Neurotransmitter

A neurotransmitter is a molecule capable of transmitting information between cells. Most often it is a nerve impulse between neurons, between nerve and muscle cells.

Acetylcholine
It is a mediator that transmits information from preganglionic neurons to postganglionic neurons in the system autonomic nerves. In parasympathetic, acetylcholine is released again at the postganglionic endings. In the sympathetic nervous system, it is released from the postganglionic terminal noradrenaline.

Nicotine receptors
They are part of ion channel. Individual channels differ from each other in structure. The Muscle type has two subunits α1 and one subunit β, γ, δ (found in embryonic muscle), but in adulthood the γ is replaced by a subunit ε. The neuronal type has a α subunit and a β subunit, there may also be a situation where both subunits have α.
 * Neuronal type;
 * muscle type;
 * ganglion type.

Muscarinic receptors
They are in the effector organs. M1, M2, M3, M4, M5

Function

 * Cognitive processes − memory and learning (decreased amount of ACh = Alzheimer's).
 * Importance in regulating wakefulness and sleep.
 * Motor skills.
 * Motivation, in the reward process.
 * In PNS – skeletal muscle activity, modulation of transmission nociception.
 * In the ANS – ganglia and parasympathetic.

Catecholamines
Tyrosine → DOPA → Dopamine →  NA (norepinephrine) →  A (epinephrine)

Dopamine


Dopamine is synthesized in nuclei A8−A17. The site of action is sympathetic ganglia.

Major dopaminergic neurons

 * A8, A9, A10= midbrain
 * A9= Substantia nigra
 * A11−A15= Midbrain
 * A12= Nucleus arcuatus
 * A17= retina

Receptors
D 1-like family − D1,D 5undefined
 * increase effects of adenylate cyclase (↑ cAMP)

D 2-like family − D2, D3, D4undefined
 * reduce the effects of adenylate cyclase (↓ cAMP)

Functions
They are of great importance in motivational behavior and addiction. In the case of an unexpected reward, the stimulation' of DA is pronounced, which disappears during repetition and learning if the presentation of the reward does not evoke the stimulation of DA. In the absence of the expected reward, the DA signal is reduced. Two phases of the stimulus:
 * stimulus phase − expectation of the pleasant
 * phase of consumption − experiencing a pleasurable stimulus

It is also applied in the consolidation of memory traces. It is important in the regulation of hypothalamic-pituitary system' and in the regulation of motor functions, but also in the transmission and processing of ''nociceptive signals.

Faults
Typically, Parkinson's disease and schizophrenia. There are also depression, substance addiction and eating disorders.

Receptors
The receptors are 'adrenergic, with affinity for A and NA being almost the same.
 * α1
 * α1A
 * α1B
 * α1D


 * α2
 * α2A
 * α2B
 * α2C
 * α2D


 * β1
 * β2
 * β3

Functions
They are used in the stress response. This is the so-called eustress, when an individual gives a double performance and the level is within the homeostatic limits'. They are also important for attention, wakefulness and sleep.



Serotonin
As a neurotransmitter, it acts vasoconstrictive. It affects sleep and thermoregulation. Also called the hormone of happiness.

Receptors
The receptors for serotonin are predominantly metabotropic, coupled to G protein. It can bind to a large number of receptor types. The information is also led to all areas of the CNS.

Functions
They are used in waking and sleeping, circadian rhythms. It is also related to pain, food intake and sexual behavior. Serotonin deficiency is associated with depression, anxieta and migraine.

Histamine
The nuclei are designated E1−E5. They project into the spinal nuclei and into the cerebellum. Efferent pathways are to the entire cerebral cortex.

Functions
Application in the regulation of sleep cycles, energy and endocrine homeostasis. In the regulation of body temperature and food intake. It is related to the regulation of secretion hypothalamic-pituitary system. Also synaptic plasticity, learning and nociceptive signals.



Glutamate
It interferes with and is found 'everywhere in the CNS. Its receptors are metabotropic, where the first, second and third groups of glutamate receptors and ionotropic receptors are located, which include 'AMPA, kainate, NMDA. The function is applied in motor coordination, memory processes (long-term potentiation), emotional processes and sensory information transfers. Decreased levels are associated with epilepsy, Huntington's chorea, ischaemic brain injury.

GABA
The receptors for GABA are ionotropic GABA A and metabotropic GABA B. Its important pathways lead to the cerebellum. The function is associated with monosynaptic and polysynaptic signal transmissions. Transmission of nociceptive information, presynaptic selection of afferent flow of information into the CNS. They cause the chloride channel to open, resulting in hyperpolarization. Decreased GABA levels are associated with Huntington's chorea, is related to epilepsy and anxiety, i.e. anxiety.

Related Articles

 * Synapse
 * Metabotropic receptors
 * G-protein
 * Acetylcholine
 * Adrenaline
 * Noradrenaline

Source

 * Lecture in physiology, second year.