Cjc. Boersma et al., DYNORPHIN 1-17 DELAYS THE VASOPRESSIN-INDUCED MOBILIZATION OF INTRACELLULAR CALCIUM IN CULTURED ASTROCYTES FROM THE RAT NEURAL LOBE, Journal of neuroendocrinology, 5(5), 1993, pp. 583-590
Opioid peptides are present in nerve terminals in the rat neural lobe
where they partially coexist with vasopressin. Morphological findings
suggest that these neuropeptides are released onto pituicytes, which i
s in agreement with a possible role for the pituicyte in oxytocin and
vasopressin release from the neural lobe. Pituicytes in culture respon
d to vasopressin with a mobilization of calcium from intracellular sto
res. In the present study this vasopressin induced increase in intrace
llular free calcium levels was both delayed and decreased by pre-expos
ure to dynorphin 1-17, while dynorphin 1-17 by itself did not affect b
asal calcium levels. All effects of dynorphin 1-17 could be blocked wi
th naloxone. The present results suggest that opioid receptors are pre
sent on pituicytes and are coupled to a second messenger pathway by wh
ich opioid peptides may inhibit inositol phosphate dependent calcium m
obilization by other neuropeptides, such as vasopressin.