The modulatory functions and neurotransmitter functions in neuronal communication make exosomes an important player in nerve regeneration, synaptic function, and immune response. This explains why alterations in their normal functioning have been linked to the development of many neurodegenerative and neurological conditions (Mavroeidi et al., 2022). Steroids are another class of substance currently classified as noncanonical neurotransmitters based on recent research submissions. In addition to their biological functions as hormones, steroids exert neurotransmitter-like effects such as signaling at the membrane and nucleus to regulate brain function; activating intracellular signaling cascades; gating membrane channels; increasing intracellular calcium release; and activating Src, MAPK, or phosphatidylinositol-3-kinase-AKT pathways. D-aspartic acid also falls into the category of noncanonical neurotransmitters.
This small molecule seemed to be abundantly distributed in the nervous tissues of both animals and humans. Researchers have demonstrated how D-aspartic acid controls neurological activities in the embryonic development stage of rats and chickens. In humans, this amino acid is found in synaptic vesicles, prompting researchers to study and classify it as an endogenous neurotransmitter. Other observations responsible for the classification of D-aspartic acid as a noncanonical neurotransmitter include its activity as a cell–cell signaling molecule, its elimination from postsynaptic neurons after its action, and its synthesis in presynaptic neurons through the D-aspartate racemase conversion from L-aspartate (Dalangin et al., 2020). To a large extent, these alterations and blocks are directly implicated in the onset of many neurological conditions. This explains why psychopharmacological interventions focused on treating mental and behavioral disorders are designed to influence neuronal signaling. This section of the course is designed to explore the primary connections between neurotransmitter functioning and their direct influence on psycho-behavioral manifestation. various serotonin reuptake inhibitors (SSRIs). For serotonin, the serotonin transporter is an important drug target for modifying neuronal transmissions affecting behavior. SSRIs are a widely prescribed class of antidepressants that selectively impact the reuptake of serotonin in humans. This action is leveraged in the design of a psychotropic drug regimen for the treatment of depression and other psycho-behavioral pathologies. However, the actions of 5-HT receptors in humans seem to be largely influenced by functional polymorphisms that occur on the serotonin transporter gene. One of these polymorphisms, the serotonin-associated transporter polymorphic region (5-HTTLPR) has been associated with different types of phenotypical, genotypical, and behavioral manifestations, which highlights several crucial aspects of serotonin function. This polymorphism also seems to be present in many cases of major psychosis. Because serotonin shows links with mood in different animal models of depression, researchers have investigated a possible link between serotonin levels and extensive behavioral problems. Support from neuroimaging techniques has further established an interplay between serotonin concentration and the risk of mental disorders in humans. Recently, imaging techniques have also been used to demonstrate the direct association between suicidality in adolescents and the functionalities of the serotonergic system. Advanced imaging techniques such as positron-emission tomography (PET) and single photon emission computed tomography (SPECT) have been utilized with relevant radio ligands to unravel the relationship between major depressive disorder (MDD), schizophrenia, addiction, mood disorders, anxiety disorders, and attention-deficit/hyperactivity disorder (ADHD) with the serotonergic system (Moncrieff et al., 2022). Although there are still clarifications to be made in the available of evidence, these studies have provided hints regarding the role of serotonin in maintaining normal mental health and monitoring the development of psychopathologies. many neurological pathologies, including ADHD. The excitatory roles of ACh are more pronounced in the central nervous system, where its involvement in different neuronal transmission stages impacts learning, memory, arousal, and neuroplasticity. Multiple psycho-behavioral anomalies such as sleep disorders and rapid eye movement during sleep have been linked with different alterations in the normal functioning of ACh.
Understanding How Major Neurotransmitters Directly Influence Behavioral Manifestations Psychopharmacological interventions in the treatment of behavioral disorders directly leverage the complex interplay among neurons, neurotransmitters, the brain, and receptors. Neuronal transmissions at both the presynaptic and postsynaptic neurons are executed with controlled intensity and precision. Alteration in the signaling pathway or blocking of the normal signaling function can disrupt the propagation of signals in the brain and between the central nervous systems and vital organs.
Serotonin in Psycho-Behavioral Manifestations L-tryptophan is the precursor of serotonin in humans. As a precursor, L-tryptophan is converted to 5-hydroxyl-L-tryptophan, which is acted on by a specific decarboxylase to generate serotonin. In the context of neurology, serotonin is widely considered to be associated with mood and the decision- making process. Researchers studying this association have reported that a normal balance in serotonin levels promotes calmness, maturity, and decisive behavior. This action extends to several other neurological and psychological processes, including learning, memory, anxiety, cognition, depression, and aggression. Serotonin appears to also have an influential role in regular physiological processes such as digestion, maintaining appetite, and the regular movement of the bowels and GI tract. In adolescents, the rapid development of the brain and other parts of the central nervous system, as well as the metabolism of bone cells, is linked to serotonin functioning. In the central nervous system, the most delicate function of serotonin as it affects psychopharmacology is in the maintenance of chemical balance in the brain, an action that in turn regulates the physiological functions of the central nervous system. There are also multiple pieces of research evidence highlighting the roles of serotonin in the peripheral nervous system as it affects behavior (Richard et al., 2022). Serotonin mediates its psycho- behavioral and neurological actions through cell membrane 5-HT receptors. The 5-HT receptors are of seven types: 5-HT1 to 5-HT7. These receptors demonstrate slight variations in the method of mediating serotonin action. For instance, all the receptors, with the exception of 5-HT1 and 5-HT5, show an inhibitory action potential. The exceptions follows excitatory potential. Most of these receptors act by modulating the cAMP level, with 5-HT1 and 5-HT5 reducing the cAMP levels. The 5-HT2, 5-HT4, 5-HT6, and 5-HT7 receptors elevate the cAMP levels. Except for 5-HT3, which is ion-channel dependent, all other receptors are G-protein coupled receptors. Serotonin reuptake that occurs through the SERT or serotonin transporter can be terminated by Acetylcholine (ACh) in Psycho-behavioral Manifestations Discovered in 1914 by Hallett Dale, ACh acts primarily as a chemical messenger in muscle and has important roles in the regulation of behavior. This explains the psychopharmacological focus on ACh as a neurotransmitter of interest in many behavioral and neurological disorders. ACh exerts control on the autonomic nervous system, where dysfunction in the production or release of ACh has been linked to the onset of
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