Astrocytes have glutamate-induced rhythmic fluctuations of Ca 2 + in their cytosol. The pituicyte, an astrocytic cell in the neural lobe of the pituitary gland, is bathed by neurosecretory peptides: vasopressin, dynorphin and oxytocin released from axon terminals. Is there release of Ca2+ into the cytosol of pituicytes in response to stimulation with these peptides? Shifts in the compartmentalization of Ca2+, which fluoresces when it forms a complex with Fluoro-3, is monitored by fluorescence changes detected with video-enhanced microscopy. In pilot experiments, 100 micromoles or greater amounts of arginine vasopressin, when added to pituicytes that have been preloaded with Fluoro-3 and maintained at room temperature, result in release of Ca2 +which pulses once or twice. Nonphysiologic amounts, i.e., 1 mM, of dynorphin and 100 micromoles of glutamate, which trigger Ca2+ release in cerebral astrocytes, do not do so in pituicytes. Do pituicytes respond to osmolarity changes of extracellular fluid? Addition of 0.5 g % sucrose to the cells had no effect on Ca2+ release. Repetition of the experiments at 37 degrees C may yield different results. Exposure of pituicytes to 10 micromoles dynorphin for 5 minutes induces the expression of the """"""""early immediate"""""""" proto-oncogene c-fos. The response is diminished by 30 minutes and is over by 3 hours. The other peptides-and neurotransmitters were used as well. This project is in abeyance.
