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Electrophysiological Effects of Kainic Acid on Vasopressin‐ Enhanced Green Fluorescent Protein and Oxytocin‐ Monomeric Red Fluorescent Protein 1 Neurones Isolated from the Supraoptic Nucleus in Transgenic Rats
Author(s) -
Ohkubo J.,
Ohbuchi T.,
Yoshimura M.,
Maruyama T.,
Ishikura T.,
Matsuura T.,
Suzuki H.,
Ueta Y.
Publication year - 2014
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12128
Subject(s) - kainate receptor , kainic acid , vasopressin , supraoptic nucleus , oxytocin , ampa receptor , medicine , glutamate receptor , endocrinology , green fluorescent protein , biology , patch clamp , nmda receptor , chemistry , receptor , microbiology and biotechnology , biochemistry , gene
The supraoptic nucleus (SON) contains two types of magnocellular neurosecretory cells: arginine vasopressin (AVP)‐producing and oxytocin (OXT)‐producing cells. We recently generated and characterised two transgenic rat lines: one expressing an AVP‐enhanced green fluorescent protein ( eGFP ) and the other expressing an OXT‐monomeric red fluorescent protein 1 ( mRFP 1). These transgenic rats enable the visualisation of AVP or OXT neurones in the SON. In the present study, we compared the electrophysiological responses of AVP‐ eGFP and OXT‐ mRFP 1 neurones to glutamic acid in SON primary cultures. Glutamate mediates fast synaptic transmission through three classes of ionotrophic receptors: the NMDA, AMPA and kainate receptors. We investigated the contributions of the three classes of ionotrophic receptors in glutamate‐induced currents. Three different antagonists were used, each predominantly selective for one of the classes of ionotrophic receptor. Next, we focused on the kainate receptors (KARs). We examined the electrophysiological effects of kainic acid (KA) on AVP‐ eGFP and OXT‐ mRFP 1 neurones. In current clamp mode, KA induced depolarisation and increased firing rates. These KA‐induced responses were inhibited by the non‐NMDA ionotrophic receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3(1H4H)‐dione in both AVP‐ eGFP and OXT‐ mRFP 1 neurones. In voltage clamp mode, the application of KA evoked inward currents in a dose‐dependent manner. The KA‐induced currents were significantly larger in OXT‐ mRFP 1 neurones than in AVP‐ eGFP neurones. This significant difference in KA‐induced currents was abolished by the GluK1‐containing KAR antagonist UBP302. At high concentrations (250–500 μ m ), the specific GluK1‐containing KAR agonist (RS)‐2‐amino‐3‐(3‐hydroxy‐5‐tert‐butylisoxazol‐4‐yl) propanoic acid (ATPA) induced significantly larger currents in OXT‐ mRFP 1 neurones than in AVP‐ eGFP neurones. Furthermore, the difference between the AVP‐ eGFP and OXT‐ mRFP 1 neurones in the ATPA currents was approximately equal to the difference in the KA currents. These findings suggest that the GluK1‐containing KARs may be more highly expressed in OXT neurones than in AVP neurones. These results may provide new insight into the physiology and synaptic plasticity of SON neurones.