Properties of sympathetic neuromuscular transmission and smooth muscle cell membranes in vascular beds.
In vascular smooth muscle tissues, the cycle of contraction-relaxation is mainly regulated by the cytosolic Ca, and many other factors, such as substances released from endothelial cells and perivascular nerve terminals (mainly sympathetic nerves). In this article, we introduce regional differences in specific features of ionic channels in vascular smooth muscle membranes (mainly on features of Ca, Na and K channels) in relation to mobilization of the cytosolic Ca. In many vascular tissues, neurotransmitters released from sympathetic nerve terminals activate post-junctional receptors, and subsequently modify ion channels (receptor-activated cation channel and voltage-dependent Ca channel), whereas in some tissues, ionic channels are not modified by receptor activations (pharmaco-mechanical coupling). However, activation of receptors, with or without modulation of ionic channels, regulates the cytosolic Ca through synthesis of second messengers. In addition, receptors distributed on prejunctional nerve terminals positively or negatively regulate the release of transmitters. Roles of neurotransmitters (mainly ATP and noradrenaline) are also discussed in relation to the generation of excitatory junction potentials.
Kitamura
K
K
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Itoh
T
T
Suzuki
H
H
Ito
Y
Y
Kuriyama
H
H
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000294:innervation*; D018377:Neurotransmitter Agents / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*
D007473:Ion Channels; D018377:Neurotransmitter Agents; D002118:Calcium