To investigate the role of Group I mGluRs in allodynia and hyperalgesia, we examined the behavioural responses of rats to noxious and non-noxious mechanical and thermal stimuli following intrathecal (i.t.) treatment (25 nmol) with the selective mGluR1/5agonist, (RS)-dihydroxyphenylglycine ((RS)-DHPG). (RS)-DHPG administration produced a persistent decrease in response latency on a 48°C hotplate, a reduction in the 50% response threshold to von Frey hairs, and an increase in responses to a tail pinch. These data suggest that activation of spinal mGluR1/5receptors plays a role in the development of persistent allodynia and hyperalgesia associated with tissue or nerve injury.