Involvement of nigrostriatal dopamine neurons in the contraversive rotational behavior evoked by electrical stimulation of the lateral hypothalamus.

This experiment was conducted to determine if nigrostriatal dopamine (DA) neurons are necessary for the contraversive rotational behavior evoked by electrical stimulation in the lateral hypothalamus. Rats were tested daily for electrical stimulation-induced rotational behavior (ESRB) for 5 days, and then given an injection of 6-hydroxydopamine (6-OHDA) or saline into the ipsilateral substantia nigra. The nearly total depletion of striatal DA (greater than 96%) completely abolished contraversive ESRB and resulted in the appearance of ipsiversive ESRB. Partial DA depletion (less than 95%) had no effect on contraversive ESRB. In animals with a partial DA depletion subsequent treatment with a low dose of alpha-methyl-p-tyrosine (40 mg/kg) attenuated contraversive ESRB, while having no effect on control animals, or the ipsiversive turning in animals with greater than 96% DA depletion. We conclude that the nigrostriatal DA system is necessary for contraversive rotational behavior evoked by lateral hypothalamic stimulation, but that only a small percentage of DA fibers are required to maintain apparently 'normal' function--at least as indicated by contraversive ESRB.