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Septohippocampal disinhibition.
K Krnjević1, N Ropert, J Casullo
1Department of Anaesthesia Research, McGill University, Montreal, Que., Canada.
Brain Research
|January 12, 1988
Summary
Medial septal stimulation significantly depresses tonic inhibition in the hippocampus. This disinhibition, observed in CA1 and CA2/3 neurons, impacts inhibitory postsynaptic potentials (IPSPs) and neuronal activity.
Area of Science:
- Neuroscience
- Neurophysiology
Background:
- The hippocampus plays a crucial role in learning and memory.
- Medial septal projections modulate hippocampal activity.
- Understanding septal influence on hippocampal inhibition is key to deciphering neural circuit function.
Purpose of the Study:
- To investigate the effects of medial septal stimulation on hippocampal CA1 and CA2/3 neurons.
- To characterize the impact of septal input on inhibitory postsynaptic potentials (IPSPs) and neuronal excitability.
Main Methods:
- Intracellular recordings were performed on CA1 and CA2/3 neurons in rats under urethane anesthesia.
- Medial septal stimulation was delivered using 10 pulse trains at approximately 100 Hz.
- Effects on ongoing and evoked IPSPs, input resistance, and membrane potential were analyzed.
Main Results:
- Medial septal stimulation caused a prolonged depression (200-500 ms) of ongoing inhibitory postsynaptic potentials (IPSPs).
- Increased input resistance and changes in membrane potential (depolarization or hyperpolarization) were observed.
- Septal stimulation weakened evoked IPSPs in pyramidal cells, reducing conductance by an average of 42%.
Conclusions:
- Medial septal stimulation strongly depresses tonic inhibition in the hippocampus.
- Septal inputs to the CA1 and CA2/3 regions exert a significant disinhibitory function.
- These findings highlight the role of the medial septum in regulating hippocampal network states through disinhibition.