The plastic variability of synaptic structure of nucleus accumbens and amygdala in anxious rats suffered from morphine withdrawal

Abstract

Objective The possible correlations between morphological contracture and plastic variability of synaptic structure in nucleus accumbens and amygdala neurons were surveyed in anxious symptom rats suffered from morphine withdrawal. Methods The escalating doses of morphine and the elevated plus-maze were applied to validate anxiety-like behavior in rats. The electron microscope was applied to detect the parameters involving the synaptic stereology and structural plasticity of synaptic interface structure of the nucleus accumbens and amygdala neurons in the control group, the morphine-withdrawal group and the cured group ( n = 6 ), associated with the stereological ways. Results ( 1 ) Compared with the control group and the cured group, reductions of frequency and time of open-arm were observed in the morphine-withdrawal group ( P ＜ 0. 01 or P ＜ 0. 05 ). ( 2 ) Higher numerical density ( Nv ) [( 1. 012 ±0. 036 )/μm3] of synapses of nucleus accumbens was detected in the anxious rats ( P ＜ 0. 01 ) than in the controls [( 0. 701 ±0. 138 )/μm3] and the cured rats [( 0. 751 ±0. 254 )/μm3] . No significant difference between the surface density ( Sv ) and the mean profile area ( S ) of synapse of the nucleus accumbens was discovered. Compared with the control group [( 0. 247 ± 0. 117 )/μm3] and the cured one [( 0. 246 ±0. 116 )/μm3] , higher values of Nv [( 0. 427 ±0. 178 )/μm3] in amygdala were detected in anxious rats ( P＜0.01 or P＜0.05 ). Similarly, higher score of Sv [( 0.047 ±0.018 )μm2/μm3] in amygdala was observed in the anxious rats ( P ＜ 0. 01 ) than those of the control group [( 0. 030 ±0. 012 )μm2/μm3] and cured group [( 0. 030 ±0. 015 )μm2/μm3] . However, anxious rats [( 0. 124 ±0. 066 )μm2] appear to be lower S of synapse in amygdale ( P ＜ 0. 05 ) than those of the control group [( 0. 157 ±0. 119 )μm2] and the cured group [( 0. 159 ±0. 114 )μm2] . ( 3 )No significant difference among postsynaptic density, length of synaptic thickening, widths in synaptic interface structure on junctions and curvature of synaptic cleft region was detected in the nucleus accumbens and amygdala neurons. Conclusion In the present study, the results suggest that anxious rats suffered from morphine withdrawal could possibly be related to the plastic variability of synaptic morphological structure in nucleus accumbens and amygdale. Key words: Morphine; Substance withdrawal syndrome; Anxiety; Nucleus accumbens; Amygdala; Synapses; Neuronal plasticity