Pentylenetetrazol and strychnine convulsions in brain weight selected mice.

The seizure sensitivities to pentylenetetrazol (Ptz, 25-100 mg/kg) and strychnine (S, 2 mg/kg) were tested in two mice lines selected for large (LB) and small (SB) brain weight (brain weight difference being approximately 75 mg). The selection was based on a regression line connecting body and brain weight. SB mice were more sensitive to both drugs-their seizure latencies were shorter and lethality higher than in LBs. The seizures generated by Ptz and S are known to affect different neurotransmitter systems. The interstrain differences in seizure susceptibility are probably determined by SB mice nervous system traits rather than by differences in the particular neurochemical trait. The data on neocortical cytoarchitectonics obtained during our previous brain selection experiment could serve as the indirect evidence favouring such a suggestion.