Effects of intrathecal substance P and a substance P antagonist on a reflex to noxious heat are independent of changes in tail skin temperature.

Substance P or the substance P receptor antagonist (D-Arg1,D-Trp7.9,Leu11)-substance P (Spantide) was injected into the lumbar subarachnoid space in mice, and the ability to change the tail-flick reflex and the tail skin temperature was investigated. Tail-flick latency (the time needed to evoke the tail-flick reflex by noxious radiant heat) was reduced for 1-4 min after intrathecal administration of substance P (5 micrograms), but the tail skin temperature was not significantly changed. Nor was the tail skin temperature significantly changed after intrathecal injection of Spantide (5 micrograms), but this compound significantly increased tail-flick latencies 5-30 min after injection. Analysis of co-variance showed that the effects of substance P or Spantide on tail-flick latency were significant, whereas the influence of tail skin temperature on tail-flick latency was non-significant. Thus, intrathecal substance P induces a short-lasting increase in nociceptive sensitivity, and intrathecal Spantide produces an antinociceptive effect of longer duration. The results seem not to be the result of changes in tail skin temperature.     

Effects of substance P antagonists on the atropine-sensitive and atropine-resistant responses of guinea-pig ileum to substance P

The effects of substance P (SP) antagonists on the atropine-sensitive and atropine-resistant responses to SP of guinea-pig isolated ileum were investigated. The atropine-resistant response to SP was the contractile response on untreated preparations, and the atropine-sensitive response was the response to high concentrations of SP (5 X 10(-7) M) on preparations desensitized to SP with a concentration of SP of 3 X 10(-7) M. The SP antagonists tested, (D-Pro2,D-Phe7,D-Trp9)-SP, (D-Pro2,D-Trp7,9)-SP, (D-Arg1,D-Pro2,D-Trp7,9,Leu11)-SP and (D-Arg1,D-Trp7,9,Leu11)-SP (spantide), did not have similar orders of potency on the atropine-sensitive and atropine-resistant responses to SP, spantide being more potent than the other antagonists on the atropine-resistant response but no more potent on the atropine-sensitive response than (D-Pro2,D-Phe7,D-Trp9)-SP or (D-Arg1,D-Pro2,D-Trp7,9,Leu11)-SP. These findings are consistent with the hypothesis that neuronal receptors for SP differ from those on smooth muscle in guinea-pig ileum.     

The release of leukotriene B4 from human skin in response to substance P: evidence for the functional heterogeneity of human skin mast cells among individuals

Substance P is located in cutaneous nerve fibres and induces wheal and flare responses, accompanied by granulocyte infiltration, upon intradermal injection. Studies with animal skin and rat peritoneal mast cells have suggested that substance P induces the release of histamine and leukotriene B4 (LTB4), a potent chemoattractant for granulocytes, from skin mast cells. However, the release of LTB4 has not been detected from mast cells enzymatically isolated from human skin. In order to investigate the mechanism of granulocyte infiltration induced by substance P in human skin, we studied the release of LTB4 and histamine in response to substance P, and the effect of dexamethasone using human skin obtained from 22 nonallergic individuals. Histamine was released from all skin tissue samples in a dose-dependent manner. However, the amount of LTB4 release, both constitutive and inducible, was variable among skin preparations. Substance P induced a large release of LTB4 from the skin of eight donors (twice to six times that of the spontaneous release), but no or only negligible release from the skin of 14 donors. The amount of constitutive release of LTB4 correlated with the amount of tissue histamine. Dexamethasone selectively abolished the inducible release of LTB4, without an effect on histamine release and the constitutive release of LTB4. These results suggest that substance P induces the release of LTB4 in a certain population of human individuals by a glucocorticosteroid-dependent mechanism, and plays an important role in neurogenic inflammation with granulocyte infiltration.     

Further evidence that substance P partly mediates the action of cholecystokinin octapeptide (CCK-8) on the guinea pig ileum but not gall bladder: studies with a substance P antagonist

The substance P antagonist, [D-Pro4-D- Trp7 ,9,10]substance P4-11, caused a pig parallel shift to the right of the cholecystokinin (CCK-8) dose-response curve in guinea pig ileum longitudinal muscle without changing the maximal contraction. The shift of the CCK-8 dose response was markedly reduced after desensitization of the tissues to substance P (SP). The SP antagonist had no effect upon CCK-8 responses of the guinea pig gall bladder, [125I]CCK pancreatic binding or contractions of the guinea pig ileum produced by acetylcholine or electrical stimulation. The data provide additional evidence for the involvement of SP in the action of CCK-8 on the guinea pig ileum but not the gall bladder.     

No release of histamine and substance P in capsaicin-induced neurogenic inflammation in intact human skin in vivo: a microdialysis study

Background Studies in rodents ‘skin have indicated substance P to be the main inflammatory mediator involved in neurogenic inflammation, acting partly by release of histamine from skin mast cells. The mediators released in neurogenic inflammation in human skin remain to be determined. Objectives To determine the effects of intradermally injected and topically applied capsaicin on the release of histamine and substance P and skin responses in intact human skin in vivo. Methods Extracellular skin levels of histamine and substance P were measured by microdialysis technique and assayed by enzyme and radio immunoassays. Two kinds of dialysis fibres (210μm, 2 kDa, and 500 μm, 20 kDa) were inserted intradermally into forearm skin for studies of histamine release to topically administered capsaicin and intradermally injected capsaicin and substance P. Results Baseline histamine skin levels were 8.0 ± 0.7 nM. Intradermally injected capsaicin (0.3–30μM, 7.5–750 pmol) caused significantly and dose-related flare and pain reactions, but no significant histamine release or weals. Intradermally injected substance P (1 and 3 μM, 25 and 75 pmol) released significant amounts of histamine (peak levels being 90 and 475 nM), evoked weal-and-flare reactions, but did not cause pain. Capsaicin 2% ointment, applied on the skin for 2.5 h, increased skin blood flow by 300–400% as measured by laser Doppler flowmetry, elicited a longstanding burning sensation, but did not release histamine. Substance P-like immunoreactivity (SP-LI) was below the 1.8 pM detection limit following insertion of 20 kDa dialysis fibre and after intradermal injection of capsaicin 3μM. Intradermal injection of injection of 1 μM of substance P increased SP-LI levels to values greater than 4500 pM, confirming the ability of the dialysis fibre to recover this peptide. Conclusions Capsaicin-induced neurogenic activation does not involve the release of histamine from mast cells or detectable amounts of substance P release from sensory nerves in normal human skin in vivo.     

Psychogalvanic reflex and changes in electrical parameters of dry skin

The change in electrical characteristics of the skin owing to the psychogalvanic reflex has been investigated. The importance of using parallel values of admittance data is underlined because sweat-duct conductivity is anatomically in parallel with the rest of the skin. The response has been found to be mainly conductive, but small capacitive changes can appear. The effect of conductivefilm formation on the inside of the duct walls is discussed and emphasised. It is postulated that the dorsal side of the hand is as reflex-sensitive as palmar sites, but the lack of continuous sweat-gland activity and the conductive duct-wall films of dry skin often make the response disappear on nonpalmar skin sites. GSR on non-palmar skin sites can be a source of error if not adequately considered because just a deep breath may double skin conductance in seconds. To explain the rapid, positive waves often seen in the skin-potential response a new theory based upon electrokinetic phenomena is proposed.     

Effects of substance P on adult rat sensory ganglion neurones in vitro

Intracellular recordings were performed in vitro from dorsal root ganglion cell bodies isolated from adult rats. A- and C-type cells were distinguished according to the conduction velocity at their axons. Pressure application of substance P from extracellular electrodes caused a depolarization of some cells. This depolarization was accompanied by changes in membrane resistance. These results suggest that the cell bodies of spinal ganglion cells of adult animals may possess substance P receptors.     

Antinociceptive and neurotoxic actions of substance P analogues in the rat's spinal cord after intrathecal administration

Intrathecal administration of both (D-Pro2,D-Trp7,9)-substance P (DPDT) and (D-Arg1,D-Trp7,9,Leu11)-substance P (DADTL) elicited antinociception in hot-plate and tail-flick test, with DADTL as the most potent. The animals injected with 2.0 micrograms DADTL, and several animals administered with DPDT at the same dose, developed bilateral motor blockade of the hind-legs, persisting for up to 3 days after DADTL. The effect of DPDT appeared to be reversible at this dose. On histopathological examination it was found that these animals with persistent paralysis had widespread neuronal necrosis in the lumbar region of the spinal cord. It is concluded that the peptides have antinociceptive effects after the intrathecal administration in rats, but that there is a small margin between the dose producing this effect and that causing irreversible toxic reactions in the spinal cord.     

Distribution of capsaicin-sensitive nerve fibres containing immunoreactive substance P in cutaneous and visceral tissues of the rat

Treatment of newborn rats with capsaicin causes a selective and permanent degeneration of unmyelinated sensory fibres, some of which contain immunoreactive substance P (ISP). Following treatment of newborn rats with capsaicin (50 mg/kg), the ISP content was decreased by 66-75% in various skin areas and in the oral and nasal mucosae as measured at the age of 3-4 months. There was no significant depletion of ISP in the mucosa of the tongue. The ISP content of trachea, lungs, myocardium, hepatic duct, ureter and urinary bladder, was decreased by 60-84%. The ISP concentrations in stellate and mesenteric ganglia were reduced by 54 and 81%, respectively. These results indicate a widespread innervation of cutaneous and visceral tissues by sensory nerve fibers containing ISP.     

Influence of skin temperature on heat pain threshold in humans

We compared the effect of skin temperature on the critical threshold temperature eliciting heat pain with the effect of skin temperature on the response latency to the first heat pain sensation in healthy human subjects. Also, we determined the effect of the duration of a heat stimulus ramp on pain threshold. Furthermore, we determined the effect of skin temperature on mechanically induced pain. We found that the latency to the first pain sensation induced by a radiant heat stimulus was significantly decreased with an increase in the skin temperature (25–35 °C). However, independent of the rate of the stimulus rise (3–10 °C/s) and independent of the stimulus location (hairy vs glabrous skin), the threshold temperature for eliciting the heat pain sensation, determined with a contact thermostimulator, was not changed by a change in the skin temperature in the same subjects. With a fast rate of stimulus rise, a higher pain threshold was obtained than with a slow rise of stimulus temperature. However, this difference was found only with subject-controlled ascending stimuli (method of limits) but not with experimenter-controlled, predetermined stimulus ramps (method of levels). The heat pain threshold was higher in the glabrous skin of the hand than in the hairy skin of the forearm. With increasing stimulus duration (2.5–10s), the threshold temperature eliciting the heat pain sensation was significantly decreased. The mechanically induced pain threshold was not influenced by the skin temperature. The results indicate that the critical temperature for eliciting heat pain is independent of the skin temperature in humans. However, a change in skin temperature is an important source of an artefactual change in heat pain sensitivity when the radiant heat method (latency or energy) is used as an index of pain sensitivity. With a method dependent on reaction time (the method of limits), the heat pain threshold was artefactually increased, with fast rates of stimulus rise due to the long delay of slowly conducting heat pain signals in reaching the brain. With an increase in the duration of the heat stimulus, the critical temperature for eliciting pain sensation was significantly decreased, which may be explained by central neuronal mechanisms (temporal summation).     

Acute continuous exposure to cigarette smoke produces discrete changes in cholecystokinin and substance P levels in the hypothalamus and preoptic area of the male rat

FUXE, K., SIEGEL, R.A., ANDERSON, K., ENEROTH, P., MASCAGNI, F. & AGNATI, L.F. 1985. Acute continuous exposure to cigarette smoke produces discrete changes in cholecystokinin and substance P levels in the hypothalamus and preoptic area of the male rat. Acta Physiol Scand 125, 437–443. Received 8 January 1985, accepted 7 May 1985, TSSN 0001–6772. Department of Histology, Karolinska Institute, Stockholm, Sweden, Research and Development Laboratory, Department of Obstetrics and Gynaecology, Karolinska Hospital, Stockholm, Sweden, Deutsches Primaten Zentrum, Gottingen, FRG, and Department of Human Physiology, University of Modena, Italy. By means of a Walton Horizontal Smoking Machine, male rats were exposed to the smoke from 1–4 cigarettes burned in a continuous fashion. Cholecystokinin (CCK) and substance P levels (determined by means of radio-immunoassay) were measured in discrete hypothalamic and preoptic regions. Acute continuous exposure to cigarette smoke induced increases in CCK levels in the paraventricular hypothalamic region as well as decreases in CCK levels in the median eminence. Furthermore, this treatment resulted in decreased CCK and substance P levels in the medial preoptic region. The results have been interpreted to indicate that CCK and substance P containing neuronal systems can be regulated by cholinergic nicotine-like receptors.     

Temporal changes in spinal cord expression of mRNA for substance P,dynorphin and enkephalin in a model of chronic pain

We have used a partial sciatic nerve ligation model to examine the time course for changes in the expression of mRNA for three peptides related to pain transmission at spinal sites (dynorphin, enkephalin and substance P), during the development of allodynia. Enhanced expression of mRNA for dynorphin and substance P was observed in the dorsal horn on the same side as the partial nerve ligation. Increased expression of dynorphin mRNA was biphasic. The initial increases in expression of dynorphin mRNA occurred at 3 h, and a secondary peak was observed 1–3 days after surgery. The secondary increases coincided roughly with increased substance P mRNA expression. However, both dynorphin and substance P mRNA returned to control values after 1 week despite continuing allodynia. No significant changes in expression of mRNA for enkephalin were observed. The elevation of substance P mRNA in intrinsic spinal cord neurons may be secondary to changes in immediate early genes c-fos and jun-B, whereas the expression of dynorphin and enkephalin mRNA is differently regulated. The results also suggest that changes in the expression of the three neuropeptides are not critically involved in the development and maintenance of chronic pain or allodynia.     

A structure-activity profile of substance P and some of its fragments on supraspinal neurones in the rat

A presynaptic inhibitory role for opioid peptides in the control of C-fibre-evoked activity in the dorsal horn has been investigated. The excitability of C-fibre terminals in the dorsal horn of decerebrate spinal rats was tested using intraspinal terminal stimulation and recording the size of the antidromic C wave from the dorsal roots. Naloxone (1-2 mg/kg) failed to alter the baseline terminal excitability of the C-fibres, but reduced the increase in terminal excitability produced by A-fibre afferent conditioning stimuli. The inhibition of postsynaptic C-evoked activity in lamina 5 cells produced by A-afferent fibre conditioning stimuli was also reduced by naloxone. This effect may reflect the reversal of an opioid-mediated presynaptic inhibition, although blockade of a direct postsynaptic inhibitory action could also be involved.     

Effects of artificial dawn on sleep inertia,skin temperature,and the awakening cortisol response

The effect of artificial dawn during the last 30 min of sleep on subsequent dissipation of sleep inertia was investigated, including possible involvement of cortisol and thermoregulatory processes. Sixteen healthy subjects who reported difficulty with waking up participated in random order in a control and an artificial dawn night. Sleep inertia severity was measured by subjective ratings of sleepiness and activation, and by performance on an addition and a reaction time task measured at 1, 15, 30, 45, 60, and 90 min after waking up at habitual wake up time at workdays. At all intervals, saliva samples were collected for cortisol analysis. Sleep electroencephalogram was recorded during the 30 min prior to waking up; core body temperature and skin temperatures were recorded continuously until 90 min after waking up. Subjective sleepiness was significantly decreased and subjective activation increased after waking up in the artificial dawn condition as compared with control, in which lights were turned on at waking up. These effects can be explained by effects of artificial dawn on skin temperature and amount of wakefulness during the 30 min prior to the alarm. Artificial dawn accelerated the decline in skin temperature and in the distal‐to‐proximal skin temperature gradient after getting up. No significant effects of artificial dawn on performance, core body temperature, and cortisol were found. These results suggest that the physiology underlying the positive effects of artificial dawn on the dissipation of sleep inertia involves light sleep and an accelerated skin temperature decline after awakening.     

Effects of the substance P antagonist (D-Arg1, D-Pro2, D-Trp7, 9, Leu11)-SP on the miotic response to substance P,antidromic trigeminal nerve stimulation,capsaicin, prostaglandin E1, compound 48/80 and histamine

The effects of the substance P analogue (D-Arg¹, D-Pro², D-Trp^{7, 9}, Leu¹¹)-SP on the ocular inflammatory responses (miosis, vasodilation, protein leakage into the aqueous humour and eye pressure rise) to antidromic trigeminal nerve stimulation (trigeminal stimulation), intracameral injections of substance P (SP), capsaicin, prostaglandin E₁ (PGE₁), compound 48/80 and histamine were investigated in albino rabbits. The effects of nerve blockade with tetrodotoxin and blockade of histamine receptors on the responses to compound 48/80 and histamine were also investigated. Histamine H, receptors were blocked with clemastin and H₂ receptors with cimetidin. Formation of endogenous prostaglandins was prevented with indomethacin. The pupil size and the eye pressure were measured. The aqueous humour was collected immediately after the animal was killed, and analyzed for protein concentration. (D-Arg¹, D-Pro², D-Trp^{7, 9}, Leu¹¹)-SP had no significant miotic effect, but tended to cause a break-down of the blood-aqueous barrier. Miosis caused by SP, trigeminal stimulation, capsaicin, PGE₁, compound 48/80 or histamine was blocked by (D-Arg¹, D-Pro², D-Trp^{7, 9}, Leu¹¹)-SP. Histamine miosis was significantly reduced by blockade of nerve conduction or histamine receptors, while miosis caused by compound 48/80 was not. Nerve blockade abolished the rise in intraocular pressure caused by compound 48/80. Our results indicate that (D-Arg¹, D-Pro², D-Trp^{7, 9}, Leu¹¹)-SP is a specific SP blocker in the sphincter pupillae muscle. They are strong evidence for the hypothesis that trigeminal stimulation and capsaicin cause miosis by release of SP or a related substance (SPLI), and it seems likely that the miosis caused by PGE₁ and compound 48/80 is also caused by SPLI release. Histamine miosis is probably mediated both by SP receptors and histamine receptors in the pupillary sphincter muscle.     

Intrathecal substance P modulates the depressant effect of 5-methoxy-N,N-dimethyltryptamine on a reflex response to radiant heat in mice

The effect of intrathecal (i.th.) substance P (SP) on antinociception elicited by the serotonin (5-HT) receptor agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) was investigated in mice by means of the tail-flick method. Substance P (0.07, 0.7 or 7 micrograms) induced a behavioral syndrome for 1-2 min, but had no apparent toxic or neurologic effects and did not alter the tail-flick response to noxious radiant heat 30 min after injection. The depressant effect of 5-MeODMT (3 mg/kg) on tail-flick responses was, however, markedly attenuated when administered 30 min after SP. The tail skin temperatures of vehicle- and SP-injected mice were nearly identical 30 min after i.th. injection as well as after administration of 5-MeODMT. The results indicate a functional interaction between SP and 5-HT in spinal nociceptive processes, and it is suggested that i.th. SP modulates the function of 5-HT receptors.     

Effects of age and streptozotocin-induced diabetes on contents and effects of substance P and vasoactive intestinal polypeptide in the lower urinary tract of the rat

Andersson , P. O., Fahrenkrug , J., Malmgren , A. & Uvelius , B. 1992. Effects of age and streptozotocin-induced diabetes on contents and effects of substance P and vasoactive intestinal polypeptide in the lower urinary tract of the rat. Acta Physiol Scand 144 , 361–368. Received 29 January 1 991 , accepted 11 October 1991. ISSN 0001–6772. Departments of Physiology, Clinical Pharmacology and Urology, University of Lund, Lund, Sweden and Department of Clinical Chemistry, Bispebjerg Hospital, Copenhagen, Denmark. The urinary bladder and urethral content of substance P and vasoactive intestinal polypeptide and the in vitro effects of the peptides on the bladder were studied at 6 weeks and 6 months of streptozotocin-induced diabetes in the rat. The results were compared with those obtained in age-matched control animals. Both short-term and long-term streptozotocin treatment induced a clearcut increase in bladder weight. Bladder substance P content was increased in both groups of diabetic animals but substance P concentration was similar in control and diabetic animals. Vasoactive intestinal polypeptide content was slightly higher in diabetic animals than in controls but vasoactive intestinal polypeptide concentration was significantly lower in the bladders from both short-term and long-term diabetic animals. The bladder contractile response to substance P was similar in all groups of animals and vasoactive intestinal polypeptide was found to be devoid of contractile or relaxatory effects in the rat bladder. No change in urethral weight was seen with diabetes. There were no clear-cut changes in the urethral contents or concentrations of substance P and vasoactive intestinal polypeptide. The study also enabled comparisons between younger (3 months) and older (9 months) rats. This comparison showed a decrease in the concentrations and contents of substance P and vasoactive intestinal polypeptide between young and older rats. The changes were seen in both the bladder and the urethra and were similar in diabetic and normal animals.