Effect of topically administered atropine on tear production in dogs.

Baseline tear production values were established for both eyes of 19 dogs, using the Schirmer tear test. Atropine sulfate, 1% solution, was administered topically in the left eye of each dog once daily for 14 days. Tear production was then determined for both eyes at 15, 30, 60, 120, 180, 240, and 300 minutes, and 3, 6, 9, 12, and 15 days. A final Schirmer tear test reading was obtained for each eye 5 weeks after the last atropine treatment to check for the possibility of prolonged effect. Both eyes had statistically significant (P less than 0.05) decrease in tear production that was most marked at 120 minutes after atropine instillation, then returned to baseline values by 300 minutes after instillation. Although atropine was placed in the left eye only, statistically significant difference was not apparent in Schirmer tear test values between the left and right eyes. Tear production continued to decrease in both eyes over time, becoming statistically significant (P less than 0.05) on day 9. However, on days 12 and 15, tear production in the untreated eye plateaued, but that in the treated eye continued to decrease. Five weeks after the last treatment with atropine, both eyes still had a statistically significant (P less than 0.05) decrease in tear production, although Schirmer tear test values had increased from day-15 values and appeared to be returning to baseline. Association was not evident between age or body weight and magnitude of response to topically applied atropine.

Dysautonomia in a cat.

Autonomic dysfunction was diagnosed in a 2.5-year-old spayed domestic shorthair cat. The cat had an 8-day history of progressive anorexia, signs of depression, constipation, weight loss, and intermittent regurgitation. Physical examination findings were signs of depression, dehydration, cachexia, bradycardia, bilateral nonresponsive mydriasis, prolapse of both nictitating membranes, dry oral and nasal mucous membranes, and urinary bladder atony. Thoracic radiography revealed megaesophagus. The cat lacked esophageal motility and had a decreased gastric emptying rate. Providing adequate fluid intake, electrolyte balance, and nutrition is a major problem in the management of dysautonomic cats. We were able to provide adequate nutritional support for this patient, using total parenteral feeding and, later, enteral nutrition using a nasogastric tube. Results of an ocular pharmacologic study indicated that the mydriasis and prolapse of the nictitating membrane were attributable to complete autonomic denervation of the eye. Using the method described, topical, autonomic-stimulating agents may assist the clinician in diagnosing dysautonomia in the feline. This report describes a syndrome that is well recognized in the United Kingdom and has the potential to develop in the United States.

Electrophysiologic studies of cutaneous nerves of the forelimb of the cat.

The cutaneous innervation of the forelimb was investigated in 20 barbiturate-anesthetized cats by using electrophysiological techniques. The cutaneous area (CA) innervated by each cutaneous nerve was delineated in at least six cats by brushing the hair in the CA with a small watercolor brush while recording from the nerve. Mapping of adjacent CA revealed larger overlap zones (OZ) than were noted in the dog. Remarkable findings were that the brachiocephalic nerve arose from the axillary nerve and the CA comparable to that supplied by the cutaneous branch of the brachiocephalic nerve in the dog was supplied by a cutaneous branch of the suprascapular nerve. The CA supplied by the communicating branch from the musculocutaneous to the median nerve was similar in both species except that the communicating branch arose proximal to any other branches of the musculocutaneous nerve in the cat, whereas it was a terminal branch in the dog. The superficial branch of the radial nerve gave off cutaneous brachial branches in the cat proximal to the lateral cutaneous antebrachial nerve. The CA of the palmar branches of the ulnar nerve did not completely overlap the CA of the palmar branches of the median nerve as occurred in the dog; thus an autonomous zone (AZ) for the CA of the palmar branches of the median nerve is present in the cat, whereas no AZ existed for the CA of this nerve in the dog.