[Changes in Mg++ concentration of CSF after subarachnoid hemorrhage and Mg++--effects on the contractions of bovine cerebral artery].

Fifteen patients with subarachnoid hemorrhage (SAH) were divided into two groups; eight patients exhibiting vasospasm (VS) (VS-group), and another seven patients exhibiting no vasospasm (NS-group) during a period of 2-3 weeks after the occurrence of hemorrhage. The cerebrospinal fluid (CSF) of the patients in the VS-group demonstrated a slight but significant decrease in [Mg++] from 1.15 to 0.95 mM on the 6-8th day after the hemorrhage, whereas CSF in the NS-group showed no significant change in [Mg++]. CSF [Ca++] remained relatively unchanged in both groups. The decrease in CSF [Mg++] in the VS-group was not associated with a decrease in [Mg++] in their blood. Probably, it was due to local derangement of the blood-CSF barrier near the site of the actual hemorrhage. Whether or not such a small decrease in CSF [Mg++] could actually influence the occurrence of vasospasm was examined experimentally in vitro. Using helical strips of the bovine middle cerebral arteries, the changes in muscular tension during isometric contraction were recorded on the polygraph. Generally the vascular contractions induced by High K+ (4 X 10(-2) M), PGF2 alpha (10(-6) M), and Oxy-hemoglobin (Oxy-Hb, 3 X 10(-6) M) were augmented when [Mg++] of the perfusing media was reduced from 1.2 to 0.9 mM, and depressed when [Mg++] was increased to 2.4 mM. In descending order, a greater effect of [Mg++] was seen in Oxy-Hb-, and in High K+-, and PGF2 alpha-induced contractions.(ABSTRACT TRUNCATED AT 250 WORDS)