Effect Of Low Doses Of Naloxone Combined With Ephedrine On Motor Recovery And Neural Plasticity After Cerebral Ischemia In Rats

Objective:Through dynamic observation on motor function after cerebral ischemia/reperfusion in rats, the effect of low doses of naloxone combined with ephedrine on animals'motor function recovery was investigated. Meanwhile, through detection of GAP-43,SYP and MAP2 in the cortex peripheral to ischemic focus, the molecular mechanism by which ephedrine accelerates motor function recovery was further investigated, so as to provide theoretical basis for clinical selection of drugs for the rehabilitative treatment of cerebral embolism.Methods:SD rats (clean grade) were used to prepare middle cerebral artery occlusion (MCAO) models by using modified Longa ligation. Rats were subjected to 2h ischemia followed by reperfusion. Rats were randomized to the sham-operated group, the spontaneous recovery group, the ephedrine group, the naloxone+ephedrine group, and the naloxone group. 1, 2, 3, and 4 weeks after the operation, beam walking test was performed to evaluate motor function improvement. Ischemic brain tissue was microscopically observed dynamically. Apoptotic cells were observed by TUNEL. GAP-43,SYP and MAP2 protein expression profile was observed immunohistochemically and densitometrically in the peripheral of the ischemic focus.Results:⑴Beam walking tests indicated that in terms of the score-time curve, the ephedrine group was left to the naloxone group and the spontaneous recovery group, while the naloxone+ephedrine group was left to the ephedrine group , demonstrating that the rehabilitation speed was higher in the ephedrine group than that in the spontaneous recovery group, and was even higher in the naloxone+ephedrine group than that in the ephedrine group.⑵TUNEL:The positive cells significantly increased around ischemia area at 1 week then decreased gradually. Apoptosis reduced evidently in the group treated with ephedrine compared with spontaneous recovery group at different weeks(P<0.05), while the positive cells in the naloxone+ephedrine group was more less than that in the ephedrine group (P<0.05). There was no significant difference between the naloxone group and the spontaneous recovery group (P>0.05).⑶GAP-43 immunoreactive stains reached a peak at week 1, and began to reduce since week 2. At week 4, there were no significant differences between the spontaneous recovery group and the sham-operated group (P>0.05). Densitometric determination demonstrated that at three time points, GAP-43 in the ephedrine group was higher than that in the spontaneous recovery group (P<0.05), while GAP-43 in the naloxone+ephedrine group was even higher than that in the ephedrine group (P<0.05), but there was no significant difference between the naloxone group and the spontaneous recovery group (P>0.05).⑷The SYP expression reached a peak at week 2. Densitometric determination demonstrated that at all time points, the SYP expression was higher in the ephedrine group than that in the spontaneous recovery group (P<0.05), while the SYP expression was higher in the naloxone+ephedrine group than that in the ephedrine group (P<0.05), but there was no significant difference between the naloxone group and the spontaneous recovery group (P>0.05).⑸MAP2 immunoreactive stains reached a peak at week 2 and then decreased. At week 4, there were no significant differences between the spontaneous recovery group and the sham-operated group (P>0.05). Densitometric determination demonstrated that the MAP2 immunoreactive density was higher in the ephedrine group than that in the naloxone group and the spontaneous recovery group at three time points (P<0.05), while the MAP2 immunoreactive density was higher in the naloxone+ephedrine group than in the ephedrine group (P<0.05), but there was no significant difference between the naloxone group and the spontaneous recovery group (P>0.05).Conclusions:Our previous studies have demonstrated that the adrenotrophic ephedrine may promote motor function recovery after cerebral ischemia in rats and upregulate the expression of specific neural proteins, such as GAP-43, SYP, and MAP2. However, the combined use of low doses of naloxone and ephedrine may exert synergistic action, enhance the efficacy of ephedrine, further upregulate the expression of GAP-43, SYP, and MAP2 proteins, thus accelerating the formation of neonatal synapses. The study furtherly confirms that to enhance the expression of molecules responsible for cerebral neural remodeling and structural reconstruction is one of the mechanisms by which ephedrine promotes neural rehabilitation.