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 evaluate the ability of atropine sulfate, butylscopolammonium bromide combined with metamizole sodium, and flunixin meglumine to ameliorate the clinical adverse effects of imidocarb dipropionate in horses. Animals—28 horses with piroplasmosis. Procedures—28 horses were randomly assigned to 4 equal groups according to the pretreatment administered. Fifteen minutes before administration of 2.4 mg of imidocarb dipropionate/kg IM, horses in the first group were pretreated with 0.02 mg of atropine sulfate/kg IV, the second group with a combination of 0.2 mg of butylscopolammonium bromide/kg IV and 25 mg of metamizole sodium/kg IV, the third group with 1.1 mg of flunixin meglumine/kg IV, and the fourth (control) group with 1 mL of saline (0.9% NaCl) solution/50 kg IV. Physical examination, including evaluation of rectal temperature, heart and respiratory rates, capillary refill time, mucous membrane color, hydration status, abdominal sounds, signs of abdominal pain, salivation, diarrhea, and number of defecations, was performed. Results—Imidocarb dipropionate use in the control group was associated with serious adverse effects including signs of abdominal pain (4/7 horses) and diarrhea (2/7). Horses pretreated with atropine had no diarrhea, but 6 had signs of abdominal pain. Only 1 horse that received butylscopolammonium-metamizole pretreatment had signs of abdominal pain and 3 had diarrhea, which was numerically but not significantly different than the control group. Of horses pretreated with flunixin, 3 had signs of abdominal pain and 3 had diarrhea. Conclusions and Clinical Relevance—A combination of butylscopolammonium bromide and metamizole sodium may be useful to ameliorate the adverse effects of imidocarb dipropionate in horses, although group size was small and significant differences from the control group were not found.

Objective-To quantitatively and qualitatively compare electroretinography (ERG) recordings in awake, sedated, and anesthetized dogs. Animals-Six 6-month-old Beagles. Procedures-A brief ERG protocol for dogs was used. Following 1-minute and subsequent 5-minute dark adaptation, mixed rod-cone responses were recorded bilaterally with a handheld multispecies ERG device with dogs in each of 3 states of consciousness: awake, sedated (dexmedetomidine and butorphanol), and anesthetized (atropine and hydromorphone, followed by propofol and midazolam and anesthetic maintenance with isoflurane). Low- and high-frequency noise levels were quantified via Fourier analysis, and the effect of consciousness state on signal amplitude, implicit time, and noise was analyzed via repeated-measures ANOVA. In addition, 13 veterinary ophthalmologists who were unaware of the dogs' consciousness states subjectively graded the ERG recording quality, and scores for each tracing were compared. Results-ERG amplitudes were highest in awake dogs and lowest in anesthetized dogs. Implicit times were shortest in awake dogs and longest in anesthetized dogs. Differences in b-wave amplitudes and a-wave implicit times were significant. Neither low- nor high-frequency noise levels differed significantly among consciousness states. Furthermore, no significant differences were identified among observers' scores assigned to ERG tracings. Conclusions and Clinical Relevance-Anesthesia and sedation resulted in significant attenuation and delay of ERG responses in dogs. Chemical restraint of dogs had no consistently significant effect on low- or high-frequency noise levels or on observer perception of signal quality.