Increased 5-HT2 receptor number in brain as a probable explanation for the enhanced 5-hydroxytryptamine-mediated behaviour following repeated electroconvulsive shock administration to rats.

Following electroconvulsive shock (ECS) administration daily for 10 days there was an increase (35%) in 5-hydroxytryptamine2 (5-HT2) receptor number in rat frontal cortex 24 h after the last ECS, compared with handled controls. A similar increase was seen after intermittent ECS administration (5 ECS over 10 days) given during halothane anaesthesia, compared with halothane-treated controls. The dissociation constant was also increased at this time. A single ECS had no effect. Treatment of rats with pentylenetetrazol, p-chlorophenylalanine or alpha-methyl p-tyrosine during the intermittent ECS administration abolished the increase in 5-HT2 receptor binding. Since enhanced 5-HT-mediated behavioural responses are seen after repeated ECS but not when the ECS is given with the drug treatments outlined above, it is suggested that ECS-induced enhancement of 5-HT-mediated behaviour results from an increase in 5-HT2 receptor number.