Neurotransmitter

A chemical signal released by a neuron that changes a target cell's activity through its receptors. Its effect depends on the receptor and ionic mechanism rather than being intrinsically excitatory or inhibitory in every context.

A peptide used in neural signalling. Release, receptor distribution and interactions with other transmitters affect its function.

A peptide signal involved in endocrine and neural stress regulation. Its actions within a defined local circuit need not match a whole-organism hormone concentration.

A major transmitter commonly associated with inhibitory signalling through appropriate receptors. Its cellular effect depends on receptor and ionic conditions; suppressing an inhibitory neuron can disinhibit its targets.

Regulation of neural processing by chemical signals that can alter excitability, plasticity, gain or network state. Effects depend on receptor, target and timescale rather than only transmitter identity.

Observations establish what signals naturally covary with defined events; interventions estimate consequences of changing a specified target. Convergence requires matching cell population, projection, timescale and behavioural endpoint, with direct target engagement measurements and controls for off-target drug effects.

A signal acting in neuromodulation. The same molecule can have different functions at different receptors and targets; the label does not imply slow action or a single diffuse behavioural purpose.

A catecholamine transmitter involved in arousal, attention and other state-dependent functions, also called noradrenaline.

A monoamine transmitter also called 5-hydroxytryptamine. Distinct receptors and circuits can have different effects; blood levels are not a direct reading of synaptic transmission in the brain.

A neurotransmitter involved in multiple neural functions. Some phasic dopamine-neuron responses are consistent with reward-prediction-error signalling, and timed interventions can affect learning. This does not mean that every dopamine neuron or every timescale carries one identical scalar error.^[ref]

A subtype of receptor for dopamine involved in neural signalling and targeted by many antipsychotic medications. Receptor blockade is a pharmacological action, not a complete psychological description of treatment response.

Acetylcholine is a neurotransmitter that acts through nicotinic ionotropic receptors and muscarinic metabotropic receptors. The receptor and the target cell's machinery determine the response; acetylcholine itself does not specify whether coupling is direct or mediated by intracellular signal transduction. ^[ref]