Endometritis is a very common pathology in animals which changes endometrial leukotriene (LT) formation and muscarinic 2 and 3 receptor subtypes (M2R/M3R) and α-7 nicotinic acetylcholine (ACh) receptor (α-7 nAChR) expression patterns. With the relationship between ACh, its receptors and LT production remaining unclear, the role of M2R, M3R and α-7 nAChR in action of ACh on the 5-lipoxygenase (5-LO), LTA4 hydrolase (LTAH) and LTC4 synthase (LTCS) protein abundances in the inflamed porcine endometrium and on the tissue secretion of LTB4 and LTC4 were studied.

A 12-year-old, castrated male Yorkshire terrier dog presented with frequent regurgitations that had begun 45 days earlier and become more progressive. Radiographs revealed an air-trap region behind the cranial esophageal sphincter muscle in the esophagus and esophagographies with barium contrast showed mild esophageal dilation with decreased motility. Esophageal motility increased within 5 min of neostigmine methylsulfate administration and acetylcholine receptor antibodies titer increased to beyond the normal range. Based on these findings, acquired myasthenia gravis with focal form was diagnosed, making this the first such case diagnosed by an acetylcholine receptor antibody test in Korea.

During acute bouts of recurrent airway obstruction (heaves) in horses, neutrophils that are capable of increased production of reactive oxygen species accumulate in the airways. In the study reported here, the effect of hydrogen peroxide (H2O2; 1 micromolar to 0.1M), one of these reactive oxygen species products, on the responses of isolated trachealis muscle of horses was determined. Before and after incubation with H2O2, contractile responses to acetylcholine, electrical field stimulation (EFS), 127 mM KCl, and relaxation responses to isoproterenol and activation of the nonadrenergic noncholinergic inhibitory response (iNANC) were evaluated. Beginning at 1 mM, H2O2 contracted trachealis muscle in a concentration-dependent manner. This contraction was unaffected by atropine (1 micromolar), tetrodotoxin (1 micromolar), or 1 micromolar meclofenamate. Contraction of trachealis muscle in response to H2O2 is, therefore, not attributable to release of prostaglandins, acetylcholine, or other neurotransmitters. Above a concentration of 0.1 mM, H2O2 depressed the responses to EFS. acetylcholine, and KCl in a concentration-dependent manner. At 0.1M, H2O2 decreased the maximal responses to EFS, acetylcholine, and KCl by 62.7 +/- 7.2, 60.58 +/- 6.12, and 37.8 +/- 9.54%, respectively. In the presence of meclofenamate (1 micromolar), partial but significant protection against 1 to 100 mM H2O2 was observed. In tracheal strips contracted with 0.3 micromolar methacholine, H2O2 had no effect on the isoproterenol concentration-response curve. Up to a concentration of 100 mM, H2O2 had no effect on iNANC response. However, in the presence of 100 mM H2O2, this response was abolished in 2 of 4 horses. We conclude that high concentrations of H2O2 affected the responses of airway smooth muscle by actions on neurotransmission, muscarinic receptors, and downstream from receptors; some of the H2O2 effects were in part mediated by cyclooxygenase products; and H2O2 had no effect on beta-adrenergic- or iNANC-induced relaxation.

Distal airway segments (ID, 3 to 4 mm; length, 5 mm) from 2 groups of horses were isolated and suspended in tissue baths filled with Krebs solution, aerated with 5% CO2 in oxygen and maintained at 37 C. Responses to exogenous acetylcholine, isoproterenol, or electrical field stimulation were compared. Control horses (n = 30) had no history of recurrent airway obstruction, whereas principal horses (n = 15) had recurrent airway obstruction and were studied during an acute episode of airway obstruction. Although the distal airways contracted in response to the cumulative half-logarithmic addition of acetylcholine (10(-10)M to 10(-3)M) in both groups, bronchi obtained from principals were less sensitive to acetylcholine than were bronchi obtained from controls. Tetrodotoxin-sensitive electrical field stimulation-induced contractions were observed in both groups of airways, but the tension achieved in principal bronchi was less than in controls. All electrical field stimulation-induced contractions were abolished by atropine, indicating that the only excitatory innervation of equine distal airways is through the parasympathetic system. To examine the effect of isoproterenol and determine inhibitory innervation, bronchi were precontracted with histamine. Electrical field stimulation did not cause relaxation of precontracted bronchi in either group, thus indicating that distal airways lack inhibitory innervation. Isoproterenol caused similar, dose-dependent relaxation in both groups.

Strips of trachealis muscle were dissected from the mid-cervical portion of the trachea from horses that were free of respiratory tract disease. The epithelium and mucosa were removed from one group of tissues and were left intact in a second group of tissues. Each tissue was suspended in a bath filled with Krebs-bicarbonate solution that was aerated with 5% CO2 in oxygen and maintained at 37 C. Isometric tension was continuously recorded. The contractile response to square-wave electrical stimulations increased as frequency (3, 5, 10, 15, 20, 25, and 30 Hz), voltage (10, 15, 18, and 25 V), and pulse duration (0.2, 0.5, 1.0, 1.5, and 2.0 ms) increased in tissues with the epithelium and mucosa intact. A stimulus of 18 V, 20 Hz, and 0.5 ms induced maximal contraction. Atropine (10(-6) M) abolished the response to 18 V and 0.5 ms at all frequencies. The increase in active isometric tension was concentration dependent when acetylcholine (10(-9) to 10(-4) M) was added to the baths in 0.5-logarithmic increments. Tissues that were contracted in response to acetylcholine (10(-5) M) had a concentration-dependent decrease in active isometric tension when isoproterenol was added to the baths in 0.5-logarithmic increments (10(-9) to 10(-4) M). The contraction and relaxation curves were qualitatively similar, but quantitatively different in tissues with and without the epithelium and mucosa. Removing the epithelium and mucosa increased the contractile response to acetylcholine at bath concentrations of 3.1 X 10(-7) M and 10(-6) M. The presence of epithelium and mucosa enhanced the magnitude of isoproterenol-induced relaxations. We concluded that electrical stimulation released acetylcholine from isolated equine trachealis muscle, that isoproterenol induced relaxation of the trachealis muscle, and that the magnitude of the responses to exogenous agonists depended on the presence of epithelium and mucosa.

Objective-To determine the response to neostigmine of the contractile activity of the jejunum and pelvic flexure and the effects of a continuous rate infusion (CRI) of neostigmine in horses. Animals-7 adult horses and tissue from 12 adult horses. Procedures-A CRI of neostigmine (0.008 mg/kg/h) or placebo was administered to 6 horses in a crossover study design. Gastric emptying was evaluated by the acetaminophen test. The frequency of defecation and urination and the consistency and weight of feces were recorded throughout the experiment. The effect of neostigmine on smooth muscle contractile activity was evaluated in tissues from the jejunum and pelvic flexure. The effect of neostigmine and acetylcholine after incubation with muscarinic receptor antagonists (atropine and DAU 5884) and an acetylcholinesterase inhibitor (edrophonium) was also investigated in vitro. Results-No difference was observed between neostigmine and placebo for time to reach peak plasma acetaminophen concentration and absorption rate constant. A CRI of neostigmine increased fecal production and frequency of urination. Neostigmine induced a dose-dependent increase of contractile amplitude in jejunum and pelvic flexure muscle strips. Incubation of muscle strips with atropine and DAU 5884 inhibited the response to acetylcholine and neostigmine. Incubation of smooth muscle strips from the jejunum with edrophonium increased the response to acetylcholine and had no effect on the response to neostigmine in vitro. Conclusions and Clinical Relevance-A CRI of neostigmine increased fecal production and urination frequency in horses. A CRI of neostigmine did not decrease gastric emptying. Neostigmine stimulated contractile activity of jejunum and pelvic flexure smooth muscle strips in vitro.

Objective: To determine the isometric responses of isolated intrapulmonary bronchioles from cats with and without adult heartworm infection. Animals: 13 purpose-bred adult cats. Procedures: Cats were infected with 100 third-stage larvae or received a sham inoculation, and the left caudal lung lobe was collected 278 to 299 days after infection. Isometric responses of intrapulmonary bronchiolar rings were studied by use of a wire myograph. Three cycles of contractions induced by administration of 10μM acetylcholine were followed by administration of the contractile agonists acetylcholine, histamine, and 5-hydroxy-tryptamine. To evaluate relaxation, intrapulmonary bronchiolar rings were constricted by administration of 10μM 5-hydroxytryptamine, and concentration-response curves were generated from administration of sodium nitroprusside, isoproterenol, and substance P. Results: Compared with tissues from control cats, contractile responses to acetylcholine and 5-hydroxytryptamine were reduced in tissues from heartworm-infected cats. Relaxation to isoproterenol was significantly reduced in tissues from heartworm-infected cats. Relaxation to substance P was increased in tissues from heartworm-infected cats, but relaxation to sodium nitroprusside was unchanged. Conclusions and Clinical Relevance: Results suggested that despite increased bronchiolar wall thickness in heartworm-infected cats, a hyperreactive response of the bronchiolar smooth muscle is not the primary mechanism of respiratory tract clinical signs. Reduced response of the airway to isoproterenol may indicate refractoriness to bronchiolar relaxation in heartworm-infected cats.

In horses with noninduced, reversible airway obstruction (heaves), pulmonary function is improved after sedation with the alpha-adrenergic agonist xylazine. The mechanism of this effect is undetermined. Because the predominant excitatory innervation of equine airways is cholinergic, the influence of alpha 2-adrenergic receptor stimulation on the response of isolated distal airways to cholinergic stimulation was determined. Distal bronchial segments from 22 healthy horses were suspended in isolated organ baths where their mechanical responses to various stimuli could be studied. Each tissue was incubated with one of several concentrations of clonidine, clonidine vehicle, or clonidine plus tolazoline. Then, the contractile response of the tissues to either cumulative acetylcholine (ACh) addition or cumulative electrical field stimulation (EFS) was recorded. All contractile responses evoked by EFS were mediated through stimulation of cholinergic airway nerves. Clonidine had no effect on the contractile response of distal airway segments to exogenous ACh. However, clonidine (at concentrations > 10(-5) M) significantly (P < 0.05) diminished the contractile response of the distal airway segments to EFS. This inhibitory effect of clonidine was not observed in the presence of tolazoline. Similar results were observed when the less-selective alpha 2-adrenergic agonist xylazine was exposed to the isolated segments instead of clonidine. Because EFS-but not exogenous ACh-induced contractions were inhibited, alpha 2-adrenergic receptor stimulation apparently causes presynaptic inhibition of the cholinergic nerves innervating distal portions of the bronchi of horses.

The distribution of postganglionic autonomic nerve fibers in the lacrimal gland and gland of the third eyelid of dogs was studied by use of histochemical techniques. Adrenergic nerve distribution was identified by use of the sucrose-potassium phosphate-glyoxylic acid technique. A loose network of adrenergic nerves was found throughout the interstitium around acini and blood vessels and in vessel walls. Acetylcholinesterase staining was used to identify cholinergic nerve fibers. A cholinergic distribution pattern around acini and blood vessels similar to the adrenergic pattern was found, although the cholinergic innervation appeared more dense than the adrenergic. In the gland of the third eyelid, mucus-secreting lobules and lipid-secreting lobules appeared to be equally innervated by parasympathetic fibers. These lobules could not be differentiated when the sucrose-potassium phosphate-glyoxylic acid technique was used. The techniques used in this study could not demonstrate whether direct contact was made by either cholinergic or adrenergic nerve fiber with secretory or myoepithelial cells. The presence of both nerve fiber types around acini suggests an interrelationship between the sympathetic and parasympathetic nervous system in lacrimal gland secretion in dogs.

Smooth muscle strips from the midcervical portion of the trachea and bronchial smooth muscle strips from third-generation airways of horses were placed in tissue baths, and isometric contractile force was measured. Active force was measured in response to electrical stimulation and exogenous acetylcholine. Square-wave electrical stimuli were applied at various voltages (10, 12, 15, 18, 20, 25 V), frequencies (3, 5, 10, 15, 20, 25, 30 Hz), and pulse durations (0.2, 0.5, 1.0, 1.5, 2.0 ms). Isometric contractile force increased as voltage, frequency, and pulse duration increased. Maximal contractile response to electrical stimulation was obtained at 18 V, 25 Hz, and 0.5 ms. Atropine (10-6M) or tetrodotoxin (3 X 10-6M) blocked the contraction, indicating that the contractile response was attributable to the release of neurotransmitter from cholinergic nerves. Cumulative concentration-response curves to acetylcholine (10-9M through 10-4M) were determined. Isometric contractile force increased as acetylcholine concentration increased. There was a significant (P less than 0.05) difference in the 50% effective dose for acetylcholine in tracheal smooth muscle and bronchial smooth muscle. The mean (+/- SD) contractile response to maximal electrical stimulus was 89% (+/- 7.4%) of that in response to 10-4M acetylcholine in tracheal smooth muscle and was 68% (+/- 10.4%) of the response to 10-4M acetylcholine in bronchial smooth muscle.