Hyperbaric oxygen for nitric oxide synthase-positive neurons of rats following cerebral ischemia/reperfusion injury

Yizhan CAO; Xing JIN; Qing ZHA; Boliang WANG; Yuexia ZHONG; Guoqiang FU; Baojian HE

ABSTRACT

BACKGROUND:

Nitric oxide (NO) plays an important role in the ischemic brain injury, and hyperbaric oxygen (HBO) can improve ischemia/reperfusion (I/R)-caused nerve injury. Whether the effect of HBO is associated with NO? Its mechanism needs to be further investigated.

OBJECTIVE:

To observe the changes of expression of nitric oxide synthase (NOS)-positive neurons of rats following acute focal cerebral I/R injury and HBO treatment.

DESIGN:

Randomized controlled animal experiment.

SETTING:

Department of Emergency, Tangdu Hospital, Fourth Military Medical University of Chinese PLA; Department of Laboratory Medicine, Xi'an Gaoxin Hospital; The General Hospital of the Air Force of Chinese PLA.MATERIALS Sixty-six healthy male Sprague-Dawley rats were chosen and randomized into 5 groups sham-operation group (n =5), sham-operation +HBO treatment group (n =5), model group (n =28), modeling +HBO treatment group (n =28). Ischemia 5,12, 24 and 72 hours four time points were set in the later 2 groups, 7 rats at each time point.

METHODS:

①Rats in the model group and modeling+ HBO treatment group were created into models of middle cerebral artery ischemia according to the method from Koizum. Then, an embolus was inserted for ischemia; One hour later, the embolus was drawn out. Inserting embolus was omitted in the other two groups.②Rats in the sham operation + HBO treatment group and modeling + HBO treatment group were placed in HBO chamber at ischemia 2, 9, 21, 45 and 69 hours, separately, and given HBO treatment for 1 hour (0.25 MPa absolute pressure).MAIN OUTCOME

MEASURES:

The rats in each group were sacrificed at corresponding time points, and their brains were harvested. The distribution and morphology of NOS positive cells in cortical area, preoptic area, lateral and medial corpora striata of infarct region at the level of optic chiasma were observed with nicotinamide-adenine dinucleotide phosphate -diaphorase (NADPH-d) histochemical method.

RESULTS:

After supplement, 66 rats were involved in the final analysis. ①After ischemia, NOS-positive neurons changed in morphology, mainly presenting prominences were reduced or disappeared, neurons changed from ellipse or triangle into global shape, and shrank; Body of neuron darkly dyed; Both nucleus and cytoplasm were deeply dyed into dark blue; NOS-positive neurons with changed morphology were mostly in lateral corpora striatum, followed by preoptic area and medial corpora striatum, and those in the cortical area were few. NOS-positive neurons with changed morphology were not found in the sham-operation group and sham-operation + HBO treatment group. ②In the model group, NOS-positive neurons with changed morphology were increased with elongation of I/R time. At each time point, NOS-positive neurons in cortical area, preoptic area and medial corpora striatum in modeling + HBO treatment group were less than those in model group, but NOS-positive neurons in two groups both reached their peaks at ischemia 72 hours [Cortical area (15.46±3.02) vs.(30.52±4.73)/visual field; Preoptic area(28.56±4.05) vs. (68.81±7.84)/visual field; medial corpora striatum(21.09±3.83) vs.(45.71±5.24)/visual field; all P＜0.01].

CONCLUSION:

HBO obviously inhibits the degeneration of NOS-positive neurons in acute focal cerebral I/R injury regions of rats, such as cortical area, preoptic area, medial corpora striatum, and so on