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Neuroimaging in Nuclear Medicine
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Anne Larsson Strömvall, Susanna Jakobson Mo
Like a key in a keyhole locking up a door, a neurotransmitter fits into special receptors, which in the receiving neuron triggers a specific process leading to action, a nerve impulse. There may be different kinds of receptors for each kind of neurotransmitter. Dopamine, for example, fits several kinds of dopamine receptors, called the D1, D2, D3, D4, and D5 receptors. The strength of the signal that is transmitted between two neurons depends on the amount of neurotransmitter in the synapse and the amount of time the neurotransmitter is allowed to act on the receptors. Therefore, there are specialized proteins or enzymes that degrade or recycle the released neurotransmitter in order to tune the signal. For example, neurotransmitters called monoamines (dopamine, serotonin, and noradrenaline) have their own transporter proteins (monoamine transporter proteins, MAPs) located at the nerve terminals. These reabsorb the neurotransmitter back into the nerve terminal. In this way, MAPs regulate the amount of available neurotransmitter in the synapse and thereby the response is tuned. In addition, some of the released neurotransmitter is recycled and may be re-used the next time. The dopamine transporter (DAT) is a well-known transporter protein, exclusively found on dopamine producing neurons. Apart from the MAPs, monoaminergic neurotransmission is regulated by enzymes called monoamine oxidase (MAO). The MAOs reduce the amount of available monoaminergic neurotransmitters in the synaptic cleft by decomposition.
Chronobiology and Human Health
Published in Lisa Heschong, Visual Delight in Architecture, 2021
It is also interesting to note that many fundamental elements of this system have multiple functions, most of which are still poorly understood. Consider, for example, the role of dopamine. At the start of the day, increasing light and declining levels of melatonin signal the time to begin the manufacture of dopamine, a neurotransmitter often described as the ‘pleasure’ chemical in the popular press, because it is associated with the reward system in the brain. Dopamine, along with its precursors and antagonists, has become a key component of drugs used in the treatment of depression, schizophrenia, ADHD, and the motor tremors of Parkinson’s disease. However, outside of the brain, dopamine also has important functions in regulating blood pressure, plus the activity of the kidney, the pancreas, and the intestine, among others. Furthermore, dopamine rhythms are critical to vision: it is also manufactured in the retina, exclusively during daylight hours, where it enhances the activity of cone cells to improve the clarity of daytime vision. Dopamine is also found in most all multicellular organisms, including the simplest of flatworms and jellyfish, where it is consistently connected to forms of motor control.9 Thus, dopamine seems to be an ancient organic molecule, which has been repurposed many times throughout evolution to fulfill many functions, but all of those likely having something to do with behaviors or metabolic activities which are most necessary or appropriate during daylight hours.
Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The main interconnections between these nuclei are shown in Figure 12.7. The basal ganglia do not have direct input or output connections with the spinal cord. Their primary input is from the cerebral cortex, and their primary output is to the thalamus and brainstem nuclei. The output nuclei of the basal ganglia are mainly the GPi and the SNr, although a direct connection has been reported from the STN to the pontine nuclei, and thence to the cerebellum. There is also evidence of a reciprocal connection between the cerebellar dentate nucleus and both the GPi and SNr (not shown in Figure 12.6). The excitatory connections represented by thin arrows in Figure 12.6 are glutamatergic, whereas the inhibitory connections represented by thin arrows are GABAergic. The thick arrows represent dopaminergic projections involving the neurotransmitter dopamine. These projections are excitatory or inhibitory, depending on the type of receptor in the target neurons in the dorsal striatum. The excitatory dopamine receptors are termed D1, whereas the inhibitory receptors are termed D2. Both receptors are G protein second-messenger systems (Section 6.3), involving an increase of cAMP in D1 receptors and a decrease of cAMP in D2 receptors. The basal ganglia contain about 80% of the brain’s dopamine.
Importance of positive emotions in software developers’ performance: a narrative review
Published in Theoretical Issues in Ergonomics Science, 2022
Riba Maria Kurian, Shinto Thomas
Furthermore, research shows that software developers experience low motivation and symptoms of work withdrawal as a result of negative affect (Graziotin et al. 2017). However, since positive emotions can co-occur with negative emotions during stressful situations (Folkman 2008), they plausibly have advantageous impacts on the developers’ motivation and work involvement. Research confirms that positive emotions stimulate the production of dopamine, which triggers further positive emotions (Fredrickson and Joiner 2002). These increased dopamine levels reinforce people’s ability to persevere during difficulties by regulating their motivation and intrinsic means of accomplishing their targets (Asociación RUVID 2013). Dopamine is part of the human internal reward system, which regulates pleasure; furthermore, scientific evidence has shown that dopamine encourages people to initiate, act, and persevere and that it is released when they seek to experience a desired state or address problems (Salamone and Correa 2012). Accordingly, this positive association between positive emotions and increased dopamine levels boosts developers’ level of perseverance, and subsequently support them with enhanced performance, work involvement, and the potential to develop high-quality products, thus tackling issues of motivation which is a critical force in software development activities.
Vitamin D supplementation alters the expression of genes associated with hypertension and did not induce DNA damage in rats
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Carla Da Silva Machado, Alexandre Ferro Aissa, Diego Luis Ribeiro, Lusânia Maria Greggi Antunes
The bradykinin B2 receptor (encoded by Bdkb2) is involved in many processes, including smooth muscle contraction, inflammation, edema, cell proliferation, and BP regulation (Suchkova et al. 2014). Dopamine type 3 and type 5 receptors (DRD3 and DRD5), encoded by Drd3 and DRd5 genes, are known to influence vasodilation and alter cardiac contractility (Contreras et al. 2002; Horn and Murphy 1991). ITPR1, ITPR2, and ITPR3 are calcium channels that are modulated by inositol 1,4,5-triphosphate in response to the neurohumoral factors mediated by activation of α- and β-adrenergic receptors. In the heart, the ITPR2 subtype is the most expressed isoform, and enhanced expression of its gene (Itpr2) is related to induction of arrhythmias in rodents (Lipp et al. 2000; Rinne and Blatter 2010). The SCNN1A and SCNN1G proteins transport sodium between cells in response to cell signaling indicating low concentrations of sodium, therefore play a key role in BP homeostasis (Su and Menon 2001). Our data demonstrated vitamin D3 supplementation plays a role in control of cardiac gene expression in hypertensive and normotensive models.
Cognitive flexibility in humans and other laboratory animals
Published in Journal of the Royal Society of New Zealand, 2021
Quenten Highgate, Susan Schenk
To determine if an animal model is a valid representation of the human condition, we can assess its’ predictive validity, construct validity, and face validity (Willner 1984; Willner and Belzung 2015). Predictive validity is the extent that our knowledge of the human condition informs our animal model. For example, individuals suffering from Parkinson’s Disease have low levels of the neurochemical dopamine and are cognitively inflexible (Owen et al. 1993; Richards et al. 1993; Cronin-Golomb et al. 1994). If dopamine levels were also implicated in behavioural flexibility, there would be some evidence of predictive validity, which is the case (Stefani and Moghaddam 2006).