Somatostatin antagonist induces catalepsy in the aged rat

Rationale 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 brain somatostatin deficiency and aging. Objectives This study aimed to examine whether an inhibition of the brain somatostatin system can initiate catalepsy, a model of extrapyramidal disorders, in young and aged rats. Methods The animals of 100–110 and 540–560 days of age were used. Catalepsy was measured using the bar test. The inhibition of the brain somatostatin activity was simulated by intracerebroventricular administration of a somatostatin antagonist, cyclosomatostatin. Results Cyclosomatostatin dose-dependently induced catalepsy in aged, but not in young rats. The cataleptic response was reversed by a somatostatin analog, octreotide. Conclusions The combination of aging and brain somatostatin deficiency can lead to catalepsy in rats. Since both factors are frequently observed in PD patients, the present results might be of relevance for pathogenesis of extrapyramidal signs in this disease.