Effects of nitric oxide upon olfactory receptor neurones in Xenopus laevis

We have studied olfactory receptor neurones under voltage-clamp conditions using the patch clamp technique. Application of sodium nitroprusside (SNP) activated a cation conductance if the GTP concentration in the pipette was in the millimolar range. With 10 microM GTP, SNP had no effect on the holding current but it abolished the normally occurring wash-out of responses to odorants. This effect could also be obtained by adding 150 nM cGMP to the pipette solution. We conclude that there is a NO/cGMP system in Xenopus' olfactory neurones and that cGMP plays an important role in the transduction process in that it guarantees ongoing responsiveness to odorants.