Is alpha-chloralose plus halothane induction a suitable anesthetic regimen for cerebrovascular research?
The aim of this study was to determine whether alpha-chloralose, when associated with an initial period of halothane, is a suitable anesthetic regimen for cerebrovascular studies. For this purpose, rats anesthetized with alpha-chloralose plus halothane induction were first subjected to noxious stimuli, and the behavior, EEG and systemic variables were recorded. During a second step, cortical blood flow was measured with laser-Doppler flowmetry and the time-course of the cerebrovascular reactivity to hypercapnia were measured in artificially ventilated rats anesthetized with either alpha-chloralose (40 mg.kg-1, s.c.) plus halothane induction (1.5% given during the first 45-60 min) or halothane alone (1.5%). Finally, an experimental paradigm was developed that allowed the comparison of the hypercapnic reactivity, both in awake and anesthetized conditions in the same animal. Our results show that the association of alpha-chloralose with halothane leads to stable cardiovascular parameters and immobility of ventilated rats, placed in ear bars without curare, for 3 h without any sign of discomfort. Based on EEG criteria, we found that halothane induction lengthens the duration of alpha-chloralose anesthesia (253 +/- 19 vs. 200 +/- 15 min, P < 0.01). Under alpha-chloralose alone or in association with halothane induction, the vascular reactivity to hypercapnia was considerably impaired (-85% compared to the awake state, P < 0.01), but this impairment was transient, since a control reactivity was restored 150-190 min after induction of anesthesia. Under halothane alone, the vascular reactivity remained reduced throughout the experiment. These results provide evidence that alpha-chloralose plus halothane induction is a suitable anesthetic regimen which displays a temporal window of normal cerebrovascular reactivity.
Bonvento
G
G
Laboratoire de Recherches Cérébrovasculaires, CNRS UA 641, Faculté de Médecine Lariboisière-Saint Louis, Université Paris, VII France.
Charbonné
R
R
Corrèze
J L
JL
Borredon
J
J
Seylaz
J
J
Lacombe
P
P
D000758:Anesthesia; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D002698:Chloralose; D004594:Electrophysiology; D006221:Halothane; D006935:Hypercapnia / Q000503:physiopathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012106:Research; D012121:Respiration, Artificial
D002245:Carbon Dioxide; D002698:Chloralose; D006221:Halothane