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Plant-Derived Compounds as New Therapeutics for Substance Use Disorders
Published in Namrita Lall, Medicinal Plants for Cosmetics, Health and Diseases, 2022
Kevin S. Murnane, Mary Frances Vest
These transitions from abuse to dependence likely involve extended neural systems. While dopaminergic projections from the VTA to NAcc form the core of the reward circuit, this circuit is highly modulated by extended limbic regions, including the amygdala, medial prefrontal cortex (PFC) and hippocampus. In this regard, neuronal projections from the basolateral amygdala to NAcc play an important role in processing reward-related cues and drug craving (Hsu et al., 2020). Likewise, the amygdala may be involved in drug cue reactivity as triggering environments can induce similar electrophysiological activity in the NAcc and amygdala (Hsu et al., 2020; Li et al., 2015; Venniro et al., 2020). The use of plant-derived medications that target the extended reward system and these additional neural substrates may be more promising than approaches that focus exclusively on the core dopamine reward system.
Substance Use Disorder, Intentional Self-Harm, Gun Violence, and HIV/AIDS
Published in Amy J. Litterini, Christopher M. Wilson, Physical Activity and Rehabilitation in Life-threatening Illness, 2021
Amy J. Litterini, Christopher M. Wilson
SUD first begins by experimentation with substances, which leads to stimulation of the dopamine reward pathway of the brain. Depending on the form of the substance, a stimulant or a depressant, certain physiological effects are experienced by users, with some causing feelings of euphoria through reward circuit activation (e.g. cocaine, methamphetamine, and heroin). Addiction is subsequently marked by symptoms of craving, followed by increased physiologic tolerance for the substance. Tolerance is demonstrated by the need for increased amounts to achieve the desired effect, and markedly diminished effects with continued use of the same amount of the substance. Attempts to reduce, or eliminate use of the substance, are met with withdrawal symptoms, which is indicative of dependence.
Physiology of the Pain System
Published in Sahar Swidan, Matthew Bennett, Advanced Therapeutics in Pain Medicine, 2020
The limbic system is a set of brain structures on either side of the thalamus that directs emotion, behavior, motivation, long-term memory, and olfaction. The mesolimbic pathway is part of the reward circuit. Dopaminergic neurons in the ventral tegmental area (VTA) of the midbrain project to the forebrain nucleus accumbens (NAc). Burst firing of dopaminergic neurons into the NAc serves as a reward signal and is inhibited by tonic GABA input.15 Opioids inhibit GABAergic tone on these neurons, while pain relief directly engages dopamine circuitry.15 The mesolimbic pathway has been implicated in depression, anxiety, pain sensation, anticipation of analgesia or placebo-induced analgesia, and chronic pain.16 Different types of pain can impact different aspects of the VTA and result in either activation or inhibition. In this way, dopamine release is variable based on various pain signals.16 These dopaminergic pathways are variably altered with stress as well as opioids. Dynorphin and the kappa opioid receptor can play a role in impairing dopamine release in the Na.16
Acute stress reduces reward-related neural activity: Evidence from the reward positivity
Published in Stress, 2021
Kreshnik Burani, Austin Gallyer, Jon Ryan, Carson Jordan, Thomas Joiner, Greg Hajcak
Stress and aberrant reward system functioning are implicated in the etiology and pathophysiology of Major Depressive Disorder (MDD) (Admon & Pizzagalli, 2015; Hammen, 2005; Whitton et al., 2015). Many studies have found that participants with MDD are characterized by reduced activation of the reward circuit, including blunted activity in the ventral striatum (VS) and the orbitofrontal cortex (Epstein et al., 2006; Forbes et al., 2006; Pizzagalli et al., 2009). Both stress and reward circuit hypoactivation may be risk factors for, and important correlates of, MDD and depressive symptoms. One potential etiological and pathophysiological model that links stress and blunted reward processing to depression postulates that chronic stress reduces reward circuit function and may induce anhedonia (Pizzagalli, 2014) – a core symptom of MDD.
Introducing sexual dysfunction in mental care
Published in Expert Opinion on Drug Safety, 2021
Marie Gombert, Pura Ballester, Ana Segura, Ana M Peiró
In the brain, the secretion of hormones and neuropeptides is modulated consecutively to those direct and indirect signals. The hippocampus seems to control the signals coming from the external environment, while the amygdala and the hypothalamus control the response to social stimuli [13]. Stimulation of amygdala increases sexual performance and in parallel, triggers violent emotional responses. In addition, the dopaminergic system is known to be associated with sexual function as a pro-sexual neurotransmitter [14] due to the reward circuit. Sex stimulates dopamine, activating this process and inducing the pleasant sensation associated with sexual activity. During orgasm, oxytocin is secreted, regulating dopaminergic neurons exerting a mutual regulatory role [7,15]. However, chronic increased prolactin levels are associated with a delay in ejaculation and therefore an altered sexual function. In contrast with dopamine, serotonin exerts an inhibitory control on sexual function. This phenomenon appears to be mediated by an inhibition of the dopaminergic action through a regulation of dopaminergic neurons in the midbrain by serotonin, triggering the effect of dopamine in structures such as the nucleus accumbens [16]. Also, kisspeptin, a neuropeptide whose receptors are expressed in the limbic structures, participates in the control of the gonadotropic axis showing therapeutic action on sexual and reproductive disorders [17].
The Quest for Personal Significance and Ideological Violence
Published in AJOB Neuroscience, 2020
Arie W. Kruglanski, Molly Ellenberg
If, as we have delineated, the use, or even endorsement of violence, requires a strong motivational involvement in which a given need assumes temporary ascendance over others, this should be manifest in activity in the motivationally relevant areas of the brain. Consistent with this notion, Workman et al. (2020) find evidence for such activity in areas including the ventral striatum, ventromedial prefrontal cortex, and the amygdala, the three of which comprise a motivational reward circuit related to subjective value. Both moral conviction and participants’ judgements of the appropriateness of violence were related to activity in those regions, but also and even more pronouncedly to activity in the deeper levels of the prefrontal cortex such as the posterior medial prefrontal cortex as well as other limbic areas such as the hippocampus.