Affordable Access

Publisher Website

Effects of substance P on the isolated pupillary sphincter of the cat and rabbit

Neuroscience Research
Publication Date
DOI: 10.1016/s0168-0102(84)80025-5
  • Cat
  • Rabbit
  • Pupillary Sphincter
  • Acetylcholine
  • Substance P
  • Electrical Field Stimulation


Summary The effects of substance P (SP) on the isolated pupillary sphincter of the cat and rabbit were studied. The sphincter was incubated in an organ bath which was filled with Krebs solution saturated with 100% O 2 and kept at 36 ± 0.5 °C. The contractile and relaxant responses were recorded with an isotonic transducer. In rabbits, exogenously applied SP showed a potent contractile effect, and ED 50 value was 1.3 × 10 −9 M. However, in cats, SP produced little or no response at a concentration of 5 × 10 −6 M. Electrical field stimulation of the rabbit pupillary sphincter produced a muscle contraction composed of rapid and slow components. It was confirmed that the first component was cholinergic and the second component SP-ergic. By contrast, electrical field stimulation of the cat pupillary sphincter produced a rapid contraction followed by a slow relaxation. The rapid contractile component was accelerated by pretreatment with 10 −6 M physostigmine and reduced by 10 −6 M atropine, while the slow relaxant component was not affected by 10 −6 M physostigmine, 10 −6 M atropine 10 −6 M phentolamine or 10 −6 M propranolol. A releaser and depleter of SP, capsaicin (10 −5 M), produced a marked relaxant response in the cat pupillary sphincter. After desensitization to capsaicin, the slow relaxant component disappeared in response to electrical field stimulation.

There are no comments yet on this publication. Be the first to share your thoughts.