Comparative Histomorphological and Histostereological Teratogenic Effects of Prenatal Exposure to Lamotrigine and Levetiracetam on Fetal Memory Circuitry Structures in Albino Rats (Rattus Novegicus)

Abstract

Though lamotrigine and levetiracetam are the most commonly used first line anticonvulsant medicines in the management of epileptic seizures and other convulsion disorders during pregnancy, the in-utero-teratogenic effects in the development of fetal memory circuitry structures remain equivocal. Furthermore, whether or not their teratogenic effects are both dose and time-dependent also remains unclear and hence the basis of this study. In carrying out this study, a post-test-only experimental study design was adopted. The animal experimentation was done in the animal research facility in the University of Nairobi (UON), while tissue processing for histology and stereological analysis was done at JKUAT. A Sample size of 30 albino rat dams weighing between 220 to 250 grams for each of the study medicine were used in the study. This sample size was determined by use of the resource equation for One Way Analysis of Variance method (ANOVA). The 30 albino rats in each of these two study categories of levetiracetam and lamotrigine were first broadly divided into two study groups of 3 rats’ control and 27 rats’ treatment group. To evaluate whether the teratogenic effects of both medicines are dose dependent, the 27 rats in their treatment groups were further subdivided into three study sub groups of 9 rats as follows; (i) 9 rats for low doses of lamotrigine and levetiracetam group{103mg/kg bw and 3mg/kg respectively}, (ii) 9 rats for medium doses of levetiracetam and lamotrigine group {207mg/kg and 24mg/kg respectively}, (iii) 9 rats for the high levetiracetam and lamotrigine group {310mg/kg and 52mg/kg respectively}. To further evaluate whether the observed teratogenic effects are time dependent, the 9 rats in each of the three dose categories were further sub-divided into three subgroups groups of 3 rats each according to the trimesters of exposure as follows; (i) 3 rats for trimester I (TM1); (ii) 3rats for trimester II (TM2) and (iii) 3 rats for trimester III (TM3). All rats were fed on standard rodent pellets and water ad-libitum throughout the gestational period and sacrificed on day 20. The fetal brains were harvested for both histomorphological and stereological analysis. Qualitative histomorphological data was collected using a swift 3.0 microscope digital camera 20mega pixels, then exported to swift 3.0 software for analysis and labelling. Discrete data was analysed using chi-square test for independence. Quantitative data was collected using structured checklists, stored and coded in excel spreadsheets windows 10, version 2019, then was exported for analysis into SPSS programme for windows version 25 for analysis (Chicago Illinois). The findings were expressed as mean+ SD for all values. Intra and intergroup comparisons were done by one-way ANOVA followed by Tukey’s post hoc multiple comparison t- tests, while MANOVA was used as a test of interaction effects, main effects as well as pairwise comparisons. The findings whose P<.05 were considered significant. The findings of this study shown that both lamotrigine and levetiracetam are teratogenic to the development of fetal memory circuitry pathways structures including the prefrontal cortex and medial temporal lobe structurers that includes the entorhinal cortex, the subicular complex, the hippocampus, the dentate gyrus and the amygdaloid nucleus. The observed teratogenic effects for both medicines depicted a similar pattern of causing significant reduction(P<.05) in cellular density, sparse distribution of cells, atrophic changes to all cortical layers and the reduction in volume and volume density in all the cellular components in a dose and time dependent manner particularly at TM1 and TM2, with lamotrigine having more deleterious effects than levetiracetam. It is then recommended that high dosages of the two medicines where possible should be avoided at TM1 and TM2. Further studies with non-human primates are also recommended to help corroborate these findings to humans.