Increase In Substance P Release Research Articles

Protection of Ischemic Preconditioning on Renal Neural Function in Rats with Acute Renal Failure

We tested whether tolerance induced by ischemic preconditioning (IPC) in kidneys was related to renal nerves. Experimental acute renal failure (ARF) in a rat model was induced for 45 min of left renal arterial occlusion (RAO), followed by 6 or 24 h of reperfusion (ischemic reperfusion (I/R) group). The episode of IPC was four cycles of 4 min of RAO at 11 min intervals and then the I/R injury was treated as above (IPC-I/R group). After 6 h of reperfusion, polyuria was found in the I/R group associated with an enhancement of afferent renal nerve activity (ARNA) and a reflexive decrease in efferent renal nerve activity (ERNA). Changes in nerve responses were related with a reduction in neutral endopeptidase (NEP) activity and an increased release of substance P (SP). After 24 h of reperfusion, the I/R group showed oliguria which was associated with a lower ARNA, hyperactivity of ERNA and a nine-fold increase in SP release due to a further 52% loss in NEP activity. Prior IPC treatment did not affect the changed ischemia-induced excretory and nervous activity patterns during the first 6 h of reperfusion, but normalized both responses in the kidneys 24 h after ischemia. The IPC-mediated protection in oliguric ARF was related to the preservation of NEP activity to only 25% loss that caused an increase of SP amounts of only three-fold and a minor change in neurokinin 1 receptor (NK-1R) activities. Finally, both excretory and sensory responses in oliguric ARF after saline loading were significantly ameliorated by IPC. We conclude that IPC results in preservation of the renal sensory response in postischemic kidneys and has a beneficial effect on controlling efferent renal sympathetic nerve activity and excretion of solutes and water.

Estimation of proinflammatory biomarkers of skin irritation by dermal microdialysis following exposure with irritant chemicals

The aim of the present study was to quantify the release of proinflammatory biomarkers by dermal microdialysis after topical exposure with irritant chemicals, Jet fuel (JP-8) and xylene in rat skin. Occlusive dermal exposure (2h) was carried out with 230μl of JP-8 or xylene using Hill top chambers®. Linear microdialysis probes (10mm) were inserted in the dermis under urethane anesthesia. The dialysis fluid was pumped at a flow rate of 2μl/min and the dialysate was collected for 7h following probe insertion. The expression of substance P (SP), calcitonin-gene related peptide (CGRP) and prostaglandin E2 (PGE2) in the dialysate following microdialysis was measured by enzyme immunoassay (EIA). The effect of pretreatment with an SP antagonist (SR-140333) and a PGE2 inhibitor (celecoxib), 6 and 18h before the application of JP-8 was also assessed to further establish the sensitivity of the microdialysis set up. On similar lines, untreated and capsaicin treated control experiments were performed to compare with the SP release following JP-8 treatment. Further, we also investigated the SP release following topical application of xylene. The mean concentrations of SP after the application of JP-8 (90.01±3.31) and 3h after its removal (58.66±9.36) indicated that JP-8 induced significantly higher release of SP as compared to the baseline value (P<0.05). The release of SP following JP-8 treatment (58.66±9.36pg/ml) was comparable to capsaicin (58.18±11.29pg/ml). JP-8 exposure resulted in a significant increase (P<0.001) in PGE2 levels over the baseline control at the end of 1 and 2h of exposure. JP-8 treatment also produced significant increase (P<0.001) in PGE2 levels as compared to the untreated control during occlusion and 1h following its removal. There was a significant drop (P<0.05) in the PGE2 levels by the end of 3h following exposure. Pretreatment with SR-140333 and celecoxib significantly reduced (P<0.05) SP and PGE2 release induced by JP-8. The mean concentrations of SP following xylene exposure (25.50±8.80pg/ml) and 3h after its removal (34.37±5.61pg/ml) indicated its skin irritation potential. Unlike JP-8, xylene produced a significant increase in SP release only after the removal of occlusion. Pretreatment with SR-140333 significantly blocked the xylene induced SP release. CGRP was not detected in any of the samples. This study demonstrates that dermal microdialysis can be used to quantify skin irritation potential of JP-8 and related irritant chemicals.

Angiotensin blocks substance P release from renal sensory nerves by inhibiting PGE2-mediated activation of cAMP.

Activation of renal sensory nerves involves PGE2-mediated release of substance P (SP) via activation of the cAMP-PKA pathway. The PGE2-mediated SP release is suppressed by a low- and enhanced by a high-sodium (Na+) diet, suggesting an inhibitory effect of ANG. We now examined whether ANG II is present in the pelvic wall and inhibits PGE2-mediated SP release by blocking PGE2-mediated increases in cAMP. ANG II levels in renal pelvic tissue were 710 +/- 95 and 260 +/- 30 fmol/g tissue in rats fed a low- and high-Na+ diet, respectively. In a renal pelvic preparation from high-Na+-diet rats, 0.14 microM PGE2 produced an increase in SP release from 7 +/- 1 to 19 +/- 3 pg/min that was blocked by 15 nM ANG II. Treating pelvises with pertussis toxin (PTX) abolished the effects of ANG II. In pelvises from low-Na+ rats, neither basal nor bradykinin-mediated SP release was altered by PGE2. However, the bradykinin-mediated release of SP was enhanced by the permeable cAMP analog CPT-cAMP, from 4 +/- 1 to 11 +/- 2 pg/min, a response similar to that in normal-Na+-diet rats. In vivo, renal pelvic administration of PGE2 enhanced the afferent renal nerve activity (ARNA) response to bradykinin in normal- but not in low-Na+ diet rats. CPT-cAMP produced similar enhancement of the ARNA responses to bradykinin in normal- and low-Na+-diet rats, 1,670 +/- 490 and 1,760 +/- 400%.s (area under the curve of ARNA vs. time). Similarly, the ARNA responses to increases in renal pelvic pressure were similarly enhanced by CPT-cAMP in normal- and low-Na+-diet rats. In conclusion, renal pelvic ANG II modulates the responsiveness of renal sensory nerves by suppressing PGE2-mediated activation of adenylyl cyclase via a PTX-sensitive mechanism.

Effect of nitric oxide on substance P release from the peripheral endings of primary afferent neurons

To elucidate the interaction between nitric oxide (NO) and substance P (SP) in neurogenic inflammatory responses, we studied the effect of drugs related to nitric oxide (NO) on the levels of Evans blue and SP released into perfusate from the subcutaneous space in the rat instep. Noxious heat stimulation (47°C for 30 min) caused an increase in SP release in parallel with plasma extravagation. N W-nitro-L-arginine methylester ( l-NAME: 100 mg/kg, once daily) given intraperitoneally (i.p.) five times (chronic treatment) significantly suppressed the heat-evoked SP release and Evans blue leakage. FK409 (10 −4 M), which evokes a release of NO, applied locally caused a remarkable increase in the SP release into the perfusate. These results suggest that heat-induced NO generation causes SP release from the peripheral endings of small-diameter primary afferent neurons.

Involvement of substance P present in primary afferent neurones in modulation of cutaneous blood flow in the instep of rat hind paw.

1. The participation of small-diameter afferent fibres in the microcirculatory haemodynamics of cutaneous tissue was examined by studies on the effects of antidromic stimulation of primary afferent neurones on cutaneous blood flow (CBF) and tachykinin release into the subcutaneous space in the instep of the hind paw of rats. 2. Antidromic stimulation of the sectioned sciatic nerve induced a biphasic flow response, an initial transient decrease followed by an increase, with no alteration in the blood pressure. 3. Neither phase was affected by pretreatment with phentolamine (0.1 mg kg-1, i.a.), propranolol (0.5 mg kg-1, i.a.), atropine (0.5 mg kg-1, i.a.), methysergide (0.5 mg kg-1, i.a.) or mepyramine (10 mg kg-1, i.a.) plus cimetidine (10 mg kg-1, i.a.), but both were significantly inhibited by pretreatment with capsaicin (50 mg kg-1, s.c.). 4. Spantide (1-2 mumol kg-1, i.a.), a substance P (SP) antagonist, reduced the basal CBF, and also inhibited both phases of the biphasic flow response evoked by antidromic stimulation of the sectioned sciatic nerve. 5. Intra-arterial infusion of SP (0.5 mumol kg-1, i.a.) induced a biphasic flow response similar to that elicited by antidromic stimulation of the sectioned sciatic nerve. 6. Antidromic stimulation of the sectioned sciatic nerve caused a marked increase in SP release into the subcutaneous perfusate of the instep of the rat hind paw, but no detectable increase in neurokinin A release.7. We suggest that SP and its receptors are mainly responsible for the vascular response induced by stimulation of the sectioned sciatic nerve, and that small-diameter afferent fibres containing SP tonically regulate vascular tone in cutaneous microvessels.

Morphine produces a multiphasic effect on the release of substance P from rat trigeminal nucleus slices by activating different opioid receptor subtypes

Morphine (MOR) produces a concentration-dependent multiphasic effect (inhibitions and facilitations) on K +-eviked substance P (SP) release from rat trigeminal nucleus slices 47. In this study, we tested the action of selective opioid receptor antagonists on this multiphasic effect of MOR. 1 nM MOR produced an inhibition of K +-evoked release of SP that was affected only by the selective μ 1-opioid receptor antagonist naloxonazine (1 nM). MOR at 100 nM elicited an increase in SP release which was abolished selectively by the μ-opioid receptor antagonist, β-funaltrexamine (β-FNA; 20 nM) and attenuated by the σ-opioid receptor antagonist, ICI 174,864 (0.3 μM). 3 μM MOR produced an inhibition of SP release that was reversed only by ICI 174,864 (0.3 μM). MOR at even higher concentrations (30 μM) produced an enhancement of SP release that was reversed selectively by 3 nM n-binaltorphimine (n-BNI; 3 nM), a κ-opioid receptor antagonist. In slices pretreated with 20 nM β-FNA and in the presence of 0.3 μM ICI 174,864 (μ- and σ-opioid receptor blockade), both 100 nM and 3 μM MOR elicited a strong facilitation of K +-evoked SP release which was sensitive to 3 nM n-BNI. Thus, the increase in SP release produced by 100 nM may be mediated by the simultaneous stimulation of β-FNA-sensitive μ- and excitatory σ-opioid receptors whereas the facilitation of SP release induced by 30 μM MOR could be due to the activation of κ-opioid receptors. 1 nM and 3 μM MOR may inhibit SP release by stimulating naloxonazine-sensitive μ 1- and inhibitory σ-opioid receptors, respectively.

Effects of opioids on the heat stimulus-evoked substance P release and thermal edema in the rat hind paw

We examined the effect of opioids on the heat stimulus-evoked release of substance P (SP) into the subcutaneous space and the formation of edema in the rat hind paw. Immersion of the rat hind paw for 30 min into hot water adjusted to 47°C led to a marked increase in the release of SP into the subcutaneous perfusate with the formation of thermal edema. Intra-arterial infusion of morphine (10–100 μmol/kg) or ethylketocyclazocine (30–100 μmol/kg) inhibited dose dependently the heat stimulus-evoked increase in SP release and the thermal edema and the inhibitory effects were antagonized by pretreatment with N-methyl levallorphan (10 mg/kg i.p.) and Win 44,441-3 (10 mg/kg i.p.). The heat stimulus-evoked release of SP was reduced significantly during the intra-arterial infusion of [D-Ala 2,Met 5] enkephalinamide (100 μmol/kg). These results suggest that the opioid-induced inhibition of heat-induced edema could result from inhibition of the release of SP from peripheral sensory nerve endings.