Noradrenergic terminals are the primary source of α2-adrenoceptor mediated dopamine release in the medial prefrontal cortex. 2019

Paola Devoto, and Giovanna Flore, and Pierluigi Saba, and Simona Scheggi, and Giovanna Mulas, and Carla Gambarana, and Saturnino Spiga, and Gian Luigi Gessa
Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy; Guy Everett Laboratory, University of Cagliari, Cagliari, Italy; National Institute of Neuroscience, INN, Section of Cagliari, Italy. Electronic address: pdevoto@unica.it.

In various psychiatric disorders, deficits in dopaminergic activity in the prefrontal cortex (PFC) are implicated. Treatments involving selective augmentation of dopaminergic activity in the PFC primarily depend on the inhibition of α2-adrenoreceptors singly or in combination with the inhibition of the norepinephrine transporter (NET). We aimed to clarify the relative contribution of dopamine (DA) release from noradrenergic and dopaminergic terminals to DA output induced by blockade of α2-adrenoreceptors and NET. To this end, we assessed whether central noradrenergic denervation modified catecholamine output in the medial PFC (mPFC) of rats elicited by atipamezole (an α2-adrenoreceptor antagonist), nisoxetine (an NET inhibitor), or their combination. Intraventricular administration of anti-dopamine-beta-hydroxylase-saporin (aDBH) caused a loss of DBH-positive fibers in the mPFC and almost total depletion of tissue and extracellular NE level; however, it did not reduce tissue DA level but increased extracellular DA level by 70% in the mPFC. Because noradrenergic denervation should have caused a loss of NET and reduced NE level at α2-adrenoceptors, the actual effect of an aDBH-induced lesion on DA output elicited by blockade of α2-adrenoceptors and NET was evaluated by comparing denervated and control rats following blockade of α2-adrenoceptors and NET with atipamezole and nisoxetine, respectively. In the control rats, extracellular NE and DA levels increased by approximately 150% each with 3 mg/kg atipamezole; 450% and 230%, respectively, with 3 mg/kg nisoxetine; and 2100% and 600%, respectively, with combined atipamezole and nisoxetine. In the denervated rats, consistent with the loss of NET, nisoxetine failed to modify extracellular DA level, whereas atipamezole, despite the lack of NE-induced stimulation of α2-adrenoceptors, increased extracellular DA level by approximately 30%. Overall, these results suggest that atipamezole-induced DA release mainly originated from noradrenergic terminals, possibly through the inhibition of α2-autoreceptors. Furthermore, while systemic and local administration of the α2-adrenoceptor agonist clonidine into the mPFC of the controls rats reduced extracellular NE level by 80% and 60%, respectively, and extracellular DA level by 50% and 60%, respectively, it failed to reduce DA output in the denervated rats, consistent with the loss of α2-autoreceptors. To eliminate the possibility that denervation reduced DA release potential via the effects at dopaminergic terminals in the mPFC, the effect of systemic administration of the D2-DA antagonist raclopride (0.5 mg/kg IP) on DA output was analyzed. In the control rats, raclopride was found to be ineffective when administered alone, but it increased extracellular DA level by 380% following NET inhibition with nisoxetine. In the denervated rats, as expected due to the loss of NET, raclopride-alone or with nisoxetine-increased DA release to approximately the same level as that observed in the control rats after NET inhibition. Overall, these results suggest that noradrenergic terminals in the mPFC are the primary source of DA released by blockade of α2-adrenoreceptors and NET and that α2-autoreceptors, and not α2-heteroreceptors, mediate DA output induced by α2-adrenoceptor blockade.

UI MeSH Term Description Entries
D007093 Imidazoles Compounds containing 1,3-diazole, a five membered aromatic ring containing two nitrogen atoms separated by one of the carbons. Chemically reduced ones include IMIDAZOLINES and IMIDAZOLIDINES. Distinguish from 1,2-diazole (PYRAZOLES).
D008297 Male Males
D009638 Norepinephrine Precursor of epinephrine that is secreted by the ADRENAL MEDULLA and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the LOCUS CERULEUS. It is also found in plants and is used pharmacologically as a sympathomimetic. Levarterenol,Levonorepinephrine,Noradrenaline,Arterenol,Levonor,Levophed,Levophed Bitartrate,Noradrenaline Bitartrate,Noradrénaline tartrate renaudin,Norepinephrin d-Tartrate (1:1),Norepinephrine Bitartrate,Norepinephrine Hydrochloride,Norepinephrine Hydrochloride, (+)-Isomer,Norepinephrine Hydrochloride, (+,-)-Isomer,Norepinephrine d-Tartrate (1:1),Norepinephrine l-Tartrate (1:1),Norepinephrine l-Tartrate (1:1), (+,-)-Isomer,Norepinephrine l-Tartrate (1:1), Monohydrate,Norepinephrine l-Tartrate (1:1), Monohydrate, (+)-Isomer,Norepinephrine l-Tartrate (1:2),Norepinephrine l-Tartrate, (+)-Isomer,Norepinephrine, (+)-Isomer,Norepinephrine, (+,-)-Isomer
D004298 Dopamine One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action. Hydroxytyramine,3,4-Dihydroxyphenethylamine,4-(2-Aminoethyl)-1,2-benzenediol,Dopamine Hydrochloride,Intropin,3,4 Dihydroxyphenethylamine,Hydrochloride, Dopamine
D005473 Fluoxetine The first highly specific serotonin uptake inhibitor. It is used as an antidepressant and often has a more acceptable side-effects profile than traditional antidepressants. Fluoxetin,Fluoxetine Hydrochloride,Lilly-110140,N-Methyl-gamma-(4-(trifluoromethyl)phenoxy)benzenepropanamine,Prozac,Sarafem,Lilly 110140,Lilly110140
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D017207 Rats, Sprague-Dawley A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company. Holtzman Rat,Rats, Holtzman,Sprague-Dawley Rat,Rats, Sprague Dawley,Holtzman Rats,Rat, Holtzman,Rat, Sprague-Dawley,Sprague Dawley Rat,Sprague Dawley Rats,Sprague-Dawley Rats
D017397 Prefrontal Cortex The rostral part of the frontal lobe, bounded by the inferior precentral fissure in humans, which receives projection fibers from the MEDIODORSAL NUCLEUS OF THE THALAMUS. The prefrontal cortex receives afferent fibers from numerous structures of the DIENCEPHALON; MESENCEPHALON; and LIMBIC SYSTEM as well as cortical afferents of visual, auditory, and somatic origin. Anterior Prefrontal Cortex,Brodmann Area 10,Brodmann Area 11,Brodmann Area 12,Brodmann Area 47,Brodmann's Area 10,Brodmann's Area 11,Brodmann's Area 12,Brodmann's Area 47,Pars Orbitalis,Frontal Sulcus,Gyrus Frontalis Inferior,Gyrus Frontalis Superior,Gyrus Orbitalis,Gyrus Rectus,Inferior Frontal Gyrus,Lateral Orbitofrontal Cortex,Marginal Gyrus,Medial Frontal Gyrus,Olfactory Sulci,Orbital Area,Orbital Cortex,Orbital Gyri,Orbitofrontal Cortex,Orbitofrontal Gyri,Orbitofrontal Gyrus,Orbitofrontal Region,Rectal Gyrus,Rectus Gyrus,Straight Gyrus,Subcallosal Area,Superior Frontal Convolution,Superior Frontal Gyrus,Ventral Medial Prefrontal Cortex,Ventromedial Prefrontal Cortex,Anterior Prefrontal Cortices,Area 10, Brodmann,Area 10, Brodmann's,Area 11, Brodmann,Area 11, Brodmann's,Area 12, Brodmann,Area 12, Brodmann's,Area 47, Brodmann,Area 47, Brodmann's,Area, Orbital,Area, Subcallosal,Brodmanns Area 10,Brodmanns Area 11,Brodmanns Area 12,Brodmanns Area 47,Convolution, Superior Frontal,Convolutions, Superior Frontal,Cortex, Anterior Prefrontal,Cortex, Lateral Orbitofrontal,Cortex, Orbital,Cortex, Orbitofrontal,Cortex, Prefrontal,Cortex, Ventromedial Prefrontal,Cortices, Ventromedial Prefrontal,Frontal Convolution, Superior,Frontal Gyrus, Inferior,Frontal Gyrus, Medial,Frontal Gyrus, Superior,Frontalis Superior, Gyrus,Gyrus, Inferior Frontal,Gyrus, Marginal,Gyrus, Medial Frontal,Gyrus, Orbital,Gyrus, Orbitofrontal,Gyrus, Rectal,Gyrus, Rectus,Gyrus, Straight,Gyrus, Superior Frontal,Inferior, Gyrus Frontalis,Lateral Orbitofrontal Cortices,Olfactory Sulcus,Orbital Areas,Orbital Cortices,Orbital Gyrus,Orbitalis, Pars,Orbitofrontal Cortex, Lateral,Orbitofrontal Cortices,Orbitofrontal Cortices, Lateral,Orbitofrontal Regions,Prefrontal Cortex, Anterior,Prefrontal Cortex, Ventromedial,Prefrontal Cortices, Anterior,Region, Orbitofrontal,Subcallosal Areas,Sulcus, Frontal,Superior Frontal Convolutions,Superior, Gyrus Frontalis,Ventromedial Prefrontal Cortices
D050484 Norepinephrine Plasma Membrane Transport Proteins Sodium chloride-dependent neurotransmitter symporters located primarily on the PLASMA MEMBRANE of noradrenergic neurons. They remove NOREPINEPHRINE from the EXTRACELLULAR SPACE by high affinity reuptake into PRESYNAPTIC TERMINALS. The norepinephrine transporter regulates signal amplitude and duration at noradrenergic synapses and is the target of ADRENERGIC UPTAKE INHIBITORS. Neurotransmitter Transporters, Noradrenaline-Specific,Norepinephrine Plasma Membrane Transporter Proteins,Norepinephrine Plasma Membrane Transporters,NET Protein, Neuronal,Noradrenaline Plasma Membrane Transport Proteins,Noradrenaline Transporter,Norepinephrine Transporter,Norepinephrine Transporter Protein,SLC6A2 Protein,Sodium-Dependent Noradrenaline Transporter,Solute Carrier Family 6 Member 2,Neuronal NET Protein,Neurotransmitter Transporters, Noradrenaline Specific,Noradrenaline Transporter, Sodium-Dependent,Noradrenaline-Specific Neurotransmitter Transporters,Sodium Dependent Noradrenaline Transporter,Transporter Protein, Norepinephrine,Transporter, Noradrenaline,Transporter, Norepinephrine,Transporters, Noradrenaline-Specific Neurotransmitter
D058647 Adrenergic alpha-2 Receptor Agonists Compounds that bind to and activate ADRENERGIC ALPHA-2 RECEPTORS. Adrenergic alpha-2 Agonists,Adrenergic alpha-2 Receptor Agonist,Adrenergic alpha2-Agonists,Adrenergic alpha 2 Agonists,Adrenergic alpha 2 Receptor Agonist,Adrenergic alpha 2 Receptor Agonists,Adrenergic alpha2 Agonists,Agonists, Adrenergic alpha-2,alpha-2 Agonists, Adrenergic,alpha2-Agonists, Adrenergic

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