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Central acetylcholinesterase inhibition improves hemodynamic counterregulation to severe blood loss in alcohol-intoxicated rats

Department of Physiology and Alcohol and Drug Abuse Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana

Submitted 24 March 2009 ; accepted in final form 3 June 2009

Acute alcohol intoxication results in impaired hemodynamic counterregulation to blood loss and is associated with an attenuated hemorrhage-induced release of catecholamines and AVP. We speculated that restoration of the neuroendocrine response to hemorrhage would improve mean arterial blood pressure (MABP) recovery during acute alcohol intoxication. Previously, we demonstrated that intracerebroventricular (ICV) choline, a precursor of acetylcholine, transiently increases sympathetic nervous system (SNS) outflow but is not capable of improving neuroendocrine and hemodynamic compensation to hemorrhage in alcohol-treated rats. We hypothesized that prolongation of the observed effect via ICV neostigmine, an acetylcholinesterase inhibitor, would enhance SNS outflow, restore the neuroendocrine response, and in turn improve hemodynamic responses to hemorrhage during acute alcohol intoxication. ICV neostigmine (1 µg) increased MABP, catecholamines, and AVP within 5 min and reversed hypotension due to 40% hemorrhage and intragastric alcohol (30% wt/vol, 2.5 g/kg) administration in chronically catheterized male Sprague-Dawley rats (225–250 g body wt). Acute alcohol intoxication before 50% hemorrhage decreased basal MABP, accentuated hypotension midhemorrhage, suppressed the hemorrhage-induced release of norepinephrine and AVP, and prevented restoration of MABP to basal levels after fluid resuscitation with lactated Ringer solution. ICV neostigmine (0.5 µg) produced a sustained increase in MABP beginning at 30 min of hemorrhage that persisted throughout fluid resuscitation in control and alcohol-treated animals. ICV neostigmine enhanced epinephrine responses and restored the hemorrhage-induced release of norepinephrine and AVP in alcohol-treated rats. These results demonstrate that inhibition of acetylcholinesterase in the central nervous system enhances SNS outflow, restores the neuroendocrine response to severe blood loss, and thereby improves hemodynamic counterregulation during acute alcohol intoxication. This study provides evidence for a central (and not peripheral) role of alcohol in impairing hemodynamic stability during hemorrhagic shock.

ethanol; mean arterial blood pressure; sympathetic nervous system