The observation that migraine patients improve during pregnancy with return of headache upon commencement of breast feeding, led Authors to investigate the involvement of Pain Suppressor System (PSS) in pregnancy and after delivery. PSS is a complex system which utilizes neurotransmitters as beta-Endorphine-Like-Immunoreactivity (beta-ELI), 5-Hydroxytryptamine (5-HT), Dopamine (DA) and GABA. The Authors report preliminary results of beta-ELI behaviour in pregnancy and in the immediate post-partum period in rats.