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Methiopropamine is a structural analog of methamphetamine that is categorized as a novel psychoactive substance. It primarily acts as a norepinephrine–dopamine reuptake inhibitor and, secondarily, as a serotonin reuptake inhibitor. In humans, methiopropamine induces stimulation and alertness and increases focus and energy. However, significant side effects are reported, such as tachycardia, anxiety, panic attacks, perspiration, headache, and difficulty in breathing. To date, little data is available regarding its pharmacodynamic effects, thereby we aimed to investigate the acute in vivo effects induced by this drug on sensorimotor responses, body temperature, pain thresholds, motor activity, and cardiovascular and respiratory systems in CD-1 male mice. We selected a range of doses that correspond to the whole range of human reported use, in order to evaluate the threshold of adverse effects presentation. This study demonstrates that methiopropamine acts as a dopaminergic and noradrenergic stimulating drug and that the highest doses (10–30 mg/kg) impair the visual placing response, facilitate the acoustic and tactile response, induce hypothermia, increase mechanical and thermal analgesia, stimulate locomotor activity, induce motor stereotypies, and strongly affected cardiovascular and respiratory parameters, increasing heart rate, breath rate, and blood pressure but reducing oxygen saturation. On the contrary, lower doses do not show any of those effects. We hypothesize that there is a range of doses that do enhance performance but do not seem hazardous to users: this gap could induce the perception of safety and increase the abuser population.

Highlights • The mechanisms behind the effects of IN-applied substances need more attention. • The mechanisms involved in the brain-distribution of IN-OT are completely unexplored. • The possibly cascading effects of IN-OT on the intrinsic OT-system require serious investigation. • IN-OT induces clear and specific changes in neural activation. • IN-OT is a promising approach to treat certain clinical symptoms., The intranasal (IN-) administration of substances is attracting attention from scientists as well as pharmaceutical companies. The effects are surprisingly fast and specific. The present review explores our current knowledge about the routes of access to the cranial cavity. ‘Direct-access-pathways’ from the nasal cavity have been described but many additional experiments are needed to answer a variety of open questions regarding anatomy and physiology. Among the IN-applied substances oxytocin (OT) has an extensive history. Originally applied in women for its physiological effects related to lactation and parturition, over the last decade most studies focused on their behavioral ‘prosocial’ effects: from social relations and ‘trust’ to treatment of ‘autism’. Only very recently in a microdialysis study in rats and mice, the ‘direct-nose-brain-pathways’ of IN-OT have been investigated directly, implying that we are strongly dependent on results obtained from other IN-applied substances. Especially the possibility that IN-OT activates the ‘intrinsic’ OT-system in the hypothalamus as well needs further clarification. We conclude that IN-OT administration may be a promising approach to influence human communication but that the existing lack of information about the neural and physiological mechanisms involved is a serious problem for the proper understanding and interpretation of the observed effects.

Background After several decades of commercial use, the flame-retardant chemicals polybrominated diphenyl ethers (PBDEs) and their metabolites are pervasive environmental contaminants and are detected in the human body. Decabrominated diphenyl ether (decaBDE) is currently the only PBDE in production in the United States. Objectives Little is known about the health effects of decaBDE. In the present study we examined the effects of neonatal decaBDE exposure on behavior in mice at two ages. Methods Neonatal male and female C57BL6/J mice were exposed to a daily oral dose of 0, 6, or 20 mg/kg decaBDE from postnatal days 2 through 15. Two age groups were examined: a cohort that began training during young adulthood and an aging cohort of littermates that began training at 16 months of age. Both cohorts were tested on a series of operant procedures that included a fixed-ratio 1 schedule of reinforcement, a fixed-interval (FI) 2-min schedule, and a light–dark visual discrimination. Results We observed minimal effects on the light–dark discrimination in the young cohort, with no effects on the other tasks. The performance of the aging cohort was significantly affected by decaBDE. On the FI schedule, decaBDE exposure increased the overall response rate. On the light–dark discrimination, older treated mice learned the task more slowly, made fewer errors on the first-response choice of a trial but more perseverative errors after an initial error, and had lower latencies to respond compared with controls. Effects were observed in both dose groups and sexes on various measures. Conclusions These findings suggest that neonatal decaBDE exposure produces effects on behavioral tasks in older but not younger animals. The behavioral mechanisms responsible for the pattern of observed effects may include increased impulsivity, although further research is required.

Background Although a long latency period of toxicity after exposure to methylmercury (MeHg) is known to exist in humans, few animal studies have addressed this issue. Substantiation of delayed MeHg toxicity in animals would affect the risk evaluation of MeHg. Objectives Our goal in this study was to demonstrate the existence of a latency period in a rodent model in which the toxicity of perinatal MeHg exposure becomes apparent only later in life. Our study included metallothionein (MT) knockout mice because studies have suggested the potential susceptibility of this strain to the neurodevelopmental toxicity of MeHg. Methods Pregnant MT-null and wild-type C57Bl/6J mice were exposed to MeHg through their diet containing 5 μg Hg/g during gestation and early lactation. We examined behavioral functions of the offspring using frequently used paradigms, including open field behavior (OPF), passive avoidance (PA), and the Morris water maze (MM), at ages of 12–13 and 52–53 weeks. Results At 12 weeks of age, behavioral effects of MeHg were not detected, except for OPF performance in MeHg-exposed MT-null females. At 52 weeks of age, the MeHg-exposed groups showed poorer performance both in PA and MM, and their OPF activity differed from controls. These effects of MeHg appeared exaggerated in the MT-null strain. The brain Hg concentration had leveled off by 13 weeks of age. Conclusions The results suggest the existence of a long latency period after perinatal exposure to low-level MeHg, in which the behavioral effects emerged long after the leveling-off of brain Hg levels. Hence, the initial toxicologic event responsible for the late effects should have occurred before this leveling-off of brain Hg.

A high-affinity positive modulator of the GABA, receptor complex, ganaxolone, is a 3 beta-methylated analog of the naturally occurring neuroactive steroid allopregnanolone. in the present study, ganaxolone was tested for its ability to (1) suppress seizures (clonic and tonic) and lethality induced by pentylenetetrazol (PTZ) in PTZ-kindled mice (anticonvulsive effect) and (2) to attenuate the development of sensitization to the convulsive and lethal effects of PTZ in kindled mice (anti-epileptogenic effect) when given as a pretreatment prior to each PTZ injection during kindling acquisition. Two classical antiepileptic drugs, diazepam and valproate, were tested for comparison. All three drugs dose-dependently suppressed tonic seizures and lethality induced by PTZ in kindled mice; only ganaxolone was effective against clonic seizures. Ganaxolone showed anti-epileptogenic properties as it reduced the sensitivity of kindled mice to the convulsive (clonic and tonic seizures) and lethal effects of PTZ, Diazepam showed anti-epileptogenic effects against tonic seizures and lethality, but not clonic seizures; valproate was ineffective in preventing development of any of these effects. Sensitivity to PTZ-induced seizures and lethality was not affected in mice with a history of repeated treatment with ganaxolone, diazepam, or valproate. The drugs had effects on ambulatory activity that ranged from no effect (ganaxolone) through moderate impairment (diazepam) to marked disruption (valproate). Taken together, the results of the present study add to accumulating evidence of the unique anticonvulsive/behavioral profile of neuroactive steroids. (C) 2000 Elsevier Science Ltd. All rights reserved.