Convulsive thresholds in mice: action of 6-hydroxydopamine and eboracin.

The neurotoxin, 6-hydroxydopamine, when injected intraperitoneally, protected mice from seizures induced by pentylenetetrazol (Metrazol) and altered the nature of the convulsive response induced by an auditory stimulus. Conversely, the indenopyrrole, eboracin, protected mice from seizures induced by auditory stimulation and altered the response to Metrazol. In each case the altered response was characterized by a marked prolongation of the clonic component without progression to the generalized tonic phase. It appeared, therefore, that 6-hydroxydopamine raised the threshold to tonus in audiogenic seizures, and eboracin raised it in Metrazol seizures. Eboracin raised threshold to clonic phase in audiogenic seizures whereas 6-hydroxydopamine raised it in Metrazol seizures. Our findings showed that in Metrazol and audiogenic seizures thresholds to clonus and progression to the tonic phase were mediated by different biochemical mechanisms and suggested that agents controlling induction of clonic manifestations in one seizure model may be those involved in controlling seizure spread in the other.