Raclopride or high-frequency stimulation of the subthalamic nucleus stops cocaine-induced motor stereotypy and restores related alterations in prefrontal basal ganglia circuits.

Motor stereotypy is a key symptom of various neurological or neuropsychiatric disorders. Neuroleptics or the promising treatment using deep brain stimulation stops stereotypies but the mechanisms underlying their actions are unclear. In rat, motor stereotypies are linked to an imbalance between prefrontal and sensorimotor cortico-basal ganglia circuits. Indeed, cortico-nigral transmission was reduced in the prefrontal but not sensorimotor basal ganglia circuits and dopamine and acetylcholine release was altered in the prefrontal but not sensorimotor territory of the dorsal striatum. Furthermore, cholinergic transmission in the prefrontal territory of the dorsal striatum plays a crucial role in the arrest of motor stereotypy. Here we found that, as previously observed for raclopride, high-frequency stimulation of the subthalamic nucleus (HFS STN) rapidly stopped cocaine-induced motor stereotypies in rat. Importantly, raclopride and HFS STN exerted a strong effect on cocaine-induced alterations in prefrontal basal ganglia circuits. Raclopride restored the cholinergic transmission in the prefrontal territory of the dorsal striatum and the cortico-nigral information transmissions in the prefrontal basal ganglia circuits. HFS STN also restored the N-methyl-d-aspartic-acid-evoked release of acetylcholine and dopamine in the prefrontal territory of the dorsal striatum. However, in contrast to raclopride, HFS STN did not restore the cortico-substantia nigra pars reticulata transmissions but exerted strong inhibitory and excitatory effects on neuronal activity in the prefrontal subdivision of the substantia nigra pars reticulata. Thus, both raclopride and HFS STN stop cocaine-induced motor stereotypy, but exert different effects on the related alterations in the prefrontal basal ganglia circuits.

Key role of striatal cholinergic interneurons in processes leading to arrest of motor stereotypies.

Motor stereotypy is a key symptom of various disorders such as Tourette's syndrome and punding. Administration of nicotine or cholinesterase inhibitors is effective in treating some of these symptoms. However, the role of cholinergic transmission in motor stereotypy remains unknown. During strong cocaine-induced motor stereotypy, we showed earlier that increased dopamine release results in decreased acetylcholine release in the territory of the dorsal striatum related to the prefrontal cortex. Here, we investigated the role of striatal cholinergic transmission in the arrest of motor stereotypy. Analysis of N-methyl-d-aspartic acid-evoked release of dopamine and acetylcholine during declining intensity of motor stereotypy revealed a dissociation between dopamine and acetylcholine release. Whereas dopamine release remained increased, the inhibition of acetylcholine release decreased, mirroring the time course of motor stereotypy. Furthermore, pharmacological treatments restoring striatal acetylcholine release (raclopride, dopamine D2 antagonist; intraperitoneal or local injection in prefrontal territory of the dorsal striatum) rapidly stopped motor stereotypy. In contrast, pharmacological treatments that blocked the post-synaptic effects of acetylcholine (scopolamine, muscarinic antagonist; intraperitoneal or striatal local injection) or induced degeneration of cholinergic interneurons (AF64A, cholinergic toxin) in the prefrontal territory of the dorsal striatum robustly prolonged the duration of strong motor stereotypy. Thus, we propose that restoration of cholinergic transmission in the prefrontal territory of the dorsal striatum plays a key role in the arrest of motor stereotypy.

The vesicular glutamate transporter VGLUT3 synergizes striatal acetylcholine tone.

Three subtypes of vesicular transporters accumulate glutamate into synaptic vesicles to promote its vesicular release. One of the subtypes, VGLUT3, is expressed in neurons, including cholinergic striatal interneurons, that are known to release other classical transmitters. Here we showed that disruption of the Slc17a8 gene (also known as Vglut3) caused an unexpected hypocholinergic striatal phenotype. Vglut3(-/-) mice were more responsive to cocaine and less prone to haloperidol-induced catalepsy than wild-type littermates, and acetylcholine release was decreased in striatum slices lacking VGLUT3. These phenotypes were associated with a colocalization of VGLUT3 and the vesicular acetylcholine transporter (VAChT) in striatal synaptic vesicles and the loss of a synergistic effect of glutamate on vesicular acetylcholine uptake. We propose that this vesicular synergy between two transmitters is the result of the unbalanced bioenergetics of VAChT, which requires anion co-entry for continuing vesicular filling. Our study reveals a previously unknown effect of glutamate on cholinergic synapses with potential functional and pharmacological implications.

Cocaine-induced stereotypy is linked to an imbalance between the medial prefrontal and sensorimotor circuits of the basal ganglia.

The dysfunction of basal ganglia circuits related to stereotyped motor activity was analysed using the well-established model of cocaine-induced stereotypy in the rat. We examined and compared the neurochemical and electrophysiological effects occurring in medial prefrontal and sensorimotor basal ganglia circuits of the dorsal striatum after cocaine injection in sensitized and non-sensitized rats. Acute injections of cocaine (25 mg/kg), not inducing stereotyped behaviour, affected both medial prefrontal and sensorimotor circuits in a similar way: (i) a mild and delayed increase and decrease of N-methyl-D-aspartate-evoked dopamine and acetylcholine release, respectively and (ii) a marked decrease of cortically evoked inhibition of substantia nigra pars reticulata neurons revealing an imbalance of information transmission between the direct and indirect trans-striatal pathways. In contrast, following sensitization to cocaine, a challenge injection of the same dose of cocaine, generating strong stereotyped behaviour, provoked neurochemical and electrophysiological effects only in the medial prefrontal but not in the sensorimotor circuits: (i) a strong increase of dopamine and decrease of acetylcholine release in the medial prefrontal territory of the dorsal striatum and (ii) a reduction of all inhibitory and excitatory components of the responses evoked in substantia nigra pars reticulata by medial prefrontal stimulation. Therefore, these data disclose distinct reactivity of the medial prefrontal and sensorimotor circuits of the basal ganglia to repeated cocaine administration leading to stereotyped behaviour induced by subsequent cocaine challenge. Thus, we suggest that stereotyped behaviour is correlated to an imbalance between the medial prefrontal and sensorimotor circuits of the basal ganglia resulting in a loss of control of motor behaviour.

Tachykinin regulation of cholinergic transmission in the limbic/prefrontal territory of the rat dorsal striatum: implication of new neurokinine 1-sensitive receptor binding site and interaction with enkephalin/mu opioid receptor transmission.

The tachykinin neurokinin 1 receptors (NK(1)Rs) regulation of acetylcholine release and its interaction with the enkephalin/mu opioid receptors (MORs) transmission was investigated in the limbic/prefrontal (PF) territory of the dorsal striatum. Using double immunohistochemistry, we first showed that in this territory, cholinergic interneurons contain tachykinin NK(1)Rs and co-express MORs in the last part of the light period (afternoon). In slices of the striatal limbic/PF territory, following suppression of the dopaminergic inhibitory control of acetylcholine release, application of the tachykinin NK(1)R antagonist, SSR240600, markedly reduced the NMDA-induced acetylcholine release in the morning but not in the afternoon when the enkephalin/MOR regulation is operational. In the afternoon, the NK(1)R antagonist response required the suppression of the enkephalin/MOR inhibitory control of acetylcholine release by betafunaltrexamine. The pharmacological profile of the tachykinin NK(1)R regulation tested by application of the receptor agonists [[Pro(9)]substance P, neurokinin A, neuropeptide K, and substance P(6-11)] and antagonists (SSR240600, GR205171, GR82334, and RP67580) indicated that the subtype of tachykinin NK(1)R implicated are the new NK(1)-sensitive receptor binding site. Therefore, in the limbic/PF territory of the dorsal striatum, endogenous tachykinin facilitates acetylcholine release via a tachykinin NK(1)R subtype. In the afternoon, the tachykinin/NK(1)R and the enkephalin/MOR transmissions interact to control cholinergic transmission.

Facilitation by endogenous tachykinins of the NMDA-evoked release of acetylcholine after acute and chronic suppression of dopaminergic transmission in the matrix of the rat striatum.

Using a microsuperfusion method in vitro, the effects of the NK1, NK2, and NK3 tachykinin receptor antagonists SR140333, SR48968, and SR142801, respectively, on the NMDA-evoked release of [3H]-acetylcholine were investigated after both acute and chronic suppression of dopamine transmission in striosomes and matrix of the rat striatum. NMDA (1 mm) alone or with D-serine (10 microm) in the presence of alpha-methyl-p-tyrosine (100 microm) markedly enhanced the release of [3H]-acetylcholine through a dopamine-independent inhibitory process. In both conditions, as well as after chronic 6-OHDA-induced denervation of striatal dopaminergic fibers, SR140333, SR48968, or SR142801 (0.1 microm each) reduced the NMDA-evoked release of [3H]-acetylcholine in the matrix but not in striosome-enriched areas. These responses were selectively abolished by coapplication with NMDA of the respective tachykinin agonists, septide, [Lys5,MeLeu9,Nle10]NKA(4-10), or senktide. Distinct mechanisms are involved in the effects of the tachykinin antagonists because the inhibitory response of SR140333 was additive with that of either SR48968 or SR142801. In addition, the SR140333-evoked response remained unchanged, whereas those of SR48968 and SR142801 were abolished in the presence of N(G)-monomethyl-l-arginine (nitric oxide synthase inhibitor). Therefore, in the matrix but not in striosomes, the acute or chronic suppression of dopamine transmission unmasked the facilitatory effects of endogenously released substance P, neurokinin A, and neurokinin B on the NMDA-evoked release of [3H]-acetylcholine. Whereas substance P and neurokinin A are colocalized in same efferent neurons, their responses involve distinct circuits because the substance P response seems to be mediated by NK1 receptors located on cholinergic interneurons, while those of neurokinin A and neurokinin B are nitric oxide-dependent.

Evolution of public and non-profit funding for mental health research in France between 2007 and 2011.

Since 2007, actions have been undertaken in France to foster mental health research. Our objective was to assess their utility by estimating the evolution of public and non-profit funding for mental health research between 2007 and 2011, both in terms of total funding and the share of health research budgets. Public and non-profit funding was considered. Core funding from public research institutions was determined through a top-down approach by multiplying their total budget by the ratio of the number of psychiatry-related publications to the total number of publications focusing on health issues. A bottom-up method was used to estimate the amount of project-based grants and funding by non-profit organizations, which were directly contacted to obtain this information. Public and non-profit funding for mental health research increased by a factor of 3.4 between 2007 and 2011 reaching €84.8 million, while the share of health research funding allocated to mental health research nearly doubled from 2.2% to 4.1%. Public sources were the main contributors representing 94% of the total funding. Our results have important implications for policy makers, as they suggest that actions specifically aimed at prioritizing mental health research are effective in increasing research funding. There is therefore an urgent need to further undertake such actions as funding in France remains particularly low compared to the United Kingdom and the United States, despite the fact that the epidemiological and economic burden represented by mental disorders is expected to grow rapidly in the coming years.

A 25 year adventure in the field of tachykinins.

Several aspects of our 25 year adventure in the field of tachykinins will be successively described. They concern: substance P (SP) synthesis and release in the basal ganglia, the identification and pharmacological characterization of central tachykinin NK(1), NK(2) and NK(3) binding sites and their topographical distribution, the description of some new biological tests for corresponding receptors, the identification of tachykinin NK(1) receptor subtypes or conformers sensitive to all endogenous tachykinins (substance P, neurokinin A (NKA), neurokinin B (NKB), neuropeptide gamma (NP gamma) and neuropeptide K (NPK)) and finally, the functional involvement of these receptors and their subtypes in tachykinin-induced regulations of dopamine and acetylcholine release in the striatum.

Impact of 6-hydroxydopamine lesions and cocaine exposure on mu-opioid receptor expression and regulation of cholinergic transmission in the limbic-prefrontal territory of the rat dorsal striatum.

Information processing within the striatum is regulated by local circuits involving dopamine, cholinergic interneurons and neuropeptides released by recurrent collaterals of striatal output neurons. In the limbic-prefrontal territory of the dorsal striatum, enkephalin inhibits the NMDA-evoked release of acetylcholine directly through micro-opioid receptors (MORs) located on cholinergic interneurons and indirectly through MORs of output neurons of striosomes. In this territory, we investigated the consequence of changes in dopamine transmission, bilateral 6-hydroxydopamine-induced degeneration of striatal dopaminergic innervation or cocaine (acute and chronic) exposure on (i) MOR expression in both cholinergic interneurons and output neurons of striosomes, and (ii) the direct and indirect enkephalin-MOR regulations of the NMDA-evoked release of acetylcholine. Expression of MORs in cholinergic interneurons was preserved after 6-hydroxydopamine and down-regulated after cocaine treatments. Accordingly, the direct enkephalin-MOR control of acetylcholine release was preserved after 6-hydroxydopamine treatment and lost after cocaine exposure. Expression of MORs in output neurons of striosomes was down-regulated in the 6-hydroxydopamine situation and either preserved or up-regulated after acute or chronic cocaine exposure, respectively. Accordingly, the indirect enkephalin-MOR control of acetylcholine release disappeared in the 6-hydroxydopamine situation but surprisingly, despite preservation of MORs in striosomes, disappeared after cocaine treatment. Showing that MORs of striosomes are still functional in this situation, the MOR agonist [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin inhibited the NMDA-evoked release of acetylcholine after cocaine exposure. Therefore, alteration in the regulation of cholinergic transmission by the enkephalin-MOR system might play a major role in the motivational and cognitive disorders associated with dopamine dysfunctions in fronto-cortico-basal ganglia circuits.

Functional mu opioid receptors are expressed in cholinergic interneurons of the rat dorsal striatum: territorial specificity and diurnal variation.

Striatal cholinergic interneurons play a crucial role in the control of movement as well as in motivational and learning aspects of behaviour. Neuropeptides regulate striatal cholinergic transmission and particularly activation of mu opioid receptor (MOR) inhibits acetylcholine (ACh) release in the dorsal striatum. In the present study we investigated whether this cholinergic transmission could be modulated by an enkephalin/MOR direct process. We show that mRNA and protein of MORs are expressed by cholinergic interneurons in the limbic/prefrontal territory but not by those in the sensorimotor territory of the dorsal striatum. These MORs are functional because potassium-evoked release of ACh from striatal synaptosomes was dose-dependently reduced by a selective MOR agonist, this effect being suppressed by a MOR antagonist. The MOR regulation of cholinergic interneurons presented a diurnal variation. (i) The percentage of cholinergic interneurons containing MORs that was 32% at the beginning of the light period (morning) increased to 80% in the afternoon. (ii) The MOR-mediated inhibition of synaptosomal ACh release was higher in the afternoon than in the morning. (iii) While preproenkephalin mRNA levels remained stable, enkephalin tissue content was the lowest (-32%) in the afternoon when the spontaneous (+35%) and the N-methyl-d-aspartate-evoked (+140%) releases of enkephalin (from microsuperfused slices) were the highest. Therefore, by acting on MORs present on cholinergic interneurons, endogenously released enkephalin reduces ACh release. This direct enkephalin/MOR regulation of cholinergic transmission that operates only in the limbic/prefrontal territory of the dorsal striatum might contribute to information processing in fronto-cortico-basal ganglia circuits.

The new neurokinin 1-sensitive receptor mediates the facilitation by endogenous tachykinins of the NMDA-evoked release of acetylcholine after suppression of dopaminergic transmission in the matrix of the rat striatum.

Using an in vitro microsuperfusion procedure, the NMDA-evoked release of [3H]ACh was studied after suppression of dopamine (DA) transmission (alpha-methyl-p-tyrosine) in striatal compartments of the rat. The effects of tachykinin neurokinin 1 (NK1) receptor antagonists and the ability of appropriate agonists to counteract the antagonist responses were investigated to determine whether tachykinin NK1 classic, septide-sensitive and/or new NK1-sensitive receptors mediate these regulations. The NK1 antagonists, SR140333, SSR240600, GR205171 but not GR82334 and RP67580 (0.1 and 1 microM) markedly reduced the NMDA (1 mm + D-serine 10 microM)-evoked release of [3H]ACh only in the matrix. These responses unchanged by coapplication with NMDA of NK2 or NK3 agonists, [Lys5,MeLeu9,Nle10]NKA(4-10) or senktide, respectively, were completely counteracted by the selective NK1 agonist, [Pro9]substance P but also by neurokinin A and neuropeptide K (1 nM each). According to the rank order of potency of agonists for counteracting the antagonist responses ([Pro9]substance P, 0.013 nM > neurokinin A, 0.15 nM >> substance P(6-11) 7.7 nM = septide 8.7 nM), the new NK1-sensitive receptors mediate the facilitation by endogenous tachykinins of the NMDA-evoked release of ACh in the matrix, after suppression of DA transmission. Solely the NK1 antagonists having a high affinity for these receptors could be used as indirect anti-cholinergic agents.