Learning and cholinergic neurotransmission in old animals: the effect of Hydergine.

In the present work, a study of the number of functional receptors has been made with 3HQNB given to resting awaken animals during a learning process. Ageing leads to a decrease in the ability of learning associated with an increase in the number of large movements. The number of cholinergic receptors is also reducel if we compare 22 month old animals with 4 month old animals maintained under usual conditions. Learning conditioning leads to a stimulation of the cholinergic system with a release of acetylcholine. The mediator takes the 3HQNB out of its fixation areas which causes an apparent decrease in the number of receptors. This result is more significant in young animals than in aged ones because of the possibility of activation in the cholinergic system. The treatment by dihydroergotoxine partially re-establishes the learning abilities in animals and, at the same time, increases the number of cholinergic receptors This effect could explain the actions of this drug on the memory process in ageing persons.

[Learning, hemodynamic and metabolic attendant effects in aged animals after an acute ischemic accident]. / Apprentissage et concomitances hémodynamiques et métaboliques chez l'animal âgé après un accident ischémique aigu.

The effects of ageing in normal and pathological rats were studied. Learning (spatio-temporal test) was measured simultaneously with the local cerebral blood flow, determined by a diffusible indicator (iodoantipyrine) and with the uptake and consumption of glucose, determined by the deoxyglucose. Normal ageing disturbs the learning with a decrease in acquisition speed and an increase in the number of errors. Furthermore, normal ageing induces a decrease in glucose uptake and in glucose consumption in the brain structures such as hippocampus or corpus striatum, with only a slight decrease in local cerebral blood flow. Dihydroergotoxine partially reestablishes the performances of the rats and increases the glucose consumption in the areas involved in learning. Pathological ageing, produced by the administration of microspheres and corresponding to the multi-infarct dementia, is correlated to a large decrease in glucose consumption and local blood flow. Dihydroergotoxine treatment partially suppresses the micro-infarct effects before the reestablishment of rat performance in behavioral tests.