Objective--To determine whether larkspur-derived N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids alter heart rate and electrically evoked electromyographic (eEMG) response of the external anal sphincter (EAS) in cattle and whether these effects can be reversed by acetylcholinesterase inhibitors. Animals--12 beef heifers and 4 cows. Procedures--3 or 4 heifers were used in 1 or 2 of 7 dose-response experiments; heart rate and EAS eEMG response were assessed before and 24 hours after oral treatment with larkspur (doses equivalent to 0.5 to 15 mg of MSAL-type alkaloids/kg). In 3 subsequent experiments, 3 heifers (1 of which was replaced with another heifer in the control experiment) each received 10 mg of MSAL-type alkaloids/kg and were injected IV with physostigmine (0.04 mg/kg), neostigmine (0.04 mg/kg), or saline (0.9% NaCl) solution 24 hours later, prior to assessment. Additionally, EAS eEMG response was measured in 4 cows before and after epidural administration of 2% lidocaine hydrochloride. Results--Larkspur-treated heifers developed dose-related increases in heart rate and decreases in EAS eEMG response. Twenty-four hours after administration of MSAL-type alkaloids, neostigmine decreased heart rate but did not affect eEMG response, whereas physostigmine did not affect heart rate but caused a 2-fold increase in eEMG response. In cows, epidural anesthesia did not alter eEMG response, suggesting that transdermal stimulation of the EAS pudendal innervation did not occur. Conclusions and Clinical Relevance--In cattle, cardiac effects and muscle weakness or loss of EAS eEMG response induced by larkspur-derived MSAL-type alkaloids were reversed by neostigmine or physostigmine, respectively. Treatment with anticholinesterase inhibitors may alter the clinical effects of larkspur poisoning in cattle.

Noninvasive determination of anal and genitoanal reflexes was evaluated in clinically normal cats. Thirty adult mixed-breed cats (15 sexually intact or castrated males, 15 sexually intact or spayed females) were sedated by IV administration of ketamine, acetylpromazine, and atropine. Anal reflexes were recorded from the anal sphincter muscle after ipsilateral and contralateral electrical stimulation of the perineal skin. Genitoanal reflexes were recorded from the anal sphincter muscle after electrical stimulation of the penis or clitoris. An anal sphincter response to tibial nerve stimulation was attempted. Anal reflexes from ipsilateral and contralateral stimulations and a genitoanal reflex were detected in all cats. Anal sphincter responses to tibial nerve stimulation were inconsistent (4/30) and were not included in any analyses. Anal reflexes had response latencies of 7.5 to 12.0 ms (ipsilateral stimulation) and 6.5 to 13 ms (contralateral stimulation). Genitoanal reflexes had latencies of 9.0 to 13.0 ms (males) and 6.5 to 9.0 ms (females). Anal reflex latencies were significantly (P < 0.05) longer for contralateral, opposed to ipsilateral, stimulation and were significantly (P < 0.05) longer in males than in females. Genitoanal reflex latencies were also significantly (P < 0.05) longer in males than in females, reflecting the more peripheral stimulation site in males. Anal reflex responses could be recorded in 2 feline clinic patients with such severe perineal trauma that pudendal nerve function could not be manually evaluated. A potentially favorable prognosis was given in each instance on the basis of detection of the response. One cat eventually recovered. The other was euthanatized because of other problems, and the sacral part of the spinal cord, sacral nerve roots, and pudendal nerves were found to be intact at necropsy.

To determine the suitability and estimate the sensitivity of an immunohistochemical (IHC) test for disease-associated prion protein (PrP(Sc)) in biopsy specimens of rectoanal mucosa-associated lymphoid tissue (RAMALT) for diagnosis of scrapie in sheep. 762 sheep at high risk for having scrapie and indemnified by the National Scrapie Eradication Program. The IHC test for PrP(Sc) was applied to 2 RAMALT and 2 third-eyelid biopsy specimens and a postmortem RAMALT specimen from each sheep. Results were compared with those of a reference test in which results for tissues from obex and retropharyngeal lymph nodes, tonsil, or both were considered in parallel. The reference test identified 139 sheep as having scrapie. Biopsy-related complications occurred in 3 sheep. Sensitivity of the IHC test in RAMALT ranged from 85.3% to 89.4%, depending on the anatomic location from which RAMALT was obtained. Results for the test applied to 1 RAMALT specimen were similar to results interpreted in parallel for 2 third-eyelid specimens (sensitivity, 87.0%). The proportion of inconclusive test results attributable to insufficient lymphoid follicles in biopsy specimens was lower when considering results for 2 RAMALT specimens in parallel (10.1%) than when considering results for 2 third-eyelid specimens in parallel (23.7%). Specimens of RAMALT that were inappropriately collected from an area caudal to the rectoanal interface yielded a high proportion of inconclusive results (33.3% to 50.0%). The IHC test for PrP(Sc) in RAMALT was an effective means of detecting subclinical scrapie in live, high-risk sheep.