Doses Of Substance P Research Articles

Effect of sensory neuropeptides on canine bronchial and pulmonary vessels in vitro

Sensory neuropeptides may be important in the noncholinergic component of parasympathetic vasodilation in the tracheobronchial circulation. We studied the effects of substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and calcitonin gene-related peptide (CGRP) on the isolated canine bronchial artery and used pulmonary artery and vein of similar size for comparison. CGRP (10pM-300nM) was a potent relaxant of the bronchial and pulmonary arteries, and the pulmonary vein with equal potency in all vessels. SP in low concentrations (10pM-100nM) caused vasodilation of the precontracted bronchial artery and in high concentration (10–100μM) contracted the vessel from resting tone. SP also relaxed the pulmonary artery and vein. NKA and NKB caused relaxation in all three vessels. All of the vascular effects of the sensory neuropeptides were concentration-dependent. The order of potency of the neuropeptides in the bronchial and pulmonary artery was SP>NKA>CGRP>NKB. In the pulmonary vein NKB caused a much larger relaxation than SP and NKA but it was less potent than either NKA or CGRP. Capsaicin (1 μM) caused a large contraction of the bronchial artery, similar in magnitude to the contraction caused by high dose of SP. Neuropeptide Y was also studied and found to cause no consistent constriction of any of the vessels studied. In conclusion, CGRP is a universal dilator of the bronchial and pulmonary blood vessels. SP and NKA exert their main effect on arterial vasomotor tone, whereas NKB is the only tachykinin producing marked dilation of the pulmonary vein.

Subsensitivity to substance P in SART-stressed mice.

The sensitivity of SART-stressed (repeated cold-stressed) mice to substance P (SP) was studied. The behavioral responses to intrathecal SP in the stressed mice were less marked than those in non-stressed mice. The 50% effective dose of SP, however, did not differ between the 2 groups. Also, the antagonistic effect of intrathecal [D-Pro2, D-Trp7,9]-substance P against SP was not different. These results suggest that SART-stressed mice are subsensitive to exogenous SP and that the number but not the affinity of SP receptors may be altered.

Subsensitivity to Substance P in SART-Stressed Mice

The sensitivity of SART-stressed (repeated cold-stressed) mice to substance P (SP) was studied. The behavioral responses to intrathecal SP in the stressed mice were less marked than those in non-stressed mice. The 50% effective dose of SP, however, did not differ between the 2 groups. Also, the antagonistic effect of intrathecal [D-Pro2, D-Trp7,9]-substance P against SP was not different. These results suggest that SART-stressed mice are subsensitive to exogenous SP and that the number but not the affinity of SP receptors may be altered.

Substance P(1–7) antagonizes substance P-induced aversive behaviour in mice

Substance P (SP) and its fragments were administered intrathecally into awake mice. SP and C-terminal fragments caused dose-dependent reciprocal hindlimb scratching responses. SP(5–11) was more potent than SP not only in inducing scratching response but also in inducing aversive behaviour including licking and biting. SP(1–7) induced no behavioural reactions. However, when low doses of SP(1–7) (1.0–4.0 pmol) were injected simultaneously with SP or SP(5–11) (0.1 nmol), aversive behaviours induced by SP or SP(5–11) were significantly reduced. These results indicate that SP(1–7) formed endogenously could modulate the actions of SP or SP(5–11) in the spinal cord.

Studies on the Cardiovascular Effects Produced by the Spinal Action of Substance P in the Rat

Administration of 6.5-pmol-6.5-nmol doses of substance P (SP) into the spinal subarachnoid space at T-8-T-10 in urethane-anesthetized rats increases both mean arterial pressure (MAP) and heart rate (HR) in a dose-related manner. However, in rats anesthetized with sodium pentobarbital, an increase in MAP is seen only at low doses of SP (6.5-65 pmol), while a biphasic response is obtained at 650 pmol and only a depressor response at 6.5 nmol SP. These responses also are accompanied by a tachycardia. Depending on the spinal cord level, cardiovascular responses of different time course and magnitude are elicited by SP. The amplitude of the increases in MAP and HR produced by SP (6.5 nmol) are: T-8-T-10 greater than T-1-T-3 greater than L-2-L-4 in rats anesthetized with urethane. In rats anesthetized with sodium pentobarbital, the decrease in MAP levels is greatest at T-1-T-3, while it is similar at T-8-T-10 and L-2-L-4 levels. The effects of SP on HR are more complex. The different cardiovascular responses obtained with the two anesthetics are not attributed to the relative depth of anesthesia but may be due to differential effects of the anesthetics on sympathetic nervous activity. The effect of SP on HR can be blocked by propranolol, but it remains unaffected by the surgical removal of the adrenal glands. We conclude that this cardiovascular response is most likely mediated by the postganglionic noradrenergic fibres and that adrenal medullary catecholamines are not essential. Using several inhibitors of endogenous mediators, two components to the spinal action of SP on MAP are made evident. The pressor response can be explained solely by the activation of sympathetic preganglionic fibres in the intermediolateral nucleus of the spinal cord, while the depressor response, in addition, may involve the release of a vasodilatatory substance in the periphery, the action of which persists in the presence of cholinergic, histaminergic, serotonergic, or opioid antagonists. Moreover, the adrenal glands are excluded as a possible source of this substance.

Bronchospasm Induced by Inhalation of Substance P: Effect of Sodium Cromoglycate

The aim of this study was to evaluate in vivo the effect of inhaled substance P (SP) and to determine the effect of sodium cromoglycate (SCG) on bronchospasm induced by its inhalation in 6 asthmatic patients. At the beginning of the study, all patients were asymptomatic, with an FEV1 value not less than 20%. SP was administered as aerosol, prepared in 0.9% saline to produce a dose range of 0.03-1 mg. Airway response was measured as FEV1 using a pulmonary system 47120A Hewlett-Packard instrument. The dose of SP producing a 20% change in FEV1 was calculated from the individual semi-logarithmic dose-response curve (PD20). After administration of the placebo, SP produced a dose-related bronchoconstriction with a geometric mean PD20 of 0.15 mg. After SCG, the mean PD20 value was of 0.64 mg (p less than 0.01). These results confirmed the bronchospasm induced by inhalation of SP and demonstrated that SCG is able to prevent this effect although it is impossible to define the exact mechanism of the drug.

Effects of substance P, neurokinin A and calcitonin gene-related peptide in human skin and their involvement in sensory nerve-mediated responses

The effects evoked by intradermal injections of substance P (SP), neurokinin A (NKA) or calcitonin gene-related peptide (CGRP) were studied in 51 non-atopic subjects. SP and NKA produced flare and weal, and CGRP produced an indurated erythema. The reactions to SP were strong, the flare being maximal 3–5 min after injection and the weal after 10–15 min. NKA evoked a much weaker flare and a slightly weaker weal than did SP. CGRP produced a prominent long-lasting, indurated erythema with pseudopodia surrounded by a pallor edge. The mode of action of the three peptides was studied by pretreatment of the skin with the histamine-releasing compound 48/80, the H 1-antagonist mepyramine or the local anesthetic xylocaine. The results suggest that mast-cell histamine and an intact sensory nerve supply are essential for the flare response to both SP and NKA. The weal response to SP was somewhat reduced by pretreatment with either 48/80 or xylocaine. The weal response to NKA, however, did not seem to depend upon either mast cells or sensory nerve fibres. The erythema evoked by CGRP was not suppressed by pretreatment with xylocaine, compound 48/80 or mepyramine, suggesting a direct action of CGRP on the blood vessels. The interaction between SP and CGRP was studied in subjects receiving a low dose of CGRP and increasing doses of SP or a low dose of SP and increasing doses of CGRP. CGRP did not potentiate the SP-evoked flare and weal and SP did not seem to enhance the response to CGRP.

Evidence for substance P as a functional neurotransmitter in guinea pig small intestinal mucosa

We showed previously that electrical transmural stimulation (TS) of guinea pig jejunal mucosa in vitro released neurotransmitters from submucosal plexus neurons which caused alterations in ion transport [1]. The present studies were performed to obtain information regarding the identity of the neurotransmitters. The addition of exogenous substance P (SP) to the serosal side of the tissue caused a transient increase in short-circuit current (Isc) which closely mimicked the response to TS. Both TS and SP caused net secretion of Cl − ions by stimulating movement toward the luminal side. Tetrodotoxin abolished the response to TS, inhibited approximately 70% of the response to SP but did not affect the response to urecholine, a cholinergic muscarinic agonist. In the presence of the muscarinic antagonist, atropine, Isc responses to both TS and SP were reduced suggesting that a portion of both responses was due to action on enteric nerves causing release of acetylcholine. Following desensitization of the tissue with supramaximal doses of SP the response to TS was significantly reduced but the response to urecholine was unchanged. In the presence of atropine, SP desensitization reduced the nerve-stimulated response by approximately 65%; treatment of tissue with SP antibodies reduced the response by approximately 55%. Under the same conditions Isc responses to histamine were unaltered. Our results suggest that both SP (or a structurally analogous neurotransmitter) and acetylcholine as well as additional unidentified neurotransmitter(s) are functionally important in the regulation of intestinal ion transport in guinea pig jejunum.

Facilitation of Lordosis by Injection of Substance P into the Midbrain Central Gray

Behavioral experiments tested the idea that the substance P (SP) innervation of the midbrain central gray (MCG) may be involved in the hormonal induction of sexual receptivity in female rats. SP, a SP antiserum or a reported SP antagonist were injected bilaterally into the MCG in ovariectomized, estrogen-treated females, and the lordosis response was recorded at repeated intervals. In the first experiment, three doses of SP (50,500 and 1,000 ng/cannula), a single dose of LHRH (50 ng/cannula) or vehicle were given to separate groups of females. All three doses of SP produced a rapid and long-lasting (3 h) increase in lordosis scores in moderately receptive females in tests with either manual stimulation or male rats. This facilitation was similar in latency, magnitude and duration to that produced by LHRH. In the second experiment, the basic findings of experiment 1 were replicated using blind testing. As no dose-response relation was established in experiment 1, a lower dose of SP (10 ng/cannula) was used in addition to doses of 50 and 500 ng/cannula also used in experiment 1. All three doses produced similar long-lasting increases in lordosis scores as in experiment 1. MCG injections of SP also increased lordosis scores in a second series of tests using manual stimulation alone. This demonstrates that the SP-induced facilitation does not depend on an interaction between the injections and stimuli delivered only by the male rat, eg., vaginal stimuli or ultrasonic calls. The question of the importance of endogenous SP for receptivity was examined in experiment 2 using MCG injections of a SP antiserum or the SP analogue, (D-Pro2, D-Trp7,9)-SP, which has been reported to block the excitation of locus coeruleus neurons by SP.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that substance P may be a modulator rather than a transmitter of noxious mechanical stimulation

Substance P (SP), injected intrathecally, produced a dose-related increase in responsiveness (hyperalgesia) in a pressure test for nociceptive thresholds. Pretreatment with two doses of SP produced complete desensitization to this response but did not alter base-line responsiveness. The hyperalgesic response to SP and the lack of change in base line following desensitization to SP suggest a modulator rather than a transmitter role for SP in the transmission of noxious mechanical stimulation.

Facilitation of conditioned inhibitory avoidance by post-trial peripheral injection of substance P 1

Experiments were undertaken to investigate the effects of the neuropeptide Substance P (SP) on performance of a conditioned inhibitory avoidance response in rats. A single-trial inhibitory avoidance task was employed. In Experiment 1 SP was injected IP immediately after the training trial in doses of 0.5, 5, 50, 100, 250 or 500 μg/kg; control animals were injected with diluent vehicle. The group treated with 50 μg SP/kg exhibited better avoidance than the other groups. In Experiment 2 the doses of SP used were 1, 50, 250 μg/kg, and the control animals were injected with vehicle or not injected at all. Only the 50μg SP/kg treatment group showed significantly better performance. In Experiment 3 50 μg/kg SP or vehicle was injected post-trial immediately or 5 hr after the trial. Only the group in which SP was injected immediately after the training trial showed significantly better performance when tested 24 hr later. This result rules out the possibility that SP exerts its effect by a long lasting proactive action on performance during the testing trial 24 hr later.

Substance P and human nasal mucociliary activity

Substance P (SP), a potent inflammatory agent, has been found in sensory nerve fibres in the nasal mucosa in several experimental animals as well as in man. It may participate in the inflammatory response as part of the mucosal defence against foreign materials. In experimental animals SP has been found to increase mucociliary in airway mucosa. The present study was performed in order to find out the relationship between topically applied SP and nasal mucociliary function in humans. Thirteen healthy volunteers were challenged with 65 micrograms SP or placebo in a randomized cross over fashion and mucociliary transport time was determined each time using the saccharine dye test. The dose of SP was chosen after an open dose-response study. No statistically significant change in the mucociliary transport time was found after challenge with SP as compared to placebo. The possible reasons for this are discussed.

Cardiovascular effects of calcitonin gene-related peptide in the pithed rat: Comparison with substance P

Recently it has been shown that calcitonin gene-related peptide (CGRP) and substance P (SP) are coexisting in central and peripheral nerve endings of sensory neurons. In the present study we compared the vasodepressor and plasma extravasating activity of CGRP with that of SP. Systemic administration of CGRP to pithed, vagotomized rats evoked a dose dependent, long lasting vasodilation accompanied by a parallel rise in heart rate. The tachycardic response to CGRP may indicate a direct positive chronotropic action on the heart since this effect could not be blocked by β-adrenoceptor blockade. For any equimolar dose the hypotensive effect of CGRP was much larger than that of SP. Both, CGRP and SP, showed a more pronounced decrease in mean arterial blood pressure after elevation of basal blood pressure levels by constant infusion of either phenylephrine, arginine-vasopressin, or angiotensin II. After systemic administration in equimolar doses CGRP was much less effective in producing plasma extravasation than SP. In conclusion, at equimolar doses CGRP is 10 times more potent than SP in producing vasodilatation but it possesses less than a third of the potency of equimolar doses of SP in producing plasma extravasation.

Mechanism of substance P-induced bronchoconstriction in maturing rabbit.

The maturational effects of substance P (SP) on airway function were quantitatively assessed in 30 anesthetized tracheotomized rabbits ranging in age from 2 to 29 days. Following paralysis, during mechanical ventilation with 100% O2 in a body plethysmograph, respiratory resistance (Rrs) and dynamic compliance (Cdyn) were continuously monitored. Noncumulative systemic infusions of SP (0.001-5.0 micrograms/g) produced dose-dependent decreases in pulmonary conductance (Grs), i.e., 1/Rrs, and Cdyn. The dose of SP producing a 50% decrease in Cdyn (PD50-Cdyn) significantly increased as a function of age indicating a diminution in airway sensitivity to SP. Bilateral cervical vagotomy and ganglionic blockade with hexamethonium had no effect on the airway response to SP. On the other hand, the response was significantly reduced following atropine sulfate infusion (2 mg/kg), suggesting a peripheral cholinergic contribution located distal to the airway parasympathetic ganglia. The magnitude of this cholinergic contribution increased as a function of age. Unlike atropine, antagonists to histamine and 5-hydroxytryptamine had no effect on the airway response to SP, however, the response was inhibited following infusion of the SP antagonist, D-Pro2,D-Trp7,9-SP. These findings indicate that the airway response to SP is age-related and mediated by binding of the agonist to airway smooth muscle coupled with an accelerated release of acetylcholine at the airway neuromuscular junction.

A study of [d‐Pro2, d‐Phe7, d‐Trp9]‐substance P and [d‐Trp7,9]‐substance P as tachykinin partial agonists in the rat colon

Two substance P (SP) analogues, [D-Pro2, D-Phe7, D-Trp9]-SP (DPDPDT) and [D-Trp7,9]-SP (DT79), previously described as tachykinin antagonists, have been shown to contract the rat colon muscularis mucosae preparation. The maximum response exhibited by these analogues was about 30% that of the SP maximum, suggesting that they were acting as partial agonists relative to SP. The responses to DPDPDT were unaffected by pretreatment with mepyramine, methysergide or [Sar1, Ile5, Ala8]-angiotensin II, which abolished the responses to histamine, 5-hydroxytryptamine (5-HT) and angiotensin II, respectively. Methysergide also did not affect the responses to DT79; the other antagonists were not tested against this analogue. Indomethacin and cimetidine also had no inhibitory effect. Atropine (2 microM) was present in all experiments to prevent indirect muscarinic effects. Phenoxybenzamine did not affect the dose-response curves to SP, eledoisin-related peptide (ERP), kassinin, eledoisin or physalaemin, nor did it affect the responses to individual doses of DPDPDT or DT79. However, in the absence of atropine, it shifted the carbachol dose-response curve markedly to the right, and reduced its maximum. The tachykinin antagonist [D-Pro4, D-Trp7,9,10]-SP4-11 reduced the responses to individual matched doses of DPDPDT, DT79 and SP to the same degree, whilst leaving responses to 5-HT or angiotensin II unaffected. This suggested that DPDPDT and DT79 were acting at the same receptor as SP. The inhibitory effects of DPDPDT on responses to SP, ERP and kassinin, and that of DT79 on responses to SP, were analysed. All four combinations yielded data compatible with an interaction at only one receptor, although DPDPDT appeared slightly more potent at inhibiting responses to kassinin. The results are discussed in the light of the proposed existence of multiple tachykinin receptor subtypes. The possible influence of differential metabolism of tachykinin analogues is also considered.

Alteration of shock titration thresholds in the cat following intrathecal substance P administration

Substance P (SP) was injected intrathecally (10 or 100 μg) into cats previously implanted with nerve-stimulating electrodes and the effect on shock titration thresholds was evaluated. Elevated shock thresholds were observed in 5 of 8 cats following the 100 μg dose of SP. In addition, one cat exhibited a decreased threshold and two cats showed a triphasic (increase, decrease, increase) response. Overt behavioral effects of intrathecal SP were mild, but suggested that injection of the drug was aversive.

A comparison of the miotic and inflammatory effects of biologically active polypeptides and prostaglandin E 2 on the rabbit eye

The ocular effects of some biologically active peptides were studied and compared to those of prostaglandin E 2 (PGE 2) to determine whether the responses of the eye to trauma, characterized by increased intraocular pressure (IOP), the development of anterior chamber flare and partial miosis, might be mediated by such peptides. One to 2 hr after intravitreal injection of 10 μg of PGE 2 into rabbit eyes, ocular hypertension, flare and iridial hyperemia, but only minimal miosis were observed. Maximum miosis developed within 2–3 hr after intravitreal injection of 1·0–100 μg of substance P (SP), SP-octapeptide (SP-8), coherin or eledoisin-related peptide (EDR), while 10–100 μg of vasoactive intestinal polypeptide (VIP), somatostatin or bradykinin (BK) yielded only submaximal miosis and angiotensin II, α-MSH and poly- dl-alanine had little or no miotic effect. None of these peptides caused iridial hyperemia or a cellular invasion of the anterior chamber and only high doses (100 μg) of VIP or BK caused significant increases in the protein concentration of the aqueous humor. Miotic doses of SP, SP-8 or EDR caused a significant increase in IOP in some, but not all, experiments. Thus, PGE 2 can be regarded as a mediator of the ocular irritative response although it may not account for the miosis that is associated with chemical or surgical trauma. However, this autacoid should not be regarded as the mediator of ocular inflammation since it does not elicit a cellular response. In contrast, some polypeptides, particularly SP, SP-8 and EDR are strong miotics and, at least under some circumstances, can act as effective ocular hypertensives, but these peptides do not reproduce any other signs of ocular irritation or inflammation. It is therefore concluded that none of the peptides studied here could, by itself, be the sole mediator of the initial ocular irritative response although some of them may account for the miosis and contribute to the ocular hypertension associated with this response. A combination of some of these peptides together with PGE 2 and/or other PGs may account for all aspects of the ocular irritative response and for most aspects of the ocular inflammatory response.

Modulation of cat monosynaptic reflexes by substance P

Substance P (SP) applied by iontophoresis at different current strengths to single motoneurons of cat spinal cord did not cause these units to discharge. SP produced a gradual and prolonged change in synaptic excitability as measured by response to dorsal root stimulation. The effect outlasted application of SP. The lowest effective dose of SP diminished motoneuron response to dorsal root stimulation (inhibitory modulation). Doses 2–4 times as great enhanced the response to dorsal root stimulation (facilitatory modulation) without causing the motoneuron to discharge spontaneously. These observations suggest that one physiological role of SP is modulation of synaptic transmission, i.e. alteration of efficacy of transmission without acting as a primary transmitter at the postsynaptic membrane.

Influence of substance P on the behavioral changes induced by haloperidol in rats

Locomotor activity and grooming behavior of rats were recorded for a period of 30 min following intraventricular injections of substance P(SP) in doses of 0.60 and 2.50 μg/rat. The lower dose of the peptide significantly increased locomotion for 10 min and time spent grooming for 25 min. The effects of the same two doses of SP on the hypokinesia induced by various pharmacological treatments modifying catecholaminergic systems were then examined. SP did not affect the behavioral depression produced by α-methyl-para-tyrosine (250 mg/kg), FLA-63 (25 mg/kg) and phenoxybenzamine (20 mg/kg). However, SP, in dose of 0.60 μg/rat, systematically reversed the decrease in locomotor activity induced by a relatively small dose of haloperidol, 0.1 mg/kg. The same dose of the peptide significantly counteracted the rigidity but not the hypokinesia and the catalepsy resulting from the previous administration of a higher dose of haloperidol, 3 mg/kg. The results support the hypothesis that SP may exert direct or indirect functions in motor behavior, possibly via a modulatory action on brain dopaminergic systems.

Effects of substance P and neurotensin on growth hormone and thyrotropin release [formula omitted][formula omitted] and [formula omitted][formula omitted

Conscious ovariectomized (OVX) rats bearing a cannula implanted in the third ventricle were injected with 2 μl of 0.9% NaCl containing varying doses of substance P (SP) or neurotensin (NT) and plasma GH and TSH levels were measured by RIA in jugular blood samples drawn through an indwelling silastic catheter. Control injections of physiologic saline iv or into the third ventricle did not modify plasma hormone levels. Intraventricular injection of SP or NT at doses of either 0.5 or 2 μg elevated plasma GH concentrations within 5 min and they remained elevated for 60 min. Third ventricular injection of similar doses of SP or NT had no effect on plasma TSH. An intermediate dose of 1 μg of SP or NT given iv had no effect on plasma GH but NT elevated plasma TSH. Incubation of hemipituitaries from OVX rats with varying doses of SP or NT did not alter GH release into the medium but TSH release was enhanced with NT at doses of 100 or more ng/ml of medium. It is suggested that SP acts centrally to stimulate growth hormone-releasing factor (GRF) or to inhibit somatostatin release and thereby enhance GH release and that NT acts directly on the pituitary to stimulate TSH release.