Prophylactic effect of intranasal oxytocin on brain damage and neurological disorders in global cerebral ischemia in mice

Abstract

Objectives: A few experimental studies have shown the therapeutic effects of oxytocin on focal cerebral ischemia. In this study, the prophylactic effect of intranasal oxytocin on brain damage was investigated in a cerebral ischemic model.

Materials and methods: Intranasal oxytocin (8 IU/per mouse) was prescribed daily for one week. Cerebral ischemia was performed through bilateral common carotid artery occlusion (BCCAO) for 20 min and then blood flow was restored for 24 hr. Finally, neurological disorders, spatial learning and memory, neuronal death, and neuronal apoptosis were assessed in CA1, CA3, and dentate gyrus. Also, levels of interleukin-1β (IL-1β) and Tumor necrosis factor-alpha (TNFα) were measured in the hippocampus.

Results: Induction of global ischemia leads to neurological disorders and impairment of spatial learning and memory that are improved by pre-treatment with oxytocin (P<0.01). Cresyl violet staining showed that pretreatment with oxytocin significantly reduced the number of dead nerve cells in CA1, CA3, and dentate gyrus by 40.7, 32, and 34.3%, respectively. Also, positive TUNEL cells in CA1, CA3, and dental gyrus decreased by 15, 30, and 27%, respectively. In addition, levels of TNFα and IL-1β, which were extensively increased in ischemic mice, were significantly reduced with oxytocin pre-treatment.

Conclusion: Pre-treatment of oxytocin reduces ischemic damage and improves neurological function and spatial memory. The neuroprotective effect of oxytocin is mediated by a decrease in cell death, apoptosis, and inflammatory mediators TNFα and IL-1β. Pre-treatment with oxytocin may be useful in people who are prone to stroke.

Keywords: Apoptosis; Interleukin-1β; Oxytocin; Stroke; Tumor necrosis factor.

Figure 1

Pretreatment effect of intranasal oxytocin (8 IU/per mouse) on neurological disorder scores in the sham, ischemic, and oxytocin groups. ***P<0.001, compared with the ischemic group

Figure 2

Pretreatment effect of intranasal oxytocin (8 IU/per mouse) on spatial learning and memory. Escape latency (sec) in 4-day (D4) training in the radial arm water maze (A), the proximity (cm) to the platform (B), time (sec) to find the platform location (C), and time spent in the target zone (D) in sham, ischemic, and oxytocin groups. * P<0.05, ** P<0.01 compared with sham. # P<0.05, ## P<0.01 compared with ischemic groups

Figure 3

The photomicrograph (top) shows the pretreatment effect of intranasal oxytocin (8 IU/per mouse) on the percent of dead cells in CA1, CA3, and DG in sham, ischemic, and oxytocin groups identified in cresyl violet staining. A quantitative analysis of the percentage of dead cells is also shown in the diagram (below). ***P<0.001 and **P<0.01 compared with sham. ## P<0.01 and # P<0.05 compared with ischemic groups

Figure 4

Photomicrograph (top) shows the effect of intranasal intranasal oxytocin (8 IU per mouse) on the number of apoptotic cells in CA1, CA3, and DG in sham (A), ischemic (B), and oxytocin (C) groups identified in TUNEL staining. A quantitative analysis of the percentage of TUNEL-positive cells is also shown in the diagram (below). TUNEL-positive cells (green) were expressed as a percentage of the total number of DAPI-stained nuclei (blue) (400×fluorescent microscope). ***P<0.001 compared with sham. ## P<0.01 and # P<0.05 compared with ischemic groups

Figure 5

Photograph shows the effect of intranasal intranasal oxytocin (8 IU/per mouse) on levels of TNF-α and IL-1β (Western blotting) in sham, ischemic, and oxytocin groups. Quantitative analysis shows (A) TNF-α/GAPDH and (B), IL-1β/GAPDH in the brain tissue. ***P<0.001 compared with the sham group. ### P<0.001 compared with the ischemic group