title: Angiotensin type 2 receptors in the intermediolateral cell column of the spinal cord: negative regulation of sympathetic nerve activity and blood pressure.
abstract: BACKGROUND
  Our previous study demonstrated that AT2R in brainstem nuclei participated in the regulation of sympathetic outflow and cardiovascular function. However, the functional significance of AT2R in the intermediolateral cell column (IML) of the thoracic spinal cord in normal rats remains elusive. We hypothesized that AT2R activation in the IML exerts a sympatho-inhibitory effect.
  
  
  RESULTS
  Using Western-blot analysis, immunohistochemical staining and quantitative real-time PCR, both AT1R and AT2R expressions were detected in the spinal cord. The highest AT2R protein expression was found in the IML, while AT1R expression didn't display regional differences within the gray matter. Microinjection of Ang II into the IML dose-dependently elevated mean blood pressure (MAP, employing a transducer-tipped catheter) and renal sympathetic nerve activity (RSNA, using a pair of platinum-iridium recording electrodes), which were completely abolished by Losartan, and attenuated by TEMPOL and apocynin. Activation of AT2R in the IML with CGP42112 evoked hypotension (ΔMAP: -21 ± 4 mmHg) and sympatho-inhibition (RSNA: 73 ± 3% of baseline), which were completely abolished by PD123319 and l-NAME. Blockade of AT2R in the IML with PD123319 significantly increased MAP (11 ± 1 mmHg) and sympathetic nerve activity (RSNA: 133 ± 13% of baseline). Moreover, PD123319 significantly enhanced the Ang II induced pressor response. Furthermore, in isolated IML neurons, CGP42112 treatment augmented potassium current and decreased resting membrane potential by employing whole-cell patch clamp.
  
  
  CONCLUSIONS
  In the normal condition, AT2R in the IML tonically inhibits sympathetic activity through an NO/NOS dependent pathway and subsequent potassium channel activation.
authors.affiliation: Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Chao
authors.forename: Juan
authors.initials: J
authors.lastname: Gao
authors.forename: Karma-Jaya K
authors.initials: KJ
authors.lastname: Parbhu
authors.forename: Lie
authors.initials: L
authors.lastname: Gao
mesh_terms: D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology*; D000804:Angiotensin II / Q000494:pharmacology; D057912:Angiotensin II Type 2 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044139:Receptor, Angiotensin, Type 2 / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
chemical_list: D057912:Angiotensin II Type 2 Receptor Blockers; D007093:Imidazoles; D011725:Pyridines; D044139:Receptor, Angiotensin, Type 2; D000804:Angiotensin II; C073402:PD 123319
keywords: Angiotensin type 1 receptor; Angiotensin type 2 receptor; Arterial blood pressure; Intermediolateral cell column; Renal sympathetic nerve activity