Dexamethasone and ergonovine effects on cerebrospinal fluid pressure in conscious rats.
Prior work showed that intracerebroventricular (i.c.v.) infusions of artificial cerebrospinal fluid (aCSF), at a rate of 8 microliters/min x 10 min, elevated CSF pressure (CSFp) of conscious rats after a 2-hour delay. The rise was associated with an increased resistance to outflow and decreased intracranial compliance. When maintained by a continuous infusion of 0.25 microliter/min into each lateral ventricle, CSFp recordings can be made for 24 h and a higher CSFp occurs. Here, we pretreated rats with ergonovine or dexamethasone to determine their effects on the delayed CSFp rise. Ergonovine (0.5 mg/kg i.p.) pretreatment, in a 6-hour protocol using only the 10-min infusion, slightly reduced CSFp (p < 0.05, one-tail test) but the time course of the delayed rise in CSFp was unchanged (p > 0.05). Ergonovine increased intracranial compliance (p < 0.05) 20 min after infusion when CSFp was normal, but not when CSFp was elevated at 4 h (p > 0.05). Dexamethasone (40 micrograms i.m.) pretreatment was tested in the 24-hour protocol. It reduced (p < 0.05) normal CSFp during the 2-hour lag after infusion and the CSFp rise was reduced (p < 0.05) for about 8 h. However, the time course and ending CSFp were unchanged (p > 0.05). Thus, prior cerebral vasoconstriction or a steroidal anti-inflammatory drug have partial efficacy in reducing CSFp, but do not prevent the unknown events that precede the delayed CSFp rise after i.c.v. infusions.
Morrow
B A
BA
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey.
Starcevic
V P
VP
Keil
L C
LC
Severs
W B
WB
D000818:Animals; D002555:Cerebrospinal Fluid / Q000502:physiology; D015170:Cerebrospinal Fluid Pressure / Q000187:drug effects*; D003243:Consciousness; D003907:Dexamethasone / Q000494:pharmacology*; D004874:Ergonovine / Q000494:pharmacology*; D007263:Infusions, Parenteral; D007274:Injections, Intraperitoneal; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D003907:Dexamethasone; D004874:Ergonovine