Astrocytes have glutamate-induced rhythmic fluctuation of Ca2+ in their cytosol. The pituicyte, an astrocytic cell in the pituitary gland's neural lobe , is bathed by neurosecretory peptides:vasopressin, dynorphin and oxytocin, released from axon terminals. Is there a 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 form a complex with fluo-3, is monitored by fluorescence changes detected with video enhanced microscopy. In pilot experiments, 100 micromoles or more of arginine vasopressin, added to pituicytes pre-loaded with fluo-3 and maintained at room temperature, results in the release of Ca2+ which pulses only once. Glutamate (100 micromoles) or unphysiological amounts (e.g., 1 mM) of dynorphin do not trigger Ca2+ release in pituicytes. Do pituicytes respond to osmolarity change, a stimulus for the neurons with which they are associated? The 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 m induces the expression of the proto-oncogene c-fos. The response is diminished by 30 m and disappears over 3 hours. The other peptides and neurotransmitters are to be used as well. Whether pituicytes have a trophic effect on neurosecretory axons is to be tested in vitro.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Intramural Research (Z01)
Project #
1Z01NS001805-23
Application #
3860752
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
23
Fiscal Year
1991
Total Cost
Indirect Cost
City
State
Country
United States
Zip Code