Vasopressin excites hippocampal neurones

Abstract

Hypothalmic supraoptic and paraventricular neurones were the first peptidergic cells to be described in the mammalian brain¹. Most of these large nerve cells synthesize either oxytocin or vasopressin², as well as their respective neurophysins, and project to the posterior lobe of the pituitary gland. This system of neurones is responsible for the release of these peptides into blood vessels of the posterior lobe in response to appropriate stimuli. Data obtained using immunoassay and immuno-cytochemical methods, however, have revealed vasopressin-like immunoreactive material^3,4 as well as vasopressin-positive axons^5–7 and presynaptic terminals⁸ in other central nervous system (CNS) locations. Moreover, vasopressin has been shown to affect some aspects of animal behaviour, including memory retention^9–13. It has therefore been suggested that vasopressin may act as a neurotransmitter or neuromodulator at synapses in the brain. We show here that low concentrations (10⁻⁸–10⁻⁶ M) of vasopressin powerfully and reversibly increase the rate of firing of neurones in the CA1 area of hippocampal slices front rat and that this effect can be fully antagonized by an anti-vasopressor vasopressin analogue. Hippocampal neurones obtained from Brattleboro rats were also excited by exogenous vasopressin.