Hyperprolactinemia prevents short- and long-term memory deficits in ovariectomized rats and modifies the neuronal morphology of hippocampal CA1 neurons.

Abstract

The pituitary hormone prolactin (PRL) has been traditionally associated to reproductive functions, specifically to lactogenesis. Currently, this hormone has been linked to a great diversity of brain processes such as neurogenesis, neuroprotection, learning and memory formation. Regarding this later, literature is controversial since some studies indicate that PRL, like estrogens, improve some types of memory, while other report the opposite. Implanting pituitary homografts under the renal capsule induces a 10-fold increase of plasmatic PRL in male rats, but its effect on females is unknown. On the other hand, long-term (15 weeks) removal of ovaries produces a clear deficit in memory function by avoiding the action of estrogens and progesterone on this process. The present study was aimed at exploring the putative pro-cognitive actions of endogenous PRL and its role on the morphology of pyramidal neurons from hippocampus. The novel object recognition test, a hippocampal and cortical-dependent memory task was used for evaluating short- and long-term memory, while bromocriptine, a dopaminergic agonist, was assayed to block the actions of PRL on behavioral and morphological parameters. Main results indicate that PRL prevents the cognitive deficit observed in ovariectomized rats and increases the mushroom spines in CA1 pyramidal neurons; an effect that was partially impeded by bromocriptine.