Effect of ropivacaine-induced convulsion on hippocampal synaptic development in neonatal rats

Abstract

Objective To evaluate the effect of ropivacaine-induced convulsion on hippocampal synaptic development in neonatal rats. Methods Sixty 21-day-old Sprague-Dawley neonatal rats, weighing 40-41 g, were randomly divided into 3 groups(n=20 each)using a random number table: control group(group C), single convulsion group(group SC), and recurrent convulsion group(group RC). Normal saline 0.1 ml was intraperitoneally injected in group C. Group SC received single intraperitoneal injection of 0.5% ropivacaine 33.8 mg/kg.In group RC, 0.5% ropivacaine 33.8 mg/kg was intraperitoneally injected once a day for 5 consecutive days.The rats developed convulsion were included in the study.Five rats were selected at 24 h, 3 days and 7 days after convulsion and at the age of 60 days in C and SC groups, and at 24 h, 3 days and 7 days after the last convulsion and at the age of 60 days in group RC, the rats were sacrificed, and the hippocampus was removed for examination of the ultrastructure of neurons(with a electron microscope)and for determination of the number of synapses, synaptic space and thickness of synaptic density. Results Compared with group C, the number of synapses was significantly decreased, and the synaptic space was widened at 24 h and 3 days after convulsion, and the thickness of synaptic density was thinned at 24 h after convulsion in group SC, and the number of synapses was significantly decreased, and the synaptic space was widened, and the thickness of synaptic density was thinned at 24 h, 3 days and 7 days after convulsion in group RC(P 0.05). Neurons exhibited nuclear swelling, mitochondria showed edema, and disrupted mitochondrial cristae and vacuoles were observed at 24 h and 3 days after convulsion, and these changes mentioned above were significantly attenuated at 24 h, 3 days and 7 days after convulsion. Conclusion Ropivacaine-induced convulsion exerts no effects on hippocampal synaptic development in neonatal rats. Key words: Amides; Convulsion; Drug toxicity; Synapses; Hippocampus; Child