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The sympathetic nervous system plays an essential role in the control of totalperipheral vascular resistance and blood flow,by controlling the contraction ofsmall arteries.Perivascular sympathetic nerves release ATE norepinephrine(NE)and neuropeptide Y.This review summarizes our knowledge of the intracellularCa~(2+)signals that are activated by ATP and NE,acting respectively on P2X_1 and α_1-adrenoceptors in arterial smooth muscle.Each neurotransmitter produces a uniquetype of post-synaptic Ca~(2+)signal and associated contraction.The neural releaseof ATP and NE is thought to vary markedly with the pattern of nerve activity,probably reflecting both pre-and post-synaptic mechanisms.Finally,we showthat Ca~(2+)signaling during neurogenic contractions activated by trains of sympa-thetic nerve fiber action potentials are in fact significantly different from thatelicited by simple bath application of exogenous neurotransmitters to isolatedarteries(a common experimental technique),and end by identifying importantquestions remaining in our understanding of sympathetic neurotransmission andthe physiological regulation of contraction of small arteries.
The sympathetic nervous system plays an essential role in the control of total peripheral vascular resistance and blood flow, by controlling the contraction of systemic arteries. Derivascular sympathetic nerves release ATE norepinephrine (NE) and neuropeptide Y. this review summarizes our knowledge of the intracellular Ca ~ (2 +) signals that are activated by ATP and NE, acting respectively on P2X_1 and α_1-adrenoceptors in arterial smooth muscle. Each neurotransmitter produces a uniquetype of post-synaptic Ca 2+ signal and associated contraction. The neural release of ATP and NE is thought to vary markedly with the pattern of nerve activity, probably reflecting both pre-and post-synaptic mechanisms. Finaally, we showthat Ca ~ (2+) signaling during neurogenic contractions activated by trains of sympa-thetic nerve fiber action potentials are in fact significantly different from thatelicited by simple bath application of exogenous neurotransmitters to isolatedarteries (a common experimental technique), and end by identifying importantquestions remaining in our understanding of sympathetic neurotransmission and the physiological regulation of contraction of small arteries.