Effects of substantia nigra and pallidum stimulation on hippocampal interictal activity in the cat.

In the present work the role played by substantia nigra pars compacta and globus pallidus pars interna on hippocampal bioelectrical activity is studied. Injections of sodium penicillin (i.v.) produce steady interictal spikes in the hippocampus. Substantia nigra stimulation induces regular theta rhythm and inhibits the spikes. Pallidal stimulation, on the contrary, appears to strongly enhance epileptiform activity, proceeding to generalized seizure activity. The results are discussed in the light of the interrelationships between basal ganglia and hippocampus, hypothesizing a putative feedback loop from striatal to limbic centers.