The effect of magnesium deficiency on volatile anaesthetic requirement in the rat: the role of central noradrenergic neuronal activity.
Volatile anaesthetic minimum alveolar concentration (MAC, a measure of anaesthetic requirement) increased in a time-dependent manner in rats fed a Mg2+-deficient diet. MAC values in hypomagnesemic rats were 22-30 per cent greater than those in age-matched controls at 12 and 17 days after starting the diet (p < 0.01). Noradrenergic neuronal activity, as assessed from the ratio of the concentration of 3,4-dihydroxyphenylethylene-glycol (DHPG) to that of norepinephrine (NE), decreased in the brain stem and cerebrum-cerebellum in hypomagnesemic rats owing to an increase in NE concentration in both regions of the brain (p < 0.025). We conclude that prolonged hypomagnesemia (> or = 12 days) increases volatile anaesthetic MAC in the rat. The concomitant decrease in the ratio of DHPG/NE suggests that this increase in MAC cannot be attributed to an increase in noradrenergic neuronal activity in brain.
Thomas
M L
ML
Department of Anaesthesia, The Hospital for Sick Children, Toronto, Ontario. Canada.
Crawford
M W
MW
Shams
M
M
Gow
R
R
Carmichael
F J
FJ
D018685:Anesthetics, Inhalation / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D004032:Diet; D006221:Halothane / Q000378:metabolism*; D008275:Magnesium Deficiency / Q000378:metabolism*; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives* / Q000378:metabolism; D008738:Methyl Ethers / Q000378:metabolism*; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077149:Sevoflurane; D013997:Time Factors
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D008734:Methoxyhydroxyphenylglycol; C010117:3,4-dihydroxyphenylglycol; D006221:Halothane; D009638:Norepinephrine