Effect of age on substance P levels in the rat mesenteric artery and vein

The content of substance P in the vasculature of Fischer 344 rats 6 to 27 months of age was determined by radioimmunoassay. Substance P could not be measured in the subclavian vein, femoral artery and vein or cerebral arteries of 6 month old rats. Levels of substance P in the mesenteric artery and vein of 6 month old rats averaged 4.8 +/- 1.0 and 8.3 +/- 1.8 pmole/g wet weight (n = 6-7), respectively. At 20 months of age, substance P levels in the vein were significantly increased. At 27 months, levels of substance P in both mesenteric artery and vein were increased to almost twice the values found in younger animals. This increased substance P content could reflect increased nerve density, or, more likely, an increased substance P content in each nerve ending. In the latter case, it is not possible to distinguish between increased content due to decreased nerve activity or increased content which would result in increased amounts of substance P released with each nerve impulse.     

Innervation and functional changes in mesenteric perivascular calcitonin gene-related peptide- and neuropeptide Y-containing nerves following topical phenol treatment

We have previously shown that age-related reduction of innervation and function in mesenteric perivascular calcitonin gene-related peptide-containing vasodilator nerves takes place in spontaneously hypertensive rats. The present study was performed to investigate innervation and functional changes in perivascular calcitonin gene-related peptide- and adrenergic neuropeptide Y-containing nerves after topical treatment with phenol, which damages nerve fibers, around the rat superior mesenteric artery. Under pentobarbital-Na anesthesia, 8-week-old Wistar rats underwent in vivo topical application of phenol (10% phenol in 90% ethanol) or saline (sham rats) to the superior mesenteric artery proximal to the bifurcation of the abdominal aorta. After the treatment, the animals were subjected to immunohistochemistry of the 3rd branch of small arteries proximal to the intestine and to vascular responsiveness testing on day 3 through day 14. The innervation levels of calcitonin gene-related peptide-like immunoreactivity containing fibers and neuropeptide Y-like immunoreactivity containing fibers were markedly reduced on day 3 to day 14 and on day 5 to day 14 after the treatment, compared with those in sham-operated rats, respectively. In perfused mesenteric vascular beds isolated from phenol-treated rats, adrenergic nerve-mediated vasoconstriction and calcitonin gene-related peptide nerve-mediated vasodilation in response to periarterial nerve stimulation (2-12 Hz) were significantly decreased on day 3 and day 7. Neurogenic release of norepinephrine in phenol-treated rats on day 7 was significantly smaller that that in sham-operated rats. Nerve growth factor content in the mesenteric arteries of phenol-treated rats was significantly lower than that in sham-operated rats. Administration of nerve growth factor using osmotic mini-pumps for 7 days after the phenol treatment resulted in greater density of calcitonin gene-related peptide- and neuropeptide Y-like immunoreactivity fibers than in phenol-treated rats and restored decreased vascular responses to periarterial nerve stimulation. These results suggest that topical phenol-treatment of the mesenteric artery effectively induces functional denervation of perivascular nerves, which can be prevented or reversed by nerve growth factor treatment.     

Age-related changes in adrenaline content of rat splanchnic blood vessels

The influence of ageing on the adrenaline content of the superior mesenteric artery and vein, renal artery and vein and portal vein was studied in 3-month- (young), 12-month- (adult) and 24-month-old (old) male Wistar rats using radioenzymatic assay for the measurement of catecholamine levels. Adrenaline concentrations were unchanged in the vascular wall of the blood vessels examined in adult rats, but were significantly decreased in the vascular wall of the superior mesenteric, renal and portal veins of old rats. In contrast, no age-dependent changes of adrenaline levels were found in the vascular wall of the superior mesenteric or renal arteries. The possibility that the loss of adrenaline concentrations in the venous vascular wall may be in some way related to the cardiovascular impairment occurring with age is discussed.     

动脉壁脑啡肽的含量及其免疫反应性神经的分布

本文用放射免疫法测得兔动脉壁亮氨酸脑啡肽(L-ENK)和甲硫氨酸脑啡肽(M-ENK)的含量(单位为Pg/mg组织湿重)分别是:耳动脉38.99±17.29,134.67±8.11,肾动脉31.10±7.76,93.60±18.22;肠系膜动脉25.70±13.60,88.43±18.16。动物经注射6-OHDA后,ENK含量显著下降,经利血平化后则无明显变化。用免疫组化PAP法观察到豚鼠肠系膜动脉外膜有L-ENK和M-ENK样免疫反应阳性纤维,手术摘除肠系膜神经节或注射6-OHDA,均可使ENK样免疫反应阳性纤维消失。结果表明,动脉壁内源性ENK位于支配该血管的交感神经纤维和末稍中,可能起着神经调制质的作用。     

Hemodynamic characteristics of conscious deoxycorticosterone acetate hypertensive rats

An electromagnetic flow probe was chronically implanted around the common carotid, superior mesenteric, or renal artery or the terminal aorta in deoxycorticosterone acetate (DOCA) hypertensive rats (prepared with DOCA and saline after uninephrectomy) and uninephrectomized control rats. A catheter for pressure measurement was inserted into the terminal aorta through a femoral artery. At rest the carotid and hindquarter (measured at the terminal aorta) blood flows in DOCA hypertensive rats were similar to the respective, corresponding values in normal rats with intact bilateral kidneys. The group mean of superior mesenteric flow was about 70% and that of renal flow about 40% larger than in normal rats. Cardiac output was estimated to be greater in DOCA hypertensive rats than in normal rats. In uninephrectomized control rats, superior mesenteric flow was larger than in normal rats to such an extent that an increase in cardiac output was assumed as in DOCA hypertensive rats, but renal flow was normal (about twice the unilateral renal flow in normal rats). Estimation of regional sympathetic vasoconstrictor tone from the decrease in peripheral resistance with hexamethonium and vasopressin antagonist revealed a substantial tone also in the superior mesenteric and hindquarter areas, where the tone was estimated to be almost absent in normal rats and uninephrectomized rats. It is suggested that hypertension in DOCA hypertensive rats is sustained by an increase in cardiac output and an elevation of vasoconstrictor tone in resistance vessels. Since increase in cardiac output appears to be similarly present in uninephrectomized control rats, the elevation of sympathetic tone due to administration of DOCA and salt seems to be indispensable for DOCA hypertension.     

Effects of Chronic Hypotension on the Adrenergic Nervous Plexus of the Saphenous Artery in Rats and Its Regeneration after Femoral Nerve Injury

The effects of chronic hypotension on the density and intensity of fluorescence (after treatment with glyoxylic acid) of the plexus of adrenergic fibers in the wall of the saphenous artery and on the reinnervation of this vessel were studied in Wistar rats. Regional hypotension in the vascular bed of the hind part of the rats’ bodies was induced by stenosis of the abdominal part of the aorta distal to the renal arteries. After four weeks, the saphenous artery was denervated in one limb by resection of a segment of the femoral nerve. In the limb with the nerve lesion, chronic (6–7 weeks) hypotension led to a reduction in the intensity of nerve fiber fluorescence by 20% as compared with normotensive animals (controls), though the density of the nerve plexus did not change. Partial reinnervation of the vessel was observed 2–3 weeks after femoral nerve lesioning. Measures of reinnervation in normotensive and hypotensive rats were no different at two weeks, though at three weeks rats with hypotension showed more complete recovery of innervation.     

Non-uniform effects of neurohumoral agents on the internal diameter in parallel and series arranged small arteries in rabbit hindlimb

Using X-ray angiography, the internal diameter (ID) of 31 sites of arteries in the hindlimb, i.e., the iliac, main femoral, profundal femoral, circumflex femoral, saphenous, and popliteal arteries, was measured in anesthetized rabbits. ID under the control condition was 294-1,796 micrometers, but was changed to 376-1,828 micrometers, 127-1,914 micrometers, and 423-2,098 micrometers with administration of hexamethonium bromide, noradrenaline, and phentolamine, respectively. The constrictor effects of noradrenaline and plasma catecholamine were larger in the femoral artery than in the iliac artery. At the transition site from the iliac to the femoral artery, ID per unit length increased from 190 micrometers/10 mm in the control to 320 micrometers/10 mm with noradrenaline. The constrictor effects of sympathetic nerve activity (SNA) on the profundal femoral, circumflex femoral, saphenous, and popliteal arteries varied among 19 out of 20 sites. Plasma catecholamine constricted ID at 18 sites but dilated it at 2 sites. Noradrenaline constricted ID at all 20 sites, particularly in the popliteal and saphenous arteries. It was concluded that the effects of SNA and plasma catecholamine on ID on rabbit hindlimb arteries were qualitatively and quantitatively non-uniform among different arteries and at different sites of the given artery.     

Effects of advancing age on hypothalamic neurotransmitter content and on basal and norepinephrine-stimulated LHRH release

In order to elucidate possible mechanism(s) responsible for the age-related decline in LH secretion, basal and norepinephrine (NE)-stimulated LHRH release was measured from median eminence (ME) fragments of 4-, 11-, 18- and 27-month-old male F344 rats. Serum LH levels declined significantly between 11 and 18 months and were still lower at 27 months of age, while testosterone levels declined continuously between 4 and 27 months. Hypothalamic NE and dopamine (DA) content also declined significantly with age, while serotonin and 5-hydroxy-indoleacetic acid content increased with age. Despite the decline in serum LH levels with age, in vitro basal LHRH release increased gradually with age as did NE-stimulated LHRH release. These data suggest that the age-related reduction in LH secretion by the male rat is due to a reduction in hypothalamic NE metabolism and not to an inability of the LHRH neuron to respond to NE stimulation.     

Mechanisms underlying pre- and postjunctional effects of neuropeptide Y in sympathetic vascular control

The effects of porcine neuropeptide Y (NPY) regarding sympathetic vascular control were studied in vitro on isolated rat blood vessels. The 10(-9)M NPY enhanced (about two-fold) the contractile responses to transmural nerve stimulation (TNS), noradrenaline (NA) and adrenaline (about two-fold) in the femoral artery. Higher concentrations of NPY (greater than 10(-8)M) caused an adrenoceptor-resistant contraction per se. The TNS-evoked [3H]NA efflux was significantly reduced by NPY in a concentration-dependent manner (threshold 10(-9)M). The calcium antagonist, nifedipine, abolished the contractile effects of NPY and the NPY-induced enhancement of NA contractions but did not influence the prejunctional inhibition of [3H]NA release. Receptor-binding studies showed that the ratio of alpha 1-to alpha 2-adrenoceptors in the femoral artery was 30:1. The NPY did not cause any detectable change in the number of alpha 1-or alpha 2-adrenoceptor binding sites or in the affinity of alpha 2-binding sites, as revealed by prazosin- and clonidine-binding, respectively. The NPY also inhibited the TNS-evoked [3H]NA release (by 42-86%) in the superior mesenteric and basilar arteries and in femoral and portal veins. The NPY still depressed TNS-evoked [3H]NA secretion from the portal vein in the presence of phentolamine. The NPY caused a clear-cut contraction in the basilar artery, increased the contractile force of spontaneous contractions in the portal vein, while only weak responses were observed in the superior mesenteric artery and femoral vein. The NA-induced contraction was markedly enhanced by NPY in the superior mesenteric artery, only slightly enhanced in the portal vein and uninfluenced in the femoral vein. In conclusion, in all blood vessels tested, NPY depresses the TNS-evoked [3H]NA secretion via a nifedipine-resistant action. Furthermore, NPY exerts a variable, Ca2+-dependent vasoconstrictor effect and enhancement of NA and TNS contractions.     

The origin and distribution of 5-hydroxytryptamine-like immunoreactive nerve fibres to major mesenteric blood vessels of the rat

5-Hydroxytryptamine-like immunoreactive nerve plexuses were demonstrated by indirect immunofluorescence histochemistry in whole-mount preparations and cryostat sections of blood vessels from the mesenteric vasculature of the adult rat. The major veins showed a density of innervation greater than that of the accompanying arteries. Removal of the coeliac-superior mesenteric ganglion complex resulted in almost total loss of 5-hydroxytryptamine-like immunoreactive nerves from superior mesenteric blood vessels. The results of crush lesions applied to distal vessels of the superior mesentery indicate that there were no 5-hydroxytryptamine-like immunoreactive nerve fibres extending from the enteric nervous system to these vessels. The administration of 6-hydroxydopamine resulted in a large reduction in the noradrenergic innervation, accompanied by a similar fall in the number of 5-hydroxytryptamine-like immunoreactive nerve fibres. It is suggested that the cell bodies of the 5-hydroxytryptamine-like immunoreactive nerve fibres demonstrated in the superior mesenteric vasculature are located within the sympathetic ganglia which supply the noradrenergic innervation to the same region and that the 5-hydroxytryptamine-like immunoreactivity may be co-localized with noradrenaline within sympathetic nerve fibres.     

Cardiovascular consequences of life-long exposure to dietary isoflavones in the rat

Dietary soy intake in man is proposed to provide cardiovascular protection, but it is not established whether this property is attributable to the soy protein per se or to associated dietary isoflavones. This investigation aimed to establish whether the dietary isoflavones in soy protein affect cardiovascular function. Ten days prior to mating, male and female Wistar rats were habituated to either a soy based isoflavone rich diet (plasma concentration 1.87 μmol l⁻¹ isoflavones) or the same diet after isoflavone elution (plasma isoflavone not detectable). Offspring were weaned onto and maintained on the same diet as their dam and sire for 6 months. Blood pressure, and constrictor and dilator responses in the aorta and mesenteric resistance arteries were assessed at 3 and 6 months of age. There was no effect of isoflavone removal from the diet on blood pressure, heart rate, aortic function or mesenteric artery contractile function, at either 3 or 6 months of age. Resistance mesenteric arteries from 6-month-old female rats fed the isoflavone rich diet demonstrated a modest increase in arterial distensibility compared with those fed the depleted diet, and mesenteric arteries from male and female rats fed the isoflavone rich diet showed increased sensitivity to acetylcholine. In summary, the isoflavone content of soy protein has no influence on blood pressure in healthy rats fed a diet based on soy protein, but influences small artery function.     

Regional blood flows and resistances in conscious one-kidney, one-clip renovascular hypertensive rats

Three regional blood flows were measured in one-kidney, one-clip renovascular hypertensive (one-kidney hypertensive) rats with chronically implanted electromagnetic flow probe. One-kidney hypertensive rats showed about 30% greater superior mesenteric flow, about 20% greater hindquarter flow at the terminal aorta, and an almost unchanged renal flow at the clipped renal artery when compared with control rats, but the sum of the mean values of these three regional blood flows in one-kidney hypertensive rats was almost the same as that of control rats. One-kidney hypertensive rats had a higher peripheral resistance in all the investigated vascular areas. The increase in peripheral resistance of the renal area including the clipped and removed arteries was greater than that in peripheral resistance of the superior mesenteric area or hindquarter area. These findings suggest that the remaining renal area which failed to compensate for the flow deprived by uni-nephrectomy plays a role in the etiology of this kind of hypertension.     

Regional haemodynamic responses to intracerebroventricular administration of rat calcitonin gene-related peptide in conscious, Long-Evans and Brattleboro rats

Rat calcitonin gene-related peptide (CGRP) was administered intracerebroventricularly (0.25 nmol in 5 microliter) to conscious, Long-Evans and Brattleboro rats, chronically instrumented with pulsed Doppler probes around the left renal and superior mesenteric arteries and the distal abdominal aorta. Tachycardias occurred in both strains, but only in Long-Evans rats was there a (modest) pressor effect of CGRP. However, both strains of rat showed renal vasodilatation and mesenteric vasoconstriction. These results indicate that the central pressor effect of CGRP in Long-Evans rats may not be due to generalized sympathetic activation, and make it unlikely that circulating vasopressin contributes to the mesenteric vasoconstriction.     

肺血管内皮细胞对交感神经末梢去甲肾上腺素释放的影响

ｃＧＭＰ升高抑制肾上腺能神经末梢释放去甲肾上腺素（ＮＥ），内皮细胞释放的舒张因子（ＥＤＲＦ）增加ｃＧＭＰ，故其对交感神经ＮＥ的释放可能有调节作用。本文观察去内皮细胞或抑制ＥＤＲＦ合成后肺血管对跨膜交感神经刺激（ＴＮＳ）的反应及对２－〔１４Ｃ〕－ＮＥ的摄取和释放。利用磨擦损伤内皮细胞后或使用ＬＮＭＭＡ抑制ＥＤＲＦ合成后，肺血管对ＴＮＳ刺激的反应明显增加，尤以低频率刺激为甚。肺血管对２－〔１４Ｃ〕－Ｎ     

Regional difference in sympathetic vasoconstrictor tone in conscious rats

Regional differences in sympathetic vasoconstrictor tone were studied in conscious rats. In each rat an electromagnetic flow probe was chronically implanted around the common carotid, superior mesenteric, or renal artery, or the terminal aorta. An indwelling catheter for the measurement of arterial pressure was inserted into the terminal aorta via the right femoral artery. Peripheral resistance was calculated by dividing arterial pressure by flow. The per cent decrease in peripheral resistance on the ganglion blockade with hexamethonium bromide was used as a measure of regional sympathetic vasoconstrictor tone. A significant decrease in peripheral resistance, assumed to indicate a substantial tonic discharge to resistance vessels, was observed in conscious rats only in the carotid and renal areas and not in the superior mesenteric and hindquarter (supplied by the terminal aorta) areas. Since ganglion blockade also diminished the sum of the mean regional flows, cardiac output was estimated to decrease on the ganglion blockade. This suggests that capacitance vessels are also receiving a sizable vasoconstrictor tone, because the ganglion blockade did not elevate right atrial pressure. Pentobarbital anesthesia markedly inhibited the assumed tone to the renal area and was estimated to newly generate a tone to the hindquarters.     

Organ-specific ligation-induced changes in harmonic components of the pulse spectrum and regional vasoconstrictor selectivity in Wistar rats

It has been shown previously that the amplitudes of the harmonic components of the pulse spectrum vary in specific patterns when the arteries leading to different organs are ligated, with the variations in the harmonics being linearly additive. Since ligation can be regarded as a vast increase in organ resistance, the present study examined the potential of using these ligation-induced variations in the pulse spectrum as reference parameters for an increase in vascular resistance and for regional vasoconstrictor selectivity. A vasoconstrictor, either arginine vasopressin (AVP) or angiotensin II (Ang II), was infused into anaesthetized Wistar rats via the femoral vein for 1 h. The distinct harmonic-specific drug effects on the pulse spectrum were simulated by combining renal artery and superior mesenteric artery ligations in different ratios, the ratio with the lowest mean square difference determining the regional drug selectivity. The ratios indicated that the effect of AVP on the pulse spectrum was attributable to the combined effect of ligating the renal and superior mesenteric arteries, while the effect of Ang II was attributable to ligation of the renal artery. The results are comparable with those of investigations of regional vascular resistance performed using traditional methods. Our findings indicate that the ligation-induced variations in the pulse spectrum can be used to determine regional increases in vascular resistance. This implies that blood pressure can be used as the sole parameter to determine which arterial bed has been affected by the vasoconstrictor, and how seriously.     

Constrictor and compliance responses of some arteries to nerve or drug stimulation

1. The magnitude of the maximum constrictor response to nerve stimulation was measured in the saphenous, ear, inferior and superior mesenteric, renal and carotid arteries in the rabbit and corresponding arteries, except the ear and carotid, in the guinea-pig. The responses varied from an average rise of 350 mm Hg in the rabbit saphenous to almost no response in the rabbit carotid. The guinea-pig arteries gave consistently smaller responses than the rabbit. The response magnitude was unrelated to wall thickness or the presence of an active uptake mechanism for noradrenaline. The response did correlate with the density of adrenergic innervation, with the wall thickness to lumen ratio and with the function of the artery and the amount of connective tissue in its wall.2. The magnitude of the maximum constrictor response to noradrenaline and six other agonist drugs, acetylcholine, histamine, 5-HT, KCl, vasopressin and angiotensin II, was compared. In all arteries noradrenaline was the most powerful agonist. The maximum responses to nerve stimulation and to noradrenaline were compared. In the rabbit saphenous and ear arteries this ratio was almost 1, but in arteries such as the rabbit renal it fell below 0.5.3. Artery wall stiffness was measured from the pressure/volume relationship during distension of a closed length of artery. In a relaxed artery two components only were present, an early easily distended phase and a late relatively undistensible phase. Noradrenaline caused a third, early, very stiff phase to appear in the pressure/volume curves. This is probably due to contracted muscle. The increase in stiffness varied from 617% in the rabbit saphenous to 152% in the rabbit carotid. In conducting arteries such as the carotid the change in stiffness was a more sensitive index of noradrenaline action than vaso-constriction.4. During the measurement of wall stiffness stress relaxation was not noticeable in relaxed arteries but was prominent in arteries contracted by noradrenaline. Stress relaxation involved both the changes in wall stiffness and the ability to constrict and was reversible even in the continuing presence of agonist drugs.5. Nerve stimulation, even in arteries where its vasoconstrictor effects were equal to those of noradrenaline, gave only slight increases in artery wall stiffness, suggesting that even in these densely innervated arteries only a small fraction of the muscle is activated by nerve stimulation.     

Origin of sympathetic efferent axons in the renal nerves of the cat

The origin of efferent axons in the renal nerves of the cat was examined using retrograde transport of horseradish peroxidase (HRP). Nerves on the surface of the left renal blood vessels were dissected 5-7 horseradish mm proximal to the medial margin of the kidney, transected and the central cut ends exposed to HRP. Labeled neurons were typically identified in three locations: (1) centrally along the renal nerve, (2) in the superior mesenteric ganglion, and (3) in the ipsilateral sympathetic chain ganglia (T12-L3). HRP was not detected in preganglionic neurons in the thoracolumbar spinal cord. Labeled cells ranged in size from 15 to 50 micrometers, with those in the renal nerve at the smaller end of the spectrum and those in the superior mesenteric ganglion at the larger end. In the superior mesenteric ganglion labeled cells were typically localized to a small region in the caudal pole of the ganglion around the origin of the renal nerve. The results show that the sympathetic efferent innervation of the kidney is derived from both paravertebral and prevertebral ganglia. In the latter (superior mesenteric ganglion), renal efferent neurons exhibited a topographic distribution.     

Microspectrofluorometric quantitation of autofluorescent lipopigment in the human sympathetic ganglia

The age-related changes in lipopigment autofluorescence were studied by microspectrofluorometry in three different types of human neurons: the sympathetic neurons of the stellate and superior mesenteric ganglion and pyramidal neurons of the frontal cortex. The age-related increase in lipopigment autofluorescence was more rapid in stellate ganglion but similar linear increases were found also in superior mesenteric ganglion and frontal cortex. There was an age-related shift in the autofluorescence from yellow to orange in the ganglia. This may be due to the accumulation of neuromelanin in noradrenergic neurons. Lipopigments were identified in sympathetic neurons at the age of 4 months and all neurons carried pigment granules after the age of 64 years. It is concluded that lipopigment autofluorescence is a useful marker for cellular ageing in both the peripheral and the central nervous system.     

Age changes in vasomotor reflexes and ultrastructure of sympathetic neurons in rats after chemical desympathization

The number of cells in the sympathetic ganglia of rats was reduced by means of guanethidine to 30% (group 1) and to 1% (group 2) of normal. In rats aged 2 months pressor responses to asphyxia and to stimulation of the femoral nerve were absent. In the animals of group 1 (but not of group 2) recovery of the reflexes was observed at the age of 4 months. An increase in the number of neurofibrils was demonstrated in the neurons surviving guanethidine treatment, indicating growth of the axon of these cells. Investigation of responses to the indirect sympathomimetic tyramine revealed an increase in the number of effector sympathetic endings at the periphery at the age of 4 months in the animals of group 1. It is suggested that restoration of reflex responses in the animals of this group at the age of 4 months took place on account of growth and branching of the axons of the surviving nerve cells, as a result of which the density of the effector innervation at the periphery was restored.