Neurotransmitters are generally referred to as the body’s chemical messengers. These are the molecules which are used by the nervous system to transfer messages between neurons, or either from neurons to muscles. Synaptic cleft is the region where communication between two neurons occurs, in the (the small gap between the synapses of neurons). Here, electrical signals that have travelled along the axon are converted into chemical ones via the release of neurotransmitters, which further causes a specific response in the receiving neuron.
Neurotransmitters are generally released from the synaptic vesicles into the synaptic cleft where they are allowed to interact with neurotransmitter receptors that are present on the target cell. The effect of a neurotransmitter on the target cell can be determined by the receptor to which it binds. Many neurotransmitters are synthesized from simple and abundant precursors like that of amino acids, that are readily available and more often require a small number of biosynthetic steps for conversion.
Types of Neurotransmitters
Neurotransmitters can be sorted at the highest level, into two types: small-molecule transmitters and neuropeptides. Small-molecule transmitters, such as dopamine and glutamate, that mainly act directly on neighbouring cells. The neuropeptides are small molecules such as insulin and oxytocin, which work more efficiently, modulating, or adjusting, on how cells communicate at the synapse. Till date, scientists have identified more than 60 different types of neurotransmitters in the human brain, and yet few experts say there are more left to discover. These powerful neurochemicals are mainly at the centre of neurotransmission, and, as such, are very critical to humans and their behaviour.
More often, neurotransmitters are talked about as if they possess a single role or function. Dopamine is also known as a “pleasure chemical” and GABA also known as a “learning” neurotransmitter. Here is a list of few of the most common neurotransmitters that are discussed in neuroscience:
Acetylcholine
Acetylcholine (Ach) was the first neurotransmitter to be discovered. It has a direct action small-molecule that works mainly in muscles, thereby helping us to translate our intentions to move into actual actions as signals are transferred from the neurons into the muscle fiber. But it also possesses some other roles in the brain, that includes helping direct attention and playing a vital role in facilitating neuroplasticity throughout the cortex.
Dopamine
Dopamine (DA) is mainly referred to as the “pleasure chemical” because it is released at the time when mammals receive a reward in response to their behaviour; that reward can be anything like food, drugs, or sex. It is one of the most widely studied neurochemicals, mainly because it plays various diverse roles in human behaviour and cognition. Dopamine is generally involved with motivation, decision-making, movement, attention, working memory and learning. But it is not just a pleasure chemical. New studies suggest that Dopamine also plays a vital role in Parkinson’s disease, addiction, schizophrenia, and such other neuropsychiatric disorders.
Glutamate
Glutamate (GLU) is the most widely used excitatory neurotransmitter present in the cortex. A high concentration of glutamate results in excitotoxicity, or the death of neurons as a result of stroke, traumatic brain injury or amyotrophic lateral sclerosis, the debilitating neurodegenerative disorder better called Lou Gehrig’s disease.
Serotonin
Serotonin, also known as the “calming chemical,” is best known for its mood modulating effects. A lack of serotonin is linked to depression and other related neuropsychiatric disorders. But serotonin is farther reaching and has also been implicated in helping to manage appetite, memory, sleep and most importantly decision-making behaviours.
Norepinephrine
It is both a hormone and a neurotransmitter. Few refer to it as the noradrenalin. Norepinephrine has been linked to mood, arousal, vigilance, memory, and stress. New research studies have focused on its role in both Post-traumatic stress disorder (PTSD) and Parkinson’s disease.
Gamma-Amino butyric acid (GABA)
If glutamate is the most excitatory neurotransmitter, then its inhibitory is GABA. GABA functions to inhibit neural signalling. If its inhibition to cells is too much, then it can lead to seizures and other related problems. But this neurotransmitter plays a very significant role in brain development. New research studies suggest that GABA helps in laying down important brain circuits for early development. GABA is also known as the “learning chemical.”
Drugs That Influence Neurotransmitters
The greatest practical application for the discovery and detailed understanding of how neurotransmitters function was by the development of drugs that affect chemical transmission. These drugs possess the ability of changing the effects of neurotransmitters, which can further increase the symptoms of some diseases.
Agonists vs Antagonists: Some drugs are called agonists and they function via increasing the effects of certain neurotransmitters. Other drugs are referred to as antagonists and it acts to block the effects of neurotransmission.
Direct vs Indirect Effects: These neuro-acting drugs are further broken down depending on whether they possess a direct or indirect effect. The one that possesses a direct effect works by mimicking the neurotransmitters because they are quite similar in their chemical structure. While those that possess an indirect impact work by acting on the synaptic receptors.
Drugs that influence neurotransmission involve medications that are used to treat illness including depression and anxiety, like SSRIs, tricyclic antidepressants and benzodiazepines.
Drugs like those of heroin, cocaine, and marijuana also possess an effect on neurotransmission. Heroin acts as a directly-acting agonist that mimics the brain’s natural opioids to stimulate their linked receptors. Cocaine represents an example of an indirect-acting drug which influences the transmission of dopamine.
Conclusion
Neurotransmitters play a vital role in neural communication, influencing everything from involuntary movements to learning and to mood. This system is highly complex and interconnected. Neurotransmitters act in a specific way, but they can also be affected by diseases, drugs, or even by the actions of other chemical messengers. Here, we come to an end of this topic, hope you were able to grasp a clear concept of the topic.