neuromodulator
A chemical messenger that alters neuronal activity and synaptic transmission over extended time periods, often acting at extrasynaptic sites.
Full Definition
A neuromodulator is a type of chemical messenger that influences neuronal excitability, synaptic efficacy, and network properties over timescales longer than classical neurotransmitters. Unlike neurotransmitters that typically act at specific synaptic sites, neuromodulators often act through volume transmission, affecting multiple neurons simultaneously through extrasynaptic receptors. Many neuropeptides function as neuromodulators, including substance P, neuropeptide Y, and various hypothalamic releasing factors. Neuromodulation plays crucial roles in setting behavioral states, regulating circadian rhythms, and fine-tuning neuroendocrine responses. The effects are typically slower in onset but longer-lasting than conventional synaptic transmission.
Usage
Usage note: Distinguish from neurotransmitters by emphasizing longer-duration, modulatory effects rather than point-to-point signaling.
In Context
- "The neuropeptide acts as a neuromodulator rather than a classical neurotransmitter in this circuit." — Neuroscience research paper
- "Disrupted neuromodulator signaling may explain the patient's altered sleep-wake patterns." — Sleep disorder evaluation