Fig. 6. TEM analysis of the hippocampal cellular and synaptic ultrastructure from P7 rats. (A) Symmetrical synapses (blue arrows) enriched with multiple SVs are visible in the control group. Scale bar=1 μm. (B) Nucleus with intact nuclear envelop and increased heterochromatin agglutination is evident in the P2 group (propofol 30 mg/kg; 8 h). Details in the rectangle are shown in C. Scale bar=2 μm. (C) Local dimpled appearance (red arrows), with obviously diminished organelles. Decreased mitochondrial crista and vacuolation, M. Golgi apparatus, G. (D) In the D1 group (dexmedetomidine, DEX 1 μg/kg), heterochromatin is well distributed among the nuclei of astrocytes (Ast, light purple), and within the dark-stained filaments in the cytoplasm. Scale bar=2 μm. (E, F) In the D2 or D3 group (DEX at the concentration of 10 or 20 μg/kg), SVs with clearly distinguishable boundaries are abundant. Normal asymmetrical synapses (green arrow heads) and symmetrical synapses (blue arrows) with dense PSDs are visible. Longitudinal section of a dendrite (Den, blue) is highlighted. Mitochondrion, M. Scale bar=1 μm. (G) In the D1+P2 group (1 μg/kg DEX 1 h before propofol exposure), the asymmetrical synapse (green arrow heads) contains distinctly diminished numbers of SVs, an obscure synaptic cleft, and an undefined PSD. Scale bar=1 μm. (H) In the D2+P2 group (10 μg/kg DEX 1 h before propofol exposure), the symmetric synapse (blue arrows) contains a wide cleft and thin PSD. Spine apparatus (sa) inside the dendrite spine. (I) In the D3+P2 group (20 μg/kg DEX 1 h before propofol exposure), multiple tiny glycogen granules (g) are scattered within the cytoplasm. Endoplasmic reticulum (ER) shows slight edema. The synaptic cleft of the asymmetric synapse (green arrow heads) is wide with abundant clear SVs. (J) In the Y+D1+P2 group (1 μg/kg yohimbine 0.5 h before the addition of 1 μg/kg DEX in propofol-exposed rats), three asymmetric synapses (green arrow heads) containing microtubules (t) and SVs surround the axon. Mitochondrial cristae and membrane are broken down. (K) In the Y+D2+P2 group (1 μg/kg yohimbine 0.5 h before the addition of 10 μg/kg DEX in propofol-exposed rats), a synapse with a wide cleft (yellow arrow) and thin PSD is visible. Den (light blue) is highlighted. (L) In the Y+D3+P2 group (1 μg/kg yohimbine 0.5 h before the addition of 20 μg/kg DEX in propofol-exposed rats), an obscure membrane in the asymmetric synapse (green arrow heads) can be seen with lower numbers of SVs. Multiple filaments are distributed within the thin astrocyte processes (Asp, light purple). Spine apparatus (sa) inside a Den is visible. Scale bar=500 nm unless stated otherwise (n=3).
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