A behavioral methodology for assessing non-motoric deficits in the dopamine denervated rat

Tests of sensory-motor functions in rats with deficits in brain dopamine have generally relied on responses mediated by the dopamine-deficient hemisphere for the expression of the animals' behavioral response to stimulation. The present report demonstrates that in rats with unilateral denervation of dopamine neurons, a lateralized attenuation of behavioral response to nociceptive stimulation can be observed when the indicator response is not mediated by the dopamine-deficient hemisphere. Two readily measured responses to footshock, one unconditioned (i.e. ipsiversive turning) and one conditioned (i.e. passive avoidance), were shown to be attenuated when footshock was applied to the body surface contralateral versus ipsilateral to the dopamine-deficient hemisphere. The paradigm of using responses not mediated by the lesion hemisphere to assess behavioral responses to stimuli applied to a lesion hemisphere provides a behavioral methodology for assessing behavioral deficits in sensory processing that are not confounded with lesion-induced motoric deficits.