The role of the tachykinin NK1 receptor in airway changes in a mouse model of allergic asthma

BACKGROUND: Tachykinins are present in sensory nerves and in nonneuronal cells like macrophages. Human data suggest a role for these peptides in asthma, but the exact role of tachykinins and their receptors in allergic airway inflammation is still a matter of debate. OBJECTIVE: The aim of this study was to determine the role of the tachykinin NK1 receptor in allergic airway responses in a mouse model. METHODS: Tachykinin NK1 receptor wild-type and knockout animals were sensitized intraperitoneally to ovalbumin and subsequently exposed from days 14 to 21 to aerosolized ovalbumin (1% ). On day 22, the immunologic and histologic changes were evaluated, and lung function measurements were performed. RESULTS: Mice lacking the tachykinin NK1 receptor and their wild-type litter mates developed inflammatory cell infiltrates in the airways and ovalbumin-specific IgE on sensitization and exposure to ovalbumin compared with saline-exposed controls. No differences were detected between wild-type and knockout mice. The substance P content of alveolar macrophages was not influenced by ovalbumin or by the lack of the NK1 receptor. Ovalbumin-induced hyperresponsiveness was not observed, but at baseline, the knockout mice were more reactive despite similar morphology. Ovalbumin induced more goblet cell hyperplasia in wild-type animals compared with knockout animals. No differences in airway wall thickness were observed. CONCLUSION: These data suggest that tachykinin NK1 receptors do not affect allergic airway inflammation or endogenous substance P content of alveolar macrophages but influence baseline responsiveness and promote features of remodeling such as goblet cell hyperplasia.     

Tachykinins are involved in local reflex modulation of vagally mediated striated muscle contractions in the rat esophagus via tachykinin NK1 receptors

The objective of the present study was to investigate the hypothesis of the presence of a local neural reflex modulating the vagally mediated contractions of striated muscle in the rat esophagus and to determine the possible involvement of tachykinins in such a local neural reflex. Electrical stimulation of the vagus nerve evoked twitch contractile responses that were abolished by d-tubocurarine (5 microM). Capsaicin (1-100 microM) inhibited the vagally mediated twitch contractions o f the normal rat esophageal preparations concentration-dependently but not those of the neonatally capsaicin-treated ones. NG-nitro-L-arginine methyl ester (100 microM), a nitric oxide synthase inhibitor, blocked the inhibitory effect of capsaicin and exogenous application of a nitric oxide donor (1 mM) inhibited the vagally mediated twitch contractions. Capsaicin suppressed acetylcholine release from the normal rat esophageal segments evoked by vagus nerve stimulation but not that from the neonatally capsaicin-treated ones. A selective tachykinin NK1 receptor antagonist (0.1 or 1 microM) attenuated the inhibitory effect of capsaicin. However, antagonists of tachykinin NK2, tachykinin NK3 and calcitonin gene-related peptide receptors (1 microM) did not have any effect. A tachykinin NK1 receptor agonist (1 or 5 microM) inhibited the vagally mediated twitch contractions, which was prevented by NG-nitro-L-arginine methyl ester (100 microM). These data suggest that the rat esophagus might have a local neural reflex inhibiting the vagally mediated striated muscle motility, which consists of capsaicin-sensitive sensory neurons and myenteric nitrergic neurons, and that tachykinins might be involved in the neural reflex through tachykinin NK1 receptors.     

Autoradiographic distribution of tachykinin NK2 binding sites in the rat brain: comparison with NK1 and NK3 binding sites

The autoradiographic distribution of tachykinin NK(2) binding sites was determined in the adult rat brain using [(125)I]neurokinin A in the presence of either senktide (NK(3) agonist) and [Pro(9)]substance P (NK(1) agonist) or senktide and SR 140333 (NK(1) antagonist). Indeed, this radioligand labels two subtypes of NK(1) binding sites (which present a high affinity not only for SP but also for neurokinin A, neuropeptide K and neuropeptide gamma) as well as NK(3) binding sites. The distribution of NK(2) binding sites was also compared with those of NK(1) and NK(3) binding sites, these sites being labeled with [(125)I]Bolton and Hunter substance P and [(125)I]Bolton and Hunter eledoisin, respectively. In agreement with our results obtained with membranes from various brain structures, NK(2)-sensitive [(125)I]neurokinin A labeling was mainly observed in few structures including the dorsal and ventral hippocampus, the septum, the thalamus and the prefrontal cortex. The density of NK(2) binding sites was weak when compared with those of NK(1) and NK(3) binding sites. Marked differences were observed in the distributions of NK(1), NK(2) and NK(3) binding sites. These results are discussed taking into consideration differences or similarities between the distributions of NK(2)-sensitive [(125)I]neurokinin A binding sites and of their endogenous ligands (neurokinin A, neuropeptide K and neuropeptide gamma) but also local NK(2) agonist responses blocked by NK(2) antagonists. Insights on the roles of endogenous tachykinins in several brain functions are also discussed on the basis of the respective distributions of different neurokinin binding sites.     

气道速激肽在卵蛋白致敏豚鼠模型咳嗽反应中的作用

目的：研究气道速激肽在卵蛋白致敏和激发豚鼠咳嗽发生机制中的作用。 方法： 正常和卵蛋白致敏豚鼠各20只，卵蛋白雾化吸入激发。24 h后，正常组和致敏组豚鼠随机各分为2组，每组10只，分别依次腹腔注射生理盐水，0.1 mg/kg、0.3 mg/kg和1.0 mg/kg的NK1受体拮抗剂SR140333 或NK2受体拮抗剂SR48968，观察吸入10-4 mol/L的辣椒素溶液诱导的咳嗽反应。用非侵入性方法测量正常和卵蛋白致敏豚鼠注射SR140333或SR48968前后吸入辣椒素溶液所产生的特异性气道阻力。 结果： 致敏豚鼠咳嗽反应明显高于正常对照组［(9.3±1.2)times/3 min vs (19.5±5.7)times/3 min，P<0.05］。SR140333不影响正常对照组豚鼠的咳嗽反应，而SR48968则可降低咳嗽频率达30% (P<0.05)，两者均抑制吸入辣椒素后增加的气道阻力。而在卵蛋白致敏豚鼠，SR140333或SR48968均抑制吸入辣椒素溶液诱导的咳嗽频率［(9.9±4.7)times/3 min，(8.0±1.6)times/3 min，P<0.05］和增高的气道阻力。 结论： NK受体拮抗剂抑制致敏豚鼠卵蛋白激发后增高的咳嗽反应。因此，气道速激肽可能是嗜酸性粒细胞性气道炎症所致咳嗽的重要介质。     

Role of tachykinin NK1, NK2 and NK3 receptors in the modulation of visceral hypersensitivity in the rat

Tachykinins are known to be involved in the processing of information leading to central sensitization and nociception. Using an animal model of repetitive colorectal distensions (CRD), we investigated the effect of spinal administration of tachykinin receptor antagonists in the mediation of visceral hypersensitivity. Intrathecal administration of the NK(1) receptor antagonist RP-67,580 (6.5 nmol) and the NK(3) receptor antagonist R-820 (6.5 nmol) completely blocked the CRD-induced hyperalgesia for both noxious and innocuous stimuli. The intrathecal administration of SR-48,968, a tachykinin NK(2) receptor antagonist, did not affect the visceral pain threshold of hypersensitive animals. Thus, the results from the present experiment support the concept that tachykinins with actions at spinal NK(1) and NK(3) but not NK(2) receptor sites are involved in visceral hypersensitivity mediated by nociceptive and non-nociceptive afferent inputs.     

Localization and function of NK(3) subtype tachykinin receptors of layer V pyramidal neurons of the guinea-pig medial prefrontal cortex

The NK(3) subtype of tachykinin receptor has been implicated as a modulator of synaptic transmission in several brain regions, including the cerebral cortex. The localization and expression of NK(3) receptors within the brain vary from species to species. In addition, the pharmacology of NK(3) receptor-specific antagonists shows significant species variability. Among commonly used animal models, the pharmacology of the guinea-pig NK(3) receptor most closely resembles that of the human NK(3) receptor. Here, we provide anatomical localization studies, receptor binding studies, and studies of the electrophysiological effects of NK(3) receptor ligands of guinea-pig cortex using two commercially available ligands, the NK(3) receptor peptide analog agonist senktide, and the quinolinecarboxamide NK(3) receptor antagonist SB-222,200. Saturation binding studies with membranes isolated from guinea-pig cerebral cortex showed saturable binding consistent with a single high affinity site. Autoradiographic studies revealed dense specific binding in layers II/III and layer V of the cerebral cortex. For electrophysiological studies, brain slices were prepared from prefrontal cortex of 3- to 14-day-old guinea pigs. Whole cell recordings were made from layer V pyramidal neurons. In current clamp mode with a K(+)-containing pipette solution, senktide depolarized the pyramidal neurons and led to repetitive firing of action potentials. In voltage clamp mode with a Cs(+)-containing pipette solution, senktide application produced an inward current and a concentration-dependent enhancement of the amplitude and the frequency of spontaneous excitatory postsynaptic potentials. The glutamatergic nature of these events was demonstrated by block by glutamate receptor antagonists. The effects of senktide were blocked by SB-222,200, an NK(3) receptor antagonist. Taken together, these results are consistent with a functional role for NK(3) receptors located on neurons in the cerebral cortex. In layer V pyramidal neurons of the medial prefrontal cortex, activation of the NK(3) receptor system plays an excitatory role in modulating synaptic transmission.     

Immunohistochemical localisation of cholinergic muscarinic receptor subtype 1 (M1r) in the guinea pig and human enteric nervous system

Little is known regarding the location of cholinergic muscarinic receptor 1 (M1r) in the ENS, even though physiological data suggest that M1rs are central to cholinergic neurotransmission. This study localised M1rs in the ENS of the guinea pig ileum and human colon using fluorescence immunohistochemistry and RT-PCR in human colon. Double labelling using antibodies against neurochemical markers was used to identify neuron subytpes bearing M1r.

M1r immunoreactivity (IR) was present on neurons in the myenteric and submucosal ganglia. The two antibodies gave similar M1r-IR patterns and M1r-IR was abolished upon antibody preabsorption. M1r-IR was present on cholinergic and nNOS-IR nerve cell bodies in both guinea pig and human myenteric neurons. Presynaptic M1r-IR was present on NOS-IR and VAChT-IR nerve fibres in the circular muscle in the human colon. In the submucosal ganglia, M1r-IR was present on a population of neurons that contained cChAT-IR, but did not contain NPY-IR or calretinin-IR. M1r-IR was present on endothelial cells of blood vessels in the submucosal plexus.

The localisation of M1r-IR in the guinea pig and human ENS shown in this study agrees with physiological studies. M1r-IR in cholinergic and nitrergic neurons and nerve fibres indicate that M1rs have a role in both cholinergic and nitrergic transmission. M1r-IR present in submucosal neurons suggests a role in mediating acetylcholine's effect on submucosal sensory and secretomotor/vasodilator neurons. M1r-IR present on blood vessel endothelial cells suggests that M1rs may also mediate acetylcholine's direct effect on vasoactivation.     

Differential expression of functionally identified and immunohistochemically identified NK(1) receptors on sympathetic neurons

We have used multiple-labeling immunohistochemistry, intracellular dye-filling, and intracellular microelectrode recordings to characterize the distribution of tachykinin receptors and substance P boutons on subpopulations of neurons within the guinea pig celiac ganglion. Superfusion of substance P (SP, 1 microM for 1 min) depolarized 42% of tonic neurons and inhibited afterhyperpolarizations in 66% of long afterhyperpolarizing (LAH) neurons without significant desensitization. Twenty-one percent of tonic neurons and 24% of LAH neurons responded to the NK(3) agonist senktide but did not respond to SP, indicating SP did not activate NK(3) receptors at this concentration. All effects of SP were abolished by the selective NK(1) receptor antagonist, SR140333, but not by the selective NK(3) receptor antagonist, SR142801, suggesting that exogenous SP activated a receptor with NK(1) pharmacology. No dye-filled LAH neuron and only 50% of tonic neurons responding to SP expressed NK(1) receptor immunoreactivity (NK(1)-IR). All neurons responding to SP had SP immunoreactive fibers within one cell diameter, indicating good spatial matching between SP release sites and target neurons. These results indicate that SP may act via a receptor with NK(1)-like pharmacology that has a C terminus not recognized by antibodies to the intracellular domain of the conventional NK(1) receptor. Inward currents evoked by SP acting on this NK(1)-like receptor or senktide acting through NK(3) receptors had identical current-voltage relationships. In LAH neurons, both agonists suppressed I(sAHP) without reducing I(AHP). Responses evoked by SP and senktide were resistant to PKC inhibitors, suggesting that the transduction mechanisms for the NK(1)-like receptor and the NK(3) receptor may be similar.     

Glutamate and tachykinin receptors in central sensitization of withdrawal reflexes in the decerebrated rabbit

This study assessed the involvement of NMDA and group I metabotropic glutamate receptors, and tachykinin NK1 and NK3 receptors, in central sensitization of withdrawal reflexes in the decerebrated rabbit. Reflexes evoked in the ankle flexor tibialis anterior and the knee flexor semitendinosus by electrical stimulation at the base of the toes were enhanced for 29-63 min after application of 20% mustard oil to the tips of the toes. Selective antagonists of mGlu1, mGlu5, NMDA and NR2B-subunit-containing NMDA glutamate receptors, as well as NK1, and NK3 receptors, and a non-selective blocker of all tachykinin receptors, were assessed for their effects on the magnitude and duration of the increase in reflexes induced by mustard oil. Dizocilpine, an antagonist of all NMDA receptors (1 mg intrathecal) abolished facilitation of tibialis anterior reflexes and significantly reduced the magnitude and duration of increase of the semitendinosus response. The NR2B-subtype selective antagonist CP-101,606 decreased the magnitude of facilitation of both reflexes but had no effect on duration of enhancement. Selective antagonists for the mGlu1 (CPCCOEt, 1-3 mg intrathecal), mGlu5 (MPEP, 0.2-1 mg intrathecal), NK1 (L-733,060, 0.3 mg intrathecal) or NK3 (SR 142,801, 1 mg kg(-1) i.v.) receptors had no effect on the amplitude or duration of sensitization. However, the non-selective tachykinin receptor blocker ZD-6021 (0.3 mg intrathecal) reduced the amplitude but not the duration of sensitization in the flexor reflexes. Combination of ZD-6021 with CP-101,606 (doses as above) decreased both aspects of the sensitization response. Dizocilpine reduced reflexes evoked from the heel per se, and dizocilpine, CP-101,606 and ZD-6021 reduced arterial blood pressure. Otherwise the drugs used had no effects on baseline variables. The present data confirm the importance of NMDA receptors as a critical part of the process of central sensitization, provide no evidence for a role of metabotropic glutamate receptors, and show that simultaneous blockade of all tachykinin receptors is required to reveal their role in hyperalgesia. The data further indicate that a combined pharmacological approach offers a potential way forward for the development of new antihyperalgesic agents.     

Differential effects of intraventricular injections of tachykinin NK1 and NK3 receptor agonists on normal and sham drinking of NaCl by sodium-deficient rats.

The effects of lateral ventricular injections of succinyl-[Asp6, N-Me-Phe8]-substance P (SENK; 25, 100, 200 ng), a tachykinin NK3 receptor agonist, and [Sar9, Met(O2)11]-substance P (Sar Met; 100, 200 ng), an NK1 receptor agonist, on normal (gastric fistula closed) and sham drinking (gastric fistula open) of hypertonic NaCl by sodium-deficient rats were compared. Intraventricular injections of Sar Met had no effect on NaCl intake in either condition. Injections of 100 ng and 200 ng SENK caused an equal suppression of NaCl intake in the 2 fistula conditions. The latency to drink was not affected, but the initial lick rate was significantly lower and decayed more rapidly after 100 ng SENK than after saline or 25 ng SENK. The results show that (a) the tachykinin subtypes are not equally involved in the control of need-induced salt intake; (b) negative feedback from the stomach and distal gastrointestinal tract is not required for intraventricular injections of SENK to suppress sodium appetite; (c) the activation of NK3 receptors decreases the oral excitatory influence of hypertonic NaCl in sodium-deficient rats.     

Light microscopic immunoenzyme and electron microscopic immunogold cytochemistry reveal tachykinin immunoreactivity in Merkel cells of pig skin

Light microscopic (LM) immunoenzyme and electron microscopic (EM) immunogold cytochemistry were used to demonstrate the presence and subcellular distribution of tachykinin (substance P)-like immunoreactivity in Merkel cells of pig skin. Merkel cells of sinus hair follicles were strongly immunoreactive for tachykinins. In contrast, tachykinin-like immunoreactivity was absent from or very weak in epidermal Merkel cells while subepidermal and some intraepidermal nerve fibres were clearly immunopositive for tachykinins. Postembedding immunogold cytochemistry on the EM level revealed that tachykinin-like immunoreactivity was confined to the secretory granules in Merkel cells. Tachykinin immunoreactivity was clearly absent from the axon of the Merkel cell-axon complex. The selective presence of tachykinin immunoreactivity in secretory granules strongly suggests that tachykinins are synthesized in cutaneous Merkel cells, at least of pig. This is a further indication for the concept that the Merkel cell is a member of the diffuse neuroendocrine system. However, the functional role of tachykinins like substance P and neurokinin A and of other peptides present in Merkel cells remains enigmatic.     

Depression of windup of spinal neurons in the neonatal rat spinal cord in vitro by an NK3 tachykinin receptor antagonist

The effects of the NK3 tachykinin receptor antagonist SR 142801 on synaptic transmission and spike windup induced by trains of stimuli applied to a dorsal root were investigated with intra- and extracellular recording from the neonatal rat spinal cord in vitro. SR 142801 (10 microM) reduced the depolarization (recorded from lumbar ventral roots) induced by senktide (an NK3 agonist) more strongly than the one evoked by substance P methyl ester (SPMeO; an NK1 agonist). Nevertheless, after a long (>2 h) application time, SR 142801 largely depressed the response to SPMeO as well. When NK1 or NK3 receptors were blocked by >50% in the presence of SR 142801, there was also a significant reduction in the cumulative depolarization induced by repeated stimuli to a single dorsal root. This blocking action by SR 142801 was also observed in the presence of the N-methyl-D-aspartate (NMDA) receptor antagonist D-aminophosphonovalerate (APV) and the calcium channel blocker nifedipine. Intracellular data from lumbar motoneurons showed that the spike windup was the first and most sensitive target for the SR 142801 blocking effect. Increasing stimulus strength to dorsal root fibers could partly surmount such a block. SR 142801 per se had no direct action on fast synaptic transmission, membrane potential, or input resistance. These findings indicate that SR 142801 could lead to an early, large reduction in the windup of action potential discharge by motoneurons, suggesting its ability to suppress the reflex component of central sensitization evoked by repeated dorsal root stimuli.     

Neuronal bursting induced by NK3 receptor activation in the neonatal rat spinal cord in vitro.

Intracellular recording from lumbar motoneurons and extracellular recording from ventral roots of the neonatal rat isolated spinal cord were used to study the mechanisms responsible for the excitation mediated by NK3 tachykinin receptors. The selective NK3 agonists senktide or [MePhe7]neurokinin B induced a slow depolarization with superimposed oscillations (mean period +/- SD was 2.8 +/- 0.8 s) that, in the majority of cases, showed left-right alternation at segmental level and were synchronous between L2 and L5 of the same side. During agonist wash out (5-20 min) a delayed form of hyperexcitability emerged consisting of bursts lasting 8 +/- 2 s (average interburst interval 55 +/- 21 s) with superimposed oscillations usually with homosegmental alternation and heterosegmental synchronicity. Such bursting was accompanied by depression of GABAergic dorsal root potentials evoked by dorsal root stimulation and of the recurrent inhibitory postsynaptic potential recorded from motoneurons. Despite bursting, motoneuron membrane potential returned to baseline while input resistance was increased. Bursts were a network-dependent phenomenon triggered by previous NK3 receptor activation because bursting was suppressed by glutamate receptor antagonists and was insensitive to motoneuron membrane potential or subsequent application of an NK3 receptor antagonist. NK3 receptors operated synergistically with N-methyl-D-aspartate (NMDA) and 5-hydroxytryptamine (5-HT) to trigger fully alternating locomotor-like rhythms while NK3 receptor antagonism disrupted the same rhythm. In summary, in the neonatal rat spinal cord NK3 receptors could trigger rhythmic activity predominantly with alternation at segmental level but with synchronous coupling between ipsilateral motor pools. NK3 receptor activation could also facilitate fictive locomotor patterns induced by NMDA and 5-HT.     

Species differences in the localization of 'peripheral' type cholecystokinin receptors in rodent brain

A comparison of cholecystokinin (CCK) receptor binding to sections of rat, mouse and guinea pig brain has been performed using 125I-Bolton Hunter CCK and the selective peripheral CCK receptor antagonist L-365,031. In both rat and mouse, 125I-Bolton Hunter CCK binding in the region of the interpeduncular nucleus (IPN) was inhibited by L-365,031 indicating that these receptors resemble CCK receptors found in peripheral tissues. In the mouse especially, dense regions of peripheral CCK receptors were detected either side of the IPN. By contrast, in the guinea pig IPN no evidence of L-365,031-sensitive binding could be found. The present reports shows that in different species, regional variations in brain CCK receptor binding occur not only in the case of classical 'brain' receptors, but also for the more discretely localised 'peripheral' type CCK receptors.     

Differential expression of Nk1 and NK3 neurokinin receptors in neurons of the nucleus tractus solitarius and the dorsal vagal motor nucleus of the rat and mouse

Tachykinins (substance P, neurokinin A and neurokinin B) influence autonomic functions by modulating neuron activity in nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) through activation of neurokinin receptors NK1 and NK3. Our purpose was to identify and define by neurochemical markers, the subpopulations of NK1 and NK3 expressing neurons in NTS and DMV of rat and mouse. Because the distribution of the NK1 and NK3 expressing neurons overlaps, co-expression for both receptors was tested. By double labeling, we show that NK1 and NK3 were not co-expressed in NTS neurons. In the DMV, most of neurons (87%) were immunoreactive for only one of the receptors and 34% of NK1 neurons, 7% of NK3 neurons and 12% of NK1-NK3 neurons were cholinergic neurons. None of the neurons immunoreactive for NK1 or NK3 were positive for tyrosine hydroxylase, suggesting that catecholaminergic cells of the NTS (A2 and C2 groups) did not express neurokinin receptors. The presence of NK1 and NK3 was examined in GABAergic interneurons of the NTS and DMV by using GAD65-EGFP transgenic mouse. Immunoreactivity for NK1 or NK3 was found in a subpopulation of GAD65-EGFP cells. A majority (60%) of NK3 cells, but only 11% of the NK1 cells, were GAD65-EGFP cells. In conclusion, tachykinins, through differential expression of neurokinin receptors, may influence the central regulation of vital functions by acting on separate neuron subpopulations in NTS and DMV. Of particular interest, tachykinins may be involved in inhibitory mechanisms by acting directly on local GABAergic interneurons. Our results support a larger contribution of NK3 compared with NK1 in mediating inhibition in NTS and DMV.     

Species differences in histamine receptors in the vas deferens

Histamine, specific H₁-and H₂-receptor agonists in conjunction with specific H₁-and H₂-receptor antagonists and other types of classical antagonists were used to characterize histamine receptors in the vasa deferentia of mice, rats and guinea pigs. The H₁-receptor mediates contraction while the H₂-receptor produces inhibition. There were marked qualitative and quantitative differences in the distribution of the two types of histamine receptors in the vas deferens of different species. Results indicate that mouse and rat vas deferens contain an inhibitory H₂-receptor, but virtually no excitatory H₁-receptor. In contrast, guinea pig vas deferens contained an excitatory H₁-receptor but was essentially devoid of an inhibitory H₂-receptor. The rank order of relative potencies of various agonists as well as the calculated pA ₂ values of cimetidine in the mouse and rat vas deferens suggest that the two species probably have the same H₂-receptor. High concentrations of histamine and 2-methyl histamine have a stimulant action in the mouse and rat vas deferens which was secondary to release of endogenous noradrenaline rather than to the stimulation of an excitatory H₁-receptor.     

Role of NK1 tachykinin receptors in thermonociception: effect of (+/-)-CP 96,345, a non-peptide substance P antagonist, on the hot plate test in mice.

We have tested the ability of (+/-)-CP 96,345, a novel nonpeptide substance P (SP) antagonist, to block the aversive behaviour induced by intrathecal (i.t.) administration of SP and to induce thermal antinociception in mice. (+/-)-CP 96,345 administered i.t. or i.p. selectively blocked the effect of i.t. SP while leaving the response to i.t. bombesin unaffected. At the same dose proven effective against i.t. SP, (+/-)-CP 96,345 produced thermal analgesia in the hot plate test (52 degrees C). Using isolated organs for bioassay evaluation of activity at tachykinin receptor, (+/-)-CP 96,345 was found to be a potent (pA2 8.11, c.l. 7.9-8.3) and competitive NK1 receptor antagonist while it was devoid of activity at NK2 or NK3 receptors. These findings provide clear indication for the participation of SP, via NK1 receptors, in thermal nociception.     

Complement receptor expression of primates and non-primates detected by the rosette formation technique

The expression of complement receptors were studied on erythrocytes and platelets from 14 non-human primates and 3 non-primate species by rosette formation. It was found that the reactivity of erythrocytes with the cell bound complement is deeply dependent on which species are used as the complement source. The erythrocytes from Prosimian do not react with any kind of complement, while their platelets react with many kinds of complement. New World monkey erythrocytes do not react with indicator cells binding complements from guinea pig or man, while some of them react with indicators binding complements from non-human primate species. Contrarily Old World monkey erythrocytes react with complements from guinea pig, man and non-human primate. Hominoidea erythrocytes reacted with all the complements tested. Rabbit expresses C3 receptors on their erythrocytes for rabbit C3 and on their platelets for rabbit, guinea pig or mouse C3. Guinea pig expresses receptors on their erythrocytes for guinea pig and mouse C3, and on their platelets for guinea pig, mouse, rabbit and human C3. It becomes clear that not all of erythrocytes from primate and platelets from non-primate always express complement receptors as has been stated in the text books.     

A role for tachykinins in the regulation of human sperm motility

BACKGROUND: Tachykinins and tachykinin receptors are widely distributed in the male reproductive tract and appear to be involved in reproduction. However, the function and expression of tachykinins and their receptors in human spermatozoa remain poorly studied. We analysed the effects of tachykinins on sperm motility and characterized the population of tachykinin receptors in human spermatozoa. METHODS AND RESULTS: Motility analysis was performed following World Health Organization guidelines and we found that substance P (SP), human hemokinin-1 (hHK-1), neurokinin A (NKA) and neurokinin B (NKB) produced concentration-dependent increases in sperm progressive motility. The effects of tachykinins were antagonized by the NK(1) receptor-selective antagonist SR 140333, the NK(2) receptor-selective antagonist, SR 48968 and, to a lesser extent, also by the NK(3) receptor-selective antagonist SR 142801. Immunocytochemistry studies showed expression of the NK(1), NK(2) and NK(3) tachykinin receptor proteins in spermatozoa with different major sites of localization for each receptor. Western blot analysis confirmed the presence of tachykinin receptors in sperm cell homogenates. RT-PCR demonstrated expression of the genes that encode SP/NKA (TAC1), NKB (TAC3) and hHK-1 (TAC4) but not the genes TACR1, TACR2 and TACR3 encoding NK(1), NK(2) and NK(3) receptors, respectively. CONCLUSIONS: These results show for the first time that the NK(1), NK(2) and NK(3) tachykinin receptor proteins are present in human spermatozoa. Our findings suggest that tachykinins, probably acting through these three tachykinin receptors, play a role in the regulation of human sperm motility.