MIF-1 FAILS TO MODIFY AGONIST-INDUCED ORAL ACTIVITY IN NEONATAL 6-OHDA-TREATED RATS

L-Prolyl-L-leucyl-glycinamide (MIF-1) is known to attenuate apomorphin e-induced stereotypies in adult rats that are lesioned as neonates wit h 6-hydroxydopamine (6-OHDA). To test whether MIF-1 would affect dopam ine (DA) agonist-induced and serotonin (5-HT) agonist-induced oral act ivity, both intact and neonatal 6-OHDA-treated rats were studied. Rats at 3 days from birth were injected with desipramine (20 mg/kg, IP), 1 h before 6-OHDA HBr (100 mug, salt form, in each lateral ventricle) o r its vehicle, saline-ascorbic acid (0. 1%). At approximately 6 months rats were treated with MIF-1 (0. 1, 1.0, or 10.0 mg/kg, IP), 10 min b efore SKF 38393 HCI (1.0 mg/kg, IP) or m-chlorophenylpiperazine 2HCl ( m-CPP 2HCl; 0.5 mg/kg, IP), DA D1 and 5-HT1C,2 receptor agonists, resp ectively. Although both agonists increased oral activity in control an d neonatal 6-OHDA-treated rats, MIF-1 did not modify the response. In rats that received either of the three doses of MIF-1 for 21 consecuti ve days, there was still no observed effect of MIF-1 on the oral respo nse of control and 6-OHDA-lesioned rats to SKF 38393 and m-CPP. These findings indicate that MIF-1 does not modify the oral activity respons e of super-sensitized D1 and 5-HT1C receptors in adult rats that are l esioned neonatally with 6-OHDA.