title: Vasopressin differentially modulates non-NMDA receptors in vasopressin and oxytocin neurons in the supraoptic nucleus.
abstract: Magnocellular neurons of the supraoptic nucleus release the neuropeptides oxytocin and vasopressin from their dendrites to regulate their synaptic inputs. This study aims to determine the cellular mechanism by which vasopressin modulates excitatory synaptic transmission. Presumably by electroporation through perforated patch, we were able to successfully introduce biocytin into cells in which we performed an electrophysiological study. This method enabled us to determine that roughly half of the recorded neurons were immunoreactive to oxytocin-associated neurophysin and showed two characteristic features: an inward rectification and a sustained outward rectification. The remaining half showed a linear voltage-current relationship and was immunoreactive to vasopressin-associated neurophysin. Using these electrophysiological characteristics and post hoc immunohistochemistry to identify vasopressin or oxytocin neurons, we found that vasopressin decreased evoked EPSCs in vasopressin neurons while increasing EPSCs in oxytocin neurons. In both types of neurons, EPSC decay constants were not affected, indicating that desensitization of non-NMDA receptors did not underlie the EPSC amplitude change. In vasopressin neurons, both vasopressin and a V1a receptor agonist, F-180, decreased AMPA-induced currents, an effect blocked by a V1a receptor antagonist SR49059. In oxytocin neurons, AMPA-induced currents were facilitated by vasopressin, whereas F-180 had no effect. An oxytocin receptor antagonist blocked the facilitatory effect of vasopressin. Thus, we conclude that vasopressin inhibits EPSCs in vasopressin neurons via postsynaptic V1a receptors, whereas it facilitates EPSCs in oxytocin neurons through oxytocin receptors.
authors.affiliation: Neuroscience Research Group, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, T2N 4N1 Canada. hirasawa@ucalgary.ca
authors.forename: Michiru
authors.initials: M
authors.lastname: Hirasawa
authors.forename: Didier
authors.initials: D
authors.lastname: Mouginot
authors.forename: Michael G
authors.initials: MG
authors.lastname: Kozoriz
authors.forename: Samuel B
authors.initials: SB
authors.lastname: Kombian
authors.forename: Quentin J
authors.initials: QJ
authors.lastname: Pittman
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism / Q000502:physiology*; D003712:Dendrites / Q000378:metabolism / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D025461:Feedback, Physiological / Q000187:drug effects / Q000502:physiology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009481:Neurophysins / Q000032:analysis / Q000276:immunology / Q000378:metabolism; D010121:Oxytocin / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism / Q000502:physiology*; D018045:Receptors, Oxytocin / Q000378:metabolism / Q000502:physiology; D017483:Receptors, Vasopressin / Q000378:metabolism / Q000502:physiology; D013495:Supraoptic Nucleus / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D018690:Excitatory Amino Acid Agonists; D009481:Neurophysins; D016194:Receptors, N-Methyl-D-Aspartate; D018045:Receptors, Oxytocin; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D010121:Oxytocin; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid