Hidden prenatal malnutrition in the rat: role of beta-adrenoceptors on synaptic plasticity in the frontal cortex.

摘要

Moderate reduction in the protein content of the mother's diet (hidden malnutrition) does not alter body and brain weights of rat pups at birth, but leads to dysfunction of neocortical noradrenaline systems together with impaired long-term potentiation and visuo-spatial memory performance. As beta-adrenoceptors and downstream protein kinase signaling are critically involved in synaptic long-term potentiation and memory formation, we evaluated the beta-adrenoceptor density and the expression of cyclic-AMP dependent protein kinase, calcium/calmodulin-dependent protein kinase and protein kinase Fyn, in the frontal cortex of prenatally malnourished adult rats. In addition, we also studied if beta-adrenoceptor activation with the selective beta agonist dobutamine could improve deficits of prefrontal cortex long-term potentiation presenting these animals. Prenatally malnourished rats exhibited half of beta-adrenoceptor binding, together with a 51% and 65% reduction of cyclic AMP-dependent protein kinase alpha and calcium/calmodulin-dependent protein kinase alpha expression, respectively, as compared with eutrophic animals. Administration of the selective beta agonist dobutamine prior to tetanization completely rescued the ability of the prefrontal cortex to develop and maintain long-term potentiation in the malnourished rats. Results suggest that under-expression of neocortical beta-adrenoceptors and protein kinase signaling in hidden malnourished rats functionally affects the synaptic networks subserving prefrontal cortex long-term potentiation. beta-adrenoceptor activation was sufficient to fully recover neocortical plasticity in the PKA- and calcium/calmodulin-dependent protein kinase II-deficient undernourished rats, possibly by producing extra amounts of cAMP and/or by recruiting alternative signaling cascades.