What connects neurons and what chemicals neurons communicate? the connects the axon of one neuron with the dendrite of another neuron to relay messages. neurons transmit information to each other through synaptic gaps. the cells release chemicals known as into the synaptic gaps to communicate with one another.

Synapse connects neurons and neurotransmitters are the chemicals that help in the communication of neurons.

The given statements can be completed as-

The synapse connects the axon of one neuron with the dendrite of another neuron to relay messages.

The cells release chemicals known as neurotransmitters ( such as acetylcholine) into the synaptic gaps to communicate with one another.  

Neurotransmitter are the chemical messengers that carry chemical signal to the target neuron where it gets converted into electrical impulses. Synapse is a place or gap between the axon terminal of one neuron and the dendrite of another neuron.