Abstract

Intracellular recordings were made to study the actions of ATP and related nucleotides on neurons from the guinea pig submucous plexus. Local application of ATP, by pressure, induced a depolarization in most AH-type neurons, which had a latency of several milliseconds, lasted for about 5 sec, appeared to reverse at about +4 mV and occurred concomitantly with a reduction in input resistance. Pressure application of ATP also depolarized the S-type neurons. In most of these cells the depolarization had two phases: the first component resembled the depolarization observed in AH cells and the second component was much slower in onset and was longer lasting (30-90 sec). The slower component was associated with an increase in input resistance, reversed polarity near the potassium equilibrium potential and was observed in isolation in 30% of S neurons. Superfusion of ATP or other analogs (0.03-10 microns) induced a slow depolarization in most of S neurons with the following rank order of potency: 2-methylthio-ATP > ATP > adenosine-5'-o-3-thiotriphosphate = ADP; alpha, beta-methylene ATP and beta, gamma-methylene ATP were inactive (10-100 microM). When whole-cell recordings were used, fast superfusion with ATP or other analogs (3-1000 microM) evoked, at negative membrane potentials, a rapidly desensitizing inward current. This current reversed polarity at about 0 mV and was much reduced in low extracellular sodium concentration. The rank order of potency of the used agonists was: ATP = adenosine-5'-o-3-thiotriphosphate = 2-methylthio-ATP > > alpha,beta-methylene ATP = beta,gamma-methylene ATP; adenosine, AMP or ADP (1 mM) were inactive.(ABSTRACT TRUNCATED AT 250 WORDS)