The Sensitivity of the Crayfish Reward System to Mammalian Drugs of Abuse

Abstract

The idea that addiction occurs when the brain is not able to differentiate whether specific reward circuits were triggered by adaptive natural rewards or falsely activated by addictive drugs exist in several models of drug addiction. The suitability of crayfish (Orconectes rusticus) for drug addiction research arises from developmental variation of growth, life span, reproduction, behavior and some quantitative traits, especially among isogenic mates reared in the same environment. This broad spectrum of traits makes it easier to analyze the effect of mammalian drugs of abuse in shaping behavioral phenotype. Moreover, the broad behavioral repertoire allows the investigation of self-reinforcing circuitries involving appetitive and exploratory motor behavior, while the step-wise alteration of the phenotype by metamorphosis allows accurate longitudinal analysis of different behavioral states. This paper reviews a series of recent experimental findings that evidence the suitability of crayfish as an invertebrate model system for the study of drug addiction. Results from these studies reveal that unconditioned exposure to mammalian drugs of abuse produces a variety of stereotyped behaviors. Moreover, if presented in the context of novelty, drugs directly stimulate exploration and appetitive motor patterns along with molecular processes for drug conditioned reward. Findings from these studies indicate the existence of drug sensitive circuitry in crayfish that facilitates exploratory behavior and appetitive motor patterns via increased incentive salience of environmental stimuli or by increasing exploratory motor patterns. This work demonstrates the potential of crayfish as a model system for research into the neural mechanisms of addiction, by contributing an evolutionary, comparative context to our understanding of natural reward as an important life-sustaining process.

Simple Aesthetic Sense and Addiction Emerge in Neural Relations of Cost-Benefit Decision in Foraging

“…Reward learning likely has ancient origins, and is documented among generalist foragers in annelids, mollusks, insects, spiders, and even nematodes and flatworms. In parallel are aspects of the aesthetic sense in terms of abilities to evaluate stimuli, and specifically addictive behaviors [11][12][13][14][15][16][17][18][19] .…”

Crayfish Self-Administer Amphetamine in a Spatially Contingent Task

“…Although the reward seeking circuit ( Ferenczi et al, 2016 ; Otis et al, 2017 ) in crayfish brain is yet to be mapped out in its entirety. Nonetheless, with an amine system consisting of fewer than 1,000 neurons (30–35 dopamine neurons in the brain and nerve cord) and a well-characterized set of behaviors associated with drug reward, crayfish is a model amenable to the exploration of reward mechanisms ( Shipley et al, 2017 ). The establishment of an automated, operantly conditioned self-administration paradigm in crayfish sets the stage for more nuanced studies of the processes underlying invertebrate reward.…”

Addiction and Evolutionary Process, Common Aspects in Physio-Pathologic Pathways Use Full in Pharmaco-Toxicological Approach

“…With strongly conserved evolutionary mechanisms for behavioral sensitization, drug dependence, and drug-induced reward seeking, crayfish demonstrate significant vulnerability to human drugs of addiction. Research in crustaceans thus offers a valuable perspective for studying the neural implementation of conserved behavioral phenomena, including motivation, escape, aggression, drug-sensitive reward" [15].…”