Dynorphin Funtion, Mechanism, Withdrawal, Anxiety

The nervous system of the human body comprises of a well-organized network of neurons responsible for the transmission of stimulus and related information through signals in the whole body. It coordinates the functions of the body for the proper functioning and maintenance through the transmission of these signals generated by the release of specified chemicals known as neurotransmitters.

Dynorphin is a neurotransmitter that belongs to the class of opioid peptides. It does not exist in this functionally active form but derived from another product named prodynorphin through metabolism. Prodynorphin exists in the synaptic vesicles that can be found in the presynaptic terminals of neurons. It exists in an inactive form in these vesicles and upon the depolarization of the neurons proprotein convertase 2 (PC2) enzyme releases which accelerate the metabolism of prodynorphin. This cleavage of prodynorphin leads to the production of more than one metabolic product including; dynorphin A, dynorphin B, and big dynorphin.

Usually, the complete process of metabolism does not occur which results in the production of only one metabolic product, big dynorphin. It is 32 amino acids containing products that comprise both dynorphin A and dynorphin B.All of these metabolic products consist of a big proportion of the amino acids basic residues specifically including; lysine and arginine as well as hydrophobic. Dynorphin A consists of 29.4% and 41.2%, while dynorphin B 23.1% and 30.8% and big dynorphin consists of 31.2% and 34.4% of basic amino acid residues and hydrophobic residues, respectively.

Dynorphins are widely dispersed among different parts of the central nervous system (CNS) but they are more abundant in few areas including; hypothalamus, midbrain, pons, medulla, and spinal cord. These are stored in as large as 80-120nm diameter vesicles which are dense-core and comparatively stronger than the vesicles storing other neurotransmitters. Because of these structural characteristics, strong triggers are required for the release of these molecules from their storing units into the synaptic cleft.

Dynorphin Funtion, Mechanism, Withdrawal, Anxiety

Dynorphin Function Function

Due to their specified presence in the different areas of the brain, they exert their effect directly on the CNS functions including; memory, learning, emotional control, pain, and stress. Despite their very short duration of actions, they are involved in many other physiological functions depending upon their varying sites of production.

A very comprehensive description of functions performed by the dynorphins is given in the following;

Analgesia:dynorphins are considered important for their action in response to the pain stimuli and generally called the modulator to the pain triggering stimulus.

Appetite and circadian rhythms:dynorphins that produce in the hypothalamus of the brain are generally considered responsible for the induction of appetite. These also have control over ultimate weight control as well as circadian rhythms leading to the maintenance of homeostasis.

Addiction:The continuous exposure of cocaine to the human body ultimately leads to the production of dynorphins in the striatum region of the brain which is responsible for the addiction control.

Stress and depression: dynorphins are considered responsible for the aversive behaviors leading to stress and depression among the subjects.

Temperature regulation:dynorphins are also found to be responsible for the temperature regulations when they are produced in the periaqueductal gray (PAG) area of the brain to interact with the μ-opioid receptor (MOR).

Dynorphin Function Mechanism

Dynorphins have a very simple mechanism of action in which they mainly target both types of the κ-opioid receptor (KOR) including K1 and K2. KOR is considered as the primal receptors for the dynorphins but the peptide family also shows some attraction for several other receptors including; μ-opioid receptor (MOR),N-methyl-D-aspartic acid (NMDA)-type glutamate receptorand δ-opioid receptor (DOR). But the degree of affinity for each receptor depends upon the type and location of the dynorphins. As well as the potency of different types of dynorphins depends upon their affinities towards the specified receptors.

Dynorphin Function Withdrawal

It has been stated that dynorphins play a vital role in the withdrawal of different abusive drugs including cocaine and alcohol, as dynorphins have a primary affinity towards κ-opioid receptor (KOR).

Kappa-opioid receptor (KOR) is responsible for the generation of response against the typical chemical concentrations and behavior produced as a result of continuous exposure to abusive drug products. A well as it also plays an important role in restricting the vulnerability of the individuals for the pharmacological actions of abusive drug products.

Dynorphin Function Dynorphin Anxiety

The general mechanism of anxiety induction in the subjects is related to the overexcitation of the neural network in the amygdala portion of the brain. This excitation leads to the release of somatostatins (SOMs) responsible for the arousal of anxious behavior.

Meanwhile, this mechanism triggers the release of dynorphins which potentially interrupt in this process leading to the tapering off of somatostatins release which results in the inhibition of induction of stress or anxiety among subjects.

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