Synaptic connectivity in hippocampal neuronal networks cultured on micropatterned surfaces

Embryonic rat hippocampal neurons were grown on patterned silane surface in order to organize synapse formations in a controlled manner. The surface p atterns were composed of trimethoxysilylpropyl-diethylenetriamine (DETA) li nes separated by tridecafluoro-1,1,2,2-tetrahydrooctyl-1-dimethylchlorosila ne (13F) spaces. Pre- and post-synaptic specializations were identified by immunostaining for synapsin I and microtubule-associated protein-2 (MAP-2). Functional synaptic connections were examined by recording simultaneously from pairs of neurons using the whole-cell configuration of the patch-clamp technique. Spontaneous and evoked synaptic currents were recorded in neuro ns cultured for 2-14 days. The formation of functional connections was acco mpanied by the appearance of spontaneous synaptic currents (SSCs), which co uld be detected after similar to 3 days in culture in the absence of evoked synaptic currents (ESCs). ESCs were detected only after similar to 7 days in culture, mostly in the form of unidirectional synaptic connections. Othe r forms of synaptic connectivity, such as bidirectional and autaptic connec tions, were also identified. Both transient GABAergic and glutamatergic sig nals mediated the transmissions between communicating cells. These results demonstrate the combination of various types of synaptic connections formin g simple and complex networks in neurons cultured on line (DETA)-space (13F ) patterns. Finally, precisely synchronized SSCs were recorded in neuron pa irs cultured on pattern indicating the existence of a fast-acting feedback mechanism mediated by pre-synaptic GABAA receptors. (C) 2000 Elsevier Scien ce B.V. All rights reserved.