Peripheral magnesium sulfate enters the brain and increases the threshold for hippocampal seizures in rats.
OBJECTIVE
Our objectives were to determine whether magnesium sulfate crosses the blood-brain barrier and whether it has central anticonvulsant action.


METHODS
In experiment 1 34 female Long-Evans rats were divided into six groups: control (n = 7); single magnesium sulfate injection and evaluation after 20 minutes in 3 conditions: normal rats (n = 7), sham-operated animals (n = 5), and after electrical stimulation by hippocampal electrode (n = 5); single injection and evaluation after 2 hours (n = 5); and prolonged (2 hours) serum magnesium elevation (n = 5). Serum, cerebrospinal fluid, and specific brain areas were analyzed for magnesium concentrations. In experiment 2 threshold for electrical seizure was measured in eight rats before and after intraperitoneal injections of magnesium sulfate versus saline solution.


RESULTS
In experiment 1 there was a significant correlation between blood and cerebrospinal fluid magnesium concentrations (r = 0.80, p < 0.0001). Magnesium concentrations were increased in the cortex and hippocampus, with the largest changes occurring after two hours of sustained serum magnesium concentrations (p < 0.01). Induction of hippocampal seizure activity resulted in further elevations in cerebrospinal fluid magnesium concentrations but did not change brain concentrations. In experiment 2 magnesium sulfate increased the electrical threshold required to induce seizures by 34% (p = 0.01).


CONCLUSIONS
Magnesium sulfate enters the cerebrospinal fluid and brain and has a central anticonvulsant effect.
Hallak
M
M
Department of Obstetrics and Gynecology, Wayne State University/Hutzel Hospital, Detroit, MI 48201.
Berman
R F
RF
Irtenkauf
S M
SM
Evans
M I
MI
Cotton
D B
DB
D000818:Animals; D001921:Brain / Q000378:metabolism*; D004056:Differential Threshold / Q000187:drug effects; D004558:Electric Stimulation; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008278:Magnesium Sulfate / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012640:Seizures / Q000503:physiopathology*
D008278:Magnesium Sulfate