Neuromodulation

[3] Major neuromodulators in the central nervous system include: dopamine, serotonin, acetylcholine, histamine, norepinephrine, nitric oxide, and several neuropeptides.

[4][5][6] Neuromodulators can be packaged into vesicles and released by neurons, secreted as hormones and delivered through the circulatory system.

Some neuromodulators end up spending a significant amount of time in the cerebrospinal fluid (CSF), influencing (or "modulating") the activity of several other neurons in the brain.

[citation needed] Most other neurotransmitters, on the other hand, e.g. glutamate, GABA and glycine, are used very generally throughout the central nervous system.

Despite containing a relatively small number of neurons, when activated, the noradrenaline system plays major roles in the brain including involvement in suppression of the neuroinflammatory response, stimulation of neuronal plasticity through LTP, regulation of glutamate uptake by astrocytes and LTD, and consolidation of memory.

[13] The dopamine or dopaminergic system consists of several pathways, originating from the ventral tegmentum or substantia nigra as examples.

[citation needed] Although changes in neurochemistry are found immediately after taking these antidepressants, symptoms may not begin to improve until several weeks after administration.

The cholinergic system has been found to be involved in responding to cues related to the reward pathway, enhancing signal detection and sensory attention, regulating homeostasis, mediating the stress response, and encoding the formation of memories.

[17] GABA is an amino acid that is the primary inhibitory neurotransmitter for the central nervous system (CNS).

GABAa receptors inhibit neurotransmitter release and/or neuronal excitability and are a ligand-gated chloride channel.

[citation needed] Neuromodulators may alter the output of a physiological system by acting on the associated inputs (for instance, central pattern generators).

Stern et al. (2007) suggest that neuromodulators must act not only on the input system but must change the transformation itself to produce the proper contractions of muscles as output.

Sustained Influence provides long-term stability to the entire process, and baseline regulation ensures that the neurons are in a continued state of readiness to respond to any signals.

Acetylcholine, noradrenaline, dopamine, norepinephrine, and serotonin are some of the main components in tonic transmission to mediate arousal and attention.

Lastly, as the name suggests, stimulus-driven effects react to sensory input, external stressors, and reward stimuli, which involve dopamine, norepinephrine, and serotonin.