Abstract
1. Rats which had been pretreated with intraventricular injections of 6-hydroxydopamine (6-OHDA) to cause a selective depletion of brain noradrenaline (NA) to 20.7% of control brain NA and brain dopamine (DA) to 34.6% of control brain DA retained an unimpaired ability to regulate their body temperatures on exposure to heat or cold. This is discussed in relation to the possible role of brain NA in the central control of body temperature.2. Intraventricular injections of 6-OHDA in normal rats at room temperature caused an acute, dose dependent hypothermia of up to 4.5 degrees C which lasted for 4-5 hours. Depletion of brain NA and DA by prior treatment with 6-OHDA markedly reduced the hypothermic response to a subsequent dose of 6-OHDA. Selective depletion of brain NA without affecting brain DA did not reduce the response to 6-OHDA. The acute hypothermic response to 6-OHDA, may therefore, be related to a release of DA in the brain.