Types of Neurotransmitters

 Types of Neurotransmitters

Neurotransmitters, at the highest level, can be sorted into two types: small-molecule transmitters and neuropeptides. Small-molecule transmitters, like dopamine and glutamate, typically act directly on neighboring cells. The neuropeptides, small molecules like insulin and oxytocin, work more subtly, modulating, or adjusting, how cells communicate at the synapse. To date, scientists have identified more than 60 distinct types of neurotransmitters in the human brain, and most experts say there are more left to discover. These powerful neurochemicals are at the center of neurotransmission, and, as such, are critical to human cognition and behavior.

Acetylcholine

Acetylcholine (Ach) was the first neurotransmitter discovered. It is a direct action small-molecule that works primarily in muscles, helping to translate our intentions to move into actual actions as signals are passed from the neurons into the muscle fiber. But it also has other roles in the brain, including helping direct attention and playing a key role in facilitating neuroplasticity across the cortex.

Dopamine

Dopamine (DA) is often referred to as the “pleasure chemical” because it is released when mammals receive a reward in response to their behavior; that reward could be food, drugs, or sex.

DA is involved with motivation, decision-making, movement, reward processing, attention, working memory, and learning. But it isn’t just a pleasure chemical. New work suggests DA also plays an important role in Parkinson’s disease, addiction, schizophrenia, and other neuropsychiatric disorders.

Glutamate

Glutamate (GLU) is the most excitatory neurotransmitter in the cortex. Too much glutamate results in excitotoxicity, or the death of neurons due to stroke, traumatic brain injury, or amyotrophic lateral sclerosis, the debilitating neurodegenerative disorder better known Lou Gehrig’s disease. Yet, it’s not all bad news. The excitement GLU brings is important to learning and memory: long term potentiation (LTP), the molecular process believed to help form memories, occurs in glutamatergic neurons in the hippocampus and cortex.

Serotonin

Serotonin (5HT), sometimes called the “calming chemical,” is best known for its mood modulating effects. A lack of 5HT has been linked to depression and related neuropsychiatric disorders. But 5HT is farther reaching, and has also been implicated in helping to manage appetite, sleep, memory, and, most recently, decision-making behaviors.

Norepinephrine

Norepinephrine (NE) is both a hormone and a neurotransmitter. Some refer to it as noradrenalin. It has been linked to mood, arousal, vigilance, memory, and stress. Newer research has focused on its role in both post-traumatic stress disorder (PTSD) and Parkinson’s disease.

gamma-Aminobutyric acid (GABA)

If GLU is the most excitatory neurotransmitter, then its inhibitory correlate is GABA. GABA works to inhibit neural signaling. If it inhibits cells too much, it can lead to seizures and other problems. But this neurotransmitter also plays an important role in brain development. New research suggests that GABA helps lay down important brain circuits in early development. Like DA, GABA also has a nickname: the “learning chemical.” Studies have found a link between the levels of GABA in the brain and whether or not learning is successful.

Other Neurotransmitters

Neurochemicals like oxytocin and vasopressin are also classified as neurotransmitters. Made and released from the hypothalamus, they act directly on neurons and have been linked to pair-bond formation, monogamous behaviors, and drug addiction. Hormones like estrogen and testosterone can also work as neurotransmitters and influence synaptic activity.

Other neurotransmitter types include

corticotropin-releasing factor (CRF), galanin, enkephalin, dynorphin, and neuropeptide Y. CRH, dynorphin, and neuropeptide Y have been implicated in the brain’s response to stress. Galanin, encephalin, and neuropeptide Y are often referred to as “co-transmitters,” because they are released and then work in partnership with other neurotransmitters. Enkephalin, for example, is released with glutamate to signal the desire to eat and process rewards.

As neuroscientists are learning more about the complexity of neurotransmission, it’s clear that the brain needs these different molecules so it can have a greater range of flexibility and function