SummaryThe time course of rectal temperature in mice was measured following a single and the last of 10 once-daily electroconvulsive shocks (ECS). In addition, temperature measurements were carried out following a single ECS 1 and 2 weeks after a course of 10 once-daily ECS treatments. After a single ECS, the animals showed a decrease of 2.3 ± 0.3°C, lasting for at least 90 min. Following the last of 10 ECS, the maximum response was markedly attenuated to 0.7 ± 0.1°C, and this attenuated response was present at least 1 week later. This effect may be mediated by alterations in postsynaptic α2-adrenoceptor or presynaptic 5-HT1Areceptor sensitivity, or may reflect a more fundamental resetting of temperature mechanisms.