Study of the morphological, electrophysiological and behavioral effects of unilateral kainic acid injection into the cat's substantia nigra

Activity in monkey substantia nigra neurons related to a simple learned movement

Single cell activity was recorded in the pars compacta (SNc) and pars reticulata (SNr) of the substantia nigra (SN) in 4 unanesthetized Macaca fascicularis to determine the motor role of the nucleus. Animals were trained to perform a simple task that involved moving a lever by elbow flexion-extensions, in the horizontal plane using the hand contralateral to the recording site. Two monkeys learnt to execute the task on both sides. Electromyograms (EMG) of limb muscles were recorded simultaneously with SN neurons. Discharge rate modulation related to specific movement phases was present in 35% of the neurons. A significant positive correlation of the discharge rate with movement velocity and amplitude was found in SNc and SNr neurons. Some SNr cells discharged in anticipation of the EMG, suggesting a participation of the nucleus in the preparation of movement. The activity of SNr neurons was also related to movement of the left and right upper limb. In conclusion, the SN seems to play an important role in the control of specific motor mechanisms, probably modulating movement velocity, amplitude and direction, with little participation of somatosensory feedback. The involvement of the SNr in the coordination of bilateral arm activity is discussed.

Localization studies of gamma-hydroxybutyrate receptors in rat striatum and hippocampus

Quantitative autoradiography using [3H] gamma-hydroxybutyrate was used in combination with anatomic and neurotoxic lesions to localize the gamma-hydroxybutyrate (GHB) receptors in the striatum and hippocampus of rat brain. 6-Hydroxydopamine (6-OHDA) lesions of the nigro-striatal pathway failed to reduce [3H] gamma-hydroxybutyrate binding in the striatum. In contrast, kainic acid (KA) lesions of the caudate-putamen (CPu) resulted in about 45% loss of binding. For hippocampus, lesions of septo-hippocampal pathway did not modify receptor density but intrahippocampal kainic acid injection largely attenuated (50%) [3H] GHB binding. These results demonstrate that gamma-hydroxybutyrate receptors in the CPu and dorsal hippocampus are principally located on intrinsic neurons which may participate in the functional expression of the role gamma-hydroxybutyrate has in these structures.

Comparative study of the behavioral changes evoked by d-amphetamine and apomorphine in adult cats. Dose-response relationship

The behavioral effects of d-amphetamine and apomorphine administration were studied in 17 adult cats. The doses of amphetamine administered were 0.1, 0.5, 1.0 and 5.0 mg/kg; those of apomorphine, 0.1, 0.5, 1.0 and 2.0 mg/kg. These two drugs evoked in the same animal marked differences in behavioral responses. Amphetamine induced a dose-dependent hypomotility, which was marked with the higher doses. In addition, rhythmic, bilateral slow movements of the head as a mode of stereotypy, indifference to the environment and dose-dependent increase in respiratory rate. Apomorphine elicited limb flicking, dose-dependent hypermotility and increase in olfactory behavior, the last two reactions with stereotypy characteristics. The animals appeared as if being scared, hyperreacting to sudden stimuli and showing total indifference to the surrounding environment. There were marked differences in behavioral responses evoked by these two agonists of the catecholaminergic system. These data do not conform with the behavioral reactions reported in the rat by other investigators. The disagreement with other communications is probably due to differences in reactivity of the species employed. The processes involved in the diversity of the behavioral responses of the cat to the administration of amphetamine and apomorphine have not been delucidated.

Extracellular unit responses in the pulvinar-lateral posterior complex of the cat through electrical stimulation of substantia nigra reticulata and lateralis

Extracellular single-unit responses of neurons in the ipsilateral pulvinar-lateral posterior complex were recorded in 10 encéphale isolé cats with stimulating electrodes implanted in the substantia nigra pars reticulata and pars lateralis. Fifteen percent of 101 pulvinar-lateral posterior complex thalamic neurons increased their spike discharges when the substantia nigra was stimulated and none decreased its activity. The excitatory effect of this stimulation is discussed in relation to the eventual excitatory or inhibitory character of the efferent projection from the substantia nigra pars reticulata and lateralis to the pulvinar-lateral posterior complex.