BackgroundThe functional heterogeneity of the hippocampus along its longitudinal axis at the level of behavior is an established concept; however, the neurobiological mechanisms are still unknown. Diversifications in the functioning of intrinsic hippocampal circuitry including short-term dynamics of synaptic inputs and neuronal output, that are important determinants of information processing in the brain, may profoundly contribute to functional specializations along the hippocampus. The objectives of the present study were the examination of the role of the GABAA receptor-mediated inhibition, the μ-opioid receptors and the effect of stimulation intensity on the dynamics of both synaptic input and neuronal output of CA1 region in the dorsal and ventral hippocampus. We used recordings of field potentials from adult rat hippocampal slices evoked by brief repetitive activation of Schaffer collaterals.ResultsWe find that the local CA1 circuit of the dorsal hippocampus presents a remarkably increased dynamic range of frequency-dependent short-term changes in both input and output, ranging from strong facilitation to intense depression at low and high stimulation frequencies respectively. Furthermore, the input–output relationship in the dorsal CA1 circuit is profoundly influenced by frequency and time of presynaptic activation. Strikingly, the ventral hippocampus responds mostly with depression, displaying a rather monotonous input–output relationship over frequency and time. Partial blockade of GABAA receptor-mediated transmission (by 5 μM picrotoxin) profoundly influences input and output dynamics in the dorsal hippocampus but affected only the neuronal output in the ventral hippocampus. M-opioid receptors control short-term dynamics of input and output in the dorsal hippocampus but they play no role in the ventral hippocampus.ConclusionThe results demonstrate that information processing by CA1 local network is highly diversified between the dorsal and ventral hippocampus. Transient detection of incoming patterns of activity and frequency-dependent sustained signaling of amplified neuronal information may be assigned to the ventral and dorsal hippocampal circuitry respectively. This disparity should have profound implications for the functional roles ascribed to distinct segments along the long axis of the hippocampus.

中文翻译：

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CA1网络输入和输出的短期动态在大鼠背侧和腹侧海马之间有很大差异

背景海马体在行为层面沿其纵轴的功能异质性是一个既定的概念；然而，神经生物学机制仍然未知。内在海马回路功能的多样化，包括突触输入和神经元输出的短期动态，它们是大脑中信息处理的重要决定因素，可能会对海马体的功能特化产生深远的影响。本研究的目的是检查 GABAA 受体介导的抑制作用、μ-阿片受体以及刺激强度对背侧和腹侧海马 CA1 区突触输入和神经元输出动力学的影响. 我们使用了由 Schaffer 侧枝短暂重复激活引起的成年大鼠海马切片的场电位记录。 结果我们发现背侧海马的局部 CA1 回路呈现出显着增加的输入和输出频率依赖性短期变化的动态范围，分别在低刺激频率和高刺激频率下从强烈的促进到强烈的抑制。此外，背侧 CA1 回路的输入-输出关系受突触前激活的频率和时间的影响很大。引人注目的是，腹侧海马体的反应主要是抑郁，在频率和时间上表现出相当单调的输入-输出关系。GABAA 受体介导的传递的部分阻断（通过 5 μM picrotoxin）深刻影响背侧海马体的输入和输出动力学，但仅影响腹侧海马体的神经元输出。M-阿片受体控制背侧海马体的短期输入和输出动态，但它们在腹侧海马体中不起作用。结论结果表明CA1局部网络在背侧和腹侧海马之间的信息处理高度多样化。传入活动模式的瞬时检测和放大的神经元信息的频率依赖性持续信号传导可以分别分配给腹侧和背侧海马回路。