Maturation of convulsogenic activity induced by leptazol in the albino rat.

1. Maturation of the excitatory and inhibitory neuromechanisms at various levels of the central nervous system was demonstrated by the convulsogenic activity induced by leptazol in the developing albino rat.2. The somatomotor end points considered (myoclonic jerk, myoclonic seizure, tonic seizure and catalepsy) were not observed in all age groups. Tonic seizure was seen at birth, myoclonic jerks at 2 weeks of age, myoclonic seizure and catalepsy at 3 weeks of age.3. The convulsive sequences described presented three different patterns, defining three age groups: the infant pattern (infant group: newborn-1 week old animals); the transitional pattern (transitional group: 2 week old animals); and the adult pattern (adult group: 3 week old-adult animals).4. Effective doses were determined for the three types of convulsive sequence: MJ50 for the myoclonic major sequence (maximal end point: myoclonic jerk), MS50 for the myoclonic major sequence (maximal end point: myoclonic seizure) and the TS50 for the myoclonic-tonic-clonic sequence (maximal end point: tonic seizure).5. The correlation of the convulsive patterns with the dose and latency variations suggests that: (a) the neuromechanisms responsible for the tonic seizure and clonic seizure, located at brainstem and spinal cord levels, function at birth and reach maturity at 3 weeks of age; (b) the neuromechanisms responsible for the myoclonic manifestations and for catalepsy, located at the striato-thalamocortical level, start functioning at 2-3 weeks of age, indicating the later maturation of the more cephalic structures.