Neurokinin‐1 receptor expression and antagonism by the NK‐1R antagonist maropitant in canine melanoma cell lines and primary tumour tissues

We interrogated the neurokinin‐1 receptor (NK‐1R)/substance P (SP) pathway in canine melanoma tumour tissues and cell lines. NK‐1R messenger RNA (mRNA) and protein expression were observed in the majority of tumour tissues. Immunohistochemical assessment of archived tissue sections revealed NK‐1R immunoreactivity in 11 of 15 tumours, which may have diagnostic, prognostic and therapeutic utility. However, we were unable to identify a preclinical in vitro cell line or in vivo xenograft model that recapitulates NK‐1R mRNA and protein expression documented in primary tumours. While maropitant inhibited proliferation and enhanced apoptosis in cell lines, in the absence of documented NK‐1R expression, this may represent off‐target effects. Furthermore, maropitant failed to suppress tumour growth in a canine mouse xenograft model derived from a cell line expressing mRNA but not protein. While NK‐1R represents a novel target, in the absence of preclinical models, in‐species clinical trials will be necessary to investigate the therapeutic potential for antagonists such as maropitant.     

The action of low dose endotoxin on equine bowel motility

Post operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1 micrograms/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestine an increase in abnormally arranged regular activity and a decrease in irregular activity was observed. There was no significant prolongation in stomach to anus transit time as assessed by the passage of plastic spheres. The bowel motility patterns induced by endotoxin could be mimicked by the intravenous infusion of PGE2 and less potently by PGI2 (prostacyclin), but not by PGF2 alpha. This study provides evidence that systematic endotoxin present in clinical cases of colic may play a role in the pathogenesis of equine ileus. The acute effects of endotoxin on bowel motility appear to be mediated indirectly by prostaglandins, and the inhibitory effects may be mediated mainly by PGE2.     

Expression of the ether-a-go-go (ERG) potassium channel in smooth muscle of the equine gastrointestinal tract and influence on activity of jejunal smooth muscle

OBJECTIVE: To determine whether ether-a-go-go (ERG) potassium channels are expressed in equine gastrointestinal smooth muscle, whether ERG channel antagonists affect jejunal muscle contraction in vitro, and whether plasma cisapride concentrations in horses administered treatment for postoperative ileus (POI) are consistent with ERG channels as drug targets. SAMPLE POPULATION: Samples of intestinal smooth muscle obtained from 8 horses free of gastrointestinal tract disease and plasma samples obtained from 3 horses administered cisapride for treatment of POI. PROCEDURE: Membranes were prepared from the seromuscular layer of the duodenum, jejunum, ileum, cecum, large colon, and small colon. Immunoblotting was used to identify the ERG channel protein. Isolated jejunal muscle strips were used for isometric stress response to ERG channel blockers that included E-4031, MK-499, clofilium, and cisapride. Plasma concentrations of cisapride were determined in 3 horses administered cisapride for treatment of POI after small intestinal surgery. RESULTS: Immunoblotting identified ERG protein in all analyzed segments of the intestinal tract in all horses. The selective ERG antagonist E-4031 caused a concentration-dependent increase in jejunal contraction. Clofilium, MK-499, and cisapride also increased jejunal contraction at concentrations consistent with ERG channel block; effects of E-4031 and cisapride were not additive. Peak plasma cisapride concentrations in treated horses were consistent with ERG block as a mechanism of drug action. CONCLUSIONS AND CLINICAL RELEVANCE: The ERG potassium channels modulate motility of intestinal muscles in horses and may be a target for drugs. This finding may influence development of new prokinetic agents and impact treatment of horses with POI.     

Gastrointestinal motility disorders and gastrointestinal prokinetic therapy.

Gastrointestinal motility disorders represent a diagnostic and therapeutic challenge. Disorders of gastrointestinal motility may result in accelerated transit, delayed transit, impaired relaxation, or inappropriate relaxation. The delayed transit disorders are the most important motility disorders of companion animals and may involve the esophagus (hypomotility and megaesophagus), stomach (delayed gastric emptying), small intestine (postoperative ileus and intestinal pseudo-obstruction), or colon (constipation and megacolon).     

Effect of prolonged general anesthesia with sevoflurane and laparoscopic surgery on gastric and small bowel propulsive motility and pH in dogs

ObjectiveTo determine if general anesthesia with sevoflurane and laparoscopic surgery changed gastric and small bowel propulsive motility or pH in dogs.Study designProspective, controlled trial.AnimalsTwelve, 19–24 months old, female, Treeing Walker Hound dogs, weighing 23–30 kg.MethodsDogs were anesthetized for a median of 8.5 hours during another study to determine the minimum alveolar concentration of sevoflurane using a visceral stimulus. Gastric and small bowel motility were determined using a sensor capsule that measures pressure, pH and temperature. Gastric transit time and motility index were calculated. For 8/12 dogs, gastric motility, pH and transit time were measured. In 4/12 dogs, small bowel motility and pH were measured.ResultsAnesthesia decreased gastric and small bowel motility but did not change luminal pH. Mean gastric contraction force decreased from median (range) 11 (8–20) to 3 (1–10) mmHg (p < 0.01) and gastric motility index decreased from 0.63 (0–1.58) to 0 (0–0.31; p = 0.01). Frequency of contractions did not change, 3.7 (1.6–4.4) versus 2.8 (0.1–5.1) contractions minute^?1 (p = 0.1). Gastric motility returned to normal 12–15 hours following anesthesia. Gastric emptying was prolonged from 12 (5.3–16) to 49 (9.75–56.25) hours (p < 0.01). Mean small bowel contraction force decreased from 34 (24–37) to 3 (0.9–17) mmHg (p < 0.02) and motility index decreased from 3.75 (1–4.56) to 0 (0–1.53; p = 0.02). Frequency of contractions did not change, 0.5 (0.3–1.4) versus 1.4 (0.3–4.6) contractions minute^?1 (p = 0.11). Small bowel motility returned within 2 hours after anesthesia. Laparoscopy did not result in changes to gastric or small bowel parameters beyond those produced by general anesthesia.Conclusions and clinical relevanceThe force of gastric and small bowel contractions decreased during sevoflurane anesthesia for laparoscopy. Although gastric motility returned to normal within 12–15 hours the impairment of gastric emptying lasted 30–40 hours, predisposing dogs to postoperative ileus.     

Clostridium perfringens epsilon toxin inhibits the gastrointestinal transit in mice

Epsilon toxin produced by Clostridium perfringens type B and D is a potent toxin that is responsible for a highly fatal enterotoxemia in sheep and goats. In vitro, epsilon toxin produces contraction of the rat ileum as the result of an indirect action, presumably mediated through the autonomic nervous system. To examine the impact of epsilon toxin in the intestinal transit, gastric emptying (GE) and gastrointestinal transit (GIT) were evaluated after intravenous and oral administration of epsilon toxin in mice. Orally administered epsilon toxin produced a delay on the GIT. Inhibition of the small intestinal transit was observed as early as 1 h after the toxin was administered orally but the effects were not observed after 1 week. Epsilon toxin also produced an inhibition in GE and a delay on the GIT when relatively high toxin concentrations were given intravenously. These results indicate that epsilon toxin administered orally or intravenously to mice transitorily inhibits the GIT. The delay in the GIT induced by epsilon toxin could be relevant in the pathogenesis of C. perfringens type B and D enterotoxemia.     

The neurokinin-1 antagonist activity of maropitant, an antiemetic drug for dogs, in a gerbil model

Maropitant is a novel synthetic nonpeptide neurokinin type 1 (NK1) selective receptor antagonist, recently developed for use in the dog as an antiemetic. The in vivo functional activity of maropitant was investigated in the gerbil foot-tapping model, to determine the ability of maropitant to penetrate the central nervous system and inhibit foot-tapping induced by the selective NK1 agonist GR73632. In comparison with CP-122,721, a previously characterized NK1 receptor antagonist, maropitant (1 mg/kg by s.c. injection) was found to inhibit foot-tapping for significantly longer (P < 0.01). Inhibition of foot-tapping by maropitant was 100% at 2 h and approximately 50% at 8 h postdosing. The mean brain:plasma concentration ratio at 8 h post-treatment was 3.59. These data demonstrate the central functional action of maropitant as a selective and potent NK1 receptor antagonist and help to support and explain its clinical potential as a broad-spectrum antiemetic agent.     

Distribution of the neurokinin-1 receptor in equine intestinal smooth muscle

REASON FOR PERFORMING STUDY: Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract. OBJECTIVES: To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract. METHODS: Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transcribed; NK1R mRNA was then quantified using real-time PCR. RESULTS: NK1R mRNA was found at all levels of the sampled intestinal tract. The smooth muscle of the proximal small intestine and the ventral colon exhibited the highest level of NK1R mRNA expression in the equine intestinal tract. CONCLUSIONS: Tachykinins probably affect intestinal contractility and propulsion in the proximal small intestine and in the ventral colon.     

Selection of indigenous lactic acid bacteria to reinforce the intestinal microbiota of newly hatched chicken – relevance of in vitro and ex vivo methods for strains characterization

Based on the natural benefits of the indigenous microbiota, lactic acid bacteria (LAB) from poultry origin were isolated from hens and broilers intestine, and their probiotic potential was further studied. The tolerance to digestion, adhesion, capture of a mannose-binding lectin, absence of virulent factors and antibiotic resistances were studied. Different in vitro and ex vivo assays were performed to select tolerant and adherent strains because standardized protocols have not been defined. Fourteen strains highly tolerant to gastrointestinal digestion were genetically identified. Hydrophobic surfaces were not required for the bacterial adhesion and only nine strains adhered ex vivo to the intestinal mucosa. Three strains captured a lectin of the same specificity of Type-1 fimbriae. Virulence factors were absent but some strains evidenced multiple antibiotic resistances. These results provide bases for a future standardization of methods for the selection of probiotic strains intended to reinforce the microbiota of newly hatched chickens.     

In vitro effects of lidocaine on the contractility of equine jejunal smooth muscle challenged by ischaemia‐reperfusion injury

Reasons for performing study: Post operative ileus (POI) in horses is a severe complication after colic surgery. A commonly used prokinetic drug is lidocaine, which has been shown to have stimulatory effects on intestinal motility. The cellular mechanisms through which lidocaine affects smooth muscle activity are not yet known. Objectives: To examine the effects of lidocaine on smooth muscle in vitro and identify mechanisms by which it may affect the contractility of intestinal smooth muscle. Hypothesis: Ischaemia and reperfusion associated with intestinal strangulation can cause smooth muscle injury. Consequently, muscle cell functionality and contractile performance is decreased. Lidocaine can improve basic cell functions and thereby muscle cell contractility especially in ischaemia‐reperfusion‐challenged smooth muscle. Methods: To examine the effects of lidocaine on smooth muscle function directly, isometric force performance was measured in vitro in noninjured and in vivo ischaemia‐reperfusion injured smooth muscle tissues. Dose‐dependent response of lidocaine was measured in both samples. To assess membrane permeability as a marker of basic cell function, release of creatine kinase (CK) was measured by in vitro incubations. Results: Lidocaine‐stimulated contractility of ischaemia‐reperfusion injured smooth muscle was more pronounced than that of noninjured smooth muscle. A 3‐phasic dose‐dependency was observed with an initial recovery of contractility especially in ischaemia‐reperfusion injured smooth muscle followed by a plateau phase where contractility was maintained over a broad concentration range. CK release was decreased by lidocaine. Conclusion: Lidocaine may improve smooth muscle contractility and basic cell function by cellular repair mechanisms which are still unknown. Improving contractility of smooth muscle after ischaemia‐reperfusion injury is essential in recovery of propulsive intestinal motility. Potential relevance: Characterisation of the cellular mechanisms of effects of lidocaine, especially on ischaemia‐reperfusion injured smooth muscle, may lead to improved treatment strategies for horses with POI.     

Efficacy of maropitant in the prevention of delayed vomiting associated with administration of doxorubicin to dogs

Background: Vomiting, nausea, inappetence, and diarrhea are common delayed adverse effects of doxorubicin. Maropitant, a neurokinin‐1 receptor antagonist, is known to prevent acute vomiting in dogs receiving cisplatin. Objective: To evaluate the efficacy of maropitant in preventing delayed vomiting after administration of doxorubicin to dogs. Animals: Fifty‐nine dogs with cancer. Methods: This randomized, double‐blind, placebo‐controlled study used a cross‐over design. Dogs were randomized into 1 of 2 treatment groups. Group A received maropitant after the 1st doxorubicin, and placebo after the 2nd. Group B received placebo first, and maropitant second. Maropitant (2 mg/kg) or placebo tablets were administered PO for 5 days after doxorubicin treatment. Owners completed visual analog scales based on Veterinary Cooperative Oncology Group‐Common Terminology Criteria for Adverse Events to grade their pet's clinical signs during the week after administration of doxorubicin. Statistical differences in gastrointestinal toxicosis and myelosuppression between maropitant and placebo treatments were evaluated. Results: Significantly fewer dogs had vomiting (P= .001) or diarrhea (P= .041), and the severity of vomiting (P < .001) and diarrhea (P= .024) was less the week after doxorubicin when receiving maropitant compared with placebo. No differences were found between maropitant and placebo for other gastrointestinal and bone marrow toxicoses. Conclusions and Clinical Importance: Maropitant is effective in preventing delayed vomiting induced by doxorubicin. Its prophylactic use might improve quality of life and decrease the need for dose reductions in certain dogs.     

Survey of prokinetic use in horses with gastrointestinal injury

OBJECTIVE: To report prokinetic strategies used to manage horses after gastrointestinal surgery. DESIGN: Electronic questionnaire. SAMPLE POPULATION: Diplomates of the American College of Veterinary Surgeons (ACVS) who perform equine intestinal surgery. PROCEDURE: A survey (21 questions) designed to determine use of prokinetic agents was sent electronically to 112 ACVS Diplomates known to perform equine intestinal surgery. Several clinical scenarios were also described to determine which, if any, prokinetic agent respondents would select. RESULTS: Responses were obtained from 58 (52%) surgeons from 44 clinics. Selection of prokinetic agent for specific gastrointestinal conditions was relatively uniform whereas there was considerable variation in dose administered. For postoperative ileus (POI) associated with most intestinal lesions, 2% lidocaine was most commonly selected. Other prokinetics in decreasing frequency of use were erythromycin lactobionate, metoclopramide, and cisapride. Prokinetic agents were more commonly administered after small intestine strangulating obstructions and less commonly for large intestinal lesions. No novel agents were identified by respondents. CONCLUSIONS: Prokinetic drugs are commonly used for the management and/or attenuation of POI in horses, but dosages and routes of administration are variable. CLINICAL RELEVANCE: Although prokinetics are commonly used for management of POI in horses there is clearly a need for more controlled studies to define efficacious dosing and a need to develop new prokinetic drugs.     

Motility of the equine gastrointestinal tract: Physiology and pharmacotherapy

Normal gastrointestinal (GI) motility patterns are necessary to maintain transit of ingesta and to facilitate digestion and absorption of nutrients. Disorders of the equine GI tract are frequently encountered by the equine practitioner and these disorders are often associated with an interruption in normal intestinal motility patterns, thus complicating treatment of the primary disease. Consequently, numerous treatments have been investigated in horses to facilitate the return of normal intestinal motility. The purpose of this article is to provide a brief review of the anatomy and physiology of the GI tract in the horse and review medications available to the equine veterinarian that may potentially promote intestinal motility.     

Effect of epidural and intravenous use of the neurokinin-1 (NK-1) receptor antagonist maropitant on the sevoflurane minimum alveolar concentration (MAC) in dogs

ObjectiveTo determine the effect of maropitant, an NK-1 receptor antagonist on the minimum alveolar concentration (MAC) of sevoflurane after intravenous and epidural administration to dogs.Study designProspective experimental study.AnimalsSeven, adult, spayed-female dogs (24.8 ± 1.9 kg).MethodsEach dog was anesthetized twice with sevoflurane in oxygen, with at least 10 days separating the anesthetic events. The minimum alveolar concentration (MAC) of sevoflurane was determined using the tail-clamp technique. During the first anesthetic event, the MAC of sevoflurane was determined initially and again after intravenous administration of maropitant (5 mg kg^?1) and an infusion (150 μg kg^?1 hour^?1). During the second anesthetic event, an epidural catheter was advanced to the 4th lumbar vertebra and MAC was determined after administration of saline and maropitant (1 mg kg^?1) epidurally. All MAC determinations were done in duplicate. The MAC values were adjusted to sea level and compared using student's t-test.ResultsThe baseline MAC for sevoflurane was 2.08 ± 0.25%. Intravenous maropitant decreased (p < 0.05) MAC by 16% (1.74 ± 0.17%). In contrast, epidural administration of either saline or maropitant did not change (p > 0.05) the MAC (2.17 ± 0.34% and 1.92 ± 0.12%, respectively).Conclusion and clinical relevanceMaropitant decreased the MAC of sevoflurane when administered intravenously to dogs but not after epidural administration.     

Effects of intestinal ischemia on in vitro activity of adjacent jejunum in samples obtained from ponies.

OBJECTIVE: To determine whether intestinal ischemia would alter activity of the jejunum in vitro or alter staining characteristics for certain types of enteric neurotransmitters. SAMPLE POPULATION: Jejunal samples obtained from 10 ponies. PROCEDURE: Jejunal samples were obtained from locations proximal and distal to an area of small intestine made ischemic for 60 minutes. A portion of each sample was stained to detect substance P-like immunoreactivity, cholinergic and adrenergic neurons, and nitric oxide synthase. Portions of the remaining samples were suspended in muscle baths. General activity patterns (frequency and amplitude of contraction), responses to neuronal depolarization induced by electrical field stimulation (EFS), and responses to 1 microM norepinephrine (NE) were compared with responses of a normal section of small intestine obtained prior to ischemic insult. RESULTS: Staining patterns were not altered. Proximal and distal sections had evidence of decreased contractility, compared with the normal section. Contraction frequency also was decreased, and distal sections had lower contraction frequency than proximal sections. Relaxation responses were decreased in distal sections. Responses to NE differed significantly for distal and proximal sections, compared with normal sections. CONCLUSIONS AND CLINICAL RELEVANCE: Short-term ischemia can significantly affect adjacent bowel. Contractile and relaxation responses are impaired. Discrepancies in intestinal motility patterns and alterations in response to NE for sections proximal and distal to ischemic intestine could lead to clinical ileus or slowed transit of ingesta.     

EFFECT OF SEDATION ON TRANSIT TIME OF FELINE GASTROINTESTINAL CONTRAST STUDIES

The effect of commonly used sedatives on gastrointestinal motility and transit time in cats was evaluated using barium sulfate in gastrointestinal contrast studies. Control studies were performed in nonsedated animals, and the results were compared with those obtained from each of five sedation studies (ANOVA; p < 0.05). The ketamine/acepromazine transit time (18 minutes) was shortened significantly compared with the control group (42 minutes), and both ketamine/acepromazine and ketamine alone resulted in significant increase in the number of gastric contractions. The level of sedation was evaluated subjectively and compared with the transit times to determine a chemical restraint method for potential clinical use that would have the least effect on transit time and motility yet provide adequate sedation. When sedation is necessary and motility is not a primary concern, the ketamine/acepromazine combination if recommended. If a gastrointestinal motility problem is suspected, the ketamine/valium combination should be used.     

Gastrointestinal motility modulation by stress is associated with reduced smooth muscle contraction through specific transient receptor potential channel

Excessive stress response causes disability in social life. There are many diseases caused by stress, such as gastrointestinal motility disorders, depression, eating disorders, and cardiovascular diseases. Transient receptor potential (TRP) channels underlie non-selective cation currents and are downstream effectors of G protein-coupled receptors. Ca²⁺ influx is important for smooth muscle contraction, which is responsible for gastrointestinal motility. Little is known about the possible involvement of TRP channels in the gastrointestinal motility disorders due to stress. The purpose of this study was to measure the changes in gastrointestinal motility caused by stress and to elucidate the mechanism of these changes. The stress model used the water immersion restraint stress. Gastrointestinal motility, especially the ileum, was recorded responses to electric field stimulation (EFS) by isometric transducer. EFS-induced contraction was significantly reduced in the ileum of stressed mouse. Even under the conditions treated with atropine, EFS-induced contraction was significantly reduced in the ileum of stressed mouse. In addition, carbachol-induced, neurokinin A-induced, and substance P-induced contractions were all significantly reduced in the ileum of stressed mouse. Furthermore, the expression of TRPC3 was decreased in the ileum of stressed mouse. These results suggest that the gastrointestinal motility disorders due to stress is associated with specific non-selective cation channel.     

Comparison of the Comformation of 20 International Level and the 20 Low Level Jumping Horses Using a 3-D Video Morphometric Measurement Method

The endocannabinoid anandamide may regulate intestinal motility through activation of CB1 receptors. Anandamide is then inactivated by fatty acid amide hydrolase (FAAH), a membrane bound enzyme. Under pathological conditions, inactivation of such enzymatic activity may lead to inhibition of the intestinal motility. Here, preliminary reports on the distribution of Fatty Acid Amide Hydrolase (FAAH) immunoreactivity in the mouse gastrointestinal neurons, and the pharmacological effects of N-arachidonoylserotonin (AA-5HT), a selective inhibitor of FAAH, are reported. FAAH was revealed by an indirect immunofluorescence. Laminar preparations containing the myenteric or the submucous plexus adhered, were peeled off after the whole gut wall had been stretched out and fixed in 4% paraformaldehyde. They were subsequently incubated with a polyclonal anti-serum directed against a region near the N-terminus of the human FAAH and revealed by a FITC-conjugated goat anti-rabbit secondary anti-serum. FAAH-immunoreactive neurons were observed within the myenteric ganglia throughout the GIT. The positive nerve cells varied in size and density of immunoreactivity. Stomach and large intestine showed the highest neuronal density. AA-5HT significantly reduced both gastric emptying and gastrointestinal tract transit. Such inhibitory effect was reduced by the C1 receptor antagonist SR141716A. Both morphological and pharmacological results suggest that FAAH may play a critical role in controlling gut anandamide levels.     

Effects of the Addition of Autologous Seminal Plasma to Highly Concentrated Stallion Semen After 48 Hours of Cooled Storage

Insemination with chilled transported semen has become distinctly important in the horse-breeding industry. To ensure cell survival during cooled storage, semen is diluted with an appropriate extender and the concentration of seminal plasma (SP) is reduced. Nevertheless, SP plays an important immunomodulatory role in the female genital tract and supports sperm fertility. The aim of the present study was to evaluate the effect of the addition of autologous SP after cooled storage to highly concentrated stallion semen. Therefore, SP was removed by simple centrifugation of extended semen, aspiration of the supernatant, and resuspension of the sperm pellet with semen extender. Motion characteristics were evaluated after cooled storage for 48 hours at concentrations of 333 × 10⁶ sperm/mL in comparison with stored samples at concentration of 25 × 10⁶ sperm/mL (control). The highly concentrated semen samples were diluted with an extender containing 0%, 5%, 20%, and 80% SP directly before motility analysis. Dilution of the cooled semen with a fresh semen extender without SP (0%) increased kinematic parameters (curvilinear velocity [VCL] 137.3 vs. 151.8; straight-line velocity [VSL] 49.0 vs. 57.5; average path velocity [VAP] 69.5 vs. 79.4 μm/second; amplitude of lateral head [ALH] 3.1 vs. 3.3 μm; beat cross frequency [BCF] 31.6 vs. 33.5 Hz; P < .05) but not total motility (51% vs. 43%) and progressive motility (46% vs. 36%) compared with controls. The addition of SP after storage for 48 hours decreased sperm total motility and progressive motility regardless of SP concentration: 5 (38% and 34%), 20 (37% and 33%), and 80% SP (27% and 22%; P < .05). In contrast, kinematic parameters were enhanced by extenders containing 5% and 20% SP (VCL: 148.0 and 155.6; VSL: 59.2 and 60.9; VAP: 78.7 and 81.9; BCF: 33.4 and 35.7; ALH: 3.4 and 3.4; P < .05). However, using an extender containing 80% SP was detrimental to kinematic parameters (VCL: 151.2; VSL: 52.2; VAP: 76.9; BCF: 34.8; P < .05) except for ALH, which increased (3.5; P < .05). In conclusion, cooled storage at concentrations of 333 × 10⁶ sperm/mL did not affect sperm motility. The addition of a fresh extender or an extender containing small concentrations of SP to highly concentrated ejaculated sperm increased kinematic values after storage; however, increasing concentrations of SP decreased sperm motility.     

Evaluation of substance P as a neurotransmitter in equine jejunum

OBJECTIVE: To determine whether substance P (SP) functions as a neurotransmitter in equine jejunum. SAMPLE POPULATION: Samples of jejunum obtained from horses that did not have lesions in the gastrointestinal tract. PROCEDURE: Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscle, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 2 intensities (30 and 70 V) and various frequencies on muscle strips that were maintained at low tension or were under contraction. A neurokinin-1 receptor blocker (CP-96,345) was added to baths prior to EFS to interrupt SP neurotransmission. Additionally, direct effects of SP on muscle strips were evaluated, and SP-like immunoreactivity was localized in intestinal tissues, using indirect immunofluorescence testing. RESULTS: Substance P contracted circularly and longitudinally oriented muscle strips. Prior treatment with CP-96,345 altered muscle responses to SP and EFS, suggesting that SP was released from depolarized myenteric neurons. Depending on orientation of muscle strips and stimulation variables used, CP-96,345 increased or decreased the contractile response to EFS. Substance P-like immunoreactivity was detected in the myenteric plexus and circular muscle layers. CONCLUSIONS AND CLINICAL RELEVANCE: Substance P appears to function as a neurotransmitter in equine jejunum. It apparently modulates smooth muscle contractility, depending on preexisting conditions. Effects of SP may be altered in some forms of intestinal dysfunction. Altering SP neurotransmission in the jejunum may provide a therapeutic option for motility disorders of horses that are unresponsive to adrenergic and cholinergic drugs.