Association of derived patterns of musculoskeletal disorders with psychological problems: a latent class analysis

BACKGROUND@#Musculoskeletal symptoms often occur in more than one anatomical site. The present study aimed to define specific patterns of multisite musculoskeletal disorders and examine how these patterns are related to common psychological problems.@*METHODS@#Using the data from an interview-based health survey of 358 samples of the industrial manufacturing male employees, we derived major patterns of musculoskeletal complaints using latent class analysis and investigated its association with psychological problems score extracted from depression, anxiety, and stress measured by Depression/Anxiety/Stress Scale (DASS-21). Musculoskeletal disorders were assessed by Nordic Musculoskeletal Questionnaire (NMQ). The statistical analysis was carried out by Mplus 8.@*RESULTS@#Complaints in the lower back (42.1%) and neck (30.7%) had the highest prevalence, and in the hip (15.0%) and ankle (12.2%) the lowest. Three major patterns of musculoskeletal disorders were extracted using latent class analysis. Class 1 (12.9%) was characterized by a high rate of complaints in upper musculoskeletal sites, such as the neck, shoulder, and joints; class 2 (38.2%) was identified by a higher rate of complaints in the lower and upper back; and class 3 (48.9%) was marked by low rates of complaints in all musculoskeletal sites. After adjustment for confounding variables and specifying class 3 as the reference, it turned out that there was a statistically significant association between the psychological problems score and the chance of being in class 1 (OR = 2.47, 95% CI 1.66-3.68), but not a significant association with the chance of being in class 2 (OR = 1.51, 95% CI 0.83-2.72).@*CONCLUSION@#Musculoskeletal disorders can be summarized in the latent class-derived patterns in the adult study population and provide additional prognostics. Common psychological problems are significantly associated with the type of musculoskeletal disorder patterns. The findings in this study could be useful for dealing with prevention and treatment programs.

Effects of Temporary Inactivation and Electrical Stimulation of the Dorsal Raphe Nucleus on Morphine-induced Conditioned Place Preference

Background: The dorsal raphe nucleus (DRN) influences a wide range of behavioral and reward function. In this study, we evaluated electrical stimulation and inactivation of DRN on morphine conditioned place preference (CPP). Methods: The rats were anesthetised (n = 7 for each group) and the electrode and cannula were implanted into the DRN by stereotaxic instrument. Electrical stimulation (100μA) and reversible inactivation by lidocaine were induced into DRN and then morphine-induced CPP was investigated. Results: The stimulation of DRN in combination with effective dose of morphine showed a significant decrease only on expression phases 20s (SD 33.7) when compared with morphine group 119.85s (SD 23.7) (One way ANOVA, Tukey’s; P = 0.036). Also, this stimulation in combination with ineffective dose of morphine showed a significant increase only on acquisition phases 67.5s (SD 41.2) of CPP compared with morphine group -46s (SD 18.51) (P = 0.034). Also, there were not significant differences in inactivation of DRN by lidocaine on different phase of CPP (P = 0.091). Conclusion: It is possible that electrical stimulation of the DRN with changes in concentration of serotonin or involving other transmitters such as glutamate and gamma amino butyric acid (GABA) would be involved to these changes of CPP.

Roles of the nucleus accumbens [shell] in the acquisition and expression of morphine-induced conditioned behavior in freely moving rats

The nucleus accumbens [NAc] is a part of the rewarding cortico mesolimbic dopamine [DA] pathway. This is a heterogeneous structure divided in two sub regions termed core and shell. DA function in the NAc is critical for goal oriented behaviors, including those motivated by drug and brain stimulation reward. In the conditioned-place preference [CPP] paradigm, a test assessing animal's ability to associate drug induced effects with environmental cause to quantify drug reward for example morphine. In the present study, we investigated the influence of electrical stimulation with different current intensities on [25 and 100 micro A] with and without an effective dose of morphine [0.5 and 5 mg/kg] on CPP. Subcutaneous administration of morphine 5 mg/kg produced significant CPP in comparison with saline group. Our findings also showed that electrical stimulation of NAc [100 micro A] significantly [P < 0.01] suppressed morphine-induced CPP that reveals impaired learning and memory formation in the process of conditioning. We found that morphine induced CPP can be successfully suppressed by current intensity [100 micro A]. It was probably due to decreasing of dopamine contents and its metabolites in the NAc. Current intensity [100 micro A] in combination with ineffective dose of morphine [0.5 mg/kg] increased morphine induced CPP probability via the prove reward system. Since stimulation of dopaminergic neurons increases tendency to dependence to morphine, therefore in the present study, the stimulation of the NAc suppressed morphine induced CPP that this shows impairment of learning and memory formation

Reversal effect of intra-central henobar microinjection of L-arginine on place aversion induced by naloxone in morphine conditioned rats

Role of nitric oxide [NO] on expression of morphine conditioning using a solely classic task has been proposed previously. In this work, the involvement of NO on the expression of opioid-induced conditioning in the task paired with an injection of naloxone was investigated. Conditioning was established in adult male Wistar rats [weighing 200-250 g] using an unbiased procedure. Naloxone [0.05-0.4 mg/kg, i.p.], a selective antagonist of mu-opioid receptor, was administered once prior to morphine response testing. NO agents were administered directly into the central henobar [CeA] prior to naloxone injection pre-testing. Morphine [2.5-10 mg/kg, s.c.] produced a significant dose-dependent place preference in experimental animals. When naloxone [0.05-0.4 mg/kg, i.p.] was injected before testing of morphine [5 mg/kg, s.c.] response, the antagonist induced a significant aversion. This response was reversed due to injection of L-arginine [0.3-3 micro g/rat], intra-CeA prior to naloxone administration. However, pre-injection of L-NAME [intra-CeA], an inhibitor of NO production, blocked this effect. The finding may reflect that NO in the nucleus participates in morphine plus naloxone interaction

Blockade of the naloxone-induced aversion in morphine-conditioned wistar rats by L-arginine intra-central amygdale

Single injection of naloxone, a selective antagonist of morphine, prior to the drug conditioning testing was used to investigate on morphine dependence. Conditioning to morphine [2.5-10 mg/kg, s.c.] was established in adult male Wistar rats [weighing 200-250 g] using an unbiased procedure. Nitric oxide agents were microinjected into the central amygdale prior to naloxone-paired place conditioning testing. The results showed that morphine produced a significant dose-dependent place preference in animals. Naloxone [0.1-0.4 mg/kg, i.p.] injections pre-testing of the response to morphine [7.5 mg/kg, s.c.] caused a significant aversion at the higher doses [0.4 mg/kg, i.p.]. This response was reversed by microinjection of L-arginine [0.3-3 micro g/rat, intra-central amygdale] prior to naloxone on the day of the testing. The response to L-arginine was blocked by pre-injection of N[G]-nitro-L-arginine methyl ester [L-NAME] intra-central amygdale]. A single injection of naloxone on the test day of morphine place conditioning may simply reveal the occurrence of morphine dependence in rats, and that the nitric oxide in the central amygdale most likely plays a key role in this phenomenon