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CENTRAL CHOLINE SUPPRESSES PLASMA RENIN RESPONSE TO GRADED HAEMORRHAGE IN RATS
Author(s) -
IsbilBuyukcoskun Naciye,
Ilcol Yesim O,
Cansev Mehmet,
Hamurtekin Emre,
Ozluk Kasim,
Ulus Ismail H
Publication year - 2008
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.2008.04978.x
Subject(s) - endocrinology , plasma renin activity , medicine , atropine , choline , mecamylamine , blood pressure , vasopressin , renin–angiotensin system , acetylcholine , chemistry , physostigmine , angiotensin ii , muscarinic acetylcholine receptor , receptor
SUMMARY1 Central administration of choline increases blood pressure in normotensive and hypotensive states by increasing plasma concentrations of vasopressin and catecholamines. We hypothesized that choline could also modulate the renin–angiotensin pathway, the third main pressor system in the body. 2 Plasma renin activity (PRA), which serves as an index of the function of the peripheral renin–angiotensin system, was determined in rats subjected to graded haemorrhage following central choline administration. 3 Intracerebroventricular (i.c.v.) injection of choline (12.5–150 µg), a precursor of the neurotransmitter acetylcholine (ACh), inhibited the increase in PRA in rats subjected to graded haemorrhage by sequential removal of 0.55 mL blood/100 g bodyweight. Choline, in the range 50–150 µg, increased blood pressure. 4 Intraperitoneal (i.p.) administration of 150 µg choline failed to alter blood pressure and plasma renin responses to graded haemorrhage. Administration of a higher dose (90 mg/kg, i.p.) of choline decreased blood pressure and enhanced PRA in the first two blood samples obtained during the graded haemorrhage. Physostigmine (10 µg, i.c.v.), ACh (10 µg, i.c.v.), carbamylcholine (10 µg, i.c.v.) and cytidine 5′‐diphosphocholine (CDP‐choline; 250 µg, i.c.v.) increased blood pressure and attenuated plasma renin responses to graded haemorrhage. 5 Inhibition of PRA by i.c.v. choline was abolished by i.c.v. pretreatment with mecamylamine (50 µg), but not atropine (10 µg). Blood pressure responses to choline (150 µg) were attenuated by pretreatment with both mecamylamine and atropine. 6 Inhibition of PRA in response to central choline administration was associated with enhanced plasma vasopressin and catecholamine responses to graded haemorrhage. Pretreatment of rats with a vasopressin antagonist reversed central choline‐induced inhibition of plasma renin responses to graded haemorrhage without altering the blood pressure response. 7 In conclusion, central administration of choline inhibits the plasma renin response to graded haemorrhage. Nicotinic receptor activation and an increase in plasma vasopressin appear to be involved in this effect.