Vasopressin-induced calcium signaling in cultured cortical neurons

• Published in: Brain research 1998-05, Vol.793 (1), p.244-254
• Main Authors: Son, Michael C., Brinton, Roberta Diaz
• Format: Article
• Language: English
• Subjects: Animals; Antidiuretic Hormone Receptor Antagonists; Arginine Vasopressin - physiology; Biological and medical sciences; Calcium; Calcium - metabolism; Calcium channel; Calcium Channels - physiology; Calcium Signaling - drug effects; Calcium Signaling - physiology; Cell physiology; Cells, Cultured; Cerebral cortex; Cerebral Cortex - cytology; Cerebral Cortex - drug effects; Cerebral Cortex - physiology; Fetus; Fundamental and applied biological sciences. Psychology; Intracellular Fluid - metabolism; IP 1; Learning and memory; Molecular and cellular biology; Neurons - physiology; Phosphatidylinositols - metabolism; Rats; Rats, Sprague-Dawley; Receptors, Vasopressin - agonists; Receptors, Vasopressin - metabolism; Signal transduction; Vasopressin
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(98)00185-1

Earlier autoradiographic studies from our laboratory detected vasopressin recognition sites in the mammalian cerebral cortex [R.E. Brinton, K.W. Gee, J.K. Wamsley, T.P. Davis, H.I. Yamamura, Regional distribution of putative vasopressin receptors in rat brain and pituitary by quantitative autoradiography, Proc. Natl. Acad. Sci. U.S.A., 81 (1984) 7248–7252; C. Chen, R.D. Brinton, T.J. Shors, R.F. Thompson, Vasopressin induction of long-lasting potentiation of synaptic transmission in the dentate gyrus, Hippocampus, 3 (1993) 193–204]. More recently, we have detected mRNA for the V1a vasopressin receptors (V1aRs) in cultured cortical neurons [R.S. Yamazaki, Q. Chen, S.S. Schreiber, R.D. Brinton, V1a Vasopressin receptor mRNA expression in cultured neurons, astroglia, and oligodendroglia of rat cerebral cortex, Mol. Brain Res., 45 (1996) 138–140]. To determine whether these recognition sites are functional receptors, we have pursued the signal transduction mechanism associated with the V1a vasopressin receptor in enriched cultures of cortical neurons. Results of these studies demonstrate that exposure of cortical neurons to the selective V1 vasopressin receptor agonist, [Phe 2,Orn 8]-vasotocin, (V 1 agonist) induced a significant accumulation of [ 3 H] inositol-1-phosphate ( [ 3 H] IP 1). V 1 agonist-induced accumulation of [ 3 H] IP 1 was concentration dependent and exhibited a linear dose response curve. Time course analysis of V 1 agonist-induced accumulation of [ 3 H] IP 1 revealed a significant increase by 20 min which then decreased gradually over the remaining 60 min observation period. V 1 agonist-induced accumulation of [ 3 H] IP 1 was blocked by a selective V1a vasopressin receptor antagonist, (Phenylac 1, d-Tyr(Me) 2, Arg 6,8, Lys-NH 2 9)-vasopressin. Results of calcium fluorometry studies indicated that V 1 agonist exposure induced a marked and sustained rise in intracellular calcium which was abolished in the absence of extracellular calcium. The loss of the rise in intracellular calcium was not due to a failure to induce PIP 2 hydrolysis since activation of the phosphatidylinositol pathway occurred in the absence of extracellular calcium. V 1 agonist activation of calcium influx was then investigated. V 1 agonist-induced 45 Ca 2+ uptake was concentration dependent with a biphasic time course. Preincubation with the L-type calcium channel blocker, nifedipine, blocked V 1 agonist-induced calcium influx suggesting V 1 agonist-induced L-type calcium