Incomplete suppressive effects of acetylsalicylic acid on the heat sensitization of canine testicular polymodal receptor activities.

1. Using canine testis-spermatic nerve preparations in vitro, we studied the effects of acetylsalicylic acid (ASA), an inhibitor of cyclooxygenase, on the polymodal receptor response to heat stimulation itself and on the sensitizing effects on the heat and bradykinin responses induced by strong heat stimulation (55 degrees C for 30 s). 2. Greater heat responses tended to be strongly suppressed by ASA (550 microM), with a significant correlation observed between the response magnitude and the magnitude of the suppression (r = 0.88 for the response at 45 degrees C; r = 0.83 for the response at 48 degrees C). The change in the heat response at 48 degrees C from 1.18 +/- 0.19 to 0.62 +/- 0.11 imp/s was statistically significant (n = 21, P < 0.01). 3. After stimulation at 55 degrees C in the presence of ASA, resting discharges at 34 degrees C appeared in only 2 of the 21 units tested. The responses at 45 and 48 degrees C, however, were significantly potentiated after this stimulation (those at 45 degrees C from 0.12 +/- 0.05 to 2.19 +/- 0.51 imp/s, mean +/- SE; those at 48 degrees C from 0.62 +/- 0.11 to 2.42 +/- 0.49 imp/s; P < 0.01, n = 21 for both). Sensitization was observed up to 50 min after stimulation at 55 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)