Fig. 2. Cellular and functional recovery after 6-OHDA injection. (A) Behavioural response following amphetamine challenge in non-operated controls (n=4), and in animals 3 days after sham (n=9) or 6-OHDA injection (n=21). Data represent the number of times per minute that the newt's tail crosses a line in a grid (mean±s.d.; Student's t-test; ^*, P<0.05; ^**, P<0.01). (B) Correlation of motor behaviour with lesion size 3 days after lesioning. The loss of TH⁺ cells strongly correlates (r²=0.83) with a decrease in locomotor activity in response to amphetamine challenge. Each data point represents 1 animal (for sham-lesioned animals, data represent mean±s.d.). (C) Time course of behavioural recovery as assessed by acute amphetamine challenge (lesion, n=19; sham, n=9). (D) Time course of TH⁺ cell regeneration following 6-OHDA injection. Sham, n=4-14 animals per group per time point (d3, n=4; d5, n=6, d7, n=5; d10, n=6; d17, n=5; d24, n=4; d30, n=14). Lesioned, n=5-18 animals per group per time point (d3, n=5; d5, n=6; d7, n=5; d10, n=6; d17, n=5; d24, n=6; d30, n=18). Mean±s.e.m.; Student's t-test; ^*, P<0.05; ^**, P<0.01. (E-G) Photomicrographs showing TH⁺ neurons in TM following (E) sham operation, (F) 3 days post-lesion and (G) 30 days after 6-OHDA injection. Scale bar: 150 µm.