Propofol Causes Consciousness Loss by Affecting GABA-A Receptor in the Nucleus Basalis of Rats

Objective. Propofol is a classical anesthetic and induces consciousness loss, and gamma-aminobutyric-acid-type-A (GABA-A) receptor is its target. Righting reflex is associated with conscious response. The nucleus basalis (NB) acts as a major relay between the reticular activating system and the frontal cortex (FC). Propofol may mediate righting reflex by affecting GABA-A receptor in NB. Methods. Fifty male SD rats (250-350？g) were divided into parts I and II. In part I, 20 male SD rats were randomly divided into control group (CG) and NB-lesion group (NG, ibotenic acid-induced NB lesion). In part II, 30 male SD rats were treated with saline (0.9% NaCl, SG group), muscimol (a GABA-A receptor agonist, MG group), and gabazine (a GABA-A receptor antagonist, GG group) in NB, respectively. Two weeks later, the activity of the rats was measured between CG and NG groups. The rats were intravenously injected with propofol (50？mg/kg/h) to test the time of loss of righting reflex (LORR) in all rats. When LORR occurred, the rats received single administration of propofol (12？mg/kg) to measure the time of return of righting reflex (RORR). Electroencephalogram (EEG) activity of the frontal cortex (FC) was recorded. Results. The numbers of NB neurons were reduced by 44% in the NG group compared to the CG group ( ) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant ( ). The dose-response curve of propofol shifted to the left in the NG group, and the statistical difference for the time of LORR was insignificant between the two groups ( ). However, the time of RORR and FC delta power increased in the NG group compared with the CG group ( ). In part II, the time of RORR and FC powder increased in the MG group when compared to the SG group while reverse results were observed in the GG group ( ). There was no significant influence on the time of LORR and ED50 among the three groups ( ). Conclusions. The unilateral NB lesion increased the recovery time and FC delta power, and the NB region might be involved in the emergence after propofol administration. Propofol plays a crucial role for causing conscious loss by affecting GABA-A receptor in NB