title: Impaired sodium-evoked paraventricular nucleus neuronal activation and blood pressure regulation in conscious Sprague-Dawley rats lacking central Gαi2 proteins.
abstract: OBJECTIVE
  We determined the role of brain Gαi2 proteins in mediating the neural and humoral responses of conscious male Sprague-Dawley rats to acute peripheral sodium challenge.
  
  
  METHODS
  Rats pre-treated (24-h) intracerebroventricularly with a targeted oligodeoxynucleotide (ODN) (25 μg per 5 μL) to downregulate brain Gαi2 protein expression or a scrambled (SCR) control ODN were challenged with an acute sodium load (intravenous bolus 3 m NaCl; 0.14 mL per 100 g), and cardiovascular parameters were monitored for 120 min. In additional groups, hypothalamic paraventricular nucleus (PVN) Fos immunoreactivity was examined at baseline, 40, and 100 min post-sodium challenge.
  
  
  RESULTS
  In response to intravenous hypertonic saline (HS), no difference was observed in peak change in mean arterial pressure between groups. In SCR ODN pre-treated rats, arterial pressure returned to baseline by 100 min, while it remained elevated in Gαi2 ODN pre-treated rats (P < 0.05). No difference between groups was observed in sodium-evoked increases in Fos-positive magnocellular neurons or vasopressin release. V1a receptor antagonism failed to block the prolonged elevation of arterial pressure in Gαi2 ODN pre-treated rats. A significantly greater number of Fos-positive ventrolateral parvocellular, lateral parvocellular, and medial parvocellular neurons were observed in SCR vs. Gαi2 ODN pre-treated rats at 40 and 100 min post-HS challenge (P < 0.05). In SCR, but not Gαi2 ODN pre-treated rats, HS evoked suppression of plasma norepinephrine (P < 0.05).
  
  
  CONCLUSIONS
  This highlights Gαi2 protein signal transduction as a novel central mechanism acting to differentially influence PVN parvocellular neuronal activation, sympathetic outflow, and arterial pressure in response to acute HS, independently of actions on magnocellular neurons and vasopressin release.
authors.affiliation: Department of Pharmacology & Experimental Therapeutics and the Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA.
authors.forename: C Y
authors.identifier: http://orcid.org/0000-0003-2917-4138
authors.initials: CY
authors.lastname: Carmichael
authors.affiliation: Department of Pharmacology & Experimental Therapeutics and the Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA.
authors.forename: A C T
authors.initials: AC
authors.lastname: Carmichael
authors.affiliation: Department of Pharmacology & Experimental Therapeutics and the Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Kuwabara
authors.affiliation: Department of Integrative Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Cunningham
authors.affiliation: Department of Pharmacology & Experimental Therapeutics and the Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Wainford
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003243:Consciousness; D004797:Enzyme-Linked Immunosorbent Assay; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000502:physiology*; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000097:blood
chemical_list: D012964:Sodium; D051960:GTP-Binding Protein alpha Subunit, Gi2
keywords: Gα-subunit proteins; blood pressure regulation; central nervous system; paraventricular nucleus; sodium