Dihydroergocryptine improves behavioral deficits of aged male rats

Dihydroergocryptine (DHECP), an ergot alkaloid with potent dopaminergic activity, was injected acutely or subchronically to aged (24 months old) male rats of the F344 strain, at the dose of 0.05 or 0.1 mg/kg. The immobility in the "despair" test (constrained swim) was longer in 24-month-old rats than in younger animals. This behavioral change was reduced in rats treated subchronically with DHECP, but no significant change was found in animals with acute treatment. Aged rats showed an increased haloperidol-induced catalepsy and a reduced motor performance and coordination as compared to animals of 2 and 10 months of age. Acute treatment with DHECP was followed by an attenuation of haloperidol-induced catalepsy and an improvement of motor performance and coordination of aged rats. Similar results were obtained after subchronic treatment with DHECP, but the effect on the rotorod behavior was more potent after subchronic treatment than after acute injection of the drug. It is possible that the improvement of behavioral deficits of aged rats after the treatment with DHECP depends on the facilitating effect of this drug on central dopamine transmission that may be impaired in these animals.