Administration of 17‐ β estradiol in the medial preoptic area prevents reduction of body temperature during cold exposure in ovariectomized rats

Abstract

BACKGROUNDWe reported that ovariectomized rats could not maintain body temperature (Tcore) well in the cold; however, local administration of 17‐β estradiol (E2) in the medial preoptic area (MPO) restored the cold intolerance. The E2 administration had no effect on UCP1 mRNA level in the interscapular brown adipose tissues, suggesting less influence on metabolic heat production.PURPOSETo test the hypothesis that the local E2 administration in the MPO affects heat dissipation, the tail surface temperature was assessed by thermography.METHODSAfter ovariectomy for 9‐wk old rats, a stainless steel canula was placed in the MPO for local administration of E2 or cholesterol. A rat was placed at 10 or 25°C for 2h, 48 h after the administration E2 or cholesterol. Tcore and tail temperature (Ttail) were measured by telemetry and thermography.RESULTSBoth the groups showed decrease in Ttail at 10°C; however the reduction was greater in the estrogen group than in the cholesterol group.CONCLUTIONWithout estrogen in the MPO, heat dissipation from the tail in ovariectomized rats may not be fully suppressed in the cold, resulting in reduction of Tcore.