Studies on the mechanism of shock. Central serotoninergic neuron activity after trauma in the rat.

An attempt has been made to assess the effect of injury (limb ischaemia, scald) on the central serotoninergic system of the rat by studying the effect of these injuries on the tryptophan concentration, the tryptophan hydroxylase activity and the metabolism of serotonin in the hypothalamus, mid-brain and hind-brain. The effects of a serotonin uptake inhibitor and an antagonist on the survival time and mortality rate after limb ischaemia have been examined as well as the effects of central lesions produced by the injection of 5.6- and 5.7-dihydroxytryptamine into a lateral cerebral ventricle and the i.p. injection of (+/-)-4-chloroamphetamine. A few changes indicative of increased activity in the central serotoninergic system were found--an increase in tryptophan hydroxylase activity after 4 h bilateral hind-limb ischaemia, better survival of fed rats pre-treated with 5,6-dihydroxytryptamine--but for the most part the changes were not as great as those produced by starving or exposure to cold. Hence the effect of trauma on this system seems small.