In clonal pituitary GH₃ cells, spontaneous action potentials drive the opening of Ca_v1 (L-type) channels, leading to Ca²⁺ transients that are coupled to prolactin gene transcription. Nerve growth factor (NGF) has been shown to stimulate prolactin synthesis by GH₃ cells, but the underlying mechanisms are unknown. Here we studied whether NGF influences prolactin gene expression and Ca²⁺ currents. By using RT-PCR, NGF (50 ng ml^-1) was found to augment prolactin mRNA levels by ~80% when applied to GH₃ cells for 3 days. A parallel change in the prolactin content was detected by Western blot. Both NGF-induced responses were mimicked by an agonist (Bay K 8644), and prevented by a blocker (nimodipine), of L-type channels. In whole-cell patch-clamp experiments, NGF enhanced the L-type Ca²⁺ current by ~2-fold within 60 min. This effect reversed quickly upon growth factor withdrawal, but was maintained for days in the continued presence of NGF. In addition, chronic treatment (24 h) with NGF amplified the T-type current, which flows through Ca_v3 channels and is thought to support pacemaking activity. Thus, NGF likely enhances the amount of Ca²⁺ that enters per action potential and may also induce a late increase in spike frequency. MC192, a specific antibody for the p75 neurotrophin receptor, but not tyrosine kinase inhibitors (K252a and lavendustin A), blocked the effects of NGF on Ca²⁺ currents. Overall, the results indicate that NGF activates the p75 receptor to cause a prolonged increase in Ca²⁺ influx through L-type channels, which in turn up-regulates the prolactin mRNA.