The substance P receptor subtype modulating catecholamine release from adrenal chromaffin cells

Tachykinin receptor types: Classification and membrane signalling mechanisms

The use of selective agonists in both functional and binding studies has provided unequivocal evidence for the existence of three types of tachykinin receptor (NK(1), NK(2) and NK(3)); there is also preliminary evidence for the existence of further subtypes. These results have been confirmed by the development of selective antagonists and by the identification and cloning of three distinct cDNA sequences. All three receptors belong to the superfamily of G protein coupled receptors and are linked to the phosphoinositide transmembrane-signalling pathway. The purpose of this article is to review recent developments in the pharmacology of each receptor with emphasis on the NK(3) type. In particular, the need to use selective agonists and antagonists to identify each receptor type is stressed.

Biologic activity of the tachykinins on lamb and sheep gallbladder

In this study, we examined the activity of the tachykinins (TKs) on lamb and sheep isolated gallbladder and whether the TKs are involved in the capsaicin-induced activity in these tissues. Substance P (SP) and physalaemin (PHYS) contracted lamb gallbladder, PHYS-induced striking tachyphylaxis. This tissue was nearly insensitive to neurokinin A (NKA), neurokinin B (NKB), septide, and capsaicin. As in lamb tissues, SP and PHYS both contracted sheep gallbladder although PHYS induced no tachyphylaxis. At doses that had no effect on lamb tissue, NKA, NKB, septide, and capsaicin contracted sheep gallbladder. Our findings indicate that TK receptors differ in adult and young ovine gallbladder. The activity of PHYS on lamb gallbladder could depend on the existence of an unusual binding site, carrying one or more residues critical for the N-terminal sequence present in PHYS but not in SP.

Interactions between tachykinins and diverse, human nicotinic acetylcholine receptor subtypes

Nicotinic acetylcholine receptors (nAChR) are diverse members of the ligand-gated ion channel superfamily of neurotransmitter receptors and play critical roles in chemical signaling throughout the nervous system. Reports of effects of substance P (SP) on nAChR function prompted us to investigate interactions between several tachykinins and human nAChR subtypes using clonal cell lines as simple experimental models. Acute exposure to SP inhibits carbamylcholine- or nicotine-stimulated function measured using 86Rb+ efflux assays of human ganglionic (alpha 3 beta 4) nAChR expressed in SH-SY5Y neuroblastoma cells (IC50 approximately 2.3 microM) or of human muscle-type (alpha 1 beta 1 gamma delta) nAChR expressed in TE671/RD clonal cells (IC50 approximately 21 microM). SP also acutely blocks function of rat ganglionic nAChR expressed in PC12 pheochromocytoma cells (IC50 approximately 2.1 microM). Neurokinin A and eledoisin inhibit function (extrapolated IC50 values between 60 and 160 microM) of human muscle-type or ganglionic nAChR, but neurokinin B does not, and neither human nAChR is as sensitive as PC12 cell alpha 3 beta 4-nAChR to eledoisin or neurokinin A inhibition. At concentrations that produce blockade of nAChR function, SP fails to affect binding of [3H]acetylcholine to human muscle-type or ganglionic nAChR. SP-mediated blockade of rat or human ganglionic nAChR function is insurmountable by increasing agonist concentrations. Collectively, these results indicate that tachykinins act noncompetitively to inhibit human nAChR function with potencies that vary across tachykinins and nAChR subtypes. They also indicate that tachykinin actions at nAChR could further contribute to complex cross-talk between nicotinic cholinergic and tachykinin signals in regulation of nervous system activity.

Immunohistochemical correlation of human adrenal nerve fibres and thoracic dorsal root neurons with special reference to substance P

Applying a double-labelling immunofluorescence technique, six types of substance P-containing nerve fibres were distinguished in the human adrenal gland according to the immunohistochemical colocalization of (I) calcitonin gene-related peptide (CGRP), (II) cholecystokinin, (III) nitric oxide synthase, (IV) dynorphin, (V) somatostatin, and (VI) vasoactive intestinal polypeptide. Fibre populations I to IV in their mediator content resembled the respective subpopulations of primary sensory neurons in human thoracic dorsal root ganglia, while populations V and VI revealed no correspondence with dorsal root neurochemical coding. Nerve fibres with the combination substance P/nitric oxide synthase occurred only in the adrenal cortex, whereas all other fibre types were present in both cortex and medulla. As revealed by immuno-electron microscopy, substance P-immunolabelled axon varicosities (a) exhibited synaptic contacts with medullary chromaffin cells or with neuronal dendrites, (b) were directly apposed to cortical steroid cells and (c) were separated from fenestrated capillaries only by the interstitial space. These findings provide immunochemical support for an assumed sensory innervation of the human adrenal gland, and additionally suggest participation of substance P in efferent autonomic pathways. Furthermore, the results are indicative for a differentiated involvement of substance P in the direct and indirect regulation of neuroneuronal and neuroendocrine interactions.

Functional studies with substance P analogues: effects of N-terminal, C-terminal, and C-terminus-extended analogues of substance P on nicotine-induced secretion and desensitization in cultured bovine adrenal chromaffin cells

Substance P (SP) and SP analogues, including C-terminal, N-terminal, and C-terminus-extended analogues, have been investigated for their ability to modulate nicotine-induced secretion from bovine adrenal chromaffin cells in culture. Secretion was monitored by measuring the release of endogenous catecholamines by electrochemical detection following separation on HPLC and the release of endogenous ATP with an on-line luciferin-luciferase bioluminescence technique. SP is known to have the following two effects on nicotine-induced secretion of catecholamines (see Livett and Zhou, 1991): inhibition of the nicotinic response and protection against nicotinic desensitization. Secretion induced by 10(-5) M nicotine was inhibited 70-80% by SP, SP-methyl ester, and the C-terminus-extended analogue SP-Tyr12-NH2, 65% by (Ala3)SP-NH2, 45% by the C-terminal analogue SP(4-11), and 20 and 5% by the N-terminal analogues SP(1-7) and SP(1-5), respectively, when these peptides were present at 3 x 10(-5) M concentrations. The order of potency was SP = SP-methyl ester = SP-Tyr12-NH2 > (Ala3)SP-NH2 > SP(4-11) > SP(1-7) > SP(1-5). SP, SP-methyl ester, and (Ala3)SP-NH2 protected against nicotinic desensitization by 40-55%, and SP(4-11) protected by 20% (all at 3 x 10(-5) M). In contrast, the N-terminal analogues SP(1-7) and SP(1-5) and the C-terminus-extended analogue SP-Tyr12-NH2 at 3 x 10(-5) M did not protect against nicotinic desensitization. Cyclo-SP(3-9), Ac-SP(3-9)-NH2, SP(3-9), and SP(3-6) had neither inhibitory nor facilitatory effects on secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of beta-amyloid peptides on nicotine-induced Ca2+ influx in PC12h cells in culture

Synthetic beta-amyloid peptides and the neuropeptide substance P (SP) were examined for their ability to modulate nicotinic response in PC12h cells, a subclone of PC12 cells, SP, beta A1-40 and its peptide fragment beta A25-35-NH2 significantly inhibited an increase in cytoplasmic calcium concentrations ([Ca2+]i) induced by nicotine in a dose-dependent manner. Furthermore, beta A1-40 was found to inhibit the [Ca2+]i increase induced by depolarization with a high concentration of potassium. These findings show that both beta A1-40 and beta A25-35-NH2 may mimic the function of SP on inhibition of nicotinic response through different mechanisms.

Effects of substance P on the binding of agonists to the nicotinic acetylcholine receptor of Torpedo electroplaque

The effect of the neuropeptide substance P on the binding of the cholinergic ligands to the nicotinic acetylcholine receptor of Torpedo electroplaque membranes was examined at a physiological concentration of NaCl (150 mM). Substance P had no effect on the initial rate of 125I-alpha-bungarotoxin binding at concentrations of < 100 microM. The peptide did not bind to the high-affinity local anesthetic site but allosterically modulated [3H]phencyclidine binding, positively in the absence of agonist and negatively in the presence of agonist. Substance P increased the apparent affinity of the cholinergic agonists carbamylcholine and acetylcholine at equilibrium. The effect of substance P on the equilibrium binding of [3H]acetylcholine was examined directly, and the peptide appeared to increase the affinity of the binding of the second molecule of agonist, with no effect on the binding of the first. This indicates that substance P can affect the cooperative interactions between agonist binding sites. Substance P appeared to increase the rate of carbamylcholine-induced desensitization; however, the data are also consistent with an allosteric mechanism that does not involve the desensitized state. To attempt to differentiate between these mechanisms, the rates of recovery were determined after exposure to peptide and/or agonist. The kinetics of recovery are consistent with stabilization of the desensitized state by substance P if the peptide remains bound long enough to allow rapid recovery to the low-affinity state. However, an allosteric modulation of agonist binding that does not involve the desensitized state cannot be ruled out.

An amyloid peptide, beta A4 25-35, mimics the function of substance P on modulation of nicotine-evoked secretion and desensitization in cultured bovine adrenal chromaffin cells

The amyloid protein (beta A4) is found in the CNS of patients with Alzheimer's disease; however, the pathogenic role of this protein is not known. In the present study, a peptide fragment of beta A4 (beta A4 25-35; Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-NH2), which contains the conserved C-terminal sequence of substance P (X-Gly-Leu-Met-NH2), and the neuropeptide substance P (SP) were examined for their ability to modulate nicotine-evoked secretion from cultured bovine adrenal chromaffin cells. Secretion of the released endogenous catecholamines was monitored by electrochemical detection after separation by HPLC. Secretion induced by 10(-5) M nicotine was inhibited by SP and beta A4 25-35. The IC50 of SP and beta A4 25-35 was 3 x 10(-6) and 3 x 10(-5) M, respectively. SP and beta A4 25-35 both protected against nicotine receptor desensitization. However, beta A4 25-35 was approximately 10-fold less effective than SP in its protective effect. The present work shows that beta A4 25-35 can mimic the modulatory actions of SP on the nicotinic response of cultured bovine chromaffin cells, i.e., inhibition of the nicotinic response and protection against nicotinic desensitization. These modulatory actions may be associated with changes in nicotinic receptor levels reported to occur in Alzheimer's disease.

Substance P inhibits carbamylcholine-stimulated 22Na+ efflux from acetylcholine receptor-enriched Torpedo electroplaque membrane vesicles

The effect of substance P on nicotinic acetylcholine receptor function was examined in Torpedo electroplaque membranes. The peptide inhibited carbamylcholine-stimulated 22Na+ efflux in a concentration-dependent manner. By irreversibly blocking spare receptors with alpha-bungarotoxin, the IC50 for substance P was shown to be less than 3 microM. Inhibition by substance P was slow relative to receptor activation by carbamylcholine, consistent with an enhancement of desensitization or a slow allosteric block.

G protein activation: a receptor-independent mode of action for cationic amphiphilic neuropeptides and venom peptides

The neuropeptide substance P, the venom peptide mastoparan and the synthetic polyamine compound 48/80 activate rat peritoneal mast cells, leading to rapid histamine release by exocytosis. Although these effects are inhibited by pertussis toxin and involve a transient increase in IP3, no selective membrane receptors have been identified. However, it has recently been shown that these compounds activate G proteins in vitro. Here Yves Landry and colleagues discuss the proposal that direct activation of G protein is the physiological mechanism of action of substance P on rat peritoneal mast cells, this mechanism being mimicked by mastoparan and 48/80, and possibly by other cationic amphiphilic peptides such as kinins. These compounds might be of help in defining the interaction between membrane receptors and G proteins.

Pharmacological profile of a tachykinin antagonist, spantide, as examined on rat spinal motoneurones

1. The pharmacological profile of a tachykinin antagonist, [D-Arg1, D-Trp7,9, Leu11] substance P (spantide), was studied on motoneurones of the isolated spinal cord of the newborn rat. For this purpose, potentials were recorded from a lumbar ventral root extracellularly and drugs were bath-applied in the presence of tetrodotoxin (TTX). 2. Neurokinin A (NKA), a NK2-receptor selective agonist, induced concentration-dependent depolarizations, which were antagonized by spantide. Analyses of concentration-response curves suggested a competitive type antagonism with a pA2 of 6.5. 3. Depolarizations induced by acetyl-Arg6-septide, a NK1-receptor selective agonist, were also antagonized by spantide with a pA2 of 6.5. 4. Spantide (0.5-16 microM) had no depolarizing action on the ventral root in the presence of TTX. 5. Spantide antagonized the depolarizing action of substance P (SP) when SP was applied at low concentrations (0.1-0.3 microM) or by short duration pulses in artificial cerebrospinal fluid containing TTX, but much higher concentrations of spantide (4-10 microM) were needed to exert an antagonistic action against SP than against acetyl-Arg6-septide or NKA. 6. Thyrotrophin-releasing hormone, L-glutamate, GABA, and noradrenaline, also induced depolarizations of the ventral root in the presence of TTX but the responses to these agonists were not depressed by spantide (16 microM). 7. These results suggest that there is a subtype of tachykinin receptors on neonatal rat spinal motoneurones to which NKA, acetyl-Arg6-septide and spantide bind competitively with high affinity. The present results also suggest the existence on rat motoneurones of another class or other classes of tachykinin receptors that are less sensitive to the antagonistic action of spantide.

A novel substance P binding site in bovine adrenal medulla

Radioligand binding techniques were used to characterize the substance P (SP) binding site on membranes prepared from bovine adrenal medullae. 125I-labelled Bolton-Hunter substance P (BHSP), which recognises the C-terminally directed, SP-preferring NK1 receptor, showed no specific binding. In contrast, binding of [3H]SP was saturable (at 6 nM) and reversible, with an equilibrium dissociation constant (Kd) 1.46 +/- 0.73 nM, Bmax 0.73 +/- 0.06 pmol/g wet weight and Hill coefficient 0.98 +/- 0.01. Specific binding of [3H]SP was displaced by SP greater than neurokinin A (NKA) greater than SP(3-11) approximately SP(1-9) greater than SP(1-7) approximately SP(1-4) approximately SP(1-6), with neurokinin B (NKB) and SP(1-3) very weak competitors and SP(5-11), SP(7-11) and SP(9-11) causing negligible inhibition (up to 10 microM). This potency order is quite distinct from that seen with binding to an NK1 site, a conclusion confirmed by the lack of BHSP binding. It appears that Lys3 and/or Pro4 are critical for binding, suggesting an anionic binding site. These data suggest the existence of an unusual binding site which may represent a novel SP receptor. This site appears to require the entire sequence of the SP molecule for full recognition.

Substance P modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre

Substance P produced a dose-dependent, long-lasting hyperpolarization of the membrane of the Schwann cells of the giant nerve fibre of the tropical squid. A survey of the effectiveness of a range of other naturally occurring tachykinin agonists suggested that the receptors present on the squid Schwann cell belong to the subtype SP-P or NK1, for which substance P is the preferred agonist. A survey of the effectiveness of a range of substance P fragments indicated that the direct hyperpolarizing effects of the substance P molecule were mediated by peptides with an intact amidated C-terminal. However, a second subset of receptors that can be activated by N-terminal fragments and analogues lacking an amidated C-terminal was also present in this preparation. The non-subtype-specific antagonist D-Arg1,D-Trp7,9,Leu11 substance P (spantide) was a potent blocker of the effects of substance P in this preparation. Activation of the substance P receptors did not interact with the effects induced by activation of either the nicotinic cholinergic receptors or octopaminergic receptors present in this preparation. However, it did potentiate the effects of activation of the receptors for vasoactive intestinal peptide (VIP), either in response to bath application of the peptide or due to their activation by the release of an endogenous VIP-like peptide after stimulation of the giant axon.

Effect of substance P on nicotine-induced desensitization of cultured bovine adrenal chromaffin cells: possible receptor subtypes

The neuropeptide substance P (SP) has been reassessed for its ability to modify nicotine-induced catecholamine secretion from cultured bovine, adrenal chromaffin cells. SP exhibited biphasic effects in its actions of inhibiting the nicotinic secretory response and protecting against desensitization. At low concentrations, up to 3 microM, SP partially inhibited or partially protected the nicotine response by 15-20%, and at high concentrations (30 microM), SP markedly inhibited or markedly protected the nicotinic response by 80 or 92%, respectively. The SP antagonist (D-Arg1-D-Pro2-D-Trp7,9-Leu11-SP) completely blocked both effects produced by low concentrations of SP, but not those produced by high concentrations. It is concluded that SP is more potent at protecting against desensitization than at inhibiting the nicotinic response and that SP might modulate CA release through activation of two receptor subtypes.

Mammalian tachykinins modulate the nicotinic secretory response of cultured bovine adrenal chromaffin cells

We have studied the modulatory actions of two members of the tachykinin family (neurokinin A and B) on endogenous catecholamine (CA) secretion from cultured adrenal chromaffin cells. Their ability to modulate the nicotinic response was compared to that of substance P (SP). Both neurokinin A and neurokinin B were found to have two distinct actions similar to SP, on nicotine-induced CA release: (1) an inhibitory action at low nicotine concentrations; and (2) a protective action against desensitization by high nicotine concentrations. However, on a molar basis, the efficacy of neurokinin A or B to modulate the nicotinic response (both inhibition or protection) was 30 times less than SP. We have also tested the ability of a SP antagonist (D-Arg1-D-Pro2-D-Trp7,9-Leu11-SP) to antagonize the modulatory actions of SP on the nicotinic response. The results suggest the possibility that SP's actions on the bovine adrenal chromaffin cells might be mediated through two receptor subtypes of two different affinities.

Modulation of adrenal catecholamine release by DA2 dopamine receptors in the anaesthetized dog

1. The effects of DA2 agonist, quinpirole (50 micrograms/kg, i.v.) and a DA2 antagonist, domperidone (50 micrograms/kg, i.v.) on the release of adrenal catecholamines were evaluated in the anaesthetized and vagotomized dog. 2. Stimulations (5 V pulses of 2 ms duration for 3 min) of the splanchnic nerve at frequencies of 1, 3 and 5 Hz were applied randomly before and after injection of the drug. 3. The results show that quinpirole reduces significantly the release of adrenaline at 1 and 3 Hz but not at 5 Hz, while the release of noradrenaline is reduced at 1 Hz but not at 3 and 5 Hz. Inversely, domperidone potentiates significantly the release of both catecholamines at 3 and 5 Hz, but not at 1 Hz. 4. There was no change in basal release of adrenal catecholamines, adrenal blood flow or heart rate after both drug treatments. 5. The mean arterial pressure was not affected by domperidone treatment but there was a significant reduction in basal mean arterial pressure after the injection of quinpirole. 6. There was no change in any of these parameters during electrical stimulation. 7. Therefore, these results strongly suggest that DA2 dopamine receptors are present at the level of the adrenal medulla and that their activation could mediate an inhibitory modulation on the adrenal catecholamines release within a certain range of electrical stimulation.

Stimulatory effect of substance P on sympathetic ganglia and spinal cord in culture

Studies with organotypic culture of sympathetic ganglia and spinal cord revealed that substance P at concentrations of 10(-5) to 10(-12) M and 10(-5) to 10(-14) M exerts a marked growth-stimulating effect on sympathetic ganglia and spinal cord, respectively. In the presence of substance P, the intensity of sympathetic ganglion growth exceeds control values 3.0-4.8 times. The growth zone size of spinal cord explants increases under these conditions 2.0-5.2-fold. A feasible physiological significance of regulatory peptides in the growth and regeneration of nervous tissue as well as the role of noci-antinociceptive systems in histogenesis and regeneration are discussed.

Effects of substance P on nicotinic acetylcholine receptor function in PC12 cells

The effects of substance P on the functioning of nicotinic acetylcholine receptors in PC12 cells were examined. Carbachol-stimulated 22Na+ uptake was used to assess the functional state of the nicotinic receptor. We found that incubation of the cells with substance P alone caused a loss of receptor function. Receptors recovered from this effect with a t1/2 of 0.94 +/- 0.10 min. Since receptors recovered from carbachol-induced desensitization at a significantly slower rate (t1/2, 1.77 +/- 0.21 min), it was concluded that the two inactive states are not kinetically equivalent. The effects of substance P on carbachol-induced loss of receptor activity were also examined. Substance P had no effect on a component of carbachol-induced loss of activity that was nonrecoverable (inactivation). However, substance P had several effects on the recoverable loss of activity induced by carbachol (desensitization). Substance P caused a shift to the left in the EC50 for carbachol-induced desensitization at equilibrium. If cells were simultaneously incubated with carbachol and substance P7-11, a low-potency analog of substance P, an increase in the rate of formation of a state of the receptor that was kinetically indistinguishable from the state induced by carbachol alone was observed. However, not all inhibition of nicotinic cholinergic function could be explained by an increased rate of formation of a desensitized receptor and it is concluded that substance P causes both enhanced desensitization and block of the nicotinic receptor-linked channel.

Properties of tachykinin receptors examined by intracellular recording from chick sympathetic ganglia

The physiological and pharmacological properties of tachykinin receptors have been examined by intracellular recording from intact chick lumbar sympathetic ganglia in vitro. In these ganglia, both substance P and eledoisin are potent agonists, producing a slowly developing depolarization in ganglion neurons which is associated with an increase in input resistance and inhibition of the M-current. In contrast, physalaemin is a considerably less potent tachykinin in chick ganglia, and kassinin is without activity even at high doses. The rank order of potencies of tachykinin agonists is consistent from cell to cell, indicating that a single type of tachykinin receptor may be responsible for the observed responses. A putative tachykinin antagonist, (D-Arg1,D-Pro2,D-Trp7,9,Leu11)-substance P, exhibits no intrinsic activity in the ganglia but does block the responses to subsequently applied substance P and eledoisin. This tachykinin antagonist also inhibits a portion of the slow excitatory postsynaptic potential (EPSP) elicited in ganglion neurons by repetitive nerve stimulation. Since substance P has been identified within nerve fibers in the ganglia, it appears that this or another endogenous tachykinin mediates a portion of the slow EPSPs observed in the ganglia. Acetylcholine acting via muscarinic receptors is also capable of producing slow EPSPs in the ganglia, since perfusion with atropine can reduce the size of some slow EPSPs. It is concluded that chick sympathetic neurons contain both tachykinin and muscarinic receptors, and that these receptors are involved in slow synaptic responses in the ganglion neurons which increase the excitability of the cells.

Vasoactive intestinal peptide and substance P increase levels of enkephalin-containing peptides in adrenal chromaffin cells

The neuropeptides substance P and vasoactive intestinal peptide (VIP), reported to exist in the splanchnic nerve terminals innervating the adrenal medulla, elevate the levels of enkephalin-containing peptides (ECPs) in cultured bovine adrenal medullary chromaffin cells. Cellular ECP stores were increased over 48 hr by 72 and 46 percent, respectively, following incubation with 5 microM VIP or 10 microM substance P, maximally effective concentrations. The results suggest that VIP and substance P may be trans-synaptic modulators of chromaffin cell ECP stores.