background: musculoskeletal pain is a major clinical problem, but researchers lack viable animal models to study this phenomenon. however, formalin injections are widely used to produce tonic and neurogenic nociceptive responses in rodents. rodents can present a potential animal model for pain. objectives: to develop a muscle pain model with intramuscular injection of formalin in rats. material...

INTRODUCTION Opioid analgesia can be explored with quantitative sensory testing, but most investigations have used models of phasic pain, and such brief stimuli may be limited in the ability to faithfully simulate natural and clinical painful experiences. Therefore, identification of appropriate experimental pain models is critical for our understanding of opioid effects with the potential to i...

in this study, the effects of subcutaneous (sc) injection of pilocarpine (a cholinomimetic agent) and atropine (a muscarinic receptors antagonist) were investigated on a tonic model of orofacial pain in rats. the contribution of the endogenous analgesic opioid system was assessed using naloxone (an opioid receptors antagonist). tonic orofacial pain was induced by sc injection of a diluted forma...

Two firing modes of thalamocortical (TC) neurons, tonic and burst firings, are thought to reflect the divergent states of sensory signal transmission from the thalamus to the cortex. However, the behavioral consequences of changes in the thalamic firing between the two modes have not been well demonstrated. Moreover, although the firing modes of TC neurons are known to be affected by corticotha...

This study utilized the methodology of Functional Measurement theory to investigate the additivity of painful and non-painful thermally induced experiences at one body site with those produced by brief noxious and innocuous electrical stimuli at another. Forty healthy young subjects were tested, using a Peltier thermode to induce tonic pain and an electrocutaneous stimulator for presenting phas...

Following tissue injury, spinal neurons increase in spontaneous activity and in responsiveness to peripheral stimulation. These changes in spinal neurons may underlie abnormal pain behavior. Nicotinic acetylcholine receptor (nAChR) agonists are analgesic when evaluated in animal models of pain, but it is not known if the nAChRs differentially modulate acute and tonic pain. To test this, mecamyl...

Inhibition of N-methyl-D-aspartate (NMDA)-mediated neurotransmission has been demonstrated to provide antinociceptive actions in a number of animal models of tonic and neuropathic pain. However, both competitive and noncompetitive NMDA receptor antagonists are ataxic at analgesic doses. Partial agonists and antagonists of the NMDA-associated glycine site have demonstrated antinociceptive action...

The role of mu-opioid receptors (MORs) in the inflammatory pain processing mechanisms within the ventrobasal complex of the thalamus (VB) is not well understood. This study investigated the effect of modulating MOR activity upon nociception, by stereotaxically injecting specific ligands in the VB. Nociceptive behaviour was evaluated in two established animal models of inflammatory pain, by usin...