C-FOS expression in the rat brain in response to substance P and neurokinin B

Substance P, the principal neurokinin peptide in the mammalian brain and the natural ligand for the NK(1) tachykinin receptor, plays an integrative role in the regulation of cardiovascular, neuroendocrine and behavioural responses to stress. In rats, stimulation of periventricular NK(1) receptors in the forebrain induces a distinct pattern of cardiovascular responses which is accompanied by intense grooming behaviour. Ligands for NK(3) receptors induce a different pattern of cardiovascular and behavioural responses which comprises an increased release of vasopressin from the posterior pituitary and wet-dog shakes behaviour. To define the brain areas in the rat which respond to stimulation of forebrain NK(1) and NK(3) receptors and participate in the generation of these responses, the induction of c-Fos immunoreactivity was examined in brains following intracerebroventricular injections of substance P and neurokinin B in conscious rats. Stimulation of central NK(1) receptors by substance P (25, 100 and 500 pmol) injected into the lateral ventricle elicited grooming behaviour (face washing and hind limb grooming) and resulted in a marked c-Fos expression in the paraventricular, dorsomedial and parabrachial nuclei and in the medial thalamus. At 25 pmol, substance P did not significantly increase c-Fos expression, at 100 pmol, maximal c-Fos activation was induced in all four brain regions which responded to the peptide. Intracerebroventricular pretreatment of rats with the selective and high-affinity, non-peptide NK(1) receptor antagonist, RP 67580 (500 pmol), but not with its inactive enantiomer, RP 68651, completely abolished the behavioural response to substance P and reduced the substance P-induced c-Fos expression in all brain areas to nearly control levels. Intracerebroventricular injection of the natural ligand for NK(3) receptors, neurokinin B (500 pmol), elicited wet-dog shakes behaviour and activated c-Fos expression in localized regions of the forebrain including the organum vasculosum laminae terminalis, subfornical organ, median preoptic nucleus, paraventricular, supraoptic and anterior hypothalamic nuclei, medial thalamus and in the ventral tegmental area. These results demonstrate that the neurokinins, substance P and neurokinin B, induce specific and different patterns of c-Fos expression in distinct regions of the rat brain. Brain areas which selectively responded to substance P have been traditionally linked to the central regulation of cardiovascular and neuroendocrine reactions to stress or involved in the processing of nociceptive responses. On the other side, brain areas activated by neurokinin B are known to be involved in the central regulation of blood pressure, water and salt homeostasis or control of behaviour.     

Similar effects of substance P on learning and memory function between hippocampus and striatal marginal division

Substance P is an endogenous neurokinin that is present in the central and peripheral nervous systems. The neuropeptide substance P and its high-affinity receptor neurokinin 1 receptor are known to play an important role in the central nervous system in inflammation, blood pressure, motor behavior and anxiety. The effects of substance P in the hippocampus and the marginal di- vision of the striatum on memory remain poorly understood. Compared with the hippocampus as a control, immunofluorescence showed high expression of the substance P receptor, neuro- kinin 1, in the marginal division of the striatum of normal rats. Unilateral or bilateral injection of an antisense oligonucleotide against neurokinin 1 receptor mRNA in the rat hippocampus or marginal division of the striatum effectively reduced neurokinin 1 receptor expression. Indepen- dent of injection site, rats that received this antisense oligonucleotide showed obviously increased footshock times in a Y-maze test. These results indicate that the marginal division of the striatum plays a similar function in learning and memory to the hippocampus, which is a valuable addi- tion to our mechanistic understanding of the learning and memory functions of the marginal division of the striatum.     

Substance P and the neurokinins: novel peptide neurotransmitters in psychopharmacology

A new neurotransmitter system is a family of 3 related peptides known as neurokinins. The best known of these is substance P. The others are known simply as neurokinin A and neurokinin B. The specific receptor subtypes that correspond to these 3 neurokinins are neurokinin 1 receptors for substance P, neurokinin 2 receptors for neurokinin A, and neurokinin 3 receptors for neurokinin B. These neurotransmitters appear to play a key role in the regulation of emotions, and antagonists of their receptors may be novel psychotropic drugs of the future.     

Activation of macrophages by neuropeptides

Macrophages play a key role in the initiation and execution of immunoinflammatory responses. Evidence is reviewed which indicates that neuropeptides are capable of up- or down-regulating their state of activation. Substance P, neurokinin A, neurotensin, bombesin, gastrin-releasing peptide, endorphins, enkephalins, somatotropin, and somatostatin elicit various responses in monocytes and macrophages, presumably as a consequence of receptor stimulation. However, formal evidence for the existence of functional surface receptors on these cells is available only for substance P. Activation of macrophages by neuropeptides is yet another example of neuroimmune modulation. These interactions may be involved in the regulation of local immunity in tissues with dense neuropeptidergic innervation and could also contribute to tissue damage under a number of inflammatory conditions.     

The role of substance P in depression: therapeutic implications

Substance P (for "powder"), identified as a gut tachykinin in 1931 and involved in the control of multiple other autonomic functions, notably pain transmission, is the focus of intense fundamental and clinical psychiatric research as a central neurotransmitter, neuromodulator, and immunomodulator, along with sister neurokinins A and B (NKA and NKB), discovered in 1984. Substance P is widely distributed throughout the central nervous system, where if is often colocalized with serotonin, norepinephrine, and dopamine. Many neurokinin (NK) receptor antagonists and agonists have been synthesized and some clinically tested. A double-blind study of MK869, a selective NK1 receptor antagonist that blocks the action of substance P, showed significant activity versus placebo and fewer sexual side effects than paroxetine in outpatients with major depression and moderate anxiety. Substance P, which is degraded by the angiotensin-converting enzyme (ACE), may mediate modulation of therapeutic outcome in affective disorders by functional polymorphism within the ACE gene: the D allele is associated with higher ACE levels and increased neuropeptide degradation, with the result that patients with major depression who carry the D allele have lower depression scores and shorter hospitalization. ACE polymorphism genotypinq might thus identify those patients with major depression likely to benefit from NK1 receptor antagonist therapy.     

Immunocytochemical localization of neurokinin B in the rat spinal dorsal horn and its association with substance P and GABA: an electron microscopic study

Substance P and neurokinin B are tachykinins that derive from different precursors. Both tachykinins are known to be involved in the processing of pain-related information. Initial studies suggested an antinociceptive effect for neurokinin B, but more recent data indicate that neurokinin B facilitates nociception. Unfortunately, morphologic correlates are lacking, as little is known about the distribution of neurokinin B, especially at the ultrastructural level. Because of its potentially important role in the processing of pain-related information, we decided to investigate the synaptic interactions of neurokinin B-immunoreactive profiles in laminae I-III of the rat cervical spinal dorsal horn and their relation to substance P-immunoreactive structures. An antibody raised against a portion of the neurokinin B precursor peptide was used for the detection of neurokinin B. Neurokinin B-like immunoreactivity occurred in all superficial laminae, with the highest density in inner lamina II and the lowest in lamina III. Neurokinin B-like immunoreactive axonal boutons were mainly dome-shaped and established symmetric synaptic contacts with dendrites or cell bodies. Neurokinin B-like immunoreactivity was also detected in dendritic profiles in all superficial laminae. Some of these dendritic profiles were part of synaptic glomeruli in inner lamina II and lamina III. Double-labeling for neurokinin B and substance P showed a lack of appositions and synapses between neurokinin B and substance P-positive profiles. Furthermore, very few profiles double-labeled for the two peptides were observed. Double-labeling for gamma-aminobutyric acid (GABA) and neurokinin B showed a complete absence of neurokinin B/GABA co-localization. Furthermore, neurokinin B-positive profiles were never presynaptic to GABA-immunoreactive profiles, but frequently neurokinin B-positive dendrites were postsynaptic to GABA-immunoreactive boutons. These results suggest that neurokinin B participates in circuits separate from those involving substance P, as virtually no anatomic correlation was found between the two neuropeptides.     

Substance P excites globus pallidus neurons in vivo

Substance P is a member of the neurokinin family. Previous studies have reported the existence of substance P and its high-affinity receptor, neurokinin-1 receptor, in globus pallidus. Employing in vivo extracellular recording combined with behavioural tests, the effects of substance P in globus pallidus of rats were studied. Micropressure ejection of the selective neurokinin-1 receptor agonist [Sar9,Met(O2)11] substance P increased the spontaneous firing rate of pallidal neurons in a concentration-dependent manner, with increases of 27.3% at 0.01, 33.4% at 0.03, 45.5% at 0.1, 38.4% at 0.3 and 36.4% at 1.0 mm. The selective neurokinin-1 receptor antagonist SR140333B prevented the excitatory effects induced by [Sar9,Met(O2)11] substance P. In behaving rats, we observed the postural effects of neurokinin-1 receptor activation in the globus pallidus. Consistent with electrophysiological results, unilateral microinjection of [Sar9,Met(O2)11] substance P (0.1 mm) led to a SR140333B-sensitive contralateral deflection in the presence of systemic haloperidol administration. Combining electrophysiological and behavioural findings, we concluded that substance P produces excitatory effects on globus pallidus neurons via neurokinin-1 receptors.     

Cannabinoid CB1 receptor facilitation of substance P release in the rat spinal cord,measured as neurokinin 1 receptor internalization

The contribution of CB1 receptors in the spinal cord to cannabinoid analgesia is still unclear. The objective of this study was to investigate the effect of CB1 receptors on substance P release from primary afferent terminals in the spinal cord. Substance P release was measured as neurokinin 1 (NK1) receptor internalization in lamina I neurons. It was induced in spinal cord slices by dorsal root stimulation and in live rats by a noxious stimulus. In spinal cord slices, the CB1 receptor antagonists AM251, AM281 and rimonabant partially but potently inhibited NK1 receptor internalization induced by electrical stimulation of the dorsal root. This was due to an inhibition of substance P release and not of NK1 receptor internalization itself, because AM251 and AM281 did not inhibit NK1 receptor internalization induced by exogenous substance P. The CB1 receptor agonist ACEA increased NK1 receptor internalization evoked by dorsal root stimulation. The effects of AM251 and ACEA cancelled each other. In vivo, AM251 injected intrathecally decreased NK1 receptor internalization in spinal segments L5 and L6 induced by noxious hind paw clamp. Intrathecal AM251 also produced analgesia to radiant heat stimulation of the paw. The inhibition by AM251 of NK1 receptor internalization was reversed by antagonists of μ‐opioid and GABA_B receptors. This indicates that CB1 receptors facilitate substance P release by inhibiting the release of GABA and opioids next to primary afferent terminals, producing disinhibition. This results in a pronociceptive effect of CB1 receptors in the spinal cord.     

Substance P and affective disorders: new treatment opportunities by neurokinin 1 receptor antagonists?

Substance P (SP) is a neuropeptide which is abundant in the periphery and the central nervous system, where it is colocalized with other neurotransmitters such as serotonin or dopamine. SP has been proposed to play a role in the regulation of pain including migraine and fibromyalgia, asthma, inflammatory bowel disease, emesis, psoriasis as well as in central nervous system disorders. This review summarizes our current knowledge of the role of SP in the pathogenesis of neuropsychiatric disorders with special emphasis on affective disorders including bipolar disorders. It also reviews current treatment approaches with neurokinin 1 receptor antagonists which appear to be promising drugs for the future treatment of affective disorders.     

Regional distribution of substance P, neurokinin alpha and neurokinin beta in rat spinal cord, nerve roots and dorsal root ganglia, and the effects of dorsal root section or spinal transection

The regional distribution of 3 mammalian tachykinins (substance P, neurokinin alpha and neurokinin beta) in the rat spinal cord and related structures was investigated using a method of radioimmunoassay combined with high performance liquid chromatography. Substance P and neurokinin alpha were found to be distributed in a very similar manner with fairly constant molar ratios i.e. ratios of substance P to neurokinin alpha were 3.69 in the dorsal root ganglia, 3.49 in the dorsal root and 3.09 in the dorsal horn of the cervical spinal cord. On the other hand, the distribution of neurokinin beta was different from other tachykinins; although concentrated in the dorsal horn, neurokinin beta in the dorsal root ganglia or in the dorsal roots was negligibly small in amount. When the cervical dorsal roots were sectioned unilaterally, substance P and neurokinin alpha were decreased in a parallel fashion in the dorsal horn, whereas neurokinin beta was not. In addition neurokinin alpha was selectively and significantly decreased in the dorsal horn of the intact side when compared to that in the unoperated control rat. Since the magnitude of a decrease of neurokinin alpha in molar basis was approximately the same as a decrease of substance P, these findings suggest that the neurokinin alpha and substance P-containing primary afferent fibres could project partly to the contralateral dorsal horn as well. When the thoracic spinal cord was transected, substance P (and neurokinin alpha) was decreased in the ventral part of the lumbar spinal cord, suggesting the presence of tachykinin(s)-containing descending fibres.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood pressure modulation by substance P in the rat nucleus tractus solitarius

Substance P in a dose of 0.1-10 ng injected into the nucleus tractus solitarii (NTS) of the rat caused hypotension, bradycardia and apnea whereas a dose of 100 ng led to no response. A substance P antagonist injected into the NTS abolished the cardiovascular responses to substance P. The antagonist alone increased blood pressure and heart rate. The data suggest a role for substance P in the cardiovascular regulation by the NTS.     

Comparison of the effects of substance P, neurokinin A, physalaemin and eledoisin in facilitating a nociceptive reflex in the rat

The postulated existence of different types of tachykinin receptor in the spinal cord provided the basis for the present study; substance P, neurokinin A, eledoisin and physalaemin were administered intrathecally in the awake, restrained rat to compare their effects on reaction time in the tail-flick test. Each peptide was delivered via a chronically implanted subdural catheter to the lower lumbar vertebral level of the spinal cord. Intrathecal administration of 10 micrograms of substance P (6.5 nmol), eledoisin (8.0 nmol) or physalaemin (7.9 nmol) decreased the reaction time, respectively, to 22.5, 24.3 and 20.8% of the mean preadministration control values at 1 min after injection; similar administration of 6.5 nmol of neurokinin A produced a smaller decrease in reaction time, to only 49.5% of preadministration values. These effects were transient, the reaction times returning to preadministration values within 5 min. Each peptide also produced an initial vocalization followed by increased restlessness. Analysis of the dose-response curves indicated that the rank order of potency of the fitted curves for these peptides was physalaemin greater than or equal to substance P greater than or equal to eledoisin greater than neurokinin A. The results suggest that the receptor involved in facilitation of the tail-flick reflex resembles a substance P receptor rather than a receptor for one of the other endogenous neurokinins and that this receptor may bear some resemblance to the SP-P type postulated to exist in peripheral tissues.     

Cellular expression of the neurokinin 1 receptor in the human antrum

The localization of the neurokinin 1 receptor in rat and guinea pig gastrointestinal tract has been extensively studied but not in human tissues. The present study used antibodies to characterize the cellular expression of neurokinin 1 receptors in human antrum. Cryostat sections (40-80 microm) were immunostained for the neurokinin 1 receptor double labeled with substance P, von Willebrand's factor, c-kit, fibronectin, S-100, serotonin, gastrin and somatostatin. Neurokinin 1 receptor-immunoreactivity was observed on neurons within the myenteric and submucosal plexuses surrounded by substance P-immunoreactive fibers and on von Willebrand's factor-immunoreactive endothelial cells lining blood vessels throughout the antral wall. c-Kit-immunoreactive interstitial cells of Cajal and gastrin cells were co-stained by the monoclonal neurokinin 1 receptor antibody. Finally, there was no evidence for the presence of the neurokinin 1 receptor on fibroblasts, Schwann, somatostatin, serotonin or smooth muscle cells. This study clearly demonstrates an expanded cellular expression of the neurokinin 1 receptor in the human antrum.     

Neurokinin receptor mRNA localization in human midbrain dopamine neurons

The structurally related neurokinin peptides, substance P and neurokinin A, are found in abundance within the substantia nigra of a variety of mammalian species. Although it has been established recently that the neurokinin-3 (NK3) receptor is the predominant neurokinin receptor found in rat substantia nigra and adjacent midbrain nuclei, the nature of the neurokinin receptor expressed in human midbrain has not been elucidated. In the present study, neurokinin receptor messenger RNA (mRNA) content within rat and human midbrain were directly compared by using quantitative in situ hybridization histochemistry. In contrast to the high abundance of NK3 receptor mRNA within dopamine (DA) cells of the rat midbrain, neurokinin-1 (NK1), but not NK3, receptor mRNA was localized to human midbrain DA cells. Within the human midbrain, the abundance of NK1 receptor mRNA differed significantly among the distinct DA cell-containing nuclei, with the highest level of expression seen in several subdivisions of the substantia nigra. Thus different neurokinin receptor subtypes apparently mediate the effects of substance P and neurokinin A on human versus rat DA neurons. J. Comp. Neurol. 382:394-400, 1997. © 1997 Wiley-Liss, Inc.     

Neurokinin-1 receptor deletion modulates behavioural and neurochemical alterations in an animal model of depression

The substance P/NK1 receptor system plays an important role in the regulation of stress and emotional responding and as such had been implicated in the pathophysiology of anxiety and depression. The present study investigated whether alterations in the substance P/NK1 receptor system in brain areas which regulate emotional responding accompany the depressive behavioural phenotype observed in the olfactory bulbectomised (OB) mouse. The effect of NK1 receptor deletion on behavioural responding and monoamine levels in discrete brain regions of the OB model, were also examined. Substance P levels in the frontal cortex and NK1 receptor expression in the amygdala and hippocampus were enhanced following olfactory bulbectomy. Although NK1 receptor knockout (NK1−/−) mice did not exhibit altered behavioural responding in the open field test, noradrenaline levels were enhanced in the frontal cortex, amygdala and hippocampus, as were serotonin levels in the frontal cortex. Locomotor activity and exploratory behaviour were enhanced in wild type OB mice, indicative of a depressive-like phenotype, an effect attenuated in NK1−/− mice. Bulbectomy induced a decrease in noradrenaline and 5-HIAA in the frontal cortex and an increase in serotonin in the amygdala, effects attenuated in OB NK1−/− mice. The present studies indicate that alterations in substance P/NK1 receptor system underlie, at least in part, the behavioural and monoaminergic changes in this animal model of depression.     

Intranigral injection of dynorphin in combination with substance P on striatal dopamine metabolism in the rat

The effects of intranigral injection of dynorphin(1-13), substance P and their combination on striatal dopamine (DA) metabolism as well as circling behavior were studied in rats. Dynorphin(1-13) produced a significant dose-dependent increase of dihydroxyphenyl acetic acid (DOPAC) concentration as well as the number of contralateral circling. No change in dopamine (DA) concentration was observed. Substance P caused a dose-dependent increase of DOPAC concentration. At large doses it also produced an increase in DA concentration. Combined intranigral dynorphin(1-13) and substance P brought about an additive effect for the increase of DOPAC and the number of contralateral circling. No additive effect was found when dynorphin(1-13) and neurokinin A were injected together intranigrally.     

The neurokinin-1 receptor antagonist WIN51,708 attenuates the anxiolytic-like effects of ventralpallidal substance P injection.

We reported previously that the neurokinin substance P has anxiolytic-like effects when administered into the nucleus basalis of the rat ventral pallidum. The present study aimed to determine the possible involvement of the neurokinin-1 receptor in the anxiolytic action of intrabasalis substance P injection. Behavioral testing was performed in the rat elevated plus-maze model of anxiety. Microinjection of substance P (1 ng) into the nucleus basalis increased sojourn times on the open arms, excursions into the end of the open arms and scanning over the edge of an open arm, indicative of an anxiolytic-like profile. The non-peptide neurokinin-1 receptor antagonist WIN51,708, administered i.p. 20 min prior to intrabasalis substance P injection, antagonized the anxiolytic effects of the neurokinin in a dose-dependent manner. WIN51,708 at 10 mg/kg diminished, while at the higher dose of 20 mg/kg the antagonist completely blocked, the effect of substance P on anxiety-related behaviors. These findings suggest that the anxiolytic-like effects of substance P in the nucleus basalis are mediated through neurokinin-1 receptive sites.     

Release of neuropeptide FF (FLFQPQRF-NH2) from rat spinal cord.

Neuropeptide FF (FLFQPQRF-NH2), originally isolated from bovine brain, is an FMRF-NH2-like peptide with morphine-modulating activity. Neuropeptide FF (NPFF) is highly localized in the dorsal spinal cords where there are also specific NPFF binding sites. Furthermore, there have been studies indicating that NPFF may participate in the regulation of pain threshold in the spinal cord. However, whether NPFF can be released from the spinal cord is not known. The present experiments, using an in vitro superfusion of an isolated whole rat spinal cord, demonstrated that high concentrations of KCl or substance P caused a release of NPFF immunoreactive material (IR) from the spinal cord into the perfusion medium in a calcium-dependent manner. Substance P (1-11) also produced a detectable release of NPFF-IR in vivo although the response was quite variable. The released NPFF-IR was analyzed by an HPLC study and found to consist of NPFF and other minor immunoreactive peptides. Further studies with substance P-related peptides showed that the in vitro release of NPFF-IR could also be induced by substance P (1-7) but not by [pGlu5,Me-Phe8,Sar9]-substance P (5-11) or substance K. These results suggest that the specific substance P receptor (SP-N), which is recognized by both substance P (1-11) and substance P (1-7) rather than the tachykinin receptor, is involved in NPFF secretion from the spinal cord. In view of the role of substance P (1-11) and substance P (1-7) in sensory transmission, the results of this study further support the role of NPFF in the modulation of antinociception in the spinal cord.