Chemical responses of polymodal receptors of the scrotal contents in dogs.

1. Chemical responses of polymodal receptors of the superior spermatic nerve were studied by single unit recording in dogs. The responses were similar to those found in the muscular polymodal receptors of dogs. 2. Solutions of hypertonic NaCl, KCl and bradykinin caused responses in more than 90% of these polymodal units. The responses were related to the dose of these three chemical but discharge patterns differed substantially. Responses to Na citrate were very capricious, and those to acetylcholine and histamine were weak. 3. When bradykinin was applied repeatedly the responses of the subsequent trials decreased if the repetition interval was short (less than 15 min), but an increase of response was observed if the repetition interval was long (30-60 min). 4. Indomethacin 10 micrograms.ml-1 suppressed or abolished the response to 1 microgram.ml-1 bradykinin without significant influence on the response to 60 mmol.l-1 KCl at the same receptive site. Involvement of prostaglandins in the response of the polymodal units to bradykinin is suggested.