Royal jelly increased map-2 expression in hippocampal neurons of hypothyroid rats: an immunohistochemical study

We investigated microtubule-associated protein 2 (MAP-2) immunoreactivity of hippocampal neurons and the potential role of royal jelly (RJ) in regulating MAP-2 during experimental hypothyroidism (HT). Thirty adult female Wistar albino rats were randomized into five groups: the control group was untreated, the sham control group was treated with 10 mg/kg 0.9% sterile saline injected intraperitoneally (i.p.), The RJ group was treated with 100 mg/kg RJ by oral gavage, the HT group was treated with 10 mg/kg propylthiouracil (PTU) i.p. to induce experimental hypothyroidism, and the HT + RJ group was treated with 10 mg/kg PTU i.p. + 100 mg/kg RJ by oral gavage. Oral and i.p. administrations were performed once daily for 20 days. Thyroid stimulating hormone (TSH) and free thyroxine (fT4) levels in the serum were measured biochemically, MAP-2 was measured immunohistochemically in the hippocampus and an immunohistochemical H score was calculated. MAP-2 immunoreactivity appeared in the cytoplasm of neuron cell bodies and dendrites in the hippocampal CA3 and CA1 regions in the control, sham control and RJ groups. MAP-2 immunoreactivity decreased significiantly in the HT group compared to control, sham control and RJ groups. Also, vascular dilation and swollen cells were observed following PTU administration. The degeneration that was observed in the HT group decreased by RJ administration. By contrast, MAP-2 immunoreactivity increased following administration of RJ. Experimental hypothyroidism reduced significiantly MAP-2 immunoreactivity in both the CA3 and CA1 regions and caused degeneration, including edema and vascular dilation, in the hippocampus. RJ increased MAP-2 expression and exhibited a therapeutic effect on the degenerative changes.