Mu- and kappa-opiate agonists modulate ingestive behaviors in the slug, Limax maximums

Administration of he prototypical mu opiate agonist, morphine sulphate, 1-10 mg/kg, produced over three hours a significant dose-dependent increase in the ingestive responses of free-feeding slugs Limax maximus although lower doses, attenuated feeding. The mixed mu and kappa opiate agonist, ketocyclazocine hydrochloride also induced significant increases in food consumption. The results indicate that activation of differential opiate receptors in invertibrates has similar effect on feeding behavior as occur in mammals, suggesting early evolutionary development of food involvement in the control of feeding.