AMINOPHYLLINE AND THEOPHYLLINE DERIVATIVES AS ANTAGONISTS OF NEURONAL DEPRESSION BY ADENOSINE - A MICROIONTOPHORETIC STUDY

Abstract

Aminophylline, theophylline, etamiphyllin and diprophylline were tested as antagonists of neuronal inhibition produced by microiontophoretically applied adenosine, when ejected as cations or anions [in rats]. Aminophylline was an effective adenosine antagonist when ejected as an anion, especially from alkaline solution. Anionic theophylline was effective but less so and on a smaller proportion of neurons. Ethylenediamine and hydroxyl ions had no effect on adenosine responses. GABA depressions were unaffected by any of the methylxanthines at the time of adenosine blockade. Cationic ejection from aminophylline or ethylenediamine barrels produced a depression of unit firing on .apprx. 1/3 of the cells tested, but no antagonism of adenosine was observed. The anionic ejection of aminophylline, etamiphyllin or diprophylline from alkaline solution yields potentially useful antagonists of adenosine for iontophoretic experiments.