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Alpha 2 adrenergic receptors mediate increased venous tone following 5‐HT1A‐receptor agonist administration in rats subjected to hypovolemic shock
Author(s) -
Tiniakov Ruslan,
Scrogin Karie
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a773-a
Subject(s) - mean circulatory filling pressure , saline , agonist , 8 oh dpat , medicine , endocrinology , anesthesia , blood pressure , chemistry , receptor , central venous pressure , heart rate , 5 ht receptor , serotonin
Previously, we found that ganglionic blockade prevented the 5‐HT 1A ‐receptor agonist, 8‐OH‐DPAT, from raising venous tone in rats subjected to circulatory shock. Here we tested whether α 2 ‐adrenergic receptors mediate this increase in venous tone. Blood pressure (BP) and mean circulatory filling pressure (MCFP) were measured during sustained hypotensive hemorrhage (50 mm Hg for 30 min) and subsequent injection of 8‐OH‐DPAT (30 nmol/kg, iv) or saline. Each group was pre‐treated with the α 2 ‐adrenergic receptor antagonist, L‐659,066 (100 mg/kg, iv) or saline, 10 min prior to 8‐OH‐DPAT or vehicle. 8‐OH‐DPAT raised BP to a greater extent than saline (+42 ± 3 vs. +13 ± 4 mm Hg, 35 min after injection, *P <0.05). 8‐OH‐DPAT also raised MCFP (3.2 ± 0.7*, 3.0 ±0.5*, 3.2 ±0.5*, 3.7 ±0.6* mm Hg, 5, 15, 25 and 35 min after injection, *P<0.05 vs. saline), while saline had no effect (1.5 ± 0.4, 1.6 ± 0.3, 1.9 ± 0.4, 1.4 ± 0.4 mm Hg). L‐659.066 alone attenuated recovery of BP (49 ± 11 vs. 69 ± 4 mm Hg, 35 min after injection, P<0.05) and lowered MCFP (0.8 ± 0.3* 0.9 ± 0.3*, 0.7 ± 0.5* mmHg, *P<0.05) compared to saline‐treated rats. L‐659,066 also attenuated the pressor effect of 8‐OH‐DPAT (+42 ± 3 vs. +13 ± 9 mmHg, for saline and L‐659,066‐treated groups respectively, 35 min post‐injection, P<0.01) and abolished the effect of 8‐OH‐DPAT on MCFP (0.9 ± 0.3*, 1.1 ± 0.4*, 1.1 ± 0.4*, 0.5 ± 0.4* mm Hg vs. 8‐OH‐DPAT alone). We conclude that 5‐HT 1A ‐receptor agonists increase venous tone in rats subjected to circulatory shock, in part, by sympathetic‐mediated activation of peripheral α 2 ‐adrenergic receptors. Supported by HL 076162 and 072354.