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.     

Neural actions of several substance P antagonists in the rat spinal cord

Four substance P (SP) antagonists were tested on anaesthetized rats, by injecting 8 microgram amounts into the spinal cord (T8-T9), and by observing their effects on the hypothalamo-neurohypophysial responses to a presumably painful stimulus, the superfusion of the hepatic portal vein with 1 microM bradykinin. Only two antagonists, the new D-Pro4,D-Trp7,9,10,Val8-SP4-11 and D-Pro4,D-Trp7,9,10-SP4-11 were capable of inhibiting the responses by 50-60%, the former compound having 3 times less agonistic activity. The results suggest that substitution of the aromatic phenylalanine by the non-polar valine in position 8 may significantly improve the overall characteristics of neurally active SP antagonists.     

Interaction of substance P with dispersed pancreatic acinar cells from the guinea pig

Binding of ¹²⁵I-[Tyr⁸]-SP to isolated pancreatic acinar cells was inhibited in a concentration-dependent way by SP, [Tyr⁸]-SP and longer C-terminal fragments of SP. SP_6–11 was the shortest sequence to bind significantly to SP-receptors as well as to stimulate amylase release from dispersed pancreatic acini. SP_7–11 and shorter fragments did not inhibit binding of ¹²⁵I-[Tyr⁸]-SP and did not stimulate secretion of amylase significantly. SP augmented the stimulatory effect of cholecystokinin on amylase release. Two SP-antagonists, [D-Pro², D-Trp^{7, 9}]-SP and [D-Pro^{2, 4}, D-Lys³, D-Gln^{5, 6}, D-Trp^{7, 9}]-SP inhibited binding of ¹²⁵I-[Tyr⁸]-SP in a concentration dependent manner and tended at a high concentration to reduce release of amylase evoked by submaximal concentrations of SP.     

Evidence for the involvement of substance P in the atropine-resistant peristalsis of the guinea-pig ileum

In the isolated, vascularly perfused guinea-pig ileum, peristalsis could be induced by raising the intraluminal pressure in the presence of atropine. Atropine-resistant peristalsis was greatly inhibited or abolished by the substance P antagonist (D-Pro2, D-Trp7.9)-substance P, substance P desensitization, hexamethonium and by the enkephalin analogue FK 33-824. It is concluded that substance P neurones of the intestine play an important role in the atropine-resistant peristalsis of the guinea-pig ileum.     

Sympathetic control of substance P releasing enteric neurones in the guinea pig ileum

The contractile response of the isolated guinea-pig ileum to cholecystokinin octapeptide (CCK-8) that remained in the presence of atropine was greatly inhibited by the substance P antagonist D-Pro2,D-Trp7,9-substance P. This indicates that the atropine-resistant contraction to CCK-8 is mediated by the release of substance P from enteric neurones. Activation of alpha-adrenergic receptors by noradrenaline, clonidine or mesenteric sympathetic nerve stimulation inhibited the atropine-resistant contraction to CCK-8 but did not affect the contractile effect of substance P. It is concluded that alpha-adrenergic receptors exert an inhibitory influence on the release of substance P from enteric neurones.     

Pharmacological characterization of four related substance P antagonist

The purpose of this pharmacological study was to further characterize 4 related substance P (SP) analogues, namely (D-Pro², D-Phe⁷, D-Trp⁹)-SP (I), (D-Pro², D-Trp^7.9)-SP (II), (D-Arg¹, D-Pro², D-Phe⁷, D-Trp⁹)-SP (III) and (D-Arg¹, D-Pro², D-Trp^7.9)-SP (IV). At a concentration of 10^-4 M they were found to have little or no smooth muscle-contracting effect on the guinea-pig ileum, analogues I and II having substantially less agonist activity than III and IV. Pretreatment with the analogues inhibited the contractile responses to SP, but not to histamine or acetylcholine. Of the 4 analogues, II was found to be the most potent SP antagonist. The contractile responses to physalaemin and eledoisin were also inhibited by analogue II. The concentration-response curves for SP were shifted in parallel to higher concentrations in the presence of the analogues. The pA₂-values derived from Schild plots were 4.61 for (I), 5.43 for (II), 4.69 for (III) and 5.11 for (IV). Except for (I) the slopes of the regression lines of the Schild plots were close to unity. The data are consistent with simple competitive antagonism over the concentration ranges investigated. Without being secretagogues per se, the analogues inhibited SP-stimulated salivary secretion in the rat. Physalaemin-stimulated secretion was inhibited by analogue II. The inhibitory effect of sequences with D-Arg¹ instead of L-Arg¹ seemed to be of longer duration. Not one of these analogues blocked the blood pressure-lowering effect of SP, which indicates the existence of more than one type of SP receptor. This study has shown that 4 related SP analogues specifically inhibit the actions of SP and structurally related peptides physalaemin and eledoisin, both in vitro and in vivo. Analogues II-IV seem to inhibit in a simple competitive manner. (D-Pro², D-Trp^7.9)-SP was the most potent of the 4 SP antagonists.     

Coexistence of substance P- and methionine5-enkephalin-like immunoreactivity in nerve cells of the myenteric ganglia in the cat ileum

Intramural ganglia of colchicine-injected cat ileum were examined immunohistochemically using antisera to substance P (SP), vasoactive intestinal polypeptide (VIP) and methionine5-enkephalin (ENK). SP- and ENK-like immunoreactive nerve cells were preferentially located in the myenteric ganglia, whereas VIP-like immunoreactive nerve cells were distributed in both myenteric and submucous ganglia. A small number of nerve cells in the myenteric ganglia showed immunoreactivities to both ENK and SP antisera, but not to VIP antiserum. These findings provide supportive evidence for the coexistence of SP and ENK in a small population of neurones in the cat myenteric plexus.     

Effect of substance P on thermoregulation parameters during different cooling modes

The modulatory effect of ionophoretic application of substance P to the skin on the formation of the cold-triggered thermal protection reactions depends on the rate of cooling. During rapid cooling substance P enhances heat production, while during slow cooling it promotes constriction of skin blood vessels aimed at reduction of heat emission. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 6, pp. 643–645, June, 2006     

Regional differences in the response to substance P of the longitudinal muscle and the concentration of substance P in the digestive tract of the guinea-pig

Substance P-like immunoreactivity in extracts of guinea-pig gut was measured by radio-immunoassay using an antiserum directed against the C-terminal portion of substance P. The concentrations of substance P-like immunoreactivity were highest in the small intestine, high in the large intestine, low in the stomach, and lowest in the oesophagus. In the small intestine, the concentrations rose progressively from the proximal to the distal end, and most of the substance P-like immuno-reactivity was present in the extramucosal parts of the wall of the intestine. The longitudinal muscle with adhering myenteric plexus contained 28–30% of the substance P-like immunoreactivity content of the whole wall of the small intestine. Gel chromatography of an extract of the ileum yielded a single peak of immunoreactivity eluting at the position of substance P.In the fundus, substance P was much less effective than acetylcholine in contracting the longitudinal muscle. In most parts of the intestine, substance P produced as large a contraction as acetylcholine. The contractile response to substance P was not sustained, but dwindled to a lower maintained plateau. The rate and extent of the fade of contraction depended on the concentration of substance P; they were most pronounced in the anterior small intestine and less pronounced in regions toward the colon. The fade of contraction probably reflected desensitization of substance P receptors on the muscle cells. Atropine had no effect on the initial peak response to substance P, but caused the contraction to wane faster and to a greater extent. Thus, substance P appears to stimulate the release of acetylcholine in both the small and large intestine.The findings suggest a physiological role of substance P in the motility of the small and large intestine. It is conceivable that substance P is involved in the control of cholinergic activity which, in the guinea-pig's intestine, maintains the pacesetting properties of the longitudinal muscle.     

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-Trp^{7, 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 μg), but the tail skin temperature was not significantly changed. Nor was the tail skin temperature significantly changed after intrathecal injection of Spantide (5 pg), 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 nonsignificant. 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.     

Time course of effect of capsaicin on ultrastructure and histochemistry of substance P-immunoreactive nerves associated with the cardiovascular system of the guinea-pig

Capsaicin, a neurotoxin which depletes substance P from primary afferent nerve fibres, was injected systematically into adult guinea pigs. The effects of capsaicin were studied by immunohistochemistry, electron microscopy and radioimmunoassay at times from 5 min to 1 year. Within 5 min after a single injection of capsaicin (50 mg/kg) substance P immunofluorescence appeared less intense and less homogeneous than normal (i.e. it appeared granular). Large nerve trunks remained evident, but there were fewer fine single nerve fibres. With increasing time there was a progressive decrease in the number of immunoreactive fibres; by 4 h there was a marked reduction in the number of fibres and by 24 h only an occasional fibre was evident. In animals sacrificed 2 or more hours after treatment large brightly fluorescent swellings were seen in many nerves. Depletion of substance P-immunoreactivity persisted for as long as 365 days after treatment. Electron microscopy revealed alterations in capsaicin-sensitive nerve fibres within 5 min after treatment. Many fibres appeared swollen and there was disruption of their internal morphology, e.g. loss of microtubules and filaments and presence of an amorphous flocculent material in the axons. With increasing time after treatment, electron-dense profiles, indicative of degenerating nerve fibres, were commonly seen associated with Schwann cells. These findings demonstrate that the effects of systemic administration of capsaicin to adult guinea pigs occur rapidly in capsaicin-sensitive nerve fibres. The long lasting depletion of substance P-containing fibres is due to their degeneration.     

Possible involvement of neurokinin receptors in CNS and neuromuscular synapse in the realization of the effects of CAPAH and substance P

Nootropic non-anticholinesterase organophosphorus preparation CAPAH and substance P produced similar and dose-dependent effects on the amplitude and temporal parameters of miniature endplate potentials in mammalian neuromuscular synapse. Neurokinin receptor antagonist Win-51.708 abolished the effects of these agents. In behavioral experiments substance P moderated the mnemotropic and antidepressant effects of CAPAH. It was assumed that neurokinin receptors are the targets of CAPAH and substance P in CNS and neuromuscular synapse.     

Effect of substance P and its fragments on the microhemodynamics: Experimental study

Research Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Institute for Biologically Active Substances, Academy of Sciences of the USSR G. N. Kryzhanovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 109, No. 2, pp. 113–115, February, 1990.     

In the eye (D-Pro2, D-Trp7,9)-SP is a substance P agonist,which modifies the responses to substance P,prostaglandin E1 and antidromic trigeminal nerve stimulation

A substance P analogue, (D-Pro², D-Trp^7,9)-SP, has been described to have SP antagonistic and SP agonistic effects in different tissues. We have investigated the effects of (D-Pro², D-Trp^7,9)-SP on the sphincter pupillae muscle, the blood aqueous barrier (BAB) and the intraocular pressure (IOP) in the albino rabbit eye. We also investigated the modifying effects of (D-Pro², D-Trp^7,9)-SP on miosis, BAB damage and IOP rise caused by SP, prostaglandin E₁ (PGE₁), capsaicin and on the miosis caused by electrical intracranial antidromic trigeminal nerve stimulation (NV stim). Endogenous PG synthesis was inhibited by systemic indomethacin i. v., cholinergic influence on the pupil size was inhibited with biperiden, i. v., adrenergic nerve influence by cervical sympathectomy just prior to the expts. Tubocurarine chloride was used to cause relaxation of striated muscles in the expts with NV stim. We found 100 μg (D-Pro², D-Trp^7,9)-SP to cause miosis, breakdown of the BAB with heavy leakage of Evans blue into the ciliary processes and aqueous humor, and a rise in IOP. At 10 μg (D-Pro², D-Trp^7,9)-SP caused slight miosis and did not inhibit the miosis caused by SP or capsaicin, but caused a significant reduction of the miotic response caused by PGE₁ and NV stim. The rise in protein concentration in the aqueous humor caused by SP or PGE₁ was slightly but significantly lower after pretreatment with (D-Pro², D-Trp^7,9)-SP. Thus (D-Pro², D-Trp^7,9)-SP was found to act as a SP agonist on the sphincter pupillae muscle, on the BAB and IOP. However, (D-Pro², D-Trp^7,9)-SP seemed to have some SP antagonistic effects on mechanisms that require sensory nerve conduction e. g. miosis caused by PGE₁ and NV stim. The antagonistic mechanism is not clear. The SP analogue may have an unspecific membrane stabilizing effect or a toxic effect or block SP receptors on the sensory nerve fibers. Such effects of (D-Pro², D-Trp^7,9)-SP may explain also why the rise in protein concentration in the aqueous humor caused by SP and PGE₁ was lower in eyes pretreated with (D-Pro², D-Trp^7,9)-SP.     

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.     

Effect of intranasal substance P on the Parkinsonian syndrome

Laboratory of General Pathology of the Nervous System, Research Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Odessa Medical Institute. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 113, No. 1, pp. 16–19, January, 1992.