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.

Electrical Synaptic Transmission.

Explanation:

The first messenger may be defined as the primary messenger that are required by the cell for the further signaling. The first messenger can be any hormone or chemical.

The paracrine, autocrine and chemical signaling requires primary messenger for the initiation of cell signaling. The electrical synaptic transmission occurs through saltatory conduction by jumping at the synapse also known as the junction between two consecutive neurons.

Thus, the correct answer is option (2).