title: The comparison of the effects of acute and repeated morphine administration on fast synaptic transmission in magnocellular neurons of supraoptic nucleus, plasma vasopressin levels, and urine volume of male rats.
abstract: The activity of the magnocellular neurons (MCNs) of supraoptic nucleus (SON) is regulated by a variety of excitatory and inhibitory inputs. Opioids are one of the important compounds that affect these inputs at SON synapses. In this study, whole-cell patch clamp recording of SON neurons was used to investigate the effect of acute and repeated morphine administration on spontaneous inhibitory and excitatory post synaptic currents (sIPSCs and sEPSCs) in MCNs. While acute bath application of morphine to brain slice of intact rat produced an increase in sEPSCs frequency and a decrease in sIPSCs frequency, repeated in-vivo administration of morphine produced opposite effect. Moreover, repetitive i.c.v. administration of morphine for three consecutive days caused significant increase in urine volume, but had no significant alteration in water consumption compared to control group. The increase in urine volume was consistent with a significant decrease in plasma arginine vasopressin (AVP) levels after repetitive i.p. morphine administration. The results suggest that acute administration of morphine stimulates whereas repeated administration of morphine inhibits the MCNs. Morphine-induced MCN inhibition could result in diminished plasma AVP levels and eventually an increase in urine volume of rats.
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences. ; Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences. ; Department of Physiology, Faculty of Medicine, Army University of Medical Sciences.
authors.forename: Mitra
authors.initials: M
authors.lastname: Yousefpour
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences. ; Department of Pharmacology and Toxicology, Faculty of Pharmacy, Shahid Beheshti University of Medical Sciences.
authors.forename: Nima
authors.initials: N
authors.lastname: Naderi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Mansouri
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences. ; Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences.
authors.forename: Mahyar
authors.initials: M
authors.lastname: Janahmadi
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences.
authors.forename: Amir-Mohammad
authors.initials: AM
authors.lastname: Alizadeh
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences. ; Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences.
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Motamedi
keywords: Arginine vasopressin; Morphine; Supraoptic nucleus; Urine volume; sEPSC; sIPSC