Who is HOT and who is LOT? Detailed characterization of prescription opioid‐induced changes in behavior between 129P3/J and 129S1/SvlmJ mouse substrains

Abstract

Genetic factors are theorized to contribute to the substantial inter-individual variability in opioid abuse/addiction. To advance the behavioral genetics of prescription opioid abuse, our prior work identified the 129S1/SvlmJ (S1) and related 129P3/J (P3) mouse substrains, respectively, as low and high opioid-taking. Herein, we related our prior results to measures of sucrose reward/reinforcement, basal anxiety, opioidinduced place-conditioning, locomotor activity and Straub tail reaction, as well as behavioral and physiological signs of withdrawal. Substrains were also re-examined for higher-dose oxycodone and fentanyl intake under limited-access drinking procedures. S1 mice failed to acquire sucrose self-administration under various operantconditioning procedures and exhibited lower sucrose intake in the home-cage.However, sucrose intake under limited-access procedures escalated in both substrains with repeated sucrose experience. S1 mice exhibited less spontaneous locomotor activity, as well as less opioid-induced locomotor activity and Straub tail reaction, than P3 mice and failed to exhibit an oxycodone-induced place-preference.The lack of conditioned behavior by S1 mice was unrelated to behavioral signs of withdrawal-induced negative affect or dependence severity, but might reflect high levels of basal anxiety-like behavior. Intriguingly, S1 and P3 mice initially exhibited equivalent oxycodone and fentanyl consumption in the home-cage; however opioid intake escalated only in P3 mice with repeated opioid experience. No sex differences were observed for any of our measures. These data provide additional evidence for robust differences in opioid addiction-related behaviors between P3 and S1 substrains and suggest that anxiety, learning, and/or motivational impairments might confound interpretation of operant-and place-conditioning studies employing the S1 substrain. K E Y W O R D Sdependence, fentanyl, negative affect, oxycodone, self-administration, strain differences, withdrawal

Fentanyl-induced antinociception, reward, reinforcement, and withdrawal inHnrnph1mutant mice

“…For several decades, an opioid withdrawal-induced negative affective state has been successfully recapitulated in rodent models of morphine dependence using a variety of different behavioral assays (Hand et al 1988;Bhattacharya et al 1995;Grasing et al 1996;Schulteis et al 1998). More recently, genetic variability in the manifestation of oxycodone and fentanyl withdrawal-induced negative affect was highlighted through studies of different 129 mouse substrains (Jimenez et al 2017;Szumlinski et al 2019).…”

“…Male mice were employed exclusively in this initial operant-conditioning study due to limited availability of female mice at the time the experiment was performed. As in recent studies (Szumlinski et al 2019), each right lever-press resulted in delivery of 20 µl of the sucrose solution and a 20 s presentation of a tone/light stimulus-complex. Left lever presses resulted in no programed consequences.…”

“…Sucrose training proceeded for 12 days, by which point, mice of both genotypes had exceeded the minimum requirements for successful acquisition of the operant response (a minimum of 10 active lever-presses in 60 min + greater than 70% responding on the active lever for 3 consecutive days). Then, the sucrose solution was substituted for an unadulterated 3 mg/L fentanyl solutiona concentration demonstrated recently to be readily consumed by mice under free-access conditions in the home-cage (Szumlinski et al 2019) -and mice underwent daily, 60 min testing sessions for an additional 10 days. In the initial fentanyl self-administration study, the concentration of the fentanyl reinforcer was then progressively increased across days (10, 30, 100, 300 and 1000 mg/L), with each concentration presented until responding stabilized (less than 15% variability across three consecutive presentations) or for a maximum of 10 days of self-administration.…”

“…The 1-day test battery was very similar to a battery that we employed in a recent opioid study (Szumlinski et al 2019), as well as prior studies of alcohol withdrawal-induced negative affect (Lee et al 2016(Lee et al , 2017a(Lee et al , 2018. The battery consisted of testing for acoustic startle and prepulse inhibition of acoustic startle, followed, in order, by testing in the light-dark shuttle box test, novel object encounter, marble-burying and the Porsolt forced swim tests.…”

“…The day following the behavioral test battery, fentanyl-experienced mice were then injected in the morning (~0800 h) with 0.8 mg/kg fentanyl. Eight hours later, mice were injected with 10 mg/kg naltrexone and tested for physiological signs of withdrawal as described previously (Jimenez et al 2017;Szumlinski et al 2019) and detailed in the Supplementary Information. To accommodate all the mice, behavioral testing was conducted in cohorts of 8 mice, with ~24 mice tested per day.…”