br Novel mechanisms of fipronil resistance in planthoppers

Novel mechanisms of fipronil resistance in planthoppers
Conclusion
Conflict of interest
Introduction Methamphetamine, a widely abused drug, is mainly used as a psychostimulant although it is occasionally used at low doses for medical purposes, such as in attention deficit or hyperactivity disorder [7]. In the mesolimbic system of the brain, dopaminergic neurons projecting from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) are thought to play a pivotal role in the rewarding effects of abused drugs. Methamphetamine administration results in increased dopamine (DA) release in the NAc, known as the reward center; this increase in DA levels is responsible for the reinforcing effects of the psychostimulant, driving individuals to abuse [8], [19]. Acutely, methamphetamine tends to reduce appetite and increase motor activity, respiration, heart rate, and body temperature. Chronic administration induces a number of psychiatric problems, such as anxiety, confusion, insomnia, loss of memory, and aggressive behavior. Cardiomyopathy and decreased immune function are also associated with methamphetamine use [21], [28]. In addition, the chronic use of methamphetamine produces structural and functional changes in the brain. Therefore, the development of an innovative treatment for methamphetamine abuse is urgently needed [26]. Acupuncture, a traditional therapy practiced in eastern Asia, has been gaining interest as a useful treatment for drug addiction [1], [2]. Indeed, a lot of studies have demonstrated that acupuncture is effective in suppressing the reinforcing effects of abused drugs such as cocaine, nicotine, morphine, and alcohol [3], [5], [6], [9], [10], [11], [12], [13], [14], [15], [16], [17], [20], [23], [29], [30], [32]. Notably, one study showed that acupuncture attenuated hyper locomotor activity and abnormal c-Fos gene E3330 in the NAc induced by acute methamphetamine administration [6]. In addition, acupuncture has shown to suppress the behavioral sensitization and conditioned place preference induced by methamphetamine, with regulating the levels of dopamine, tyrosine hydroxylase and monoamine oxidase in the NAc [8]. This suggests that acupuncture may have a suppressive effect on methamphetamine abuse.
Materials and methods
Results
Discussion The first experiment investigated whether acupuncture had inhibitory effects on methamphetamine self-administration behavior. After methamphetamine self-administration training, the animals had shown similar baseline numbers of infusions, implying that they had taken similar amount of methamphetamine (Fig. 1A). On the test day, however, acupuncture at the specific acupoint HT7, but not at the control acupoint LI5, markedly suppressed the methamphetamine self-administration behavior. Acupuncture at HT7 reduced the infusion of methamphetamine to 21.66% of the control group (Fig. 1C). When compared to the baseline, acupuncture at HT7 suppressed the percentage of infusions in the test session to 25.43% of the control level (Fig. 1D). Active lever responses were decreased to 21.15% of the control group (Fig. 1B). In a previous study, acupuncture had a suppressive effect on the hyper locomotor activity and c-Fos expression in the NAc induced by an acute methamphetamine [6], indicating that acupuncture inhibited the reinforcing effect of methamphetamine. Those results parallel the present study. In Oriental medicine, brain functionally has a strong relationship with the heart and belongs to Fire among the five elements. Also in meridian theory, Fire corresponds to the heart meridian. Accordingly, HT, the Source point of heart meridian, is thought to be relevant for neuropsychiatric diseases associated with the brain, like addiction. Indeed, HT7 has shown ameliorating effects in a number of drug addiction studies [3], [4], [6], [12], [13], [23], [30], [32]. Therefore, it is reasonable that acupuncture at HT7 inhibited methamphetamine self-administration.