Effects of the Excitatory Amino Acid Antagonist Kynurenic Acid on Synaptic Transmission to Supraoptic Neuroendocrine Cells

摘要

The magnocellular neuroendocrine system of the mammalian hypothalamus regulates physiological functions by releasing the peptide hormones oxytocin and vasopressin from the neurohypophysis Although several substances are known to promote hormone release, relatively little research has been aimed at testing the hypothesis that excitatory amino acids (EAAS) mediate synaptic transmission in this neuroendocrine system. In the present experiments, intracellular recordings in slices of rat hypothalamus revealed that kynurenic acid, a specific antagonist of EAA receptors, strongly and reversibly blocked excitatory postsynaptic potentials (EPSPs) in supraoptic neurons. The profound antagonism of EPSPs by kynurenic acid strongly suggests that EAAs may be an important class of fast excitatory neurotransmitters within this central regulatory nucleus.