Differential Activation by Restraint Stress of a Mechanism to conserve Brain Catecholamines and Serotonin in Mice differing in Excitability

Abstract

THE relatively great reactivity of highly emotional animals must be correlated with neural function, but there seem to have been no previous reports of differential effects of stress on specific neurotransmitters in the brains of animals which differ in excitability. We have found that restraint stress can cause a greater elevation of brain catecholamines and serotonin in mice made hyperexcitable by 8–12 weeks of isolation than in their less excitable littermates housed in groups. This differential elevation of brain amines occurs in spite of the slower turnover of these neurotransmitters in isolated mice in normal non-stressed conditions^1–3,6. Furthermore, after inhibition of catecholamine biosynthesis by α-methyltyrosine, stress facilitated the depletion of norepinephrine and dopamine in mice that had been kept isolated, but retarded their depletion in mice that had been housed in groups. It seems that restraint stress, which presumably imposes an increased demand for brain catecholamines and serotonin to maintain neurotransmission, rapidly activates a mechanism to conserve these amines and activates it to different degrees in mice which differ in emotional reactivity.