Vasopressin and oxytocin: Modulators of neurohypophysial blood flow

P. D. Hurn, D. A. Wilson, R. B. Hansen, D. F. Hanley, R. J. Traystman

Research output: Contribution to journalArticle

Abstract

We examined the role of arginine vasopressin (AVP) as a mediator of neurohypophysial (NH) blood flow regulation in anesthetized dogs. First, we evaluated the NH hyperemia that occurs during hemorrhagic hypotension in the presence (n = 7) and absence (n = 7) of the selective AVP-V1 receptor antagonist [d(CH2)5Tyr(Me)]AVP. AVP-V1 blockade did not alter NH transient or steady-state flow responses to a standardized decrease to 80 mmHg mean arterial blood pressure. We then determined whether exogenous AVP alters NH and regional cerebral blood flow (CBF) (n = 8). Sequential intracarotid infusions resulted in sagittal sinus blood AVP concentrations ranging from 6.97 ± 3.3 x 103 to 2.45 ± 0.47 x 106 pg/ml. No change in NH blood flow (control 428 ± 162 vs. 487 ± 75 ml · min-1 · 100 g-1) was observed even at the highest blood level. However, CBF at the highest AVP level increased from a control value of 20 ± 3 to 40 ± 4 ml · min-1 · 100 g- 1, while cerebral oxygen consumption remained unchanged. Administration of a selective AVP-V1 receptor antagonist, [d(CH2)5-Tyr(Me)]AVP, blocked AVP- induced elevation in CBF in a third set of dogs (n = 5). Oxytocin was also given by intracarotid infusion at a constant rate (1-200 μg/ml) in a final group (n = 5). NH blood flow was unchanged at all doses, whereas CBF increased from control (24 ± 2 to 38 ± 5 ml · min-1 · 100 g-1) at the highest dose. We conclude that neither AVP nor oxytocin is an important regulator of blood flow in the neurohypophysis; however, both peptides exhibit dilator effects in other brain areas.

Original languageEnglish (US)
Pages (from-to)H2027-H2035
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number6 34-6
DOIs
StatePublished - 1993

Keywords

  • V receptor antagonist
  • arginine vasopressin
  • cerebral blood flow
  • neurohypophysis
  • oxytocin
  • pituitary blood flow

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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