Effects of lysergic acid diethylamide (LSD) and adjuvant-induced inflammation on desensitization to and metabolism of substance P in the mouse spinal cord

Relationship of substance P, 5-hydroxyindole acetic acid and tryptophan in serum of fibromyalgia patients

The serotonergic system has repeatedly been discussed to be involved in the pathophysiology of fibromyalgia (FM), which is a syndrome of widespread pain and sleep disturbance. Elevated levels of substance P (SP), a mediator of nociception, have been described in FM. In this study the possible relationship between SP and serotonin (5-HT) together with its precursor tryptophan (TRP) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) was evaluated in 51 serum samples of fibromyalgia patients. These parameters were compared with clinical data such as pain intensity or sleep quality. A strong negative correlation between SP and 5-HIAA (P = .000) as well as between SP and TRP (P = .009) could be demonstrated. High serum concentrations of 5-HIAA and TRP showed a significant relation to low pain scores (5-HIAA: P = .030; TRP: P = .014). Moreover, 5-HIAA was strongly related to good quality of sleep (P = .000), while SP was related to sleep disturbance (P = .005). These data are valid to support the hypothesis of a systemic involvement of 5-HT and SP in fibromyalgia.

Advances in fibromyalgia: possible role for central neurochemicals

The neurophysiologic term allodynia has been applied to fibromyalgia because people with that disorder experience pain from pressure stimuli which are not normally painful. The nociceptive neurotransmitters of animal studies are now relevant to this human model of chronic, widespread pain. Evidence is presented to implicate several chemical pain mediators (including serotonin, substance P, nerve growth factor, and dynorphin A) in the pathogenesis of fibromyalgia. This perception is hopeful because it offers many new options for the development of innovative therapy.

Substance P receptor desensitization in the dorsal horn: possible involvement of receptor-G protein complexes

The repeated administration of a high dose of substance P (SP) onto the spinal cord has been shown to attenuate behavioral responses to an intense heat (tail-flick) or noxious mechanical stimulus (paw pressure). Studies performed to investigate the action of spinal SP have suggested that changes in behavioral responses involve endogenous opiate or neurokinin systems. This study was performed to investigate whether the binding characteristics of SP receptors in the dorsal horn are altered following successive administration of SP. Two populations of [3H]-SP binding sites were distinguished on the basis of their binding affinity. Gpp(NH)p, a stable analogue of GTP, decreased the size and affinity of the high affinity binding component selectively labelled with [125I]-Bolton Hunter-SP. Repeated intrathecal administration of SP (15 micrograms) which reduced behaviors also reduced the number and affinity of high affinity binding sites. Thus, attenuated behaviors in response to repeated administration of SP are paralleled by an alteration of SP binding in the dorsal horn. The altered agonist affinity seen under desensitizing conditions raises the possibility that SP receptor desensitization involves an uncoupling of receptor-G protein complexes.