Reduction of vasoconstriction mediated by neuropeptide Y Y<sub>2</sub> receptors in arterioles of the guinea‐pig small intestine

Neild, T O; Lewis, Carolyn J.

doi:10.1111/j.1476-5381.1995.tb15865.x

Cited by 13 publications

(13 citation statements)

References 8 publications

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“…two reasons. First, in previous experiments in our laboratory the constriction caused by brief applications of the high-K+ solution was found to be unaffected by 30 nM w-conotoxin GVIA, suggesting that neurotransmitter release was not involved (Neild & Lewis, 1995). Second, in experiments in which the nerves around these arterioles were stimulated deliberately (Hirst, 1977) the constriction was not local, but spread uniformly for several millimetres throughout the arteriolar tree.…”

Section: Determination Of B From Network Anatomymentioning

confidence: 99%

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Segal

Neild

1996

The Journal of Physiology

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with an Appendix by Timothy 0. Neild 1. Blood flow control requires co-ordinated activity among many branches of arteriole networks, which may be achieved by conduction of membrane potential changes between arteriolar smooth muscle cells and endothelial cells. 2. We investigated the effect of branching upon the passive conduction of electrical signals through the syncytium of electrically coupled cells in arteriole networks (n = 12) prepared from the guinea-pig submucosa. To describe the effect of branching on cable properties, the expansion parameter B was calculated (B = 1 for an unbranched cable; B > 1 with branching) for a point in each arteriole network based on anatomy. 3. An estimate of B(B') was also obtained by measuring the spread of depolarization caused by a high-K+ stimulus applied to one region. Membrane potential (-74 + 4 mV (± S.D.) at rest) was recorded from smooth muscle cells (verified with intracellular dye labelling). A micropipette containing 120 mm KCl was positioned at 150 ,sm increments along an arteriole (width, 50-75 #sm) up to -1 2 mm from a stationary recording site, producing stable depolarization which decreased as separation distance increased. The dissipation of depolarization with separation was greater when recording near branch origins rather than continuous segments. 4. B ranged in value from 0 99 to 2-28. In any one experiment, values of B and B' were correlated (correlation coefficient, r = 0 71; P < 0 05), but B' was consistently greater than B, and we discuss methodological factors which could lead to erroneously high values for B'.5. For pooled electrophysiological data, depolarization decayed to 37 % (1/e) of initial values in -700 ,sm, consistent with B > 1. In contrast, the conduction of vasoconstriction and vasodilatation exceeds 2 mm in arteriole networks in previous studies. To explain this discrepancy, we suggest that active electrical events in cells of the arteriole wall augment passive electrical conduction during blood flow control.

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Section: Determination Of B From Network Anatomymentioning

confidence: 99%

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Segal

Neild

1996

The Journal of Physiology

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“…Although NPY is well known as a neuropeptide found in sympathetic vasoconstrictor neurons [17, 26], it is also found in some populations of vasodilator neurons [17, 26, 28, 38]. In some vascular beds, NPY may promote vasodilation by activating Y2 receptors on smooth muscle that inhibit vasoconstriction by modulating voltage-sensitive calcium channels [39]. Although the existence of neurogenic dilation of saccular arteries supplying the cheek pouch remains to be ascertained, functional studies have revealed no evidence of perivascular vasodilator nerves in the hamster retractor muscle [6, 14], which is consistent with the negligible presence of VIP-IR axons found in this vascular bed.…”

Section: Discussionmentioning

confidence: 99%

Heterogeneity of Vascular Innervation in Hamster Cheek Pouch and Retractor Muscle

Grasby

Morris²,

Segal³

1999

J Vasc Res

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The hamster cheek pouch and its retractor muscle have provided valuable insights into microvascular physiology of an epithelial tissue and striated muscle, respectively. Nevertheless, the innervation of these vascular beds has not been resolved. This study has investigated the nature of autonomic and sensory innervation of these vascular beds and has tested whether it varies within or between tissues. Multiple-labelling immunohistochemistry identified autonomic and peptide-containing sensory nerve fibres. Presumptive sympathetic vasoconstrictor axons with immunoreactivity (IR) for tyrosine hydroxylase (TH) and neuropeptide Y (NPY) innervated feed arteries and arterioles (but not veins or venules) of the retractor and anterior (muscular) cheek pouch; these axons were absent from the posterior (epithelial) region of the cheek pouch, as confirmed by catecholamine fluorescence. Presumptive autonomic vasodilator axons with IR for vasoactive intestinal peptide (VIP) consistently innervated feed arteries and proximal arterioles of the cheek pouch, but generally not those of the retractor muscle nor distal arterioles of either tissue. Sparse presumptive sensory axons with IR for calcitonin gene-related peptide (CGRP) and substance P were found near arterial and venous vessels in all regions of the cheek pouch and retractor muscle; CGRP-IR was also located in motor end plates associated with striated muscle fibres. Such regional differences in vascular innervation by autonomic and sensory neurons may selectively effect local and regional control of blood flow between and within vascular beds.

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“…This potentiation is not speci®c, as the effects of other vasoconstrictors are also enhanced in various vascular tissues. 144±146 In addition to the effects of NPY described above, it has been proposed that post-junctional NPY Y 2 receptors may mediate vasodilatory responses in speci®c vascular beds, 147 potentially explaining the presence of NPY in autonomic vasodilator neurones. 26 …”

Section: Receptor Subtypes Primarily Involved In Vasoconstrictionmentioning

confidence: 99%

Heterogeneous control of blood flow amongst different vascular beds

2000

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The control and maintenance of vascular tone is due to a balance between vasoconstrictor and vasodilator pathways. Vasomotor responses to neural, metabolic and physical factors vary between vessels in different vascular beds, as well as along the same bed, particularly as vessels become smaller. These differences result from variation in the composition of neurotransmitters released by perivascular nerves, variation in the array and activation of receptor subtypes expressed in different vascular beds and variation in the signal transduction pathways activated in either the vascular smooth muscle or endothelial cells. As the study of vasomotor responses often requires pre‐existing tone, some of the reported heterogeneity in the relative contributions of different vasodilator mechanisms may be compounded by different experimental conditions. Biochemical variations, such as the expression of ion channels, connexin subtypes and other important components of second messenger cascades, have been documented in the smooth muscle and endothelial cells in different parts of the body. Anatomical variations, in the presence and prevalence of gap junctions between smooth muscle cells, between endothelial cells and at myoendothelial gap junctions, between the two cell layers, have also been described. These factors will contribute further to the heterogeneity in local and conducted responses. © 2000 John Wiley & Sons, Inc. Med Res Rev, 21, No. 1, 1–60, 2001

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Reduction of vasoconstriction mediated by neuropeptide Y Y₂ receptors in arterioles of the guinea‐pig small intestine

Cited by 13 publications

References 8 publications

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Heterogeneity of Vascular Innervation in Hamster Cheek Pouch and Retractor Muscle

Heterogeneous control of blood flow amongst different vascular beds

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Reduction of vasoconstriction mediated by neuropeptide Y Y2 receptors in arterioles of the guinea‐pig small intestine

Cited by 13 publications

References 8 publications

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Conducted depolarization in arteriole networks of the guinea‐pig small intestine: effect of branching of signal dissipation.

Heterogeneity of Vascular Innervation in Hamster Cheek Pouch and Retractor Muscle

Heterogeneous control of blood flow amongst different vascular beds

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Reduction of vasoconstriction mediated by neuropeptide Y Y₂ receptors in arterioles of the guinea‐pig small intestine