Electrical properties of diaphragm and extensor digitorum longus
muscles of dystrophic mouse through its life.
Luca, Annamaria De, Sabata Pierno, and Diana Conte Camerino.
Unit of Pharmacology, Department of Pharmacobiology, Faculty of
Pharmacy, University of Bari, Italy
APStracts 3:0285C, 1996.
The membrane electrical properties of diaphragm (DIA) and extensor
digitorum longus (EDL) muscle fibers of dystrophic mdx and control
mice from 4 weeks to 14-19 months of age were recorded with
intracellular microelectrode technique. Up to 8 weeks of age the DIA
and EDL muscles did not differ between the two strains. From 8 up to
20 weeks the mdx DIA fibers showed a higher membrane resistance (Rm),
due to significantly lower values of resting chloride conductance
(GCl), and an overexcitability with respect to age-matched controls.
Oppositely, the mdx EDL muscle fibers had significantly lower Rm and
higher values of GCl than age-related controls at 8, 10 and 13 weeks,
along with a decreased membrane excitability. These differences were
no longer detectable at 20 weeks. The DIA and EDL muscles from 14-19
month-old controls showed a decrease of GCl and an increase of
potassium conductance (GK) with respect to adult animals. In aged mdx
animals these changes were very dramatic in DIA fibers, whereas no
differences with respect to adults were found in the EDL muscle. Thus
GCl is an index of the dystrophic condition of mdx muscles. In the
degenerating DIA, the impairment of GCl can account for some of the
pathological features of the muscle. In the EDL muscle, the changes
of GCl can follow the high regenerative potential of the hindlimb
muscles of the mdx phenotype.
Received 16 January 1996; accepted in final form 27 August 1996.
APS Manuscript Number C17-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996