Intrathecal administration of substance P enhances cutaneous plasma protein extravasation in pentobarbital anaesthetized rats

In pentobarbital-anaesthetized rats, the intrathecal administration of substance P (SP) at T9 spinal cord level enhances plasma protein extravasation (PE) in cutaneous tissues of the back, the hind paws and the ears. This vascular response is maximum at 15 min after administration of SP (6.5 nmol), and the most striking in the skin of the hind paws. Contrary to SP, neurotensin (NT) administered intrathecally failed to enhance PE. Both peptides are however potent enhancers of PE following intravenous injection. PE elicited by intrathecal administration of SP is significantly reduced in both spinal rats and in capsaicin treated animals. These results suggest that SP but not NT may play a role as a spinal chemical mediator in peripheral vascular permeability through a supraspinal reflex mechanism involving sensory afferents.     

Intra-dose variation in plasma protein binding of sodium valproate in epileptic patients.

1 The fluctuations in protein binding of sodium valproate during one dosing interval were studied in five patients stabilized on valproate and taking concurrent anticonvulsant therapy. 2 The patients took their usual morning dose of valproate (400-800 mg) and serial blood samples were collected by venepuncture at 0, 1, 2, 3, 4, and 6 h post-dose. 3 Free valproate was separated from protein bound drug by plasma ultrafiltration and the ultrafiltrate and total plasma valproate concentrations were measured by a gas chromatographic method. 4 The maximum and minimum concentrations in the ultrafiltrates occurred at the same times as in the plasma. However, the percentage fluctuation was always greater in the ultrafiltrates (range 192-412%) compared with the plasma (range 153-374%) due to the concentration-dependent nature of valproate protein binding. 5 If free valproate levels are to be monitored, knowledge of sampling time and dosage history is important for interpretation of the results.     

GABAA receptor-mediated stimulation of non-adrenergic non-cholinergic neurones in the dog ileocolonic junction.

1. The inhibitory effects of gamma-aminobutyric acid (GABA), the GABAA receptor agonist homotaurine and the GABAB receptor agonist (+/-)-baclofen were investigated on circular muscle strips of the dog terminal ileum and ileocolonic junction. 2. In the presence of atropine, GABA and homotaurine induced concentration-dependent relaxations, similar to the non-adrenergic non-cholinergic (NANC)-mediated relaxations evoked by electrical stimulation or by acetylcholine. The ileocolonic junction was more sensitive to GABA and homotaurine than the ileum. (+/-)-Baclofen had no effect. Cross desensitization only occurred between GABA and homotaurine. 3. The GABAA receptor antagonist bicuculline shifted the concentration-response curves to GABA and homotaurine to the right. The maximal relaxation to GABA remained unaffected. 4. GABA-induced relaxations were not inhibited by timolol, guanethidine, domperidone, hexamethonium and desensitization to ATP, but were abolished by tetrodotoxin. 5. Bicuculline, and pretreatment with GABA or (+/-)-baclofen had no effect on the NANC-evoked relaxations to electrical stimulation and acetylcholine. 6. In conclusion, GABA stimulates GABAA receptors located on inhibitory NANC neurones in the dog ileocolonic junction. Our results suggest that it is unlikely that GABA is the final inhibitory NANC neurotransmitter.     

Decrease of substance P in primary afferent neurones and impairment of neurogenic plasma extravasation by capsaicin

1 Rats were pretreated with capsaicin (50 mg/kg, s.c.) on the 2nd, 10th, or 20th day of life. Three months later immunoreactive substance P (I-SP) was determined in skin, sensory nerves and the central nervous system. Neurogenic plasma extravasation was also examined.2 Pretreatment at the age of 2 or 10 days resulted in a decrease (26 to 69%) of I-SP in skin, saphenous and vagus nerve, dorsal roots, dorsal half of the spinal cord, and medulla oblongata. The I-SP content of the ventral half of the spinal cord, of midbrain, hypothalamus, striatum, cortex, and cerebellum remained unchanged. Neurogenic plasma extravasation was inhibited by more than 80%.3 In contrast to this irreversible effect of capsaicin on newborn rats, pretreatment of 20 day old rats led to reversible depletion of I-SP and to reversible impairment of neurogenic plasma extravasation.4 Capsaicin pretreatment of adult rats caused a marked depletion of I-SP in the skin of the hind paw and an impairment of neurogenic plasma extravasation. A similar decrease of I-SP was seen after chronic denervation of the skin.5 Intra-arterial infusion of substance P (threshold dose 5 x 10(-13) mol/min) or physalaemin induced dose-dependent plasma extravasation. Somatostatin, vasoactive intestinal polypeptide, caerulein and the enkephalin-analogue FK 33-824 were ineffective in doses 100 fold higher.6 The results indicate that the action of capsaicin on substance P neurones is restricted to primary sensory neurones. Since in every case a decreased substance P content of the skin was associated with impaired neurogenic plasma extravasation, it is suggested that release of substance P is involved in neurogenic plasma extravasation.     

苯妥英钠对丙戊酸钠药动学的影响

目的：研究苯妥英钠（PHT）对丙戊酸钠（VLA）在癫痫治疗中的药动学影响及VAL在唾液中与血液中浓度的相关性。方法：监测病人血清中PHT和VAL浓度,用药动学软件PKBP－N1拟合。结果：与VAL单用相比,PHT可显著降低VAL的血中药物浓度,AUC（P＜0．05）,缩短t1/2。VAL的唾液浓度与其血中浓度相关性不显著（P＞0．05）。结论：在癫痫联合用药治疗中,PHT对VAL的药动学有显著影响,故需监测二者的血药浓度,以达到合理用药。此外,不能用唾液中VAL的浓度作为药物浓度指标。     

Serotonin inhibits release of substance P evoked by tooth pulp stimulation in trigeminal nucleus caudalis in rabbits.

The influence of the serotonin (5-HT) system on the release of immunoreactive substance P after electrical stimulation of the lower incisor pulp was examined by perfusion of the superficial layers of the subnucleus caudalis of the brain stem trigeminal sensory nuclear complex of rabbits in situ. Increased release of immunoreactive substance P was observed after electrical stimulation of the pulp at 40 V. Stimulation of the nucleus raphe magnus significantly increased the release of 5-HT and completely inhibited the release of immunoreactive substance P, evoked by stimulation of the tooth pulp. Local application of 5-HT (10(-6) M) inhibited the release of immunoreactive substance P induced by stimulation and this inhibition was antagonized by methysergide (10(-4) M) applied concomitantly to the superficial layers of the trigeminal nucleus. These results suggest a functional interaction between substance P and 5-HT in the superficial layers of the trigeminal nucleus for regulation of transmission of dental pain.     

Effects of quinolone carboxylic acid derivatives on GABAA receptor-mediated stimulation of gastric acid secretion and intestinal motility.

The present study investigates the effects of some quinolone carboxylic acid derivatives on GABAA receptor-mediated excitatory responses in gastrointestinal preparations in vivo and in vitro. In stomach-perfused rats, norfloxacin, nalidixic and pipemidic acid dose dependently antagonized acid hypersecretion induced by muscimol. Under the same conditions, the quinolone derivatives failed to modify acid hypersecretion evoked by 2-deoxy-D-glucose. In the isolated guinea-pig ileum, norfloxacin, nalidixic and pipemidic acid antagonized muscimol-elicited contractions in a non-competitive manner. In contrast, these drugs did not influence ileal cholinergic contractions evoked by transmural electrical stimulation or by exogenous acetylcholine. Taken together, these results suggest that the quinolone derivatives tested act as antagonists at both central and peripheral GABAA receptors. In addition, GABAA-mediated gastrointestinal responses might represent a simple and reliable method to assay the GABAA receptor antagonist properties of new quinolone derivatives.     

Effects of PNU-109,291, a selective 5-HT1D receptor agonist, on electrically induced dural plasma extravasation and capsaicin-evoked c-fos immunoreactivity within trigeminal nucleus caudalis.

We studied the effects of PNU-109291 [(S)-(-)-1-[2-[4-(4-methoxyphenyl)-1-piperazinyl]ethyl]-N-methyl-isoc hroman-6-carboxamide], a receptor agonist showing 5000-fold selectivity for primate 5-HT1D versus 5-HT1B receptors (Ennis et al., J. Med. Chem. 41, 2180-2183), on dural neurogenic inflammation and on c-fos like immunoreactivity within trigeminal nucleus caudalis evoked by electrical and chemical activation of trigeminal afferents, respectively. Subcutaneous injection of PNU-109291 in male guinea pigs dose-dependently reduced dural extravasation of [125I]-labeled bovine serum albumin evoked by trigeminal ganglion stimulation with an IC50 of 4.2 nmol kg(-1). A dose of 73.3 nmol kg(-1) blocked the response completely. The selective 5-HT1B/1D receptor antagonist GR-127935 (> or = 2 micromol kg(-1) i.v.) prevented this effect. In addition, the number of c-fos immunoreactive cells within guinea pig trigeminal nucleus caudalis induced by chemical meningeal stimulation (intracisternally administered capsaicin) was reduced by more than 50% with PNU-109291 (> or = 122.2 nmol kg(-1) administered s.c. 45 min before and 15 min after capsaicin). These data indicate that the 5-HT1D receptor subtype plays a significant role in suppressing meningeal neurogenic inflammation and attenuating trigeminal nociception in these guinea pig models. Since 5-HT1D receptor mRNA and protein are expressed in trigeminal ganglia but not vascular smooth muscle, the 5-HT1D receptor subtype may become a useful therapeutic target for migraine and related headaches.     

Neuropeptide Y Y2 receptor-mediated attenuation of neurogenic plasma extravasation acting through pertussis toxin-sensitive mechanisms.

1. The effects of neuropeptide Y (NPY) receptor agonists (administered intravenously) were examined on plasma protein ([125I]-bovine serum albumin) leakage within dura mater evoked by unilateral trigeminal ganglion stimulation (0.6 mA, 5 ms, 5 Hz, 5 min), capsaicin (1 mumol kg-1, i.v.) or substance P (1 nmol kg-1, i.v.) in anaesthetized Sprague-Dawley rats. 2. NPY (EC50: 5.6 nmol kg-1) and NPY fragment 13-36 [NPY (13-36)] (ED50: 4.3 nmol kg-1), an NPY Y2 receptor agonist, dose-dependently attenuated [125I]-bovine serum albumin extravasation from meningeal vessels when administered 10 min prior to electrical stimulation. [Leu31, Pro34]-NPY, an NPY Y1 and Y3 receptor agonist, inhibited the response at a higher dose only (23 nmol kg-1) (P < 0.05). 3. NPY also significantly decreased plasma protein extravasation induced by capsaicin (1 mumol kg-1) but not by substance P (1 nmol kg-1). 4. Pertussis toxin (20 micrograms kg-1, administered intracisternally 48 h prior to stimulation) blocked completely the inhibitory effect of NPY and NPY (13-36) but did not inhibit extravasation alone. 5. We conclude that NPY inhibits neurogenically-mediated plasma protein extravasation acting through presynaptic pertussis toxin-sensitive NPY Y2 receptors, possibly by inhibition of neuropeptide release from perivascular trigeminovascular afferents.     

Ecabet sodium raises plasma levels of calcitonin generelated peptide and substance P in healthy humans

Ecabet sodium (ecabet), a cytoprotective drug, produces an increase in mucosal blood flow. One of the gastrointestinal motility regulatory factors has been assumed to be the induction of changes in the levels of peptides (gastrin, somatostatin and motilin) in plasma. On the other hand, recently, capsaicinsensitive afferent nerves were shown to play an important role in gastric mucosal defensive mechanism. Capsaicin stimulates afferent nerves and enhances the release of calcitonin gene-related peptide (CGRP) and substance P in the stomach. We studied the effect of ecabet on human plasma gastrin-, somatostatin-, motilin-, CGRP- and substance P-like immunoreactive substance (IS) in healthy subjects. Ecabet sodium at a dose of 3.0 g, or placebo, was orally administered in five healthy males. The blood samples were taken before and at 20, 40, 60, 90, 120, 180 and 240 min after administration, subjected to extracting procedures, and submitted to a highly sensitive enzyme immunoassay system. Single administration of ecabet caused significant (P<0.05) increases in plasma CGRP-, substance P- and somatostatin-IS concentration compared with placebo. Ecabet significantly decreased plasma gastrin-IS levels compared with placebo. In this study, we hypothesized that ecabet might stimulate capsaicin-sensitive afferent nerves indirectly and improve mucosal blood flow; this might be a key mechanism underlying its gastroprotective action.     

Capsaicin selectively reduces airway responses to histamine, substance P and vagal stimulation.

Airway responsiveness to histamine, substance P, methacholine and bilateral electrical vagal stimulation was assessed in capsaicin-treated and control guinea pigs. In animals treated with capsaicin (50 mg/kg s.c.) 7 days before experiments, airway responsiveness to histamine, substance P and vagal stimulation was significantly reduced but responsiveness to methacholine was unchanged. The findings suggest that histamine and substance P, but not methacholine, require capsaicin-sensitive sensory afferent nerves for part of their actions.     

GABAA and GABAB receptor-mediated effects on the spontaneous activity of the longitudinal layer in cat terminal ileum.

1. GABA and GABAergic agonists-muscimol and (+/-)baclofen changed the spontaneous mechanical activity in isolated cat terminal ileum. 2. GABA at doses ranging from 5 microM to 2 mM produced concentration-dependent biphasic responses consisting of a transient relaxation followed by contractions with a tonic and a phasic components. 3. The GABA-induced relaxation was sensitive to bicuculline and picrotoxinin and was mimicked by muscimol, while the GABA-induced contractions were insensitive to bicuculline and picrotoxinin and were mimicked by (+/-)baclofen. Specific cross desensitization occurred between GABA and muscimol or GABA and (+/-)baclofen. 4. The bicuculline-sensitive relaxation induced by GABA and muscimol was abolished by atropine or tetrodotoxin (TTX), while the bicuculline-insensitive contractions induced by GABA and (+/-)baclofen were not antagonized by atropine or TTX, though they were slightly suppressed. 5. The GABA effects in the longitudinal layer of cat terminal ileum were mediated by the following receptors: -GABAA prejunctional receptors whose activation causes relaxation, probably through an inhibitory action on cholinergic neurons; -GABAB prejunctional receptors whose activation cause contractions; -GABAB postjunctional receptors located on the smooth muscle membrane whose activation induces tonic and phasic contractions.     

CP-96,345, a non-peptide antagonist of substance P. III. Cardiovascular effects in mammals unrelated to actions on substance P receptors

Summary The cardiovascular effects of CP-96,345, a non-peptide antagonist of substance P, were analyzed in vivo and in vitro. In the anaesthetized rat, the i.v. injection of 3 µmolkg^–1 of CP-96,345 induced a fall in mean arterial blood pressure and a reduction in heart rate. Similar effects were obtained with the enantiomer CP-96,344 ((2R,3R)-cis-isomer of CP-96,345) which does not interact with substance P receptors. Both enantiomers, at a concentration of 10 gM, decreased the beating frequency of the isolated atria and of the isolated perfused heart of the guinea-pig to a similar extent, and caused transient coronary dilatation. CP-96,345 (10 µM) decreased the spontaneous sinus rate, prolonged the atrioventricularnodal conduction interval and the His-bundle conduction interval of the perfused guinea-pig heart. The intraventricular spread of conduction was markedly inhibited. During programmed stimulation 10 min after the beginning of the drug application, the effective refractory periods evaluated by stimulation with premature beats, as well as rate dependent effective refractory periods, of the atrioventricular node, of the atrial and of the ventricular myocardium, were prolonged. Sinus node recovery time was also prolonged. It was concluded that these cardiac effects of CP-96,345 were not caused by an action of the compound on substance P receptors. Send offprint requests to F. Lembeck at the above address     

Steroid modulation of GABAA receptor-mediated transmission in the hypothalamus: effects on reproductive function

The hypothalamus, the seat of neuroendocrine control, is exquisitely sensitive to gonadal steroids. For decades it has been known that androgens, estrogens and progestins, acting through nuclear hormone receptors, elicit both organizational and activational effects in the hypothalamus and basal forebrain that are essential for reproductive function. While changes in gene expression mediated by these classical hormone pathways are paramount in governing both sexual differentiation and the neural control of reproduction, it is also clear that steroids impart critical control of neuroendocrine functions through non-genomic mechanisms. Specifically, endogenous neurosteroid derivatives of deoxycorticosterone, progesterone and testosterone, as well and synthetic anabolic androgenic steroids that are self-administered as drugs of abuse, elicit acute effects via allosteric modulation of gamma-aminobutyric acid type A receptors. GABAergic transmission within the hypothalamus and basal forebrain is a key regulator of pubertal onset, the expression of sexual behaviors, pregnancy and parturition. Summarized here are the known actions of steroid modulators on GABAergic transmission within the hypothalamus/basal forebrain, with a focus on the medial preoptic area and the supraoptic/paraventricular nuclei that are known to be central players in the control of reproduction.     

Tolerance to the anticonvulsant effects of carbamazepine, diazepam, and sodium valproate in kindled rats.

We assessed the development of tolerance to the anticonvulsant effects of carbamazepine (CBZ), diazepam (DZP), and sodium valproate (VPA) on convulsions elicited by amygdala stimulation in kindled rats in three similar experiments. In each experiment, amygdala-kindled rats were assigned to a drug group or to a corresponding vehicle control group. The rats in the three drug groups received a total of 10 bidaily (one every 48 h) IP injections of CBZ (70 mg/kg), DZP (2 mg/kg) or VPA (250 mg/kg) at a dose that initially blocked the forelimb clonus elicited by an amygdala stimulation (400 microA, 60 Hz, 1 s) administered 1 h after the injection. The rats in the three vehicle control groups were similarly treated except that they received injections of the saline vehicle. The drug tolerance test occurred 48 h after the final tolerance-development trial; the rats from each drug group and the corresponding vehicle control group received an injection of the appropriate drug followed 1 h later by the administration of a convulsive stimulation. The drug tolerance test revealed almost total tolerance in each of the three drug groups but no tolerance in any of the three vehicle control groups. Such large tolerance effects are inconsistent with the less dramatic effects reported in previous studies; possible reasons for this inconsistency were considered.     

Inhibition of neurogenic vasodilation and plasma extravasation by substance P antagonists, somatostatin and [D-Met2, Pro5]enkephalinamide

The substance P (SP) analogues [D-Pro2, D-Phe7, D-Trp9]SP and [D-Pro2, D-Trp7,9]SP, which have been reported to be SP antagonists, inhibited the vasodilation and plasma extravasation induced by antidromic stimulation of the saphenous nerve or by i.a. infusion of SP. Somatostatin inhibited the vasodilatation and plasma extravasation induced by saphenous nerve stimulation, but had no effect on the vascular responses to i.a. infused SP. The opiate agonist [D-Met2, Pro5]enkephalinamide inhibited the vasodilation evoked by antidromic nerve stimulation in a naloxone reversible manner, but did not change the effect of i.a. infusion of SP. Calcitonin and caerulein had no effect on neurogenic vasodilatation. These results further support the concepts that neurogenic vasodilatation and plasma extravasation are mediated by SP, and that somatostatin and opiates inhibit the release of SP from peripheral sensory nerve endings.     

The influence of substance P on the response of guinea-pig isolated ileum to periarterial nerve stimulation.

1 The effects of substance P (SP) on the responses of the guinea-pig isolated ileum to periarterial nerve stimulation were studied. Electrical stimulation (2-50 Hz) of mesenteric periarterial nerves resulted in contraction of preparations pretreated with guanethidine. The responses were abolished by atropine and morphine, but unaffected by hexamethonium. 2 SP in a high concentration (0.65 mumol) inhibited reversibly, by about 40%, the responses of the guinea-pig isolated ileum to periarterial nerve stimulation. 3 SP in a very low concentration (0.18 pmol) potentiated (by about 20%) the responses of the guinea-pig isolated ileum to periarterial nerve stimulation. 4 In the presence of low concentrations (0.06-0.32 pmol) of SP, morphine (2.65 mumol) produced less inhibition of the responses to periarterial nerve stimulation, and recovery from morphine inhibition of contraction was accelerated. 5 These results indicate that SP may act as a modulator on prejunctional acetylcholine release in the guinea-pig ileum.     

丙戊酸钠对大鼠碳酸锂血清水平的影响

目的探讨丙戊酸钠对碳酸锂血清水平的影响。方法20只大鼠,♀♂各半,随机分成2组,每组各10只。研究组灌喂碳酸锂15 mg.d-15 d后,于d 6开始灌喂丙戊酸钠10 mg.d-1,2种药物共同灌喂3 wk;对照组仅喂碳酸锂15 mg.d-1。分别于d 5、12、19、26抽取尾血2 mL,用于测定碳酸锂血清水平。结果2组4次的碳酸锂血清水平分别是:研究组,(0.198±0.051)(、0.215±0.062)(、0.137±0.042)(、0.177±0.122)mmol.L-1,F=1.949,P=0.139;组内差异无显著性。对照组,(0.172±0.057)(、0.185±0.054)(、0.186±0.059)(、0.180±0.029)mmol.L-1,F=0.166,P=0.919;组内差异无显著性。研究组与对照组血清锂水平比较,仅第3次差异有统计学意义(P<0.05)。结论动物实验表明,丙戊酸钠对碳酸锂的血清水平几乎没有影响,不会引起碳酸锂水平的增高。