Effects of acute and subacute cocaine administration on the CNS dopaminergic system in Wistar-Kyoto and spontaneously hypertensive rats: I. Levels of dopamine and metabolites

Acupuncture Treatment Reduces Incidence of Parkinson's Disease in Patients With Depression: A Population-Based Retrospective Cohort Study in Taiwan

Depression is a risk factor for subsequent Parkinson's disease (PD). Some patients with depression undergo acupuncture treatment because of other diseases in Taiwan. Therefore, the present study used data from Taiwan's National Health Insurance Research Database (NHIRD) to investigate the incidence of PD in patients having depression with and without acupuncture treatment. We conducted a retrospective study of a matched cohort of 48,981 patients with newly diagnosed depression between 2000 and 2012 who were selected from the NHIRD. The 1:1 propensity score method was utilized to match an equal number of patients (N = 9,189) in the acupuncture and non-acupuncture cohorts. We employed Cox proportional hazard models to evaluate the risk of PD. The cumulative incidence of PD in both cohorts was estimated using the Kaplan–Meier method, and the difference was examined through a log-rank test. Patients with depression who received acupuncture treatment demonstrated a lower risk of PD [adjusted hazard ratio (aHR) = 0.39, 95% confidence interval = 0.31–0.49] than those who did not undergo acupuncture treatment, after adjusting for age, sex, insurance amount, geographic region, urbanization levels, comorbidities, and drugs. The cumulative incidence of PD was significantly lower in the acupuncture cohort than in the non-acupuncture cohort (log-rank test, p < 0.001). The database did not indicate the severity of depression and acupoints. The results suggest that acupuncture treatment significantly reduced the development of PD in patients with depression; however, a future study should be conducted to provide more objective evidence.

Dopaminergic Modulation of Goal-Directed Behavior in a Rodent Model of Attention-Deficit/Hyperactivity Disorder

Aside from its clinical symptoms of inattention, impulsivity and hyperactivity, patients with Attention/Deficit-Hyperactivity Disorder (ADHD) display reward and motivational impairments. These impairments may reflect a deficit in action control, that is, an inability to flexibly adapt behavior to changing consequences. We previously showed that spontaneously hypertensive rats (SHR), an inbred rodent model of ADHD, show impairments in goal-directed action control, and instead are predominated by habits. In this study, we examined the effects of specific dopamine receptor sub-type (D1 and D2) agonists and antagonists on goal-directed behavior in SHR and the normotensive inbred control strain Wistar-Kyoto (WKY) rats. Rats acquired an instrumental response for different-flavored food rewards. A selective-satiety outcome devaluation procedure followed by a choice test in extinction revealed outcome-insensitive habitual behavior in SHR rats. Outcome-sensitive goal-directed behavior was restored in SHR rats following injection prior to the choice test of the dopamine D2 receptor agonist Quinpirole or dopamine D1 receptor antagonist SCH23390, whereas WKY rats showed habitual responding following exposure to these drugs. This novel finding indicates that the core behavioral deficit in ADHD might not be a consequence of dopamine hypofunction, but rather is due to a misbalance between activation of dopamine D1 and D2 receptor pathways that govern action control.

Ontogeny of cocaine-induced behaviors and cocaine pharmacokinetics in male and female neonatal, preweanling, and adult rats

RATIONALE

Ontogenetic differences in the behavioral responsiveness to cocaine have often been attributed to the maturation of dopaminergic elements (e.g., dopamine transporters, D2High receptors, receptor coupling, etc.).

OBJECTIVE

The purpose of this study was to determine whether ontogenetic changes in cocaine pharmacokinetics might contribute to age-dependent differences in behavioral responsiveness.

METHODS

Male and female neonatal (PD 5), preweanling (PD 10 and PD 20), and adult (PD 70) rats were injected (IP) with cocaine or saline and various behaviors (e.g., locomotor activity, forelimb paddle, vertical activity, head-down sniffing, etc.) were measured for 90 min. In a separate experiment, the dorsal striata of young and adult rats were removed at 10 time points (0-210 min) after IP cocaine administration. Peak cocaine values, cocaine half-life, and dopamine levels were determined using HPLC.

RESULTS

When converted to percent of saline controls, PD 5 and PD 10 rats were generally more sensitive to cocaine than older rats, but this effect varied according to the behavior being assessed. Peak cocaine values did not differ according to age or sex, but cocaine half-life in brain was approximately 2 times longer in PD 5 and PD 10 rats than adults. Cocaine pharmacokinetics did not differ between PD 20 and PD 70 rats.

CONCLUSIONS

Differences in the cocaine-induced behavioral responsiveness of very young rats (PD 5 and PD 10) and adults may be attributable, at least in part, to pharmacokinetic factors; whereas, age-dependent behavioral differences between the late preweanling period and adulthood cannot readily be ascribed to cocaine pharmacokinetics.

In vivo basal and amphetamine-induced striatal dopamine and metabolite levels are similar in the spontaneously hypertensive, Wistar–Kyoto and Sprague–Dawley male rats

Nigrostriatal alterations are proposed to partially underlie the hypertension and hyperactivity exhibited by the spontaneously hypertensive rat (SHR). Here, in vivo microdialysis was used to measure baseline and d-amphetamine (AMPH)-stimulated striatal dopamine (DA) and metabolite levels in adult male SHR, Wistar-Kyoto (WKY), and Sprague-Dawley (SD) rats. At approximately 19 weeks of age, baseline levels of DA, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were measured after which time, each rat was injected intraperitoneally with 2 mg/kg AMPH and samples were collected for the subsequent 200 min. There were no significant strain differences in baseline levels of DA, HVA, and 5-HIAA. The baseline level of DOPAC was decreased in the WKY relative to the SD. AMPH treatment altered DA, DOPAC, HVA, and 5-HIAA to a similar extent in all strains; thus, there were no significant strain differences, nor did the area under the curve (AUC) for DA levels differ between strains. AUC for DOPAC was significantly smaller for the WKY relative to the SD strain, likely due to the lower baseline level. At the single dose of amphetamine used here, the results indicate that in vivo DA levels in the SHR are similar to the WKY and SD strains.

Effects of acute and chronic ethanol administration on neurotensinergic systems

A summary of pharmacogenetic studies designed to test the hypothesis that NT receptors might mediate or regulate some of the actions of ethanol is presented. Indeed, there are significant genetic correlations between ethanol-induced locomotor activation and high-affinity NT receptor densities in the FC. The results suggest that further studies are needed to determine the role of NT receptors in the FC and MPFC in regulating locomotor activity. In other studies, chronic ethanol treatment, under conditions that produced tolerance to ethanol and caused NT receptor downregulation in the NA and VMB, caused tolerance to locomotor inhibitory effects of centrally administered NT and blunted the effects of intra-VTA NT on dopamine metabolism in the NA and CP. The results show a relationship between NT receptor densities and pharmacological effects of ethanol.

Site and mechanism of behavioral tolerance to cocaine: a study of dopamine release in Wistar-Kyoto and spontaneously hypertensive rats

Wistar-Kyoto and spontaneously hypertensive rats received i.v. infusions of cocaine hydrochloride (60 mg/kg per day) for 3, 7, and 14 days, or saline for 7 days. Acute cocaine challenge (40 mg/kg, s.c.) was given to treated and control rats 24 hr after the termination of each infusion period. There were no strain differences in brain levels of cocaine during cocaine infusion, nor after cocaine challenges. There were no strain differences in resting levels of [3H]dopamine release. Release of [3H]dopamine decreased in nuclei accumbens of 7- and 14-day cocaine-infused animals. Release of [3H]dopamine was maximal in both brain regions 2 hr after acute cocaine challenge. After 14 days of cocaine infusion, cocaine challenge in both strains reduced [3H]dopamine release in the nucleus accumbens, but not in the striatum; the reduction being greater in Wistar-Kyoto rats. The behavioral tolerance which accompanies similar cocaine infusion regimens may be related to striatal "tolerance" to cocaine-induced dopamine release.

Up-regulation of dopamine receptors in the brain of the spontaneously hypertensive rat: an autoradiographic analysis

Recent evidence points to a dysfunction of brain dopaminergic mechanisms in the spontaneously hypertensive rat. Using in vitro receptor autoradiography, we assessed the density of D1 and D2 dopamine receptors in the brain of spontaneously hypertensive rats and their normotensive controls the Wistar-Kyoto rat. Brain sections from five- and 15-week-old rats were incubated with 1 nM [3H]SCH 23390 (D1 receptor antagonist) or 15 nM [3H]sulpiride (D2 receptor antagonist), and exposed along with radioactive standards to 3H-Hyperfilm. The binding density of selected brain regions (anteromedial prefrontal cortex, cingulate cortex, lateral septal nucleus, nucleus accumbens, caudate-putamen, globus pallidus, amygdaloid complex) were quantified using computer-assisted densitometry. These experiments showed a significant increase in the binding density of [3H]SCH 23390 in the nucleus accumbens and caudate-putamen of five- and 15-week-old spontaneously hypertensive rats. The binding density of [3H]SCH 23390 was increased in the lateral septal nucleus of five-week-old and globus pallidus of 15-week-old spontaneously hypertensive rats. The binding density of [3H]sulpiride was also greater in the nucleus accumbens of five-week-old spontaneously hypertensive rats. The present investigation demonstrates an up-regulation of D1 dopamine receptors in spontaneously hypertensive rats with established hypertension. More importantly, up-regulation of D1 and D2 dopamine receptors in the striatum of young prehypertensive spontaneously hypertensive rats suggests that dopamine may be involved in the pathogenesis of hypertension in this strain of genetically hypertensive rats.

Cocaine elevates striatal dopamine efflux in spontaneously hypertensive and Wistar-Kyoto rats

The effects of acute cocaine administration on central dopaminergic systems were examined in the striata of spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats with the use of an in vivo microdialysis technique. Increased extracellular levels of dopamine were observed for 45 to 75 minutes following acute cocaine administration in both halothane-anesthetized and conscious SHR and WKY. However, no significant differences were noted between anesthetized and conscious SHR and WKY in either baseline levels or cocaine-induced changes in extracellular levels of dopamine and its metabolites. A positive, linear correlation between extracellular levels of dopamine and cocaine was demonstrated for the 60-min period following acute cocaine administration in both SHR and WKY. The slopes of the linear regression plots obtained from the data of each 15-min sample was slightly, but significantly, higher in conscious SHR than in conscious WKY. The present results suggest a transient and dose-related stimulation of striatal dopamine release following acute cocaine administration and a linear relationship between striatal extracellular levels of dopamine and cocaine in both SHR and WKY.

Dopamine receptors mediate cocaine-induced temperature responses in spontaneously hypertensive and Wistar-Kyoto rats

The involvement of dopaminergic receptors in the responses of conscious, restrained spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats to cocaine was examined using antagonists selective for DA-1 (SCH 23390) or DA-2 (sulpiride) dopamine receptors. Following pretreatment with saline vehicle, SCH 23390 (50 mg/kg, SC), sulpiride (50 mg/kg, IP) or SCH 23390 and sulpiride, cocaine was infused (1.25 mg/kg.min, IV) until death. Cocaine caused an initial pressor and tachycardiac response, which was followed by a progressively developing secondary pressor response. Combined (DA-1 and DA-2) antagonist pretreatment abolished the initial tachycardic response to cocaine. Rectal temperature during cocaine infusion increased in 38.5% of vehicle-treated SHR (designated SHRH), but decreased in the remaining SHR (SHRL) and all vehicle-treated WKY. The time-to-onset of cocaine-induced convulsions (Tc) was reduced in vehicle-treated SHRH compared to vehicle-treated SHRL and WKY. Sulpiride elevated rectal temperature in response to cocaine in SHR and WKY but reduced Tc only in SHR. SCH 23390 abolished hyperthermic responses to cocaine in SHR without altering toxicity in SHR or WKY. Combined pretreatment virtually abolished temperature responses to cocaine in SHR and WKY, but increased the Tc only in WKY. Dopamine receptors, particularly the DA-1 subtype, are involved in cocaine-induced hyperthermia.