Somatostatin antagonist potentiates haloperidol-induced catalepsy in the aged rat

Extrapyramidal motor signs are the major features of Parkinson's disease (PD). It is unclear whether there is a link between these signs and such PD-associated factors as aging and somatostatin deficiency. In this study, the intensity of haloperidol-induced catalepsy was examined in young and aged rats with decreased brain somatostatinergic activity. Catalepsy was measured using the bar test. The inhibition of the brain somatostatin activity was simulated by i.c.v. administration of a somatostatin antagonist, cyclosomatostatin. The drug potentiated the haloperidol-induced catalepsy in aged but not young rats. This action of cyclosomatostatin was inhibited by a somatostatin receptor agonist, octreotide. The results suggest that aging and somatostatin deficiency may be of pathogenic relevance for extrapyramidal signs in PD. ► Aging fails to affect haloperidol-induced catalepsy in rats. ► In aged animals, a somatostatin antagonist, cyclosomatostatin, potentiates catalepsy. ► The action of cyclosomatostatin is inhibited by a somatostatin analogue, octreotide.