Opposing Electrophysiological Actions of 5-HT on Noncholinergic and Cholinergic Neurons in the Rat Ventral Pallidum In Vitro

2004 ◽  
Vol 92 (1) ◽  
pp. 433-443 ◽  
Author(s):  
C. Peter Bengtson ◽  
David J. Lee ◽  
Peregrine B. Osborne
Keyword(s):  
Partial Agonist ◽  
Brain Slices ◽  
Cholinergic Neurons ◽  
Receptor Activation ◽  
Dorsal Raphe ◽  
Ventral Pallidum ◽  
Inward Current ◽  
Inward Currents ◽  
Dorsal Raphé

The ventral pallidum in rat is a basal forebrain structure that contains neurons that project in the limbic striatopallidal circuitry and magnocellular cholinergic corticopetal neurons. Because 5-hydroxytryptamine (5-HT) terminals on dorsal raphe projections form close appositions with these neurons, we made patch-clamp recordings in immature rat brain slices to determine whether they are modulated by postsynaptic 5-HT receptors. Inward currents were predominantly induced by 5-HT in noncholinergic neurons, which were distinguished from cholinergic neurons by immunohistochemical and electrophysiological criteria. The inward current induced by 5-HT was mimicked and occluded when adenylyl cyclase was stimulated with forskolin, and was almost abolished when h-currents in noncholinergic neurons were blocked with cesium. Consistent with 5-HT7 receptor activation of h-curents by cAMP in other brain regions, we found inward currents were mimicked by the mixed 5-HT1/5-HT7 agonists 5-methoxytryptamine, and by 5-carboxamidotryptamine (5-CT), which was more potent than 5-HT. In contrast, 5-HT1 preferring 8-OH-DPAT was a weak partial agonist, and the 5-HT1–selective antagonist pindolol had no effect. However, despite this profile, antagonists that bind at the 5-HT7 receptor only partly reduced the agonist inward current (SB-269970 and clozapine), or had no effect (mianserin and pimozide). We found in cholinergic neurons that 5-HT predominantly induced hyperpolarizing currents, which were carried by potassium channels, and were smaller than currents induced by 8-OH-DPAT and 5-CT. We conclude from this study that ascending 5-HT projections from the dorsal raphe could have direct and opposite effects on the activities of neurons within the limbic striatopallidal and cholinergic corticopetal circuitry in the ventral pallidum.

Serotonergic and Nonserotonergic Dorsal Raphe Neurons Are Pharmacologically and Electrophysiologically Heterogeneous

2004 ◽  
Vol 92 (6) ◽  
pp. 3532-3537 ◽  
Author(s):  
Silvia Marinelli ◽  
Stephen A. Schnell ◽  
Stephen P. Hack ◽  
MacDonald J. Christie ◽  
Martin W. Wessendorf ◽  
...  
Keyword(s):  
Action Potential ◽  
Tryptophan Hydroxylase ◽  
Large Population ◽  
Receptor Activation ◽  
Dorsal Raphe ◽  
Inward Currents ◽  
Different Populations ◽  
The Brain ◽  
Dorsal Raphé

The dorsal raphe nucleus (DRN) projects serotonergic axons throughout the brain and is involved in a variety of physiological functions. However, it also includes a large population of cells that contain other neurotransmitters. To clarify the physiological and pharmacological differences between the serotonergic and nonserotonergic neurons of the DRN, their postsynaptic responses to 5-hydroxytryptamine (5-HT, serotonin) and to selective activation of 5-HT1A or 5-HT2A/C receptors and their action potential characteristics were determined using in vitro patch-clamp recordings. The slices containing these neurons were then immunostained for tryptophan hydroxylase (TPH), a marker of serotonergic neurons. It was found that subpopulations of both serotonergic and nonserotonergic neurons responded to 5-HT with outward (i.e., inhibitory) and inward (i.e., excitatory) currents, responded to both 5-HT1A and 5-HT2A/C receptor activation with outward and inward currents, respectively, and displayed overlapping action potential characteristics. These findings suggest that serotonergic and nonserotonergic neurons in the DRN are both heterogeneous with respect to their individual pharmacological and electrophysiological characteristics. The findings also suggest that the activity of the different populations of DRN neurons will display heterogeneous changes when the serotonergic tone in the DRN is altered by neurological disorders or by drug treatment.

scholarly journals Dual Orexin Actions on Dorsal Raphe and Laterodorsal Tegmentum Neurons: Noisy Cation Current Activation and Selective Enhancement of Ca2+ Transients Mediated by L-Type Calcium Channels

2008 ◽  
Vol 100 (4) ◽  
pp. 2265-2281 ◽  
Author(s):  
K. A. Kohlmeier ◽  
S. Watanabe ◽  
C. J. Tyler ◽  
S. Burlet ◽  
C. S. Leonard
Keyword(s):  
Brain Slices ◽  
Cholinergic Neurons ◽  
Cell Types ◽  
Dorsal Raphe ◽  
Central Neurons ◽  
Cation Current ◽  
Current Activation ◽  
Reticular Activating System ◽  
Selective Enhancement ◽  
Dorsal Raphé

The hypocretin/orexins (Hcrt/Orxs) are hypothalamic neuropeptides that regulate stress, addiction, feeding, and arousal behaviors. They depolarize many types of central neurons and can increase [Ca2+]i in some, including those of the dorsal raphe (DR) and laterodorsal tegmental (LDT) nuclei—two structures likely to contribute to the behavioral actions of Hcrt/Orx. In this study, we used simultaneous whole cell and Ca2+-imaging methods in mouse brain slices to compare the Hcrt/Orx-activated current in DR and LDT neurons and to determine whether it contributes to the Ca2+ influx evoked by Hcrt/Orx. We found Hcrt/Orx activates a similar noisy cation current that reversed near 0 mV in both cell types. Contrary to our expectation, this current did not contribute to the somatic Ca2+ influx evoked by Hcrt/Orx. In contrast, Hcrt/Orx enhanced the Ca2+ transients produced by voltage steps (−60 to −30 mV) by ∼30% even in neurons lacking an inward current. This effect was abolished by nifedipine, augmented by Bay-K and abolished by bisindolylmaleimide I. Thus Hcrt/Orx has two independent actions: activation of noisy cation channels that generate depolarization and activation of a protein kinase C (PKC)-dependent enhancement of Ca2+ transients mediated by L-type Ca2+ channels. Immunocytochemistry verified that both these actions occurred in serotonergic and cholinergic neurons, indicating that Hcrt/Orx can function as a neuromodulator in these key neurons of the reticular activating system. Because regulation of Ca2+ transients mediated by L-channels is often linked to the control of transcriptional signaling, our findings imply that Hcrt/Orxs may also function in the regulation of long-term homeostatic or trophic processes.

Epileptogenesis Up-Regulates Metabotropic Glutamate Receptor Activation of Sodium-Calcium Exchange Current in the Amygdala

2000 ◽  
Vol 83 (4) ◽  
pp. 2458-2462 ◽  
Author(s):  
N. Bradley Keele ◽  
Fatiha Zinebi ◽  
Volker Neugebauer ◽  
P. Shinnick-Gallagher
Keyword(s):  
Basolateral Amygdala ◽  
Metabotropic Glutamate Receptor ◽  
Partial Agonist ◽  
Brain Slices ◽  
Receptor Activation ◽  
Exchange Current ◽  
Inward Current ◽  
Mglu Receptor ◽  
Metabotropic Glutamate ◽  
Group I

Postsynaptic metabotropic glutamate (mGlu) receptor-activated inward current mediated by Na+-Ca2+ exchange was compared in basolateral amygdala (BLA) neurons from brain slices of control (naı̈ve and sham-operated) and amygdala-kindled rats. In control neurons, the mGlu agonist, quisqualate (QUIS; 1–100 μM), evoked an inward current not associated with a significant change in membrane slope conductance, measured from current-voltage relationships between −110 and −60 mV, consistent with activation of the Na+-Ca2+ exchanger. Application of the group I selective mGlu receptor agonist ( S)-3,5-dihydroxyphenylglycine [( S)-DHPG; 10–1000 μM] or the endogenous agonist, glutamate (10–1000 μM), elicited the exchange current. QUIS was more potent than either ( S)-DHPG or glutamate (apparent EC50 = 19 μM, 57 μM, and 0.6 mM, respectively) in activating the Na+-Ca2+ exchange current. The selective mGlu5 agonist, ( R,S)-2-chloro-5-hydroxyphenylglycine [( R,S)-CHPG; apparent EC50 = 2.6 mM] also induced the exchange current. The maximum response to ( R,S) -DHPG was about half of that of the other agonists suggesting partial agonist action. Concentration-response relationships of agonist-evoked inward currents were compared in control neurons and in neurons from kindled animals. The maximum value for the concentration-response relationship of the partial agonist ( S)-DHPG- (but not the full agonist- [QUIS or ( R, S)-CHPG]) induced inward current was shifted upward suggesting enhanced efficacy of this agonist in kindled neurons. Altogether, these data are consistent with a kindling-induced up-regulation of a group I mGlu-, possibly mGlu5-, mediated responses coupled to Na+-Ca2+ exchange in BLA neurons.

The actions of hydrogen sulfide on dorsal raphe serotonergic neurons in vitro

1993 ◽  
Vol 70 (1) ◽  
pp. 81-96 ◽  
Author(s):  
S. B. Kombian ◽  
R. J. Reiffenstein ◽  
W. F. Colmers
Keyword(s):  
Hydrogen Sulfide ◽  
Outward Current ◽  
Rapid Onset ◽  
Dorsal Raphe ◽  
Membrane Properties ◽  
Delayed Rectifier ◽  
Inward Current ◽  
Voltage Dependent ◽  
Dorsal Raphé

1. The actions of hydrogen sulfide (HS-) on membrane and synaptic properties of dorsal raphe (DR) serotonergic cells were studied in the in vitro brain stem slice preparation, using intracellular sharp microelectrode and whole-cell recording techniques. 2. Sulfide produced two reversible, concentration-dependent effects on resting membrane properties of DR cells: (1) 14% responded to HS- with a slow onset hyperpolarization or an outward current accompanied by an conductance increase in voltage clamp (holding potential = -60 mV; monophasic outward cell) or (2) 39% responded with a rapid-onset depolarization corresponding to a weakly voltage-dependent inward current showing little or no change in conductance between -115 and -40 mV (monophasic inward cell). In addition, 29.5% showed both the above effects, responding first with a rapid-onset depolarization and then a sustained hyperpolarization. Such cells had membrane currents very similar to those seen in the monophasic inward and outward cells (biphasic cells). Finally, 17.5% of DR cells had no measurable postsynaptic membrane response to HS-. 3. The outward current induced in the presence of HS- had a reversal potential of about -90 mV when recorded either with 2 M KCl or 145 mM potassium gluconate in the pipette and was accompanied by an increase in conductance, suggesting that it is caused by an elevated conductance to K+. 4. This current was sensitive to the removal of external Ca2+ and blockade by Cd2+, suggesting that it is activated by an elevation in internal [Ca2+]. It was also blocked by apamin or Ba2+ and Cs+, both of which revealed an underlying inward current. The outward current was insensitive to the application of a large variety of antagonists to other known voltage- and calcium-dependent K+ channels. Elevation of intracellular ATP using a patch pipette did not prevent the activation of the outward current. 5. HS- reversibly suppressed a voltage-dependent outward current activated in the voltage range of -50 to -40 mV. This current was also blocked by 10 mM tetraethylammonium, suggesting that HS- suppresses the delayed rectifier in DR cells. 6. The inward current could be observed in the presence of HS- not only in monophasic inward cells but also in monophasic outward or biphasic cells whose outward current was selectively blocked. This inward current was sensitive to the removal of extracellular Ca2+, or the the application of relatively low concentrations of Cd2+, suggesting that it is carried by Ca2+. Both these manipulations also blocked the outward current in monophasic outward or biphasic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Physiology, Pharmacology, and Topography of Cholinergic Neocortical Oscillations In Vitro

1997 ◽  
Vol 77 (5) ◽  
pp. 2427-2445 ◽  
Author(s):  
Heath S. Lukatch ◽  
M. Bruce Maciver
Keyword(s):  
Current Source ◽  
Brain Slices ◽  
Receptor Activation ◽  
Brain Regions ◽  
Oscillatory Activity ◽  
Cortical Layers ◽  
Eeg Activity ◽  
Layer 2

Lukatch, Heath S. and M. Bruce MacIver. Physiology, pharmacology, and topography of cholinergic neocortical oscillations in vitro. J. Neurophysiol. 77: 2427–2445, 1997. Rat neocortical brain slices generated rhythmic extracellular field [microelectroencephalogram (micro-EEG)] oscillations at theta frequencies (3–12 Hz) when exposed to pharmacological conditions that mimicked endogenous ascending cholinergic and GABAergic inputs. Use of the specific receptor agonist and antagonist carbachol and bicuculline revealed that simultaneous muscarinic receptor activation and γ-aminobutyric acid-A (GABAA)-mediated disinhibition werenecessary to elicit neocortical oscillations. Rhythmic activity was independent of GABAB receptor activation, but required intact glutamatergic transmission, evidenced by blockade or disruption of oscillations by 6-cyano-7-nitroquinoxaline-2,3-dione and (±)-2-amino-5-phosphonovaleric acid, respectively. Multisite mapping studies showed that oscillations were localized to areas 29d and 18b (Oc2MM) and parts of areas 18a and 17. Peak oscillation amplitudes occurred in layer 2/3, and phase reversals were observed in layers 1 and 5. Current source density analysis revealed large-amplitude current sinks and sources in layers 2/3 and 5, respectively. An initial shift in peak inward current density from layer 1 to layer 2/3 indicated that two processes underlie an initial depolarization followed by oscillatory activity. Laminar transections localized oscillation-generating circuitry to superficial cortical layers and sharp-spike-generating circuitry to deep cortical layers. Whole cell recordings identified three distinct cell types based on response properties during rhythmic micro-EEG activity: oscillation-on (theta-on) and -off (theta-off) neurons, and transiently depolarizing glial cells. Theta-on neurons displayed membrane potential oscillations that increased in amplitude with hyperpolarization (from −30 to −90 mV). This, taken together with a glutamate antagonist-induced depression of rhythmic micro-EEG activity, indicated that cholinergically driven neocortical oscillations require excitatory synaptic transmission. We conclude that under the appropriate pharmacological conditions, neocortical brain slices were capable of producing localized theta frequency oscillations. Experiments examining oscillation physiology, pharmacology, and topography demonstrated that neocortical brain slice oscillations share many similarities with the in vivo and in vitro theta EEG activity recorded in other brain regions.

Species-specific Effects of Nitromethylene Heterocycle Insecticides on Nicotinic Receptors in Locust Neurons and Mouse N1E-115 and BC3H1 Cells

1994 ◽  
Vol 22 (6) ◽  
pp. 454-461
Author(s):  
Marga Oortgiesen ◽  
Ruud Zwart ◽  
Henk P.M. Vijverberg
Keyword(s):  
Mammalian Cells ◽  
Neuroblastoma Cells ◽  
Receptor Subtypes ◽  
Inward Current ◽  
Specific Effects ◽  
Blocking Effects ◽  
Inward Currents ◽  
Species Specific ◽  
Ganglion Neurons

The effects of nitromethylene heterocycle (NMH) insecticides on subtypes of nicotinic acetylcholine (nACh) receptors were investigated in locust thoracic ganglion neurons, mouse N1E-115 neuroblastoma cells, and mouse BC3H1 muscle cells by using electrophysiological techniques. In locust neurons, all of the six NMH insecticides tested induced transient inward currents resembling nicotinic ACh-induced inward currents, while, in the continued presence of the NMH compounds, the ACh-induced inward current was blocked. The amplitude of the inward current and the blocking effects of the NMH insecticides were enhanced by concentrations between 0.1 and 10μM. Cross-desensitisation with the ACh-induced inward current confirmed that the NMH-induced inward current was governed by the activation of nACh receptors. Mammalian endplate type nACh receptors in BC3H1 cells and mammalian neuronal type nACh receptors in N1E-115 cells were much less sensitive to the NMH insecticides than the locust neuronal nACh receptors. At a concentration of 10μM, which blocked 80–100% of the ACh-induced inward current in locust neurons, NMH insecticides only partially blocked the ACh-induced inward currents mediated by the two subtypes of mammalian nACh receptors. NMH insecticides also failed to induce significant agonist effects in the mammalian cells at this concentration. The results provide a possible explanation for the selectively greater toxicity of NMH insecticides to insects than to vertebrates, at the level of nACh receptor subtypes and, hence, demonstrate that this in vitro approach is valuable for the investigation of species-specific interactions of compounds at their target site.

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