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.
Department of Pharmacology, College of Medicine, Pennsylvania State University, Hershey.
B A
BA
Morrow
V P
VP
Starcevic
L C
LC
Keil
W B
WB
Severs
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