Figure 7.

Strength–duration curves for the threshold potentials for mechanical activation of EDL muscle fibres from untreated adult and aged rats and aged rats chronically treated with (a) GH, (b) hexarelin (Hex) and (c) L-163,255. Each point is the mean value±s.e.m. of the threshold potential (in mV) recorded at each pulse duration from 10 to 52 fibres of four to seven animals. The rheobase values (R, mV) obtained from the fitting procedure in each experimental condition are as follows: untreated adult – 65.2±0.3; untreated aged – 71.4±0.3^a; GH-treated aged – 68.6±0.2^b; Hex-treated aged – 70.7±0.2^a; L-163,255-treated aged – 71.2±0.3^a. Significantly different with respect to ^auntreated adult (P<0.001) and to ^buntreated aged rats (P<0.05 or less).