Genetic differences in addiction to morphine … in ants, no less …!!!

Here is a GREAT example of “evolutionary conservation” of genetic pathways in the central nervous system (CNS) between the Order Hymenoptera (including ants) and Primata (primates, including humans). Ants are eusocial insects of the family Formicidae and––along with the related wasps and bees––belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the Cretaceous period, ~99 million years ago, and diversified after the rise of flowering plants. More than 12,500 of an estimated total of 22,000 species have been classified. They are easily identified by their elbowed antennae and the distinctive node-like structure that forms their slender waists.

Conventional definitions of drug addiction are focused on characterizing the neurophysiological and behavioral responses of mammals. Although mammalian models have been invaluable in studying specific and complex aspects of addiction, invertebrate systems have proven advantageous in investigating how drugs-of-abuse corrupt the most basic motivational and neurochemical systems. It has recently been shown that invertebrates and mammals have remarkable similarities in their behavioral and neurochemical responses to drugs-of-abuse. However, until now, only mammals have demonstrated drug-seeking and self-aministration without the concurrent presence of a natural reward (e.g. sucrose).

Using a sucrose-fading paradigm, followed by a two-dish choice test, authors [see paper below] establish ants as an invertebrate model of opioid addiction. The ant genus and species Camponotus floridanus actively seeks and self-administers morphine––even in the absence of caloric value or additional natural reward. Using HPLC equipped with electrochemical detection, authors identified the neurochemicals serotonin, octopamine and dopamine; these chemicals were subsequently quantified, establishing the concurrent neurochemical response to the opioid morphine within the invertebrate brain. With this study, authors demonstrate dopamine to be controlling opioid addiction in the brains of ants. Thus, this study establishes that ants as the first non-mammalian model of self-administration that is accurately analogous to mammals.

J Exp Biol  2o16; 219: 2865–2869

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