Dysregulation of gene induction in corticostriatal circuits after repeated methylphenidate treatment in adolescent rats: differential effects on zif 268 and homer 1a

Psychostimulants and other dopamine agonists produce molecular changes in neurons of cortico-basal ganglia-cortical circuits, and such neuronal changes are implicated in behavioural disorders. Methylphenidate, a psychostimulant that causes dopamine overflow (among other effects), alters gene regulation in neurons of the striatum. The present study compared the effects of acute and repeated methylphenidate treatment on cortical and striatal gene regulation in adolescent rats. Changes in the expression of the immediate-early genes zif 268 and homer 1a were mapped in 23 striatal sectors and 22 cortical areas that provide input to these striatal sectors, in order to determine whether specific corticostriatal circuits were affected by these treatments. Acute administration of methylphenidate (5 mg/kg, i.p.) produced modest zif 268 induction in cortical areas. These cortical zif 268 responses were correlated in magnitude with zif 268 induction in functionally related striatal sectors. In contrast, after repeated methylphenidate treatment (10 mg/kg, 7 days), cortical and striatal gene induction were dissociated. In these animals, the methylphenidate challenge (5 mg/kg) produced significantly greater gene induction (zif 268 and homer 1a) in the cortex. This enhanced response was widespread but regionally selective, as it occurred predominantly in premotor, motor and somatosensory cortical areas. At the same time, striatal gene induction was partly suppressed (zif 268) or unchanged (homer 1a). Thus, repeated methylphenidate treatment disrupted the normally coordinated gene activation patterns in cortical and striatal nodes of corticostriatal circuits. This drug-induced dissociation in cortical and striatal functioning was associated with enhanced levels of behavioural stereotypies, suggesting disrupted motor switching function.     

Cocaine effects on gene regulation in the striatum and behavior: increased sensitivity in D3 dopamine receptor-deficient mice

Central effects of psychostimulants such as cocaine are predominantly mediated by dopamine receptors. We have used mice with a targeted deletion of the D3 dopamine receptor subtype to investigate the role of this receptor in the regulation of gene expression in striatal neurons and behavior by acute and repeated treatment with cocaine (25 mg/kg). In mice lacking D3 receptors, acute administration of cocaine has more pronounced stimulatory effects on c-fos and dynorphin expression in the dorsal and ventral striatum. The behavioral response to cocaine is also increased in these mice. These findings indicate that the D3 receptor plays an inhibitory role in the action of cocaine on behavior and gene regulation in the striatum.     

Dynorphin opioid inhibition of cocaine-induced,D1 dopamine receptor-mediated immediatem-early gene expression in the striatum

Neurons in the striatum that project to the substantia nigra contain the opioid peptide dynorphin. Stimulation of D1 dopamine receptors results in increased expression of mRNA encoding dynorphin as well as expression of immediate-early genes such as c-fos in these neurons. Levels of dynorphin vary in different regions of the normal rat striatum, being highest in ventral and medial striatum. In a prior study, we have shown that both regional and temporal patterns of c-fos induction following treatment with the indirect dopamine receptor agonist cocaine are inversely related to those of dynorphin expression. These results suggested that dynorphin is involved in regulating the responsiveness of these neurons to dopamine input. In the present experiments, we examined such a potential role for dynorphin by analyzing the influence of the dynorphin (kappa opioid receptor) agonist spiradoline on immediate-early gene induction by cocaine, and we determined that this immediate-early gene response is mediated by D1 dopamine receptors located in the striatum. As a marker of neuron activation, expression of c-fos and zif 268 immediate-early genes was assessed with quantitative in situ hybridization histochemistry. Results showed that (1) intrastriatal infusion of the D1 dopamine receptor antagonist SCH-23390 (2.5–250 pmol) resulted in a dose-dependent blockade of immediate-early gene induction by cocaine (30 mg/kg); (2) systemic administration of the kappa opioid receptor agonist spiradoline (0.5–10.0 mg/kg) decreased cocaine-induced expression of c-fos and zif 268 mRNAs in striatum in a dose-dependent manner; (3) intrastriatal infusion of spiradoline (1–50 nmol) also suppressed immediate-early gene induction by cocaine, demonstrating that kappa opioid receptors located in the striatum mediate such an effect; and (4) systemic and intrastriatal administration of spiradoline also affected immediate-early gene expression in cortex. These results demonstrate that, in striatum, immediate-early gene induction by cocaine is a D1 dopamine receptor-mediated process that is inhibited by activation of kappa opioid receptors. Therefore, these findings suggest that the striatal dynorphin opioid system acts directly and/or indirectly to inhibit dopamine input to striatonigral neurons through kappa opioid receptor-mediated processes in the striatum. © 1995 Wiley-Liss, Inc.     

Dynorphin regulates D1 dopamine receptor-mediated responses in the striatum: Relative contributions of pre- and postsynaptic mechanisms in dorsal and ventral striatum demonstrated by altered immediate-early gene induction

Dynorphin, an endogenous kappa opioid receptor ligand, acts in the striatum to regulate the response of striatonigral neurons to D1 dopamine receptor stimulation. We investigated the relative contributions of both presynaptic kappa receptors on dopamine terminals and postsynaptic kappa receptors on striatal neurons by analyzing opioid regulation of D1 effects in the absence of presynaptic kappa receptors, after 6-hydroxydopamine depletion of striatal dopamine. D1-receptor-mediated immediate-early gene induction was measured by using in situ hybridization histochemistry. First, repeated treatment with the D1-receptor agonist SKF-38393 (2 mg/kg/day, 3–14 days) was used to increase dynorphin levels in rats with dopamine depletions. In the nucleus accumbens, increased dynorphin expression was accompanied by reduced induction of the immediate-early genes c-fos and zif 268 by SKF-38393. In contrast, in dorsal/lateral aspects of the dopamine-depleted striatum, this D1 response was sustained despite a large increase in dynorphin expression. These results are consistent with a requirement of dopamine terminals (presynaptic kappa receptors) for the inhibitory action of dynorphin in the dorsal/lateral striatum, but not in the ventral striatum. Second, the kappa receptor agonist spiradoline (1–10 mg/kg) reduced c-fos and zif 268 induction by SKF-38393 (2.5 mg/kg) preferentially in ventral parts of the dopamine-depleted striatum, which contain higher levels of kappa receptor mRNA and binding. These results also indicate that postsynaptic kappa receptors contribute to the inhibition of the D1 response at least in the ventral striatum. Together, these results indicate that dynorphin in the striatum functions to regulate dopamine input to striatonigral neurons, acting at both pre- and postsynaptic sites, and that the relative contributions of these mechanisms differ between dorsal and ventral striatal regions. © 1996 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, in the public domain in the United States of America.

     

Long-lasting dysregulation of gene expression in corticostriatal circuits after repeated cocaine treatment in adult rats: effects on zif 268 and homer 1a

Human imaging studies show that psychostimulants such as cocaine produce functional changes in several areas of cortex and striatum. These may reflect neuronal changes related to addiction. We employed gene markers ( zif 268 and homer 1a ) that offer a high anatomical resolution to map cocaine-induced changes in 22 cortical areas and 23 functionally related striatal sectors, in order to determine the corticostriatal circuits altered by repeated cocaine exposure (25 mg/kg, 5 days). Effects were investigated 1 day and 21 days after repeated treatment to assess their longevity. Repeated cocaine treatment increased basal expression of zif 268 predominantly in sensorimotor areas of the cortex. This effect endured for 3 weeks in some areas. These changes were accompanied by attenuated gene induction by a cocaine challenge. In the insular cortex, the cocaine challenge produced a decrease in zif 268 expression after the 21-day, but not 1-day, withdrawal period. In the striatum, cocaine also affected mostly sensorimotor sectors. Repeated cocaine resulted in blunted inducibility of both zif 268 and homer 1a , changes that were still very robust 3 weeks later. Thus, our findings demonstrate that cocaine produces robust and long-lasting changes in gene regulation predominantly in sensorimotor corticostriatal circuits. These neuronal changes were associated with behavioral stereotypies, which are thought to reflect dysfunction in sensorimotor corticostriatal circuits. Future studies will have to elucidate the role of such neuronal changes in psychostimulant addiction.     

Regulation of rat cortex function by D1 dopamine receptors in the striatum.

Interactions between the basal ganglia and the cerebral cortex are critical for normal goal-directed behavior. In the present study, we used immediate-early genes (c-fos, zif 268) as functional markers to investigated how basal ganglia output altered by stimulation/blockade of D1 dopamine receptors in the striatum affects cortical function. Systemic administration of the mixed D1/D2 receptor agonist apomorphine (3 mg/kg) increased immediate-early gene expression in the striatum and throughout most of the cortex. Unilateral intrastriatal infusion of the selective D1 receptor antagonist SCH-23390 (0.5-10 microg) blocked this response bilaterally in striatum and cortex in a dose-dependent manner. Even apparently regionally restricted blockade of striatal D1 receptors attenuated gene expression throughout striatum and cortex in both hemispheres. Intrastriatal administration of the D1 antagonist inhibited apomorphine-induced sniffing/whisking, whereas other motor behaviors were unaffected. To determine whether such changes in cortical gene expression could reflect altered cortical function, we examined the effects of blocking striatal D1 receptors on whisker stimulation-evoked immediate-early gene expression in the sensorimotor cortex. Apomorphine increased sensory stimulation-evoked gene expression in the barrel cortex, and intrastriatal infusion of SCH-23390 attenuated this effect. These results suggest that stimulation of D1 dopamine receptors in the striatum exerts a widespread facilitatory effect on cortical function.     

Topography of cocaine-induced gene regulation in the rat striatum: relationship to cortical inputs and role of behavioural context

Psychostimulants alter gene expression in projection neurons of the striatum, and such neuroplasticity is implicated in drug addiction and dependence. Evidence indicates that excitatory inputs from the cortex and thalamus are critical for these molecular changes. In the present study, we determined the topography of cocaine-induced changes in gene expression in the rat striatum and investigated whether these molecular alterations are associated with particular cortical inputs. Acute induction of c-fos (by 25 mg/kg of cocaine), and the c-fos response and dynorphin expression after repeated cocaine treatment (25 mg/kg, 4 days) were assessed as examples for short-term and longer-term molecular changes, respectively. In addition, we examined whether these molecular effects were influenced by the behaviour performed during cocaine action (running-wheel training vs. open field). Our results demonstrate that the overall topography of cocaine-induced gene regulation in the striatum is remarkably stable. Both acute and longer-term molecular changes were maximal in caudal dorsal striatal sectors that receive convergent inputs from the medial agranular and the sensorimotor cortex. In contrast, relatively minor or no effects were found in rostral and ventral striatal sectors. However, running-wheel training under the influence of cocaine enhanced the c-fos response to a subsequent cocaine challenge selectively in parts of the caudal sensorimotor striatum. These results indicate that cocaine produces molecular adaptations preferentially in cortico-basal ganglia circuits through the sensorimotor striatum, and that some of these neuronal changes are influenced by the behaviour performed during drug exposure.     

Blockade of neurotensin receptors suppresses the dopamine D1/D2 synergism on immediate early gene expression in the rat brain

A remarkable feature of dopamine functioning is that the concomitant activation of D1-like and D2-like receptors acts to intensify the expression of various dopamine-dependent effects, in particular the expression of the immediate-early genes, c-fos and zif268. Using non-peptide neurotensin receptor antagonists, including SR48692, we have determined that blockade of neurotensin receptors reduced the cooperative responses of direct acting D2-like (quinpirole) and partial D1-like (SKF38393) dopamine agonists on the expression of Fos-like antigens and zif268 mRNA. Pretreatment with SR48692 (3 and 10 mg/kg) reduced the number of Fos-like immunoreactive cells produced by the combined administration of SKF38393 (20 mg/kg) and quinpirole (1 mg/kg) in the caudate-putamen, nucleus accumbens, globus pallidus and ventral pallidum. High-affinity neurotensin receptors are likely to be involved in these D1-like/D2-like cooperative responses, as compounds structurally related to SR48692, SR48527 (3 mg/kg) and its (-)antipode, SR49711 (3 mg/kg), exerted a stereospecific antagonism in all selected brain regions. Pretreatment with SR48692 (10 mg/kg) also diminished Fos induction by the indirect dopamine agonist, cocaine (25 mg/kg), particularly at the rostral level of the caudate-putamen. In situ hybridization experiments in the caudate-putamen indicated that SR48692 (10 mg/kg) markedly reduced zif268 mRNA labelling produced by SKF38393 plus quinpirole in cells not expressing enkephalin mRNA, but was unable to affect the concomitant decrease of zif268 mRNA labelling in enkephalin-positive cells. Taken together, the results of the present study indicate that neurotensin is a key element for the occurrence of cooperative responses of D2-like and partial D1-like agonists on immediate-early gene expression.     

Daily methylphenidate administration attenuates c-fos expression in the striatum of prepubertal rats

Methylphenidate (Ritalin) is a psychostimulant drug used to treat children with attention deficit hyperactivity disorder. Despite its widespread and increasing clinical use, little is known about the long-term consequences of drug treatment. We compared the effects of a single injection of methylphenidate with that of long-term methylphenidate injections (one/day; 14 days) on immediate-early gene expression (c-fos) in the striatum of prepubertal male rats. Rats (25 days old) were injected once daily for 14 days with either saline or methylphenidate (1, 2 or 10 mg/kg), or for 13 days with saline followed by one injection of methylphenidate (1, 2 or 10 mg/kg) on day 14, and were sacrificed 2 h post-injection. Methylphenidate dose-dependently increased FOS immunoreactivity in the striatum. A single injection of methylphenidate (2 or 10 mg/kg) on day 14, following saline treatment for 13 days, caused a dramatic elevation in c-fos expression. This effect was significantly attenuated in animals treated chronically with methylphenidate (2 or 10 mg/kg) for the entire 14 days. Our data suggest that repeated methylphenidate treatment, at a clinically relevant dose (2 mg/kg), markedly inhibits immediate-early gene expression in the brain. This is the first demonstration of methylphenidate-induced modification of gene expression in developing rat striatum and may have implications for chronic methylphenidate use in children.     

Unilateral striatal dopamine depletion: time-dependent effects on cortical function and behavioural correlates

Previously, we showed that unilateral blockade of D1 dopamine receptors in the striatum inhibits immediate-early gene expression bilaterally throughout large parts of the cortex, including sensory-evoked expression in the barrel cortex. To further investigate this dopamine regulation of cortical function, we examined the effects of dopamine depletion on cortical gene regulation and behavioural correlates. Two days after unilateral infusion of 6-hydroxydopamine into the midbrain, rats displayed a (to some degree) bilateral reduction in cortical zif 268 expression that was more pronounced on the lesioned side. This decrease was found across motor, somatosensory, insular and piriform, but not cingulate, cortex, similar to the effects of blockade of striatal D1 receptors. Furthermore, whisker stimulation-evoked c-fos and zif 268 expression in the barrel cortex ipsilateral to the lesion was also attenuated by acute dopamine depletion. These cortical deficits were accompanied by a breakdown of spontaneous behaviours in an open-field test. In contrast, 21 days after dopamine depletion, both basal and sensory-evoked gene expression in the cortex were near-normal. This cortical recovery was paralleled by recovery in locomotion and in sensory-guided behaviour (scanning) related to the hemisphere contralateral to the lesion, but not in scanning by the dopamine-depleted hemisphere. Our results suggest that striatal dopamine exerts a widespread facilitatory influence on cortical function that is necessary, but not sufficient, for normal behaviour. Moreover, the mechanisms mediating this cortical facilitation appear to be subject to substantial neuroplasticity after dopamine perturbation.     

mGluR5-dependent increases in immediate early gene expression in the rat striatum following acute administration of amphetamine

Metabotropic glutamate receptor 5 (mGluR5) is densely expressed in medium-sized spiny projection neurons of the rat striatum. Activation of mGluR5 increases intracellular Ca2+, resulting in Ca(2+)-dependent cellular responses. Acute administration of the psychostimulant amphetamine (AMPH) induces immediate early gene (IEG) expression in the striatum, which is considered an important molecular event for the development of striatal neuroplasticity related to the addictive properties of drugs of abuse. This study investigated the role of mGluR5 in the mediation of IEG expression in the rat striatum induced by a single dose of AMPH (4 mg/kg, i.p.) in vivo. We found that systemic administration of the mGluR5-selective antagonist 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP) at a dose of 10 mg/kg, i.p. reduced AMPH-stimulated c-fos mRNA levels in the dorsal (caudoputamen) and ventral (nucleus accumbens) striatum as revealed by quantitative in situ hybridization. Similar results were observed in the three areas of cerebral cortex (cingulate, sensory, and piriform cortex). In contrast to c-fos mRNAs, AMPH-stimulated mRNA expression of another IEG, zif/268, was not significantly altered by the blockade of mGluR5 with MPEP in the entire striatum and the three areas of cortex. Treatment with MPEP alone had no effect on basal levels of c-fos and zif/268 mRNAs in the striatal and cortical areas. These results indicate that an mGluR5-dependent mechanism selectively contributes to c-fos expression in the striatum and cortex in response to acute exposure to AMPH.     

Different responsiveness of striatonigral and striatopallidal neurons to L-DOPA after a subchronic intermittent L-DOPA treatment

Early gene induction by L-DOPA in the striatum of dopamine denervated rats represents a useful way to study long-term modifications produced by this drug. The effects of acute and subchronic L-DOPA administration on zif-268 mRNA expression were compared in 6-hydroxydopamine-lesioned rats. Rats received a subchronic intermittent L-DOPA (6 mg/kg) treatment, which produces behavioural sensitization, a correlate of dyskinetic movements. Three days after interruption of subchronic treatment, zif-268 mRNA was evaluated after an L-DOPA challenge. Zif-268 mRNA levels increased in the lesioned dorsolateral striatum after either acute or subchronic L-DOPA administration. Double labelling of striatal cells with zif-268 and enkephalin or dynorphin mRNA probes was performed to assess neuronal activation in the indirect and direct output pathway. Single acute L-DOPA significantly increased zif-268 in all striatal neurons reflecting a hyperresponsiveness of dopamine-depleted striatum. After subchronic L-DOPA, zif-268 mRNA labelling was still increased in the striatonigral pathway, limited to dynorphin(+) neurons, whereas in all other neurons it was similar to the control value. Results suggest that striatal neurons responding to acute L-DOPA differ from those responding to subchronic L-DOPA. L-DOPA-induced behavioural sensitization was associated to a down-regulation in the responsiveness of striatopallidal and striatonigral dynorphin(-) neurons, whereas in striatonigral neurons containing dynorphin a hyperresponsiveness to L-DOPA was observed. High levels of zif-268, together with a persistent hyperresponsiveness of striatonigral dymorphinergic neurons and hyporesponsiveness of striatopallidal neurons, by creating an unbalanced state of striatal efferent neurons, may be implicated in dyskinetic movements observed in Parkinson's disease (PD).     

Stimulation of adenosine A1 receptors attenuates dopamine D1 receptor-mediated increase of NGFI-A, c-fos and jun-B mRNA levels in the dopamine-denervated striatum and dopamine D1 receptor-mediated turning behaviour

Adenosine A1 receptors antagonistically and specifically modulate the binding and functional characteristics of dopamine D1 receptors. In the striatum this interaction seems to take place in the GABAergic strionigro-strioentopeduncular neurons, where both receptors are colocalized. D1 receptors in the strionigro-strioentopeduncular neurons are involved in the increased striatal expression of immediate-early genes induced by the systemic administration of psychostimulants and D1 receptor agonists. Previous results suggest that a basal expression of the immediate-early gene c-fos tonically facilitates the functioning of strionigro-strioentopeduncular neurons and facilitates D1 receptor-mediated motor activation. The role of A1 receptors in the modulation of the expression of striatal D1 receptor-regulated immediate-early genes and the D1 receptor-mediated motor activation was investigated in rats with a unilateral lesion of the ascending dopaminergic pathways. The systemic administration of the A1 agonist N6-cyclopentyladenosine (CPA, 0.1 mg/kg) significantly decreased the number of contralateral turns induced by the D1 agonist SKF 38393 (3 mg/kg). Higher doses of CPA (0.5 mg/kg) were necessary to inhibit the turning behaviour induced by the D2 agonist quinpirole (0.1 mg/kg). By using in situ hybridization it was found that CPA (0.1 mg/kg) significantly inhibited the SKF 38393-induced increase in the expression of NGFI-A and c-fos mRNA levels in the dopamine-denervated striatum. The increase in jun-B mRNA expression could only be inhibited with the high dose of CPA (0.5 mg/kg). A stronger effect of the A1 agonist was found in the ventral striatum (nucleus accumbens) compared with the dorsal striatum (dorsolateral caudate-putamen). The results indicate the existence of antagonistic A1-D1 receptor-receptor interactions in the dopamine-denervated striatum controlling D1 receptor transduction at supersensitive D1 receptors.     

Acute methamphetamine-induced zif/268, preprodynorphin, and preproenkephalin mRNA expression in rat striatum depends on activation of NMDA and kainate/AMPA receptors

This study tested the role of N-methyl-d-aspartate and kainate/AMPA receptors in mediating mRNA expression of the immediate early gene zif/268 and the opioid peptide genes preprodynorphin and preproenkephalin in rat forebrain following a single injection of methamphetamin. At 3 h after acute methamphetamine [4 mg/kg, intraperitoneally (IP)], quantitative in situ hybridization histochemistry revealed that zif/268 mRNA expression was increased in the dorsal striatum (caudoputamen) and in the sensory cortex. Preprodynorphin was increased in both dorsal and ventral striatum (nucleus accumbens) and preproenkephalin was increased in the dorsal striatum. Pretreatment with (±)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) (10 mg/kg, IP), an N-methyl-d-aspartate receptor antagonist, blocked the methamphetamine-induced zif/268 mRNA expression in the striatum and in the region of sensory cortex representing the upper limb and nose. 6,7-Dinitro-quinoxaline-2,3-dione (DNQX) (100 mg/kg, IP), a kainate/AMPA receptor antagonist, did not reduce the ability of methamphetamine to induce zif/268 mRNA in striatal and cortical neurons. Furthermore, both antagonists caused a parallel blockade of methamphetamine-stimulated preproenkephalin mRNA expression in the dorsal and ventral striatum but did not significantly affect methamphetamine-stimulated preproenkephalin mRNA expression. CPP and DNQX reduced basal levels of zif/268 mRNA in cortical and striatal neurons but did not affect the constitutive expression of the two opioid mRNAs in the striatum. Neither antagonist had a significant effect on methamphetamine-induced demonstrate that both N-methyl-d-aspartate and kainate/AMPA receptor-mediated glutamatergic transmission is linked to modulation of the methamphetamine-stimulated opioid peptide gene expression in rat forebrain. Furthermore, N-methyl-d-aspartate receptors participate in methamphetamine-stimulated zif/268 expression.