Developmental changes in neuromuscular transmission in the rat diaphragm

J. D. Feldman, A. R. Bazzy, T. R. Cummins, G. G. Haddad

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14 Scopus citations


Neuromuscular transmission was studied in diaphragms from rats of three ages, 4-7 days old, 11-12 days old, and adults with the use of an in vitro phrenic nerve-hemidiaphragm preparation. Each hemidiaphragm was stimulated via either muscle or nerve with 1-s stimulus trains at frequencies from 10 to 100 Hz. The patterns of force development obtained in response to the two routes of stimulation were compared for each group. Diaphragms from adults developed maximum force in response to stimulation of ~40 Hz with no significant decrease in force at higher frequencies. Within each stimulus train, once peak force was achieved, it was maintained for the remainder of the stimulus and responses to nerve and muscle stimulation were almost identical. In contrast, diaphragms from 4- to 7-day-old rats developed maximum force at ~20 Hz; stimulation at ≥60 Hz induced significantly less peak force. This decrease in peak force at higher frequencies was significantly larger for nerve than for muscle stimulation. In addition, during each nerve stimulus train diaphragms from 4- to 7-day-old rats were unable to maintain peak force, which decreased at frequencies >20 Hz. The decrease in force reached ~50% of peak at stimulation frequencies ≥60 Hz. Diaphragms from 11- to 12-day-old rats showed intermediate responses. Based on the responses to phrenic nerve stimulation, we conclude that the neonatal rat diaphragm shows marked neuromuscular transmission failure that is not seen in the adult. This may be explained by failure of 1) action potential propagation along the axon, 2) transmission across the neuromuscular junction, or 3) conduction along the muscle cell membrane.

Original languageEnglish (US)
Pages (from-to)280-286
Number of pages7
JournalJournal of Applied Physiology
Issue number1
StatePublished - 1991


  • maturation
  • neuromuscular junction
  • phrenic nerve

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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