[Parathyroid hormone stimulation of nerve cell calcium conduction]

Parathyroid hormone (PTH) has been studied for its effect on the voltage-sensitive calcium channels in voltage-clamp experiments on intracellularly perfused snail neurons. A two-stage action of the hormone on the calcium current (Ica) was shown. An initial stage was a short-term one and consisted in an increase of ICa by 7-10%. The second stage developed slowly for 60-70 min, ICa increased twice. The exogenous cAMP and cGMP did not produce such an effect as PTH did. It is suggested that the phosphoinositide pathway mediates the PTH effect.