Which of the following does not require the release of a first messenger?

Paracrine Signaling

Electrical Synaptic Transmission

Chemical Synaptic Transmission

Autocrine Signalling

Electrical Synaptic Transmission

Explanation:

The first messenger are the molecules which act as an agent in the signalling pathway.

These messengers are released by the external environment which acts as a ligand and activates a transduction pathway by binding to specific receptors like hormones, neurotransmitters.

In the given question, only electrical signalling pathway does not involve the first messenger as the electrical signalling synapses involves the physical contact between them and form gap junctions.  Since the signals pass through these gap junctions therefore do not involves the first messenger.

Thus, Electrical Synaptic Transmission is correct.

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