Increased GABAergic transmission in neuropeptide Y-expressing neurons in the dopamine-depleted murine striatum

2020 ◽  
Vol 123 (4) ◽  
pp. 1496-1503
Author(s):  
Lena Rubi ◽  
Jean-Marc Fritschy

As the main input nucleus of the basal ganglia, the striatum plays a central role in planning, control, and execution of movement and motor skill learning. More than 90% of striatal neurons, so-called medium spiny neurons (MSN), are GABAergic projection neurons, innervating primarily the substantia nigra pars reticulata or the globus pallidus internus. The remaining neurons are GABAergic and cholinergic interneurons, synchronizing and controlling striatal output by reciprocal connections with MSN. Besides prominent local cholinergic influence, striatal function is globally regulated by dopamine (DA) from the nigrostriatal pathway. Little is known about whether DA depletion, as occurs in Parkinson’s disease, affects the activity of striatal interneurons. Here we focused on neuropeptide Y (NPY)-expressing interneurons, which are among the major subgroups of GABAergic interneurons in the striatum. We investigated the effects of striatal DA depletion on GABAergic transmission in NPY interneurons by electrophysiologically recording GABAergic spontaneous (s) and miniature (m) inhibitory postsynaptic currents (IPSCs) in identified NPY interneurons in slices from 6-hydroxydopamine (6-OHDA)- and vehicle-injected transgenic NPY-humanized Renilla green fluorescent protein (hrGFP) mice with the whole cell patch-clamp technique. We report a significant increase in sIPSC and mIPSC frequency as well as the occurrence of giant synaptic and burst sIPSCs in the 6-OHDA group, suggesting changes in GABAergic circuit activity and synaptic transmission. IPSC kinetics remained unchanged, pointing to mainly presynaptic changes in GABAergic transmission. These results show that chronic DA depletion following 6-OHDA injection causes activity-dependent and -independent increase of synaptic GABAergic inhibition onto striatal NPY interneurons, confirming their involvement in the functional impairments of the DA-depleted striatum. NEW & NOTEWORTHY Neuropeptide Y (NPY) interneurons regulate the function of striatal projection neurons and are upregulated upon dopamine depletion in the striatum. Here we investigated how dopamine depletion affects NPY circuits and show electrophysiologically that it leads to the occurrence of giant synaptic and burst GABAergic spontaneous inhibitory postsynaptic currents (IPSCs) and to an activity-independent increase in GABAergic miniature IPSC frequency in NPY neurons. We suggest that degeneration of dopaminergic terminals in the striatum causes functional changes in striatal GABAergic function.

2003 ◽  
Vol 90 (2) ◽  
pp. 559-565 ◽  
Author(s):  
Karima Azdad ◽  
Richard Piet ◽  
Dominique A. Poulain ◽  
Stéphane H. R. Oliet

The mechanism by which dopamine induces or facilitates neurohypophysial hormone release is not completely understood. Because oxytocin- and vasopressin-secreting supraoptic neurons are under the control of a prominent GABAergic inhibition, we investigated the possibility that dopamine exerts its action by modulating GABA-mediated transmission. Whole cell voltage-clamp recordings of supraoptic neurons were carried out in acute hypothalamic slices to determine the action of dopamine on inhibitory postsynaptic currents. Application of dopamine caused a consistent and reversible reduction in the frequency, but not the amplitude, of miniature synaptic events, indicating that dopamine was acting presynaptically to reduce GABAergic transmission. The subtype of dopamine receptor involved in this response was characterized pharmacologically. Dopamine inhibitory action was greatly reduced by two highly selective D4 receptor antagonists L745,870 and L750,667 and to a lower extent by the antipsychotic drug clozapine but was unaffected by SCH 23390 and sulpiride, D1/D5 and D2/D3 receptor antagonists, respectively. In agreement with these results, the action of dopamine was mimicked by the potent D4 receptor agonist PD168077 but not by SKF81297 and bromocriptine, D1/D5 and D2/D3 receptor agonists, respectively. Dopamine and PD168077 also reduced the amplitude of evoked inhibitory postsynaptic currents, an effect that was accompanied by an increase in paired-pulse facilitation. These data clearly indicate that D4 receptors are located on GABA terminals in the supraoptic nucleus and that their activation reduces GABA release in the supraoptic nucleus. Therefore dopaminergic facilitation of neurohypophysial hormone release appears to result, at least in part, from disinhibition of magnocellular neurons caused by the depression of GABAergic transmission.


2010 ◽  
Vol 104 (3) ◽  
pp. 1355-1369 ◽  
Author(s):  
Marc Deffains ◽  
Eric Legallet ◽  
Paul Apicella

The striatum, especially its dorsolateral part, plays a major role in motor skill learning and habit formation, but it is still unclear how this contribution might be mediated at the neuronal level. We recorded single neurons in the posterior putamen of two monkeys performing an overlearned sequence of arm reaching movements to examine whether task-related activities are sensitive to manipulations of the serial order of stimulus-target locations. The monkeys' capacity to learn sequential regularities was assessed by comparing arm movement latencies and saccadic ocular reactions when a fixed repeating sequence was replaced with a random sequence. We examined neurons classified as phasically active projection neurons (PANs) and tonically active presumed cholinergic interneurons (TANs). About one-third of the PANs (35/106, 33%) activated during specific parts of a trial displayed modulations of their level of activation when the sequential structure was changed. This differential activity consisted of either decreases or increases in activity without altering the time period during which task-related activations occurred. In addition, half of the TANs (41/80, 51%) changed their responses to task stimuli with the sequence switch, indicating that the response selectivity of TANs reflects the detection of the context that requires adaptation to changes in the serial order of stimulus presentations. Our findings suggest that task-related changes in activity of projection neurons may be an important factor contributing to the production and adjustment of sequential behavior executed in an automatic fashion, whereas putative interneurons may provide a signal for performance monitoring in specific contexts.


2000 ◽  
Vol 92 (2) ◽  
pp. 485-485 ◽  
Author(s):  
Hiroshi Baba ◽  
Peter A. Goldstein ◽  
Manabu Okamoto ◽  
Tatsuro Kohno ◽  
Toyofumi Ataka ◽  
...  

Background It has been reported previously that norepinephrine, when applied to the spinal cord dorsal horn, excites a subpopulation of dorsal horn neurons, presumably inhibitory interneurons. In the current study, the authors tested whether norepinephrine could activate inhibitory interneurons, specifically those that are "GABAergic." Methods A transverse slice was obtained from a segment of the lumbar spinal cord isolated from adult male Sprague-Dawley rats. Whole-cell patch-clamp recordings were made from substantia gelatinosa neurons using the blind patch-clamp technique. The effects of norepinephrine on spontaneous GABAergic inhibitory postsynaptic currents were studied. Results In the majority of substantia gelatinosa neurons tested, norepinephrine (10-60 microM) significantly increased both the frequency and the amplitude of GABAergic inhibitory postsynaptic currents. These increases were blocked by tetrodotoxin (1 microM). The effects of norepinephrine were mimicked by the alpha1-receptor agonist phenylephrine (10-80 microM) and inhibited by the alpha1-receptor-antagonist WB-4101 (0.5 microM). Primary-afferent-evoked polysynaptic excitatory postsynaptic potentials or excitatory postsynaptic currents in wide-dynamic-range neurons of the deep dorsal horn were also attenuated by phenylephrine (40 microM). Conclusion The observations suggest that GABAergic interneurons possess somatodendritic alpha1 receptors, and activation of these receptors excites inhibitory interneurons. The alpha1 actions reported herein may contribute to the analgesic action of intrathecally administered phenylephrine.


2000 ◽  
Vol 92 (2) ◽  
pp. 473-473 ◽  
Author(s):  
Hiroshi Baba ◽  
Koki Shimoji ◽  
Megumu Yoshimura

Background The activation of descending norepinephrine-containing fibers from the brain stem inhibits nociceptive transmission at the spinal level. How these descending noradrenergic pathways exert the analgesic effect is not understood fully. Membrane hyperpolarization of substantia gelatinosa (Rexed lamina II) neurons by the activation of alpha2 receptors may account for depression of pain transmission. In addition, it is possible that norepinephrine affects transmitter release in the substantia gelatinosa. Methods Adult male Sprague-Dawley rats (9-10 weeks of age, 250-300 g) were used in this study. Transverse spinal cord slices were cut from the isolated lumbar cord. The blind whole-cell patch-clamp technique was used to record from neurons. The effects of norepinephrine on the frequency and amplitude of miniature excitatory and inhibitory postsynaptic currents were evaluated. Results In the majority of substantia gelatinosa neurons tested, norepinephrine (10-100 microM) dose-dependently increased the frequency of gamma-aminobutyric acid (GABA)ergic and glycinergic miniature inhibitory postsynaptic currents; miniature excitatory postsynaptic currents were unaffected. This augmentation was mimicked by an alpha1-receptor agonist, phenylephrine (10-60 microM), and inhibited by alpha1-receptor antagonists prazosin (0.5 microM) and 2-(2,6-dimethoxyphenoxyethyl) amino-methyl-1,4-benzodioxane (0.5 microM). Neither postsynaptic responsiveness to exogenously applied GABA and glycine nor the kinetics of GABAergic and glycinergic inhibitory postsynaptic currents were affected by norepinephrine. Conclusion These results suggest that norepinephrine enhances inhibitory synaptic transmission in the substantia gelatinosa through activation of presynaptic alpha1 receptors, thus providing a mechanism underlying the clinical use of alpha1 agonists with local anesthetics in spinal anesthesia.


2021 ◽  
Author(s):  
Gwenaelle Laverne ◽  
Jonathan Pesce ◽  
Ana Reynders ◽  
Christophe Melon ◽  
Lydia Kerkerian-Le Goff ◽  
...  

Striatal cholinergic interneurons (CINs) respond to salient or reward prediction-related stimuli after conditioning with brief pauses in their activity, implicating them in learning and action selection. This pause is lost in animal models of Parkinson′s disease. How this signal regulates the functioning of the striatum remains an open question. To address this issue, we examined the impact of CIN firing inhibition on glutamatergic transmission between the cortex and the medium-sized spiny projection neurons expressing dopamine D1 receptors (D1 MSNs). Brief interruption of CIN activity had no effect in control condition whereas it increased glutamatergic responses in D1 MSNs after nigrostriatal dopamine denervation. This potentiation was dependent upon M4 muscarinic receptor and protein kinase A. Decreasing CIN firing by opto/chemogenetic strategies in vivo rescued long-term potentiation in some MSNs and alleviated motor learning deficits in parkinsonian mice. Taken together, our findings demonstrate that the control exerted by CINs on corticostriatal transmission and striatal-dependent motor-skill learning depends on the integrity of dopaminergic inputs.


1995 ◽  
Vol 74 (5) ◽  
pp. 2138-2149 ◽  
Author(s):  
R. Khazipov ◽  
P. Congar ◽  
Y. Ben-Ari

1. The effects of anoxia on excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) evoked by electrical stimulation in the stratum radiatum were studied in morphologically and electrophysiologicaly identified lacunosum-moleculare (LM) interneurons of the CA1 region of rat hippocampal slices. The blind whole cell patch-clamp technique was used, and anoxia was induced by superfusion of the slice with an anoxic artificial cerebral spinal fluid saturated with 95% N2-5% CO2 for 4-6 min. 2. In LM interneurons, anoxia generated currents similar to those in pyramidal cells, the most prominent being anoxic and postanoxic outward currents. The adenosine A1 type receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 200 nM) did not significantly affect anoxia-generated currents. 3. EPSCs and polysynaptic IPSCs (pIPSCs) evoked in LM interneurons by "distant" stimulation (> 1 mm) in the stratum radiatum were strongly depressed by anoxia and recovered upon reoxygenation. 4. Responses to pressure application of glutamate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA) were not significantly affected by anoxia, suggesting that the suppression of EPSCs is due to presynaptic mechanisms. 5. DPCPX (200 nM) prevented anoxia-induced suppression of EPSCs, suggesting that this suppression was mediated by presynaptic A1 adenosine receptors. 6. Monosynaptic IPSCs evoked by "close" stimulation (< 0.5 mm) in the stratum radiatum, in the presence of glutamate-receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 20 microM) and D-2-amino-5-phosphopentanoate (APV; 50 microM), were reversibly depressed but not blocked by anoxia. 7. Anoxia depressed monosynaptic GABAA receptor-mediated IPSCs (monosynaptic IPSCAs) by inducing a positive shift in the reversal potential and a decrease in slope conductance. Responses to pressure-applied isoguvacine, a GABAA receptor agonist, were reversibly depressed by anoxia, again because of a positive shift in reversal potential and decrease in conductance. Anoxic effects on slope conductances and reversal potential of isoguvacine responses and monosynaptic IPSCA coincided, suggesting that evoked transmitter release from GABAergic terminals was not affected by anoxia. 8. Anoxic depression of monosynaptic GABAB receptor-mediated IPSCs (monosynaptic IPSCBs) was due to a decrease in the slope conductance of monosynaptic IPSCB. In contrast to EPSCs, DPCPX (200 nM) failed to prevent anoxia-induced depression of mIPSCA and mIPSCB. 9. Paired-pulse depression of monosynaptic IPSCs, partially mediated by presynaptic GABAB receptors, was not affected by anoxia. 10. These data provide direct evidence for the hypothesis that inhibitory interneurons of CA1 stratum LM are functionally disconnected from excitatory inputs by anoxia. This disconnection underlies the preferential block by anoxia of IPSCs recorded in pyramidal cells, and it may occult the postsynaptic modifications in GABAA and GABAB responses. This disconnection involves adenosine-dependent inhibition of glutamate release from excitatory terminals. GABA release and its modulation by presynaptic GABAB receptors, both known to be insensitive to adenosine, seems to be resistant to anoxia.


2000 ◽  
Vol 92 (2) ◽  
pp. 507-507 ◽  
Author(s):  
Tatsuro Kohno ◽  
Eiichi Kumamoto ◽  
Hiroshi Baba ◽  
Toyofumi Ataka ◽  
Manabu Okamoto ◽  
...  

Background Although intrathecal administration of midazolam has been found to produce analgesia, how midazolam exerts this effect is not understood fully at the neuronal level in the spinal cord. Methods The effects of midazolam on either electrically evoked or spontaneous inhibitory transmission and on a response to exogenous gamma-aminobutyric acid (GABA), a GABA(A)-receptor agonist, muscimol, or glycine were evaluated in substantia gelatinosa neurons of adult rat spinal cord slices by using the whole-cell patch-clamp technique. Results Bath-applied midazolam (1 microM) prolonged the decay phase of evoked and miniature inhibitory postsynaptic currents (IPSCs), mediated by GABA(A) receptors, without a change in amplitudes, while not affecting glycine receptor-mediated miniature inhibitory postsynaptic currents in both the decay phase and the amplitude. Either GABA- or muscimol-induced currents were enhanced in amplitude by midazolam (0.1 microM) in a manner sensitive to a benzodiazepine receptor antagonist, flumazenil (1 microM); glycine currents were, however, unaltered by midazolam. Conclusions Midazolam augmented both the duration of GABA-mediated synaptic current and the amplitude of GABA-induced current by acting on the GABA(A)-benzodiazepine receptor in substantia gelatinosa neurons; this would increase the inhibitory GABAergic transmission. This may be a possible mechanism for antinociception by midazolam.


1994 ◽  
Vol 72 (6) ◽  
pp. 2903-2910 ◽  
Author(s):  
I. Araki

1. The actions of gamma-aminobutyric acid (GABA) on sacral parasympathetic preganglionic (SPP) neurons were examined in slice preparations using the whole cell patch-clamp technique. 2. Inhibitory postsynaptic currents (IPSCs), which were evoked by focal electrical stimulation, were recorded from SPP neurons in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a glutamate receptor antagonist. The IPSCs were substantially reduced by strychnine (1 microM), a glycine receptor antagonist. The remaining IPSCs were completely blocked by bicuculline (20 microM), a GABAA receptor antagonist. The mean peak amplitude of bicuculline-sensitive, GABAergic currents recorded at -60 mV was 53.6 +/- 10.9%, mean +/- SD (n = 8), of that of the total IPSCs. The GABAergic currents were reversed in polarity at about -30 mV, near the Cl- equilibrium potential. 3. GABA (5-50 microM) induced inward currents in SPP neurons with symmetrical internal and external Cl- concentrations. This response was completely blocked by 100 microM bicuculline. Muscimol (2-8 microM), a GABAA agonist, mimicked the GABA-induced responses, whereas a GABAB receptor agonist, baclofen (20-200 microM), produced responses in only a few cells. The GABA-induced currents reversed their polarity at approximately 0 mV, near the Cl- equilibrium potential. When the internal Cl- concentration was reduced, the reversal potential was shifted according to the Nernst equation for Cl-. 4. GABA-induced currents exhibited an outward "hump" between -35 and 15 mV. This voltage range coincided with that at which a depolarization-induced inward whole cell current was elicited.(ABSTRACT TRUNCATED AT 250 WORDS)


Author(s):  
Е.И. Захарова ◽  
З.И. Сторожева ◽  
А.Т. Прошин ◽  
М.Ю. Монаков ◽  
А.М. Дудченко

Цель - исследование холинергической синаптической организации функций обучения и памяти у крыс с разными когнитивными способностями. Методы. Крыс обучали на пространственной обстановочной модели в водном лабиринте Морриса. Через 2-3 сут. после окончания тренировок животных декапитировали, из неокортекса и гиппокампа с помощью центрифугирования выделяли субфракции синаптических мембран и синаптоплазмы легких и тяжелых синаптосом. В синаптических субфракциях определяли активность ключевого фермента холинергических нейронов холинацетилтрансферазы (ХАТ). Сравнивали результаты тестирования (время достижения скрытой платформы) и активность фермента у способных и неспособных к обучению крыс. Результаты. Были выявлены: 1) различия в холинергической организации исследованных функций в процессе обучения у способных и неспособных к обучению крыс, в том числе: положительные корреляции активности ХАТ в синапсах проекционных нейронов неокортекса у способных крыс со временем достижения платформы на промежуточных этапах обучения и в синапсах проекционных нейронов гиппокампа у неспособных крыс на позднем этапе обучения; разнонаправленные корреляции активности ХАТ в синапсах, предположительно, интернейронов гиппокампа (фракция тяжелых синаптосом) у способных и неспособных крыс на начальном и позднем этапах обучения; 2) индивидуальность холинергической организации функций на всех этапах обучения. Выводы. Полученные данные свидетельствуют в пользу представлений о специфике холинергической организации функций пространственного обстановочного обучения у крыс с выраженными и слабыми способностями к обучению, а также избирательной роли холинергических интернейронов гиппокампа на исходном этапе обучения и в консолидации памяти. In order to expand the knowledge about neuronal organization of the cognitive functions required for understanding plastic processes in the brain, we investigated the cholinergic synaptic organization of learning and memory functions in rats with different cognitive abilities. Methods. Rats were trained on a contextual situation model in the Morris water maze. At 2-3 days after the end of training, animals were decapitated, and subfractions of synaptic membranes and synaptoplasm of light and heavy synaptosomes were isolated from the cortex and the hippocampus by centrifugation. In synaptic subfractions, activity of the key enzyme of cholinergic neurons, choline acetyltransferase, was measured. We compared the test results (latent period to reach the hidden platform) and the enzyme activity in capable (lower quartile) and incapable of learning rats (upper quartile). Results. The following was found: 1) differences in the cholinergic organization of studied functions in capable and uncapable of learning rats during training, including: positive correlations of choline acetyltransferase activity in synapses of projection neurons in the cortex of capable rats with latency to reach the platform at intermediate stages of training and in the hippocampus ofincapable rats at late stages of training; multidirectional correlations of choline acetyltransferase activity in synapses of hippocampal, presumably, interneurons (heavy synaptosomes) in capable and incapable rats at early and late stages of training; 2) distinctness of the cholinergic organization of functions at all stages of training. Conclusions. The study demonstrated for the first time a specificity of the cholinergic organization of functions in spatial situational learning of rats with strong and poor learning abilities and a selective role of hippocampal cholinergic interneurons at the initial stage of learning and in memory consolidation.


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