Monday through Thursday evenings around five pm, I drive in to my school’s small animal hospital to collect spit from dogs. I’ve learned a lot about how to get spit out of a dog. It helps to have the right tools. If your subject is an adult human, you can ask them to drool into a cup. (Don’t actually spit! The manual doesn’t say why, but when I tried it, my spit contained long mucin strands which made it difficult to pipette up into a vial for storage.) If your subject doesn’t speak the same language as you do — mine don’t — or is otherwise recalcitrant, you might extract the spit with a small cotton rope. However, a new tool is now on the market: the Sorbette, a small sponge on a stick available from Salimetrics. (My endocrinology professor, upon hearing about Salimetrics, said: “An entire company dedicated to saliva? Who knew?”) Oh, wait. The Sorbette isn't actually all that new as technology goes: it turns out to just be an eye sponge. Not knowing much about eyes, I presume it is for adding things to or taking things away from them. But it's now also marketed to us spit collectors.
Salimetrics tells me to insert two Sorbettes under my subject's tongue and hold them there for a full minute. I should not swab. I did try this a few times. My subjects inevitably act like I have stuck a hot poker under their tongues, rolling their eyes and chewing madly. No Sorbettes have been damaged in this process, but it was only a matter of time. Also, the amount of saliva I actually acquired was too low for the assay I intended to perform on it.
So now I stick three Sorbettes in the side of the dog's mouth; this bothers them less, even with the greater mass. There also seems to be a fair amount of spit accumulating in the forward lower part of the dog’s mouth, between the outer edge of his teeth and inside his lip. And I do swab. The collection manual, when consulted, explained that swabbing is bad because it means you'll collect saliva from various different salivary glands, and so the levels of whatever you're testing might vary based on how much spit you get from which gland. This is a more important consideration for some other substances than for cortisol, which is what I care about.
Even so, the quantities of spit still occasionally leave something to be desired. My suspicion is that anxious dogs — which my study dogs are; that’s the point — just make less saliva than calm dogs, because their sympathetic nervous system is activated and telling them that making things which are useful for the process of digestion is not appropriate at this time. Eat later, worry about being stuck in the hospital now. In order to turn on the rest-and-digest parasympathetic nervous system, I have attempted waving treats under my subjects’ noses. Well, I’ve tried this once so far, and I did get a nice large sample that night. I left the treat behind with the dog; he was too anxious at the moment to ingest it, but I have hopes that he came around in my absence.
Once I have my sample, I balance it on a plate of ice and carry it upstairs to the clinical sciences laboratory, where I centrifuge it (3250 rpm, 15 minutes) so that it spins its way out of the sponge and into the tapered bottom of its vial. I then pipette it into a cryovial and secrete it in a -80° freezer. Done! When I have enough samples, I’ll perform an ELISA assay on them to find out how much cortisol is in each. I imagine I’ll report on that in detail here.