Potentiation of intrathecal DAMGO antinociception, but not gastrointestinal transit inhibition, by 5-hydroxytryptamine and norepinephrine uptake blockade

Pain and psychiatry: a critical analysis and pharmacological review

Pain is one of the most difficult medical problems to diagnose and treat and can be a common symptom of several psychiatric disorders. Pain-related issues are heterogeneous and often underestimated or misinterpreted, with the result that psychiatric interventions, which might have been beneficial from the outset, are often delayed or requested only as a last measure. Several problems arise from the definition, classification and assessment of pain, when documented according to the different scales which are commonly used, since these attempt to cover a multitude of analytical requirements, without really succeeding. An area of constant debate regards the connection between pain and various psychiatric disorders, and the difficulty in the classification of pain disorders within the currently existing framework. The pharmacological treatment of pain is complex and implies a variety of different compounds, from opioids to psychotropic medications like antidepressants and anticonvulsivants.

This paper explores the mutual and reciprocal influence between pain and psychiatric disorders reviewing the latest developments in the definition, assessment and treatment of pain, with special emphasis on the impact of pain on psychiatric disorders (and vice versa), and on the use of psychotropic drugs in the treatment of pain syndromes.

Binding of Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) and related peptides to mu 1 and mu 2 opiate receptors

Two endogenous brain peptides (Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) and Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2)), a cyclized analog and two fragments of Tyr-W-MIF-1, and hemorphin (Tyr-Pro-Trp-Thr) were tested for binding to mu 1 and mu 2 opiate receptor. All these peptides bound to both mu 1 and mu 2 sites in assays optimized to discriminate these subtypes of the mu opiate receptor in membranes from bovine thalamus. The cyclized analog of Tyr-W-MIF-1, previously shown to have potency near that of Tyr-D-Ala-Gly-N-MePhe-Gly-ol (DAMGO) and morphine in producing analgesia after intracerebroventricular (i.c.v.) injection, bound to mu 1 and mu 2 sites with affinities similar to those of DAMGO. Tyr-W-MIF-1, previously shown to induce analgesia after i.c.v. injection but with much higher potency after intrathecal (i.t.) injection, also bound to both mu 1 and mu 2 sites with an affinity between that of morphiceptin and hemorphin. Although the highest ratios of Ki's for mu 2/mu 1 were shown by hemorphin, Tyr-W-MIF-1, and Tyr-W-MIF-1, none of the compounds were significantly different in selectivity. The results indicate that the relatively lower potency of Tyr-W-MIF-1 after i.c.v., compared with i.t. injection, is not due to a lack of binding to mu 1 sites. They suggest that it has relatively high efficacy at mu 2, but low efficacy at mu 1 sites, a possibility that might explain some of the novel properties of these peptides.