Activation of dihydropyridine sensitive Ca2+ channels in rat hippocampal neurons in culture by parathyroid hormone

We examined the effects of parathyroid hormone (PTH) on rat hippocampal neurons in culture to determine whether it caused a similar intracellular calcium concentration ([Ca 2+ ] i ) increase in these cells to that seen with renal epithelial cells and found that PTH induced the effect in about 30% of the neurons. The effects appeared gradually during continuous administration of full-length PTH 1–84 or its active fragment, PTH 1–34 , but not of an inactive fragment, PTH 39–84 . However, the active fragment of the PTH-related peptide (PTHrP 1–34 ) had little effect on [Ca 2+ ] i during 60 min of administration. The PTH effect was inhibited by nifedipine, an L-type Ca 2+ channel antagonist, and facilitated by S-(-)-BAY K 8644, an L-type Ca 2+ channel agonist. Our findings suggest that PTH is one of the causal factors for the age-related increase in the density of voltage gated Ca 2+ channels in hippocampal neurons.