Direct and Systemic Administration of a CNS-Permeant Tamoxifen Analog Reduces Amphetamine-Induced Dopamine Release and Reinforcing Effects.

Amphetamines (AMPHs) are globally abused. With no effective treatment for AMPH addiction to date, there is urgent need for the identification of druggable targets that mediate the reinforcing action of this stimulant class. AMPH-stimulated dopamine efflux is modulated by protein kinase C (PKC) activation. Inhibition of PKC reduces AMPH-stimulated dopamine efflux and locomotor activity. The only known CNS-permeant PKC inhibitor is the selective estrogen receptor modulator tamoxifen. In this study, we demonstrate that a tamoxifen analog, 6c, which more potently inhibits PKC than tamoxifen but lacks affinity for the estrogen receptor, reduces AMPH-stimulated increases in extracellular dopamine and reinforcement-related behavior. In rat striatal synaptosomes, 6c was almost fivefold more potent at inhibiting AMPH-stimulated dopamine efflux than [3H]dopamine uptake through the dopamine transporter (DAT). The compound did not compete with [3H]WIN 35,428 binding or affect surface DAT levels. Using microdialysis, direct accumbal administration of 1 µM 6c reduced dopamine overflow in freely moving rats. Using LC-MS, we demonstrate that 6c is CNS-permeant. Systemic treatment of rats with 6 mg/kg 6c either simultaneously or 18 h prior to systemic AMPH administration reduced both AMPH-stimulated dopamine overflow and AMPH-induced locomotor effects. Finally, 18 h pretreatment of rats with 6 mg/kg 6c s.c. reduces AMPH-self administration but not food self-administration. These results demonstrate the utility of tamoxifen analogs in reducing AMPH effects on dopamine and reinforcement-related behaviors and suggest a new avenue of development for therapeutics to reduce AMPH abuse.

Effects of obstetric complications on volume and functional connectivity of striatum in anorexia nervosa patients.

OBJECTIVE: To investigate the volume and functional connectivity of dorsal and ventral striatal nuclei in anorexia nervosa (AN) and their relationship with early exposure to obstetric complications. METHOD: Fifty-one patients with lifetime AN (35 acute, 16 recovered) and 34 healthy controls underwent high-resolution and resting-state functional magnetic resonance imaging. RESULTS: The AN group showed reduced functional connectivity of the putamen compared with healthy women, and this reduction was more evident in patients with lifetime binge eating/purging. Both acute and recovered AN groups showed a larger left accumbens area compared with that of healthy women. The functional connectivity of bilateral nucleus accumbens and putamen showed significant negative correlations with number of obstetric complications in the AN group. DISCUSSION: This study supports the hypothesis that AN is associated with structural and functional alterations of striatal networks, and reveals the possible role of obstetric complications in the pathogenesis of striatal dysfunction.

Effects of exposure to moderate levels of ethanol during prenatal brain development on dendritic length, branching, and spine density in the nucleus accumbens and dorsal striatum of adult rats.

Reductions in measures of dendritic morphology in the agranular insular cortex have been identified as consequences of prenatal exposure to moderate levels of ethanol in the rat. Motivated by the strong connectivity between this region of frontal cortex and the striatum and a growing body of data linking specific components of the mesocortical/limbic system to effects of ethanol and ethanol self-administration, the current study investigated the effects of moderate fetal ethanol exposure on the dendritic morphology of medium spiny neurons (MSNs) in several regions of the striatum. Throughout gestation, pregnant rat dams either consumed a saccharin solution (control) or achieved average daily blood ethanol concentrations of 84 mg% via voluntary consumption of a 5% ethanol solution. The brains of adult male offspring were extracted and processed for Golgi-Cox staining. MSNs from the dorsomedial striatum, dorsolateral striatum and the nucleus accumbens core and shell were sampled for analysis. Relative to saccharin controls, robust reductions in dendritic length and branching, but not spine density, were observed in the shell of the nucleus accumbens in fetal-ethanol-exposed rats. No significant prenatal ethanol effects were found in the other regions of the striatum. These findings suggest that exposure to moderate levels of ethanol in utero can have profound effects on brain regions related to reward processing and provide possible clues relevant to understanding increased self-administration of drugs of abuse in animals exposed to ethanol during brain development.

[Effects of heroin exposure on the expression of caspase 3 in prefrontal lobe cortex, hippocampus and nucleus accumbens].

AIM: To investigate the expression of caspase 3 in the brain regions related to addiction, learning and memory in mice prenatally exposed to heroin and to ascertain whether postnatal apoptotic mechanism participates in neurobehavioral teratogenicity induced by maternal heroin abuse. METHODS: A mouse model was established by administration of diacetylmorphine (heroin, purity 98.5%, product ID No.171206-200614) 10 mg/(kg x d) subcutaneously to pregnant BALB/c mice on embryonic day (E)E8-E18. The offspring were divided into heroin(Her) and saline(Sal) groups according to the maternal treatment. The expression of caspase 3 in prefrontal lobe cortex(PFC), hippocampus(HP) and nucleus accumbens(Acb) was detected by RT-PCR and Western blot on mouse postnatal day(P)14. RESULTS: The mRNA and protein expression of caspase 3 were significantly increased in the areas of PFC, HP and Acb in Her group compared with Sal group(P < 0.05). CONCLUSION: E8-E18 prenatal exposure to heroin can induce apoptosis through caspase 3 activation in brain regions related to addiction, learning and memory, which indicates that apoptotic mechanism may be involved in neurobehavioral teratogenicity by heroin exposure in uterus.

Neurturin exerts potent actions on survival and function of midbrain dopaminergic neurons.

Glial cell line-derived neurotrophic factor (GDNF) exhibits potent effects on survival and function of midbrain dopaminergic (DA) neurons in a variety of models. Although other growth factors expressed in the vicinity of developing DA neurons have been reported to support survival of DA neurons in vitro, to date none of these factors duplicate the potent and selective actions of GDNF in vivo. We report here that neurturin (NTN), a homolog of GDNF, is expressed in the nigrostriatal system, and that NTN exerts potent effects on survival and function of midbrain DA neurons. Our findings indicate that NTN mRNA is sequentially expressed in the ventral midbrain and striatum during development and that NTN exhibits survival-promoting actions on both developing and mature DA neurons. In vitro, NTN supports survival of embryonic DA neurons, and in vivo, direct injection of NTN into the substantia nigra protects mature DA neurons from cell death induced by 6-OHDA. Furthermore, administration of NTN into the striatum of intact adult animals induces behavioral and biochemical changes associated with functional upregulation of nigral DA neurons. The similarity in potency and efficacy of NTN and GDNF on DA neurons in several paradigms stands in contrast to the differential distribution of the receptor components GDNF Family Receptor alpha1 (GFRalpha1) and GFRalpha2 within the ventral mesencephalon. These results suggest that NTN is an endogenous trophic factor for midbrain DA neurons and point to the possibility that GDNF and NTN may exert redundant trophic influences on nigral DA neurons acting via a receptor complex that includes GFRalpha1.

Neurogenesis in the mammalian neostriatum and nucleus accumbens: parvalbumin-immunoreactive GABAergic interneurons.

We study the neurogenesis of a distinct subclass of rat striatum gamma-aminobutyric acid (GABA)ergic interneurons marked by the calcium-binding protein parvalbumin (PV). Timed pregnant rats are given an intraperitoneal injection of bromodeoxyuridine (BrdU), a marker of cell proliferation, on designated days between embryonic day (E) 11 and E22. Birthdate of PV neurons is determined in the adult neostriatum and nucleus accumbens by using a BrdU-PV double-labeling immunohistochemical technique. PV-immunoreactive interneurons of the neostriatum show maximum birthrates (>10% double-labeling) between E14-E17, whereas PV-immunoreactive interneurons of the nucleus accumbens show maximum double-labeling between E16-E19. In the neostriatum, caudal PV-immunoreactive neurons are born before those at rostral levels, and lateral PV-immunoreactive neurons become postmitotic before medial neurons. In the postcommissural striatum, ventral PV-immunoreactive neurons become postmitotic before dorsal neurons. In the precommissural striatum, ventral neurons are born before dorsal neurons laterally, but a dorsoventral gradient is seen medially. At corresponding coronal levels, PV-immunoreactive neurons of the nucleus accumbens are born shortly after PV neurons of the neostriatum. Analysis of BrdU labeling intensity in the nucleus accumbens shows that medium spiny projection neurons of the shell become postmitotic before neurons of the core. Similarly, PV-immunoreactive interneurons of the nucleus accumbens shell are born before PV interneurons of the core. Compared with cholinergic interneurons of the neostriatum, PV-immunoreactive interneurons are born later, but neurogenetic gradients are similar. The period of striatum PV interneuron genesis encompasses the period for somatostatin interneurons, although the latter neurons do not show neurogenetic gradients, possibly due to heterogeneous subtypes. Consideration of basal telencephalon neurogenesis suggests that subpopulations of striatum interneurons may share common neurogenetic features with phenotypically similar populations in the basal forebrain, with final morphology and connectivity depending on local cues provided by the host environment.

The development of laterality in the forebrain projections of midline thalamic cell groups in the rat.

Bilateral forebrain (caudoputamen, nucleus accumbens and frontal cortical areas) injections of two different fluorescent retrograde tracers demonstrated that labeled cells situated in the midline nuclei of the thalamus and midbrain each project only unilaterally to the forebrain, regardless of the laterality of their perikarya. Thus, these intermingling midline perikarya send their axons primarily ipsilaterally and to a lesser degree contralaterally, but never bilaterally to the forebrain. At embryonic day 19, these midline nuclei exist as two bilaterally situated, independent structures, each projecting only ipsilaterally to the forebrain. By postnatal day 2, these perikarya fuse into a single mass on the midline. Upon fusion, many of the perikarya of the two developing subnuclei cross the midline, intermingle with each other, and thus some neurons come to have contralateral forebrain projections. These observations suggest that neurons are able to maintain their axonal projections while migrating short distances.