Quoting Kandel's Principles of Neural Science, 2013,

Amacrine cells generally receive excitatory signals from bipolar cells at glutamatergic synapses. Some amacrine cells feed back directly to the presynaptic bipolar cell at a reciprocal inhibitory synapse. Some amacrine cells are electrically coupled to others of the same type, forming an electrical network much like that of the horizontal cells.

(Page 593)

I tried searching for what a reciprocal inhibitory synapse is but could not find any relevant information.


1 Answer 1


It might be better understood if written with a comma as:

reciprocal, inhibitory synapse

though the rules for this comma usage in English might discourage this because writing "inhibitory reciprocal synapse" doesn't sound quite right. I would say the author wrote it correctly even though it is not perfectly clear.

In this context, they are separate adjectives describing the synapse: inhibitory, because it suppresses firing, and reciprocal because Cell A gives input to Cell B, and Cell B also gives input to Cell A (where Cell A is the amacrine cell and Cell B is the bipolar cell).

The word reciprocal in this context is the adjective definition of the word reciprocal:

given, felt, or done in return.

Note that it isn't the synapse itself that is reciprocal or in both directions, but that the cells have a reciprocal relationship.


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