Mechanisms of a Decapitation-Induced Increase in the Plasma Catecholamine Levels in Rats

Abstract

Decapitation induces excessive increases in the plasma catecholamine levels in the blood obtained from the body of sacrificed animals. However, the mechanisms responsible for this phenomenon remain unknown. We investigated the neuronal pathways responsible for such increases in the plasma epinephrine and norepinephrine levels. To investigate this, we completely or partially transected the spinal cord at the upper thoracic level in Sprague–Dawley rats. Functionally, the successfulness of interruption of interconnections between brain and spinal preganglionic neurons was confirmed by almost complete blockade of immobilization-induced increases in the catecholamine plasma levels. After complete transection of the spinal cord and subsequent decapitation of rats, we found significant reduction of decapitation-induced effects on the catecholamine release from the adrenal medulla and sympathetic nerve endings. Our data indicate that the activity of the sympathoadrenal system is under significant inhibitory influence from the brain structures regulating the activity of sympathetic preganglionic neurons.