of 1) baseline determination of PPI, 2) a single injection of haloperidol (0.1 mg/kg, i.p.) 30 minutes before PPI testing, 3) baseline PPI and 4) a single injection of the neurotensin receptor antagonist SR 142948A (0.1 mg/kg, i.p.) 1 hour before PPI testing. There was at least a 3 day interval between test sessions.