Divergent responses to long-term stressors in rat lines selected for different functional states of the nervous system.

The conditioned and reflex parameters in rat lines selected for the threshold of excitability (a fundamental characteristics of the functional state of the nervous system) were estimated. This measure is based on the response of the tibial nerve to electrical stimulation, which gives a general indication of the level of excitability of other parts of the nervous system. Testing was made 1-3 days after 15 days of daily stress caused by randomly presented pairing of light and unavoidable electric shock. Expression of the sensitivity to the electric current, and the reflex components of the behavior, depends on the genetically determined level of the functional state of the nervous system.