Neuronal nitric oxide synthase immunopositivity in motoneurons of the rabbit's spinal cord after transient ischemia/reperfusion injury

Abstract

1. Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. To evaluate the role of nitric oxide (NO) in the pathophysiology of the spinal cord ischemia, the expression of neuronal nitric oxide synthase (nNOS) in the motoneurons of the lumbosacral spinal cord was examined in the rabbit model of transient abdominal aorta occlusion. 2. The aim of the present study was to find if there is any consensus between the duration of transient abdominal aorta occlusion, nNOS positivity of the motoneurons and neurological hind limb impairment. 3. According to the degree of neurological damage (i.e., from the group with almost no sign of damage to a group with fully developed paraplegia), the experimental animals were divided into three groups. The respective spinal cord segments of each experimental group were compared to the control group. 4. Spinal cord ischemia (15 min) was induced by Fogarty arterial embolectomy catheter occlusion of abdominal aorta with a reperfusion period of 7 days. On seventh day, the sections of lumbosacral segments were immunohistochemically treated and L1-L7, and S1-S2 segment sections were monitored using light microscopy.

Fig. 1.

Representative microphotographs showing the changes of the nNOS immunopositivity in the ventral horn of L4 segments of the spinal cord after ischemia/reperfusion injury. (A) Control group; nNOS immunonegativity in the ventral horn (VH); we can see a very high nNOS immunopositivity in the neurons (arrowheads) around the central canal (CC) in the lamina-X. (B) Experimental group A1; ventral horn (VH); central canal (CC). (C) Experimental group A2; ventral horn (VH); central canal (CC); arrowhead points to nNOS immunopositive motoneuron. (D) Experimental group A3; ventral horn (VH); canal central (CC); arrowheads point to nNOS immunopositive motoneurons. Scale bar=200 μm in (A)–(D).

Fig. 2.

Representative microphotographs showing the changes of the nNOS immunopositivity in the ventral horn of S1 segments after ischemia/reperfusion injury. (A) Control group; ventral horn (VH); arrowheads point to nNOS immunonegative motoneurons. (B) Experimental group A1; ventral horn (VH); arrowheads point to nNOS immunopositive motoneurons. (C) Experimental group A2; ventral horn (VH); arrowheads point to nNOS immunopositive motoneurons. (D) Experimental group A3; ventral horn (VH); necrotic matrix (NM); *penumbra. Scale bar=200 μm in (A)–(D).

Fig. 3.

Representative microphotograph and optical density of nNOS immunopositivity. (A) nNOS immunopositive motoneuron in the L7 segment (A2-experimental group). Bar=100 μm. (B) The densitogram demonstrating the nNOS immunopositivity of the motoneuron (mean=155; SD=9.03). Inset (a) is enlarged in (B), including densitometry.

Fig. 4.

Representative microphotograph and optical density of nNOS immunopositivity. (A) nNOS immunopositive motoneuron in the L7 segment (C-control group). Bar=100 μm. (B) The densitogram demonstrating the nNOS immunopositivity of the motoneuron (mean=183; SD=10.62). Inset (a) is enlarged in (B), including densitometry.