探討海馬迴中 principal neuron 及 interneuron 之軸突生長能力有何差異

Abstract

Hippocampal neural network is mainly composed of two neuronal populations, the majority of the network is principal neurons, which provide the excitatory synaptic output to the circuit, and the rest is the inhibitory interneuron. Even the less number of interneuron population, because of its diverse morphology and physiological function, interneurons play an important role in the modification and integration of hippocampal neural network. In general, principal neuron can develop very long axons to target distal brain region. In contrast to principal neurons, interneurons can only extend much shorter axons to surrounding target to form local inhibitory circuit, in this study, we try to determine whether the axon growth capacity is caused by target-specify or the intrinsic capacity. Because most principal neurons in the cerebral cortex and hippocampus use glutamate as neurotransmitter, so we use vesicular glutamate transporter 1 (vGLUT1) to label hippocampal principal neurons. Calcium-binding proteins also expressed in non-overlapped hippocampal interneuronal population, so we can use calbidin and parvalbumin to label different interneuron in the hippocampus. We cultured the hippocampal neurons on the PLL-covered coverslips to mimic the real growth environment for the hippocampal neurons that axonal fibers can randomly extend to the targets, in this experiment we found that the axon growth capacity of principal neuron is significantly greater than interneurons. Then we use micro-contact printing to remove the targets in the cultured environment, results show that the axon growth capacity of interneurons can elevate a great extent to the level of principal neurons.