A chronic technique for high frequency blood sampling/transfusion in the freely behaving rat which does not affect prolactin and corticosterone secretion.

A blood sampling/blood transfusion technique is described for chronically cannulated freely behaving rats. The procedure permits high frequency sampling for several hours at a maximum rate of one blood sample per min. Prolactin and corticosterone were used as indicators of stress. In male rats the prolactin concentration in blood obtained by rapid decapitation was not significantly different from that obtained through a cannula. A blood volume reduction of 1 or 2 ml did not affect prolactin or corticosterone secretion; however, a reduction of 3 ml or more increased corticosterone secretion but did not consistently increase prolactin secretion. When blood volume reduction was compensated for by blood transfusion, frequent blood sampling did not affect prolactin or corticosterone secretion in dioestrous rats. The surges of prolactin secretion during the afternoon of pro-oestrus and pseudopregnancy were also unaffected by high frequency blood sampling. It is therefore concluded that the blood sampling/transfusion procedure described does not stress the animals. Its advantages include not only the possibility of following individual hormone profiles, but also the economic and ethical aspects of reducing the number of animals needed for experimentation.