Mechanism of delayed intracranial hypertension after cerebroventricular infusions in conscious rats.
Prior studies showed that cerebroventricular infusions of artificial cerebrospinal fluid, 8 microliter/min for 10 min, followed by a 10 min rest and a 24 h infusion of 0.5 microliters/min, raised cerebrospinal fluid pressure (CSFp) of conscious, unrestrained rats after about 2 h. Here, we report that the 10 min infusion alone evoked a delayed, prolonged rise in CSFp. Pressure during the infusion itself rose and recovered quickly, as is usually reported. Pressure/volume tests, used to calculate resistance to outflow (Ro) and compliance (C), revealed that infusions increased Ro and decreased C, after a delay (P less than 0.05). The rise in CSFp after infusion was blocked by pretreatment with acetazolamide + ouabain (P less than 0.05), but the delayed changes in Ro and C were unaffected. We suggest that the 10 min infusion of a sterile, balanced salt solution has a primary effect that increases Ro; as CSF synthesis continues, C is exhausted and the delayed rise in CSFp ensues. This non-traumatic method of raising CSFp may be a useful method to study intracranial fluid dynamics.
Morrow
B A
BA
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey 17033.
Holt
M R
MR
Starcevic
V P
VP
Keil
L C
LC
Severs
W B
WB
D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D002552:Cerebral Ventricles; D007263:Infusions, Parenteral; D007427:Intracranial Pressure / Q000187:drug effects / Q000502:physiology*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D010042:Ouabain; D000086:Acetazolamide