S. Cavun et Wr. Millington, Evidence that hemorrhagic hypotension is mediated by the ventrolateral periaqueductal gray region, AM J P-REG, 281(3), 2001, pp. R747-R752
Citations number
44
Categorie Soggetti
Physiology
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
Severe hemorrhage lowers arterial pressure by suppressing sympathetic activ
ity. This study tested the hypothesis that the decompensatory phase of hemo
rrhage is mediated by the ventrolateral periaqueductal gray (vlPAG), a regi
on importantly involved in the autonomic and behavioral responses to stress
and trauma. Neuronal activity in the vlPAG was inhibited with either lidoc
aine or cobalt chloride 5 min before hemorrhage (2.5 ml/100 g body wt) was
initiated in conscious, unrestrained rats. Bilateral injection of lidocaine
(0.5 mul of a 2% or 1 mul of a 5% solution) into the caudal vlPAG delayed
the onset and reduced the magnitude of the hypotension produced by hemorrha
ge significantly. In contrast, inactivation of the dorsolateral PAG with li
docaine was ineffective. Cobalt chloride (5 mM; 0.5 mul), which inhibits sy
naptic transmission but not axonal conductance, also attenuated hemorrhagic
hypotension significantly. Microinjection of lidocaine or cobalt chloride
into the vlPAG of normotensive, nonhemorrhaged rats did not influence cardi
ovascular function. These data indicate that the vlPAG plays an important r
ole in the response to hemorrhage.