Central Processing of Itch in the Midbrain Reward Center

Su, Xinyu; Chen, Ming; Yuan, Yuan; Liu, Ying; Guo, Su-Shan; Luo, Huoqing; Huang, Chen; Sun, Wenzhi; Li, Yong; Zhu, Michael X.; Liu, Ming-Gang; Hu, Ji; Xu, Tian‐Le

doi:10.1016/j.neuron.2019.03.030

Cited by 60 publications

(48 citation statements)

References 64 publications

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“…Consistent with addiction, the DA pathway from VTA to NAc was activated in a chronic itch animal model . Moreover, chronic itch patients reported intense pleasurable sensation, and evoked activations in the reward‐related areas induced by scratching were significantly increased .…”

Section: Clinical and Neurobiological Similarities Between Addiction mentioning

confidence: 87%

“…Change in VTA activity also correlated significantly with scratching‐induced pleasure in humans . Furthermore, a recent animal study demonstrated that the system whereby VTA DA neurons mediate reward from itch relief concorded with that in humans with involvement of the midbrain reward centre in scratching‐induced pleasantness . The urge for a pleasant sensation induced by scratching an itch can be considered similar to the positive reinforcement involved in satisfying a crave for drugs in the initial stages of drug addiction.…”

Section: Clinical and Neurobiological Similarities Between Addiction mentioning

confidence: 99%

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Addiction and the itch‐scratch cycle. What do they have in common?

Ishiuji

2019

Experimental Dermatology

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Itch is a multidimensional experience involving various brain regions associated with sensory perception and emotion, as well as an urge to scratch employing the motor system. Scratch temporarily relieves itch sensation in healthy subjects. However, in patients with chronic itch, rather than inhibit, scratch may aggravate itch. Patients with chronic itch, such as those with atopic dermatitis, experience severe itch and a strong desire to scratch. This urge to scratch is the driving force underlying the formation of the itch‐scratch‐cycle, an addictive and vicious cycle in chronic itch patients. This vicious itch‐scratch behaviour and various types of addiction (henceforth, including recreational drug use) were shown to share common sensory mechanisms. Abnormalities have been observed in central neural circuits, including the reward, motivation/drive, control and learning/memory circuits, as well as other brain systems. Reward systems, including the ventral tegmental area (VTA), nucleus accumbens (NAc) and striatum, are important for brain processing of both addiction and itch. In addition to reward, addicted individuals can experience severe disruptions in motor control, cognitive awareness, executive function, learning/memory and even emotional functions. Findings showing that addiction and itch share a common neurobiological foundation could have important mechanistic and therapeutic implications. Here we propose that similar neuroadaptations exist in addiction and chronic itch patients.

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Section: Clinical and Neurobiological Similarities Between Addiction mentioning

confidence: 87%

Section: Clinical and Neurobiological Similarities Between Addiction mentioning

confidence: 99%

Addiction and the itch‐scratch cycle. What do they have in common?

Ishiuji

2019

Experimental Dermatology

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“…The injection method and dose of the virus referred to our previous studies (Su et al, 2019). Briefly, rats were first subjected to anesthesia (3% pentobarbital sodium, 40 mg/kg, i.p.)…”

Section: Virus Injectionmentioning

confidence: 99%

“…The optical fiber implantation methods and laser light stimulation parameters referred to our previous studies and other related articles (Su et al, 2019). The specific steps were as follows: optical fibers were implanted at about 4 weeks after virus injection, rats were anesthetized with 3% pentobarbital sodium (40 mg/kg, i.p.)…”

Section: Optical Fiber Implantation and Blue Laser Light Stimulationmentioning

confidence: 99%

Optogenetic Neuronal Stimulation Promotes Functional Recovery After Spinal Cord Injury

Deng

Min

et al. 2021

Front. Neurosci.

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Although spinal cord injury (SCI) is the main cause of disability worldwide, there is still no definite and effective treatment method for this condition. Our previous clinical trials confirmed that the increased excitability of the motor cortex was related to the functional prognosis of patients with SCI. However, it remains unclear which cell types in the motor cortex lead to the later functional recovery. Herein, we applied optogenetic technology to selectively activate glutamate neurons in the primary motor cortex and explore whether activation of glutamate neurons in the primary motor cortex can promote functional recovery after SCI in rats and the preliminary neural mechanisms involved. Our results showed that the activation of glutamate neurons in the motor cortex could significantly improve the motor function scores in rats, effectively shorten the incubation period of motor evoked potentials and increase motor potentials’ amplitude. In addition, hematoxylin-eosin staining and nerve fiber staining at the injured site showed that accurate activation of the primary motor cortex could effectively promote tissue recovery and neurofilament growth (GAP-43, NF) at the injured site of the spinal cord, while the content of some growth-related proteins (BDNF, NGF) at the injured site increased. These results suggested that selective activation of glutamate neurons in the primary motor cortex can promote functional recovery after SCI and may be of great significance for understanding the neural cell mechanism underlying functional recovery induced by motor cortex stimulation.

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“…Our brains actually reward us for scratching. That sense of euphoria originates from dopaminergic neurons in the ventral tegmental area, the same reward center of the brain that' give rise to the sensation of orgasm and is implicated in drug addiction 59 . So if scratching an itch is detrimental then why do our brains encourage us to do it?…”

Section: Introductionmentioning

confidence: 99%

The itch-scratch reflex generates protective immunity

Radjavi

Lebeau

2019

Preprint

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Itch: its complex neurobiology, its exquisite evolutionary conservation, and even the undeniably euphoric sensation of the scratch it evokes, are all suggestive of a productive physiological function. Nevertheless, we still struggle to answer (or altogether overlook) the basic question of why we itch in the first place. Here, we propose a simple hypothesis: the purpose of itch sensation is to evoke scratching behavior, which in turn boosts protective immunity against the broad range of pathogenic challenges that enter at the skin. We propose that the key function of itch induced scratching is to physically disrupt the skin, serving as a "mechanical adjuvant" that amplifies and directs immune responses to the precise site of potential pathogen entry. As proof of principle, we show that the potent adjuvanticity of itch inducing Compound 48/80 is dependent on this agent's ability to elicit scratching behavior.

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Central Processing of Itch in the Midbrain Reward Center

Abstract: Highlights d Itch elicits distinct activation patterns of GABA and DA neurons in VTA d GABA neurons signal aversion toward itch d DA neurons mediate reward to scratch-induced relief of itch d VTA neurons regulate scratching behaviors in chronic itch

Cited by 60 publications

References 64 publications

Addiction and the itch‐scratch cycle. What do they have in common?

Addiction and the itch‐scratch cycle. What do they have in common?

Optogenetic Neuronal Stimulation Promotes Functional Recovery After Spinal Cord Injury

The itch-scratch reflex generates protective immunity

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