L-proline as a glutamate antagonist at a crustacean neuromuscular junction.
The fast as well as the slow contractions of the adductor muscle in the claw of Procambarus clarkii are inhibited by L-proline. This inhibition is dose dependent and decreases with increasing frequency of stimulation of the "slow" fiber. Contractions caused by perfusing the adductor muscle with L-glutamate solutions are also inhibited by L-proline. The inhibiting potency of L-proline is small; the effective concentration of this amino acid is 50--100 times that of the L-glutamate applied. It was postulated that the inhibitory effect of L-proline is based on competition for excitatory receptor sites of L-glutamate, which causes depolarization and contraction, and L-proline, which lacks these actions. Theoretical considerations suggested a linear relationship between the stimulating L-glutamate and the just-inhibiting L-proline concentrations. Experimental evidence supported this model.
D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists; D007532:Isoleucine / Q000494:pharmacology; D008433:Mathematics; D009119:Muscle Contraction / Q000187:drug effects; D009469:Neuromuscular Junction / Q000187:drug effects*; D010852:Picrotoxin / Q000494:pharmacology; D011392:Proline / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D007532:Isoleucine; D010852:Picrotoxin; D011392:Proline; D005680:gamma-Aminobutyric Acid