Nicotine-specific and non-specific effects of cigarette smoking on endogenous opioid mechanisms.

This study investigates differences in μ-opioid receptor mediated neurotransmission in healthy controls and overnight-abstinent smokers, and potential effects of the OPRM1 A118G genotype. It also examines the effects of smoking denicotinized (DN) and average nicotine (N) cigarettes on the μ-opioid system. Positron emission tomography with (11)C-carfentanil was used to determine regional brain μ-opioid receptor (MOR) availability (non-displaceable binding potential, BPND) in a sample of 19 male smokers and 22 nonsmoking control subjects.

Chronic Back Pain Is Associated with Alterations in Dopamine Neurotransmission in the Ventral Striatum.

Unlabelled: Back pain is common in the general population, but only a subgroup of back pain patients develops a disabling chronic pain state. The reasons for this are incompletely understood, but recent evidence implies that both preexisting and pain-related variations in the structure and function of the nervous system may contribute significantly to the development of chronic pain. Here, we addressed the role of striatal dopamine (DA) D2/D3 receptor (D2/D3R) function in chronic non-neuropathic back pain (CNBP) by comparing CNBP patients and healthy controls using PET and the D2/D3R-selective radioligand [(11)C]raclopride.

Alterations in endogenous opioid functional measures in chronic back pain.

The absence of consistent end organ abnormalities in many chronic pain syndromes has led to a search for maladaptive CNS mechanisms that may explain their clinical presentations and course. Here, we addressed the role of brain regional μ-opioid receptor-mediated neurotransmission, one of the best recognized mechanisms of pain regulation, in chronic back pain in human subjects. We compared μ-opioid receptor availability in vivo at baseline, during pain expectation, and with moderate levels of sustained pain in 16 patients with chronic nonspecific back pain (CNBP) and in 16 age- and gender-matched healthy control subjects, using the μ-opioid receptor-selective radioligand [(11)C]carfentanil and positron emission tomography.