| Abstract: | Pulmonary rapidly-adapting-receptors ( RARs ) are sensory nerve endings whose afferent fibers can be recorded in the vagus nerve. RARs may play a role in reflex bronchoconstriction as seen in anaphylaxis. They can be stimulated by chemical mediators of anaphylaxis, such as prostaglandin F2 alpha (PGF2 alpha). PGF2 alpha aerosol was administered to saline and bovine serum albumin (BSA)-treated guinea pigs while recording the activity of RARs . PGF2 alpha (250 micrograms/ml) given for 7-13 minutes increased both tracheal pressure and nerve activity over that produced by saline exposure in untreated guinea pigs. PGF2 alpha administered for three minutes (5-100 micrograms/ml) increased RAR nerve activity in a dose-related manner in the first five minutes of the experiment only in the BSA treated guinea pigs. Since changes in tracheal pressure did not show a significant dose-response relationship, the RARs responding to PGF2 alpha seemed to be stimulated by a direct mechanism. No correlation was shown between tracheal pressure and RAR nerve activity during PGF2 alpha treatment. Whereas, a significant correlation was found between tracheal pressure and RAR nerve activity during histamine aerosol treatment (r = 0.985). Histamine aerosol (1 to 1000 micrograms/ml, 3 min.) increased intratracheal pressure for 3 out of 4 doses. RAR nerve activity increased significantly only at the highest dose. Therefore, a possible direct effect of PGF2 alpha upon RARs exists while the effect of histamine seems dependent upon changes in airway pressure in the guinea pig. |
