You are here:
Ontogeny of Biochemical, Morphological and Functional Parameters of Synaptogenesis in Primary Cultures of Rat Hippocampal and Cortical Neurons
Citation:
Harrill, J., H. Chen, K. Streifel, D. Yang, W. Mundy, AND P. Lein. Ontogeny of Biochemical, Morphological and Functional Parameters of Synaptogenesis in Primary Cultures of Rat Hippocampal and Cortical Neurons. MOLECULAR BRAIN RESEARCH. Elsevier Science Ltd, New York, NY, 8(3):8-10, (2015).
Impact/Purpose:
The ontogenetic patterns of synapse formation were compared between two commonly used cell culture models, primary rodent hippocampal and cortical neurons. Our data indicate that the ontogeny of synaptogenesis in vitro is consistent with synaptogenesis in vivo across multiple biological levels, and that cell type-dependent differences exist in synaptogenic profiles. These results further suggest that utilization of multiple techniques can provide a more integrative view of synaptogenesis, which may provide more useful and predictive insight of how chemical exposures and pharmacologic interventions influence this critical neurodevelopmental endpoint. Based on our findings, we recommend that in vitro studies of synaptogenesis using biomarker-based assays measure excitatory and inhibitory synapse formation in parallel in order to gain a comprehensive understanding of how toxic chemicals and/or drugs affect synaptic network formation and function. High-content imaging provided a rapid and reproducible method for screening chemical effects on the formation of excitatory and inhibitory synapses. This assay could be used as part of a screening battery for developmental neurotoxicity.
Description:
AbstractBackground: Synaptogenesis is a critical neurodevelopmental process whereby pre-and postsynaptic neurons form apposed sites of contact specialized for excitatory and inhibitory neurotransmission. Many neurodevelopmental disorders are thought to reflect altered patterns of synaptic connectivity, including imbalances between excitatory and inhibitory synapses. Thus, developing rapid throughput approaches for quantifying synaptogenesis and, in particular, quantifying the balance of excitatory to inhibitory synapses, is becoming increasingly important for mechanistic, toxicologic and drug screening studies of neurodevelopmental disorders. While a number of different approaches for quantifying synaptogenesis have been described, little information is available as to the relationship of data obtained from one approach versus the others.Results: The ontogenetic patterns of synapse formation were compared between two commonly used cell culture models, primary rodent hippocampal and cortical neurons, using complementary methods that measure synapse formation at differing levels of biological complexity: 1) at the molecular level using an enzyme-linked Immunosorbent assay (ELISA) to quantify synaptophysin expression; 2) at the cellular level using high-content imaging to quantify the immunoreactivity of excitatory and inhibitory synaptic biomarkers; and 3) at the functional level using microelectrode array recordings. As determined using the synaptophysin ELISA, the rate of synaptogenesis was similar between hippocampal and cortical cultures. Quantification of excitatory and inhibitory synapses demonstrated an overall greater number of synapses in hippocampal neurons as compared to cortical neurons with marked differences in the pattern of inhibitory synapse development between these two neuronal cell types. With respect to functional assays of synaptogenesis, both the mean firing rates and mean bursting rates as a function of day in vitro (DIV) were significantly increased in cortical cultures relative to hippocampal cultures at DIV 14. This difference may reflect decreased inhibitory synaptic tone in cortical versus hippocampal cultures.Conclusions: These data demonstrate differences and similarities in the ontogeny of synaptogenesis between hippocampal and cortical neurons, depending on the biological level examined, suggesting that complementary approaches that integrate molecular, cellular and functional parameters of synaptogenesis will provide a more robust readout of toxicologic and pharmacologic effects on this critical neurodevelopmental event.
