Effects of sub-chronic amylin receptor activation on alcohol-induced locomotor stimulation and monoamine levels in mice

Abstract

Rationale Amylin receptors consist of the calcitonin receptor (CTR) and one of three receptor activity-modifying proteins (RAMPs). The identification of amylin receptors in areas processing reward, namely laterodorsal tegmental area (LDTg), ventral tegmental area (VTA), and nucleus accumbens (NAc), has attributed them a role as reward regulators. Indeed, acute activation of amylin receptors by the amylin receptor agonist salmon calcitonin (sCT) attenuates alcohol-induced behaviours in rodents. Objectives The effects of long-term administration of sCT on alcohol-related behaviours and the molecular mechanisms underlying these processes are not yet elucidated. To fill this knowledge gap, we investigated the effects of sub-chronic sCT treatment on the locomotor stimulatory responses to alcohol in mice and the molecular pathways involved. Methods We assessed the behavioural effects of sub-chronic sCT treatment by means of locomotor activity experiments in mice. We used western blot to identify changes of the CTR levels and ex vivo biochemical analysis to detect changes in monoamines and their metabolites. Results After discontinuation for 5 days of sCT treatment, alcohol did not induce locomotor stimulation in mice pre-treated with sCT when compared with vehicle, without altering secondary behavioural parameters of the locomotor activity experiment or the protein levels of the CTR in reward-related areas in the same set of animals. Moreover, repeated sCT treatment altered monoaminergic neurotransmission in various brain areas, including increased serotonin and decreased dopamine turnover in the VTA. Lastly, we identified a differential effect of repeated sCT and acute alcohol administration on alcohol-induced locomotion in mice, where sCT initially attenuated and later increased this alcohol response. It was further found that this treatment combination did not affect secondary behavioural parameters measured in this locomotor activity experiments. Conclusions These data suggest that sub-chronic sCT treatment differentially alters the ability of alcohol to cause locomotor stimulation, possibly through molecular mechanisms involving various neurotransmitter systems and not the CTR levels per se.

Salmon Calcitonin Attenuates Some Behavioural Responses to Nicotine in Male Mice

“…Similar to the present data, sCT blocks acute behavioural responses to alcohol in male mice ( Kalafateli A. L. et al, 2019 ; Kalafateli A. L. et al, 2019 ; Kalafateli et al, 2020a ; Kalafateli et al, 2020c ). Moreover, sCT, or a selective AMYR agonist, reduce alcohol intake in various models of alcohol use disorder in male and female rats ( Kalafateli A. L. et al, 2019 ; Kalafateli A. L. et al, 2019 ; Kalafateli et al, 2020a ; Kalafateli et al, 2020c ).…”

“…sCT (Tocris Bioscience, Bristol, United Kingdom) was diluted in vehicle (0.9%, NaCl solution) and was administered intraperitoneally (IP) at the dose of 5 μg/kg, 30 min prior to nicotine administration. This dose of sCT and the timeline of administration were chosen as they have been established necessary for the attenuation of alcohol-mediated behaviours in rodents ( Kalafateli A. L. et al, 2019 ; Kalafateli et al, 2020a ). All drugs and vehicle solution were injected at a volume of 10 ml/kg.…”

“…CTR(a + b), were analysed. Therefore, the brains from the mice of Experiment 2 were used similarly to previous studies ( Kalafateli et al, 2020a ). Following the locomotor activity test on Day 8, the mice were briefly exposed to isoflurane (Isoflurane Baxter) and then decapitated.…”

“…Experiment 2: Effects of repeated sCT and Nicotine Administration on Locomotor Sensitisation Repeated injections of an addictive drug, like nicotine, enhances the locomotor activity response over time, i.e., locomotor sensitisation (Segal and Mandell, 1974). This locomotor sensitisation experiment was designed similar to previous studies (Jerlhag and Engel, 2011;Wellman et al, 2011;Clifford et al, 2012;Egecioglu et al, 2013;Kalafateli et al, 2020a;. Throughout the entire protocol (Day 1-5 and Day 8), the mice were allowed to habituate to the open field boxes for 30 min prior to drug treatment.…”

“…More recent studies have established that the amylinergic pathway modulates reward processing. Indeed, activation of AMYRs reduces the acute rewarding properties of alcohol in male mice and decreases alcohol intake in various animal models of alcohol use disorder ( Kalafateli A. L. et al, 2019 ; Kalafateli A. L. et al, 2019 ; Kalafateli et al, 2020a ; Kalafateli et al, 2020c ). The decrease of these alcohol-related behaviours involves AMYRs within the LDTg, VTA and NAc shell ( Kalafateli et al, 2020b ).…”