Breeding and offspring rearing ability of C57BL/6J dystrophic mice.

The antiepileptic drug phenytoin, administered in drinking water for 104 days, was used to reduce the neural overactivity (pseudomyotonia) of C57BL/6J dystrophic (dy2J/dy2J) male mice in an attempt to improve their breeding success over a 90-day period. Male dy2J/dy2J mice have difficulty in successfully mounting females due to the pseudomyotonia affecting their hindlimb musculature. Breeding success, as judged by litter frequency, of dy2J/dy2J males receiving phenytoin (5 micrograms/ml serum) was compared with untreated dy2J/dy2J and phenotypically normal (+/?) male and female mice. Phenytoin did not enhance male dy2J/dy2J breeding success. Based on dy2J/dy2J crosses with +/? animals, the dy2J/dy2J female was a more successful breeder than the dy2J/dy2J male. In terms of litter frequency, litter size, and offspring birth weight, dy2J/dy2J females (age 8-21 wks.) bred as efficiently as +/? females of the same age. Dystrophic females were deficient in offspring rearing capabilities as evidenced by lower offspring survival rates and weaning weights.