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Hello

I have a mod file that computes depolarization induced suppression of inhibition (DSI) which relies on the depolarization of the postsynaptic cell.
For that, I need to access the calcium concentration of the postsynaptic cell that would be elevated upon depolarization.
If I call"cai" in the mod file that calculates DSI, it appears to me, that I record the net calcium concentration in all cells (not just pyramidal cells).
How can I specify calcium concentration of the pyramidal cells only?

thank you,
Alexandra

If I call"cai" in the mod file that calculates DSI, it appears to me, that I record the net calcium concentration in all cells (not just pyramidal cells)

I don't see how this could possibly be a problem. A synaptic mechanism is usually implemented as a point process. A point process is attached to a single segment, and it is easy for a point process to discover cai in the segment to which it is attached: just include the statement
USEION ca READ cai
in the NEURON block, and
cai (mM)
in the ASSIGNED block. In the remainder of the mod file, the variable cai will always refer to calcium concentration in the segment to which the point process is attached. So the equations will always refer to the proper cai.

Further comments:
The mechanism for DSI described by Zachariou and Thul in J Comput Neurosci (2014) 37:533–547 DOI 10.1007/s10827-014-0518-4 involves a lot of detail in the presynaptic terminal and postsynaptic region. A complete implementation of that mechanism would require not just a point process (to represent the GABA-A gated synaptic conductance) but also special compartments (segments) to represent what's going on in the presynaptic terminal and postsynaptic region (calcium entry, buffering, and extrusion; calcium-mediated production of 2-AG in the postsynaptic cell; release of 2-AG into the synaptic cleft where it interacts with receptors on the presynaptic terminal; modulation of v-gated ca channels in the presynaptic terminal, etc.). It may be possible to simplify some of this so that most equations would fit into the mod file that governs synaptic conductance; perhaps some of those equations could be incorporated into the NET_RECEIVE block (which would eliminate the need to add new ODEs or a kinetic scheme to the NMODL code). Significant effort would be required to discover if this is doable, and to demonstrate that the result is qualitatively similar to the few findings presented in the paper by Zachariou and Thul.

thank you Ted, I responded with a private message attaching my mod file.