Central neural mechanism of increased pain sensitivity induced by nicotine abstinence / 生理学报

Nicotine is the main addictive component in cigarettes that motivates dependence on tobacco use for smokers and makes it difficult to quit through regulating a variety of neurotransmitter release and receptor activations in the brain. Even though nicotine has an analgesic effect, clinical studies demonstrated that nicotine abstinence reduces pain threshold and increases pain sensitivity in smoking individuals. The demand for opioid analgesics in nicotine abstinent patients undergoing surgery has greatly increased, which results in many side effects, such as nausea, vomiting, and respiratory depression, etc. In addition, these side effects would hinder patients' physical and psychological recovery. Therefore, identifying the neural mechanism of the increase of pain sensitivity induced by nicotine abstinence and deriving a way to cope with the increased demand for postoperative analgesics would have enormous basic and clinical implications. In this review, we first discussed different experimental pain stimuli (e.g., cold, heat, and mechanical pain)-induced pain sensitivity changes after a period of nicotine dependence/abstinence from both animal and human studies. Then, we summarized the effects of the brain neurotransmitter release (e.g., serotonin, norepinephrine, endogenous opioids, dopamine, and γ-aminobutyric acid) and their corresponding receptor activation changes after nicotine abstinence on pain sensitivity. Finally, we discussed the limits in recent studies. We proposed that more attention should be paid to human studies, especially studies among chronic pain patients, and functional magnetic resonance imaging might be a useful tool to reveal the mechanisms of abstinence-induced pain sensitivity changes. Besides, considering the influence of duration of nicotine dependence/abstinence and gender on pain sensitivity, we proposed that the effects of nicotine abstinence and individual differences (e.g., duration of abstinence from smoking, chronic/acute abstinence, and gender) on abstinence-induced pain sensitivity should be fully considered in formulating pain treatment protocols. In summary, this paper could deepen our understanding of nicotine abstinence-induced pain sensitivity changes and its underlying neural mechanism, and could also provide effective scientific theories to guide clinical pain diagnosis and treatment, which has important clinical significance.

Spinal cord magnetic resonance imaging: methods and applications / 生理学报

Spinal cord magnetic resonance imaging (MRI) is an advanced imaging technique (mainly in the cervical cord) and has been gradually used in basic scientific research such as human sensation and motor function, and clinical applications such as spinal cord injury, myelitis, and chronic pain, etc. The development of spinal cord MRI is still at the early stage compared with brain MRI and limited by the current MRI technology and data analysis methods. This review focuses on the methods and applications of spinal cord MRI technology in the basic research fields of cognitive neuroscience and clinical application. Firstly, we will introduce the imaging principle, methods, measurement standards, and applications of most commonly used multimodal spinal cord MRI techniques, including quantitative spinal cord MRI (such as structural, diffusion, spectroscopy, myelin water, magnetization transfer, and chemical exchange saturation transfer imaging, etc.) and spinal functional MRI (fMRI). Secondly, we will discuss the technical challenges and possible solutions of spinal cord MRI data processing from the three dimensions of denoising, data processing pipeline optimization, and repeatability and reliability. Finally, we will discuss the application status and development prospects of spinal cord MRI.