Nitric oxide-mediated cGMP production in the islands of Calleja in the rat.

cGMP-immunostaining in the islands of Calleja (ICj) in slices incubated in vitro partially co-localized with nitric oxide synthase (NOS) inside the ICj. No cGMP-immunostaining was found outside the ICj in unstimulated slices, whereas the NO-donor sodium nitroprusside (SNP) stimulated cGMP in cells and fibers bordering on the ICj. These findings show an ongoing NO synthesis in in vitro slices and suggest a relatively restricted diffusion range for endogenously synthesized NO.