Extrasynaptic Neurotransmission in the Modulation of Brain Function. Focus on the Striatal Neuronal–Glial Networks

Inflammatory mechanisms are proposed to play a role in l -DOPA-induced dyskinesia. Cyclooxygenase-2 (COX2) contributes to inflammation pathways in the periphery and is constitutively expressed in the central nervous system. Considering that inhibition of nitric oxide (NO) formation attenuates l -DOPA-induced dyskinesia, this study aimed at investigating if a NO synthase (NOS) inhibitor would change COX2 brain expression in animals with l -DOPA-induced dyskinesia. To this aim, male Wistar rats received unilateral 6-hydroxydopamine microinjection into the medial forebrain bundle were treated daily with l -DOPA (21 days) combined with 7-nitroindazole or vehicle. All hemi-Parkinsonian rats receiving l -DOPA showed dyskinesia. They also presented increased neuronal COX2 immunoreactivity in the dopamine-depleted dorsal striatum that was directly correlated with dyskinesia severity. Striatal COX2 co-localized with choline-acetyltransferase, calbindin and DARPP-32 (dopamine-cAMP-regulated phosphoprotein-32), neuronal markers of GABAergic neurons. NOS inhibition prevented l -DOPA-induced dyskinesia and COX2 increased expression in the dorsal striatum. These results suggest that increased COX2 expression after l -DOPA long-term treatment in Parkinsonian-like rats could contribute to the development of dyskinesia.

Section: Resultsmentioning

confidence: 99%

“…Various subtypes of extrasynaptic dopamine receptors [123][124][125] are located in projection neurons and interneurons as well as on the afferent nerve terminal networks.…”

Section: Extrasynaptic Signalling/volume Signallingmentioning

confidence: 99%

Are cyclooxygenase-2 and nitric oxide involved in the dyskinesia of Parkinson's disease induced byl-DOPA?

Bortolanza

Padovan-Neto

Cavalcanti-Kiwiatkoski

et al. 2015

“…There is extrasynaptic VT operating at the local circuit level through diffusion over short distances (mm range) upon synaptic spillover or extrasynaptic release to activate especially high-affinity GPCRs [12,35]. An ephaptic VT has also been discussed based on flow of ions between neurons in the ECF (electrical VT) [13], first proposed by Golgi in 1906 [36].…”

Section: Different Forms Of Volume Transmission and Integration With mentioning

confidence: 99%

“…Thus, VT is illustrated as: the local extrasynaptic diffusion of neurotransmitters in the ECS; the long-distance diffusion and flow of some classical neurotransmitters and neuropeptides in the ECS; the flow of VT chemical signals via the CSF. Finally, the effects of the pressure waves in cerebral arteries on the diffusion and flow of the VT signals in the ECS and CSF are indicated (see [6,7,12,13]). …”

Section: Introductionmentioning

confidence: 99%

Extracellular-vesicle type of volume transmission and tunnelling-nanotube type of wiring transmission add a new dimension to brain neuro-glial networks

Agnati

Fuxé

2014

Self Cite

Two major types of intercellular communication are found in the central nervous system (CNS), namely wiring transmission (WT; point-to-point communication via private channels, e.g. synaptic transmission) and volume transmission (VT; communication in the extracellular fluid and in the cerebrospinal fluid). Volume and synaptic transmission become integrated because their chemical signals activate different types of interacting receptors in heteroreceptor complexes located synaptically and extrasynaptically in the plasma membrane. In VT, we focus on the role of the extracellular-vesicle type of VT, and in WT, on the potential role of the tunnelling-nanotube (TNT) type of WT. The so-called exosomes appear to be the major vesicular carrier for intercellular communication but the larger microvesicles also participate. Extracellular vesicles are released from cultured cortical neurons and different types of glial cells and modulate the signalling of the neuronal -glial networks of the CNS. This type of VT has pathological relevance, and epigenetic mechanisms may participate in the modulation of extracellular-vesicle-mediated VT. Gerdes and co-workers proposed the existence of a novel type of WT based on TNTs, which are straight transcellular channels leading to the formation in vitro of syncytial cellular networks found also in neuronal and glial cultures.

“…The major difference with synaptic transmission is in the transmission channels, which are private in synaptic transmission (axons, terminals) but diffuse in VT represented by the channels of the extracellular space. Of course, the speed is also markedly different occurring within milliseconds for synaptic transmission and seconds-minutes-hours in VT [12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

The role of transmitter diffusion and flow versus extracellular vesicles in volume transmission in the brain neural–glial networks

Borroto-Escuela

Agnati

Bechter

et al. 2015

Self Cite

112

130

One contribution of 16 to a discussion meeting issue 'Release of chemical transmitters from cell bodies and dendrites of nerve cells'. Two major types of intercellular communication are found in the central nervous system (CNS), namely wiring transmission (point-to-point communication, the prototype being synaptic transmission with axons and terminals) and volume transmission (VT; communication in the extracellular fluid and in the cerebrospinal fluid (CSF)) involving large numbers of cells in the CNS. Volume and synaptic transmission become integrated inter alia through the ability of their chemical signals to activate different types of receptor protomers in heteroreceptor complexes located synaptically or extrasynaptically in the plasma membrane. The demonstration of extracellular dopamine (DA) and serotonin (5-HT) fluorescence around the DA and 5-HT nerve cell bodies with the Falck-Hillarp formaldehyde fluorescence method after treatment with amphetamine and chlorimipramine, respectively, gave the first indications of the existence of VT in the brain, at least at the soma level. There exist different forms of VT. Early studies on VT only involved spread including diffusion and flow of soluble biological signals, especially transmitters and modulators, a communication called extrasynaptic (short distance) and long distance (paraaxonal and paravascular and CSF pathways) VT. Also, the extracellular vesicle type of VT was demonstrated. The exosomes (endosome-derived vesicles) appear to be the major vesicular carriers for VT but the larger microvesicles also participate. Both mainly originate at the soma-dendritic level. They can transfer lipids and proteins, including receptors, Rab GTPases, tetraspanins, cholesterol, sphingolipids and ceramide. Within them there are also subsets of mRNAs and non-coding regulatory microRNAs. At the soma-dendritic membrane, sets of dynamic postsynaptic heteroreceptor complexes (built up of different types of physically interacting receptors and proteins) involving inter alia G protein-coupled receptors including autoreceptors, ion channel receptors and receptor tyrosine kinases are hypothesized to be the molecular basis for learning and memory. At nerve terminals, the presynaptic heteroreceptor complexes are postulated to undergo plastic changes to maintain the pattern of multiple transmitter release reflecting the firing pattern to be learned by the heteroreceptor complexes in the postsynaptic membrane.