Effect of changing plasma prolactin levels on clinical signs of EAE in rats. Two experiments were performed. In experiment 1 (left upper and lower panels), 77 male Lewis rats were subjected either to pituitary grafting from littermate donors (n = 39) or to sham operations (n = 38); all were then immunized by s.c. injection of a mixture of spinal cord homogenate (SCH) and complete Freund's adjuvant (CFA) as described in Methods. Rats were monitored daily for clinical signs of EAE. Groups of 7–8 rats were killed by decapitation on day 1, 4, 7, 11 or 15 after immunization. In experiment 2 (right upper and lower panels), 48 male Lewis rats were immunized with SCH plus CFA mixture, and then received daily s.c. injections of bromocriptine (1 mg/kg) or saline (n = 24 each). Groups of 8 rats were killed by decapitation on day 8, 11 or 15 after immunization. Prolactin levels were measured by RIA. Data are shown as means ± SEM. ** p < 0.01 vs. grafted rats at each time interval, Student's t test. Superscripts designate significant differences among time intervals within the same experimental group, a p < 0.01 vs. sham-operated rats on days 7, 11 or 15; b p < 0.05 vs. pituitary-grafted rats on day 1; c p < 0.05 vs. pituitary-grafted rats on days 4 or 7, p < 0.01 vs. pituitary-grafted rats on day 1, one-way ANOVA, Student-Newman-Keuls test.