EFFECTIVENESS OF CAFFEINE (1,3,7 TRIMETHYLXANTHINE) AGAINST FATIGUE

¹ Department of Pharmacology and Biological Chemistry, Catholic University of Chile, Santiago de Chile

In cats anesthetized with Dial or Nembutal, or in cats which have undergone decerebration or removal of the central nervous system, studies have been made on the effect of caffeine injected intra-arterially in doses of 0.007 to 0.035 gms. on : a) the contractions of skeletal muscles ; b) the neuromuscular synaptic mechanism; c) the superior cervical ganglion stimulated by acetylcholine.

Caffeine produces an increase in the tension developed by muscle which is being stimulated indirectly (figs. 1, 2, 3, 4, 5, 6, 7, 8 and Results, Section I).

Caffeine can produce a development of tension in normal muscle (fig. 8) as well as in denervated muscle (fig. 9A). When denervated muscle is stimulated directly, caffeine can also increase the amplitude of contractions (fig. 9B, C, and D, and Results, Section II).

Caffeine is able to augment not only the amplitude of contractions of a muscle stimulated by means of acetylcholine, but also those of the nictitating membrane similarly stimulated by the latter drug (fig. 10 and 11). The enhancing action of caffeine on the contractions of the nictitating membrane stimulated by acetyl-choline is due to the effect the caffeine exerts upon the ganglion (figs. 11 and 12 and Results, Section III).

Caffeine is a decurarizing drug (fig. 13) and augments the action of prostigmine (fig. 13; Results, Sections IV and V).

The mechanism of the action of caffeine on the neuromuscular junction is discussed and the conclusion is reached that it 1owers the excitatory threshold of acetylcholine. The similarities and differences between the pharmacological action on the neuromuscular junction of caffeine on the one hand and of eserine and prostigmine on the other, is discussed.