Effects of exposure to 5-MeO-DIPT during adolescence on brain neurotransmission and neurotoxicity in adult rats

Forensic Toxicology https://doi.org/10.1007/s11419-018-0433-x ORIGINAL ARTICLE Effects of exposure to 5‑MeO‑DIPT during adolescence on brain neurotransmission and neurotoxicity in adult rats Karolina Noworyta‑Sokołowska1 · Katarzyna Kamińska1 · Joanna Rzemieniec2 · Agnieszka Wnuk2 · Jakub Wojcieszak3 · Anna Maria Górska1 · Grzegorz Kreiner4 · Małgorzata Kajta2 · Krystyna Gołembiowska1 Received: 9 May 2018 / Accepted: 4 July 2018 © The Author(s) 2018 Abstract Purpose Tryptamine hallucinogen 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is a serotonin transporter inhibitor with high affinity for serotonin 5-HT1A and 5-HT2A/C receptors. We showed previously that 5-MeO-DIPT in a single dose increased neurotransmitter release in brain regions of rats and elicited single- and double-strand DNA breaks. Herein we investigated the effects of repeated-intermittent 5-MeO-DIPT administration in adolescence on dopamine (DA), serotonin (5-HT) and glutamate release in brain regions of adult rats. Furthermore, we examined caspase-3 activity, oxidative DNA damage, the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels, and cell viability. Methods Neurotransmitter release was measured by microdialysis in freely moving animals. Caspase-3 activity was assessed colorimetrically, and oxidative DNA damage with the comet assay, while the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels were assessed by real-time polymerase chain reaction. Cell viability was studied in SH-SY5Y and Hep G2 cells by the MTT test. Results We observed changed responses of DA, 5-HT and glutamate neurons to a challenge dose of 5-MeO-DIPT when animals were treated repeatedly in adolescence with this hallucinogen. The basal extracellular levels of DA and 5-HT were decreased in the striatum and nucleus accumbens, while glutamate level was increased in the nucleus accumbens and frontal cortex. The damage of cortical DNA, increased Gpx3 and Sod1 mRNA expression and affected caspase-3 activity were also observed. Furthermore, decreased Ht1a and Ht2a mRNA expression in the frontal cortex and marked cytotoxicity of 5-MeO-DIPT were found. Conclusions These results suggest that 5-MeO-DIPT given repeatedly during adolescence affects brain neurotransmission and shows neurotoxic potential observed in adult animals. Keywords 5-MeO-DIPT · Exposure in adolescence · Neurotransmitter release · Dopamine, serotonin and glutamate · DNA damage · Cytotoxicity Introduction * Krystyna Gołembiowska nfgolemb@cyf‑kr.edu.pl 1 Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna, 31‑343 Kraków, Poland 2 Department of Experimental Neuroendocrinology, Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna, 31‑343 Kraków, Poland 3 Department of Pharmacodynamics, Medical University of Łódź, Muszyńskiego 1, 90‑151 Łódź, Poland 4 Department of Brain Biochemistry, Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna, 31‑343 Kraków, Poland 5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) synthesized by Shulgin and Carter [1] is a tryptamine hallucinogen with a street name “foxy” or “foxy methoxy”. As a substitute for MDMA, 5-MeO-DIPT has been permanently controlled in the USA as a schedule I substance under the Controlled Substances Act (69 FR 58050) [2, 3]. 5-MeO-DIPT is a competitive serotonin transporter (SERT) inhibitor and has a lower affinity for dopamine transporter (DAT) [4]. The hallucinogenic activity of 5-MeODIPT shown in mice was caused by the stimulation of postsynaptic 5-HT2A receptors [5]. Moreover, 5-MeO-DIPT had also in vitro high affinity for 5-HT1A and 5-HT2C receptors 13 Vol.:(0123456789) Forensic Toxicology [5, 6]. High concentrations of 5-MeO-DIPT produced a marked cytotoxicity assessed by a cell viability assay in COS-7 cells [3]. Chronic 5-MeO-DIPT administration decreased 5-HT levels in the rat prefrontal cortex, striatum and hippocampus [7–9], which may suggest its neurotoxicity. Clinical data indicated potent multi-organ effects of 5-MeO-DIPT as the users experienced euphoria, disinhibition, increased sociability, and visual and auditory hallucinations, but also effects like mioclonus, restlessness, insomnia, anxiety, nausea, vomiting and diarrhea [10]. According to the Drug Enforcement Administration (DEA), the doses used by human subjects range from 6 to 20 mg with the duration of symptoms for approximately 6 h [2]. The threshold dose for hallucinogenic activity was 4 mg with an effective range from 6 to 10 mg [11]. Our earlier microdialysis study in rats showed that 5-MeO-DIPT in a wide range of doses (5, 10 and 20 mg/kg) increased extracellular levels of dopamine (DA), serotonin (5-HT) and glutamate with different potencies among brain regions [12]. The decrease in DA, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) tissue contents as well as DNA damage also suggested the neurotoxicity of 5-MeO-DIPT [12]. The study also supported the idea that the hallucinogenic activity of 5-MeO-DIPT is mediated through 5-HT1A and 5-HT2A receptors, because 5-MeO-DIPT induced headtwitch response and potentiated forepaw treading induced by 7-(dipropylamino)-5,6,7,8-tetrahydronaphthalen-1-ol (8-OH-DPAT) [13]. Reports by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) [14] have indicated an increased abuse of new psychoactive substances (NPS) by adolescents. Exposure to NPS during adolescence may have an impact on brain development and may lead to neuropsychiatric disorders in adulthood. Several studies in adolescent animals showed their greater addictive potential in behavioral studies with cocaine [15] or ethanol [16]. Adolescent rats were also more sensitive than adult animals for cataleptic effect of haloperidol [17, 18] or hyperlocomotion induced by morphine [19]. The ontogenetic variations in drug response may result from age-related differences in pharmacokinetics, drug metabolism and excretion rates [20]. It was shown that exposure to ethanol and cocaine during adolescence significantly increased aggressive behavior in adult rodents [16, 21]. Moreover, adults who used marijuana before 15 years of age were 6 times more likely to be dependent on an illicit drug than adults who first used marijuana at 21 years of age or older [22]. The age of first NPS use may be a critical factor for illicit drug use in adulthood. For instance, adults who used marijuana before 15 years of age reported lifetime cocaine and heroin use and nonmedical use of other drugs [22]. Thus, NPS exposure during adolescence may result in severe, long-term and adverse effects in adult life. Unfortunately, there are no direct follow-up human studies in the 13 literature of subjects abusing NPS in adolescence and the effects in adulthood. The aim of the present study was to find out whether exposure of rats to repeated doses of 5-MeO-DIPT during adolescence [postnatal days (PND) from 30 to 40] may have impact on brain neurotransmission in adulthood. Th (...truncated)