Nociceptive behavioral responses to chemical, thermal and mechanical stimulation after unilateral, intrastriatal administration of 6-hydroxydopamine.

The basal ganglia are involved not only with motor processes such as posture, pre-movement planning and movement initiation, but also with the processing and modulation of nociceptive somatosensory information. In the current studies, unilateral, intrastriatal 6-hydroxydopamine (6-OHDA) was used to investigate how dopamine depletion alters nociceptive behavioral responses to chemical, thermal and mechanical stimulation in rats. Compared to control rats injected with intrastriatal saline, rats depleted of dopamine displayed increased nociceptive responses to chemical stimulation of the face and hyperalgesic responses to thermal stimulation of the hind paw without alterations in rearing behavior or body weight gain. Minor changes were observed in the response to mechanical stimulation of the hind paws and face. These data provide further evidence that the dopaminergic nigrostriatal pathway plays a role in the modulation of nociceptive information.