I asked the OSU vet. school about this, which was a query raised on another thread.
From: Welch, Corrie [mailto:Corrie.Welch@oregonstate.edu]
Sent: Wednesday, August 13, 2008 9:54 PM
To:
iwplit@comcast.net
Subject: Chocolate toxicity
Hi Mr. Webb,
Chocolate contains both caffeine and theobromine, which are methylxanthines. Signs of intoxication include vomiting, bloating, restlessness, polyuria, polydipsia (increased urine production and drinking) and tachycardia (high heart rates) with cardiac arrhythmias. It can progress to tremors, rigidity, collapse, seizures and death. Methylxanthines elicit their effects by inhibiting phosphodiesterases causing increased intracellular levels of cAMP. Intracellular calcium reuptake is also inhibited, enhancing cardiac and skeletal muscle contractility. Central nervous system and cardiac effects are also the result of inhibition of adenosine receptors. Dogs may also show gastrointestinal signs associated with pancreatitis presumably as a result of ingestion of the fats and sugars present in some chocolate products. There have been cumulative toxic effects reported in dogs, who usually die acutely of cardiac failure. There is one report of wildlife (fox and badger) presumed to have died from cumulative effects of chocolate ingestion.
I hope that is helpful.
Corrie A Welch, DVM, MS
Small Animal Intern
College of Veterinary Medicine
Oregon State University
Corvallis, OR 97330