Inhibition by nifedipine of the indirectly induced contractile response of the rat diaphragm.
The effects of nifedipine (30 micrograms/ml) on isometric force production of in-vitro rat diaphragm were studied during direct and indirect modes of muscle activation. During direct muscle stimulation, nifedipine potentiated isometric force during twitch and unfused tetanic stimulation. Indirectly elicited responses, evoked by stimulation of the phrenic nerve, were uniformly depressed following nifedipine. Inhibition of indirect force production increased with time, while force potentiation with direct activation remained constant. We conclude that inhibitory effects of nifedipine on the phrenic nerve-diaphragm preparation are specific for nerve or neuromuscular junction.
Miller
M J
MJ
Department of Medicine, Brockton/West Roxbury VA Medical Center, MA 02401.
Shannon
K
K
Reid
M B
MB
D000818:Animals; D003964:Diaphragm / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D009543:Nifedipine