Fig. 5. Changes in skin blood flow (A—C) and cutaneous water evaporation (CWE) (D—F) in non-acclimated (NAc; open bars) and heat-acclimated (HAc; black bars) pigeons following heat exposure (T_a=50°C) or pharmacological manipulation with propranolol or clonidine. Both skin blood flow and CWE increased in response to heat exposure in the NAc and HAc groups (A and D, respectively), and both were significantly greater in HAc pigeons. The effect of propranolol on skin blood flow (B) was dichotomous: it increased in the HAc pigeons and decreased in NAc pigeons. However, as can be seen in the HAc pigeons, clonidine dissociated skin blood flow (C) from CWE (F), reducing the former while inducing considerable CWE. Values are means ± S.E.M. ^*P<0.05, ^**P<0.005. The asterisks in parentheses indicate a significant difference between the HAc and NAc groups.

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