Chloral hydrate is a sedative hypnotic used in many species. Because
of its poor anesthetic properties it is usually combined with other
agents.
Yohimbine is a selective alpha2-antagonist used in several species
to reverse the CNS depressent effects of the alpha2 agonist
xylazine.
See any veterinary anesthesia textbook, eg. Short CE (ed) Principles
and Practice of Veterinary Anesthesia. Baltimore: Williams and Wilkins
1987. Search AGRICOLA or CAB abstracts.