Oxytocin and the modulation of pain experience: Implications for chronic pain management

In an acute environment pain has potential protective benefits. However when pain becomes chronic this protective effect is lost and the pain becomes an encumbrance. Previously unheralded substances are being investigated in an attempt to alleviate the burden of living with chronic pain. Oxytocin, a neuropeptide hormone, is one prospective pharmacotherapeutic agent gaining popularity. Oxytocin has the potential to modulate the pain experience due to its ubiquitous involvement in central and peripheral psychological and physiological processes, and thus offers promise as a therapeutic agent. In this review, we discuss previous effective applications of oxytocin in pain-free clinical populations and its potential use in the modulation of pain experience. We also address the slowly growing body of literature investigating the administration of oxytocin in clinical and experimentally induced pain in order to investigate the potential mechanisms of its reported analgesic actions. We conclude that oxytocin offers a potential novel avenue for modulating the experience of pain, and that further research into this area is required to map its therapeutic benefit.     

Catastrophizing and pain sensitivity among chronic pain patients: Moderating effects of sensory and affect focus

Background: Pain catastrophizing is a particularly harmful cognitive factor among patients with chronic pain, but little is known of mechanisms linking this factor to pain and disability.Purpose: The study examined whether attentional focus on sensory versus affective information about pain constitutes a path-way by which catastrophizing affects responses to painful stimuli.Methods: Participants were 82 chronic pain patients assigned randomly to sensory focus, affect focus, or control conditions. They underwent cold pressors first prior to and then following an information focus manipulation, and they completed the Pain Catastrophizing Scale (PCS).Results: Regressions produced significant Condition × PCS interaction effects on threshold and tolerance change from first to second cold pressor, such that PCS scores were significantly and negatively related to these changes in both sensory and affect focus conditions, but not in the control condition. Only a main effect for PCS scores emerged for self-reported pain changes. Solving regression equations for hypothetical PCS values (± 1 SD from the mean) revealed that (a) high catastrophizers decreased threshold and tolerance in the affect focus condition and showed no appreciable changes in sensory focus and (b) low catastrophziers showed increases in threshold and tolerance in sensory focus, but no appreciable changes in affect focus. Further, the degree to which patients focused on emotions during pain partly mediated effects of PCS scores on threshold and tolerance changes.Conclusion: Catastrophizing about pain may affect pain severity and distress of chronic pain patients through a bias toward processing the most disturbing elements of a painful stimulus. This study was performed in partial fulfillment of requirements for Elizabeth Michael’s doctorate under the supervision of John W. Burns. We thank Kenneth Lofland, Ph.D., Director of Psychological Services, Pain & Rehabilitation Center of Chicago, and Stephen Bruehl, Ph.D., Rehabilitation Institute of Chicago for facilitating the conduct of this study, and three anonymous reviewers whose comments were greatly appreciated.     

Self-appraised problem solving and pain-relevant social support as predictors of the experience of chronic pain

The purpose of this study was to examine the contributions of self-appraised problem-solving competence and pain-relevant social support to the prediction of pain, depression, and disability. The 234 chronic pain patients referred for participation in a comprehensive pain management program were administered self-report measures of pain, depression, disability, pain-relevant social support, and problem solving. Hierarchical multiple-regression analyses revealed that lower self-appraised problem-solving competence was related to increased pain, depression, and disability. Pain-relevant social support was directly related to pain and disability but indirectly related to depression. High levels of pain-relevant social support were found to buffer the relation between poorer self-appraised problem-solving competence and depressive symptoms. The results support the assessment of problem-solving skills in chronic pain patients and the investigation and utility of interventions aimed at increasing adaptive pain-relevant social support. This research was partially funded by a Department of Veterans Affairs Merit Review grant awarded to Robert D. Kerns, Ph.D.     

Acute versus chronic pain experience in Alzheimer's disease. a new questionnaire

The low use of analgesics in patients with Alzheimer's disease (AD), compared to nondemented elderly persons, is generally explained by (1) a lower prevalence of painful conditions in the former group and (2) undertreatment of pain due to a decrease in communicative abilities in AD. However, considering the neuropathology in limbic areas in this disorder, a decline in pain affect may also explain this phenomenon. In the present study, a newly developed questionnaire was applied to 20 elderly persons without dementia, 20 patients in an early stage and 20 patients in a midstage of AD. The questionnaire includes 10 pairs of painful situations, each pair consisting of an acute and a chronic affective painful situation. It was hypothesized that, compared to controls, AD patients during the course of the disease would report to suffer increasingly more from an acute than from a chronic, affective painful situation. The results support our hypothesis. Limitations of the present study are discussed.     

The neurobiology of pain, affect and hypnosis

Recent neuroimaging studies have used hypnotic suggestion to distinguish the brain structures most associated with the sensory and affective dimensions of pain. This paper reviews studies that delineate the overlapping brain circuits involved in the processing of pain and emotions, and their relationship to autonomic arousal. Also examined are the replicated findings of reliable changes in the activation of specific brain structures and the deactivation of others associated with the induction of hypnosis. These differ from those parts of the brain involved in response to hypnotic suggestions. It is proposed that the activation of a portion of the prefrontal cortex in response to both hypnotic suggestions for decreased pain and to positive emotional experience might indicate a more general underlying mechanism. Great potential exists for further research to clarify the relationships among individual differences in reactivity to pain, emotion, and stress, and the possible role of such differences in the development of chronic pain.     

Post-conditioning experience with acute or chronic inflammatory pain reduces contextual fear conditioning in the rat

There is evidence that pain can impact cognitive function in people. The present study evaluated whether Pavlovian fear conditioning in rats would be reduced if conditioning were followed by persistent inflammatory pain induced by a subcutaneous injection of dilute formalin or complete Freund's adjuvant (CFA) on the dorsal lumbar surface of the back. Formalin-induced pain specifically impaired contextual fear conditioning but not auditory cue conditioning (Experiment 1A). Moreover, formalin pain only impaired contextual fear conditioning if it was initiated within 1 h of conditioning and did not have a significant effect if initiated 2, 8 or 32 h after (Experiments 1A and 1B). Experiment 2 showed that formalin pain initiated after a session of context pre-exposure reduced the ability of that pre-exposure to facilitate contextual fear when the rat was limited to a brief exposure to the context during conditioning. Similar impairments in context- but not CS-fear conditioning were also observed if the rats received an immediate post-conditioning injection with CFA (Experiment 3). Finally, we confirmed that formalin and CFA injected s.c. on the back induced pain-indicative behaviours, hyperalgesia and allodynia with a similar timecourse to intraplantar injections (Experiment 4). These results suggest that persistent pain impairs learning in a hippocampus-dependent task, and may disrupt processes that encode experiences into long-term memory.     

Psychiatry and chronic pain

Pain and chronic pain have been defined by the International Association for the Study of Pain. Psychological mechanisms are recognized in the production of pain, but their importance has probably been overstated. Selection factors have not been attended to sufficiently, and traditional methods which have been relied upon for the diagnosis of hysterical pain have been misleading. Much emotional change seen with pain is a consequence of the physical disorder. Types of illness, seen by psychiatrists working with patients in pain, are described, and brief comments offered on their management.     

Self-esteem and chronic pain

The self-esteem scores of 20 ‘pain-prone’ patients were compared with the scores of 20 ‘organic-pain’ patients and two groups of 20, one group an adult control, the other a student control. Self-esteem scores of the pain-prone patients were significantly lower than for the other three groups, who did not differ significantly from each other. The pain-prone patients were given a 12-week treatment programme involving psychological intervention. Further self-esteem scores were obtained for them and the controls. Treatment was associated with a significant increase in self-esteem for the pain-prone group, while the controls showed no significant difference from their earlier self-esteem scores. This result is discussed in terms of the importance of therapy directed at the psychological dimension of pain-prone patients.     

Alzheimer patients report less pain intensity and pain affect than non-demented elderly

Pain assessment for patients with Alzheimer's disease (AD) is generally aimed at quantifying pain, i.e., the intensity and locations of pain. Based on the extensive neuropathology in limbic brain areas with this disorder, we hypothesized that, compared to control patients, AD patients would report an additional loss of qualitative aspects of pain, i.e., pain affect. This hypothesis was tested by administering specific parts of three pain questionnaires and comparing the use of analgesics in 19 AD patients with that of 18 elderly patients without dementia who were matched for the presence of painful conditions. Results reveal that AD patients, compared to controls, experience less intense pain and less pain affect. In contrast, the number of AD patients using analgesics did not differ from the number of controls. These findings suggest that pain assessment for patients with AD should be focused on both quantitative and qualitative aspects of pain.     

Comprehension of pictograms for pain quality and pain affect in adults with Down syndrome

Background Adults with Down syndrome (DS) are at risk for age-related painful physical conditions, but also for under-reporting pain. Pictograms may facilitate self-report of pain, because they seem suitable for the global visual processing in DS and for iconic representation of abstract concepts.

Method Participants (N?=?39, M age?=?41.2) assigned pain qualities to pictograms, rated pain affect levels in facial scales (pictograms vs. drawn faces), and performed cognitive tests.

Results Recognition of all intended pain qualities was above chance level. Pain affect levels of both facial scales were ordered equally well. Both facial scales were preferred equally well. Comprehension of the 3 scales was positively associated with mental age, receptive language ability, and verbal memory. Most participants (74%) had pictograms in their direct environment, mainly to communicate activities or objects.

Conclusion Using pictograms may optimise communication about pain for a subgroup of cognitively higher functioning adults with DS.     

Cognitive failure and chronic pain

Relationships between pain variables, emotional functioning, and cognitive inefficiency as assessed by the Cognitive Failures Questionnaire (CFQ) were investigated. In general, the tendency to make cognitive errors was found to be related to emotional difficulties but to be unrelated to pain variables. Four explanations were proposed: First, that increased reports of cognitive and affective difficulties may reflect a "complaining" response set; second, that the constructs of cognitive inefficiency and affective distress overlap while the constructs of the former and pain do not; third, cognitive and affective dysfunction exist in a circular relationship; and finally, that high rates of cognitive failure may predispose pain patients to have subsequent difficulties with low mood.     

Cortical excitation and chronic pain

Investigation of the basic mechanisms of chronic pain not only provides insights into how the brain processes and modulates sensory information but also provides the basis for designing novel treatments for currently intractable clinical conditions. Human brain imaging studies have revealed new roles of cortical neuronal networks in chronic pain, including its unpleasant quality, and mouse studies have provided molecular and synaptic mechanisms underlying relevant cortical plasticity. This review paper will critically examine the current literature and propose a cortical network model for chronic pain.     

Myofascial pain syndrome in the differential diagnosis of chronic abdominal pain

Myofascial pain syndrome is a painful musculoskeletal condition, and a quite common cause of chronic pain. It is characterized by the development of trigger points that are locally tender when active, and refer pain through specific patterns to other areas of the body. Its etiological factors are various; trauma, vertebral column diseases, systemic disorders, psychological distress, lack of motion, and chilling of the body parts. Myofascial pain syndrome may be misdiagnosed as arising from a visceral source especially if its probability is not kept in mind and a proper patient examination is lacking. Although there are many therapeutic approaches, trigger point injections can be diagnostic and therapeutic.