G. Dayanithi et al., Intracellular calcium signalling in magnocellular neurones of the rat supraoptic nucleus: understanding the autoregulatory mechanisms, EXP PHYSIOL, 85, 2000, pp. 75S-84S
Oxytocin and vasopressin, released at the soma and dendrites of neurones, b
ind to specific autoreceptors and induce an increase in [Ca2+](i). In oxyto
cin cells, the increase results from a mobilisation of Ca2+ from intracellu
lar stores, whereas in vasopressin cells, it results mainly from an influx
of Ca2+ through voltage-dependent channels. The response to vasopressin is
coupled to phospholipase C and adenylyl-cyclase pathways which are activate
d by V-1 (V-1a and V-1b)- and V-2-type receptors respectively. Measurements
of [Ca2+](i) in response to V-1a and V-2 agonists and antagonists suggest
the functional expression of these two types of receptors in vasopressin ne
urones. The intracellular mechanisms involved are similar to those observed
for the action of the pituitary adenylyl-cyclase-activating peptide (PACAP
). Isolated vasopressin neurones exhibit spontaneous [Ca2+](i) oscillations
and these are synchronised with phasic bursts of electrical activity. Vaso
pressin modulates these spontaneous [Ca2+](i) oscillations in a manner that
depends on the initial state of the neurone, and such varied effects of va
sopressin may be related to those observed on the electrical activity of va
sopressin neurones in vivo.