Chronic treatment with agonists of beta(2)-adrenergic receptors in neuropathic pain

Cardiovascular effects of chronic treatment with a β2-adrenoceptor agonist relieving neuropathic pain in mice

Neuropathic pain is often a chronic condition, disabling and difficult to treat. Using a murine model of neuropathic pain induced by placing a polyethylene cuff around the main branch of the sciatic nerve, we have shown that chronic treatment with β-AR agonists is effective against neuropathic allodynia. β-mimetics are widely used against asthma and chronic obstructive pulmonary disease and may offer an interesting option for neuropathic pain management. The most prominent adverse effects of chronic treatment with β-mimetics are cardiovascular. In this study, we compared the action of low doses of the selective β(2)-AR agonist terbutaline and of a high dose of the mixed β(1)/β(2)-AR agonist isoproterenol on cardiovascular parameters in a neuropathic pain context. Isoproterenol was used as a positive control for some heart-related changes. Cardiac functions were studied by echocardiography, hemodynamic measurements, histological analysis of fibrosis and cardiac hypertrophy, and by quantitative real time PCR analysis of atrial natriuretic peptide (Nppa), periostin (Postn), connective tissue growth factor (Ctgf) and β-myosin heavy chain (Myh7). Our data show that a chronic treatment with the β(2)-AR agonist terbutaline at low antiallodynic dose does not affect cardiovascular parameters, whereas the mixed β(1)/β(2)-AR agonist isoproterenol induces cardiac hypertrophy. These data suggest that low doses of β(2)-AR agonists may provide a suitable treatment with rare side effects in neuropathic pain management. This study conducted in an animal model requires clinical confirmation in humans.

Investigational pharmacology for low back pain

Study design:

Review and reinterpretation of existing literature.

Objective:

This review article summarizes the anatomy and pathogenesis of disease processes that contribute to low back pain, and discusses key issues in existing therapies for chronic low back pain. The article also explains the scientific rationale for investigational pharmacology and highlights emerging compounds in late development.

Results/conclusion:

While the diverse and complex nature of chronic low back pain continues to challenge clinicians, a growing understanding of chronic low back pain on a cellular level has refined our approach to managing chronic low back pain with pharmacology. Many emerging therapies with improved safety profiles are currently in the research pipeline and will contribute to a multimodal therapeutic algorithm in the near future. With the heterogeneity of the patient population suffering from chronic low back pain, the clinical challenge will be accurately stratifying the optimal pharmacologic approach for each patient.

Antidepressant treatment of neuropathic pain: looking for the mechanism

Neuropathic pain arises as a direct consequence of a lesion or disease affecting the somatosensory system. Among the recommended first-line treatments are antidepressant drugs – that is, molecules that were initially developed to treat other disorders of the nervous system. While their clinical efficacy against neuropathic pain was established more than 30 years ago, there is little information on the mechanism underlying their antidepressant action. However, understanding the therapeutic mechanism of these treatments could help to improve them, or even lead to new therapeutic approaches. In this article, we discuss the difficulties in conducting relevant preclinical research on neuropathic pain treatment with antidepressant drugs and we present the most recent findings on the putative mechanism, which highlight the role of β2-adrenoceptors and δ-opioid receptors.