[Learning in rats with differing emotional responsiveness and its relation to brain monoamines].

The ability for learning was studied in two groups of Wistar line rats divided by susceptibility to the audiogenic stress-stimulation as compared with the monoamines level in various brain structures. The best ability to learn avoidance reaction in a shuttlebox was shown by animals non-resistant to the stress stimulus as compared with the resistant rats, which correlated positively with the exploratory activity in "the open field". The distinct feature of the animals non-resistant to the stress stimulation consisted in a higher reactivity of the monoamine systems, mainly of the noradrenergic system. This group of animals was also characterized by a higher dopamine content and a lower noradrenaline content in the brain-stem. Decreased activity of the brain dopamine-beta-hydroxylase in animals non-resistant to the stress stimulus, has been suggested.