Cholinesterase activity : muscarinic receptor ratios in canine and feline brains

In response to findings that brain cholinesterase (ChE): muscarinic choline rgic receptor density (mChR) ratio is highly conserved between bird species (I), this study investigated the conservation of brain ChE:mChR between 2 mammalian species. Whole brains of 7 normal greyhounds, 14 normal non-greyh ound dogs, and 8 normal cats, were assayed for ChE, mChR and protein. The s ame assays were made on cerebrum, cerebellum and brainstem from the greyhou nds and 6 of the non-greyhound dogs. The Ellman assay was used to measure s erum ChE activity, mChR were labelled with tritiated quinuclidinyl benzilat e, and protein was measured by Lowry assay. Brain ChE:mChR was not highly c onserved between the species. There was a statistically significant differe nce in brain mChR between greyhounds and non-greyhounds but this did not tr anslate to a statistically significant difference in mean ChE:mChR. Measure ment of ChE:mChR is unlikely to be useful in endangered carnivores for whic h normal ChE levels are unknown, because it cannot be assumed that endanger ed species would have the same ChE:mChR as their domestic relatives.