Hi Manindra Nath Tiwari

It is possible to perform recordings in both coronal and sagittal brain slices. However, the sagittal orientation is the most suitable.

Hi Andrea,

Thanks for your reply. I wonder if there is any publication using this method. I would be grateful if you could provide me with any publication that describes the detailed procedure.

Cheers

Manindra

Hi Manindra Nath Tiwari

I do not have experience with this specific protocol. However, for stimulation in CA1 to elicit a detectable synaptic response in the anterior cingulate cortex@, it is essential that the slice preserves a functional connection between the hippocampal CA1 region and the ACC.

Such a connection is anatomically plausible and has been described in the literature, but it typically requires extended corono-hippocampal slices or specially oriented preparations designed to preserve long-range projections (hippocampus → ACC). In standard coronal brain slices, these projections are often severed due to their trajectory.

Ferreira-Fernandes et al. (2019) demonstrated that projections from CA1 to the medial mesocortex, including the ACC, do exist. However, they are sparse and anatomically fragile, making their preservation challenging in conventional slicing protocols.

Hi Manindra Nath Tiwari

To my knowledge, no study has specifically investigated this pathway using an acute slice preparation. Daniel Llano has several papers using a collicular thalamocortical prep that may offer useful methodological insights. One recent example: https://doi.org/10.7554/elife.56645

I have some suggestions, though:

• Anatomical targeting: Inject a retroAAV-Cre into ACC with a promoter of choice (excitatory, inhibitory, or pan-neuronal). Inject a Cre-dependent fluorophore (e.g., mCherry or tdTomato) into CA1. This labels CA1 neurons projecting to ACC.
• Slice planning: Perform whole-brain histology and 3D reconstruction to determine the best slicing angle and orientation.
• Slicing setup: 3D print a ramp that sets the slicing angle. Mount the brain with a flat, symmetrical surface to ensure proper alignment.
• Slice thickness and health: Use thicker slices, up to 700 micrometers, to maximize the chances of keeping the long axons intact. A critical consideration for such thick preparations is maintaining their viability. To address the risk of the slice core becoming hypoxic, it is essential to use an interface-style recording chamber. This setup ensures oxygenation from both sides of the slice, which improves tissue health and the longevity of the recording.

Hi Manindra Nath Tiwari,

I hope that two articled attached below will give you an idea how to develop your own ACC-hippocampal slice preparation for the project, OR otherwise to perform your research using opto- or chemogenetic tools:

1. Disinhibition of rat hippocampal pyramidal cells by GABAergic afferents from the septum (1997)

2. Optogenetic Activation of Septal Glutamatergic Neurons Drive Hippocampal Theta Rhythms (2016)