The participation of the nigro-thalamic pathway in the nigral control of the caudate nucleus.

: Unilateral injections of carbachol (CCh, 2 mul) to lateral parts of substantia nigra (SNlat) of the rabbit increased the alert index (participation of alert pattern in EEG), produced epileptoidal EEG discharges, sniffing, ipsi- and contralateral rotations, and abnormal movements of fore limbs, which may be regarded as an equivalent of localized seizures. Ipsilateral rotations appeared together with epileptoidal discharges confined to SNlat, while contralateral -- with discharges in ventrolateral thalamic nucleus (VLTh). The EEG discharges appeared firstly and had the longest duration in VLTh. Injection of CCh to medial substantia nigra (SNmed) did not produce contralateral turnings and rotations, and epileptoidal EEG discharges appeared primarily in SNmed. In rabbits with previously lesioned nigro-neostriatal pathway (NSP) at the level of Forel's fields, the EEG discharges produced by CCh injected into SNlat appeared firstly and were most prolonged in SNlat, while they appeared much later in caudate nucleus (NC), cerebral cortex, and VLTh. The contralateral rotations were inhibited, and ipsilateral ones -- potentiated in the lesioned rabbits.