Activity-dependent neuromodulation in Aplysia neuron R15: intracellular calcium antagonizes neurotransmitter responses mediated by cAMP

1990 ◽  
Vol 63 (5) ◽  
pp. 1075-1088 ◽  
Author(s):  
R. H. Kramer ◽  
I. B. Levitan
Keyword(s):  
Action Potentials ◽  
Direct Action ◽  
Ionic Currents ◽  
Egg Laying ◽  
Maximal Response ◽  
Maximal Effect ◽  
Spontaneous Action ◽  
High Concentrations ◽  
Bag Cells ◽  
Activity Dependent

1. The effect of electrical activity on the response to the neuromodulators serotonin (5-HT) and the neuropeptide egg-laying hormone (ELH) was studied in the Aplysia bursting pacemaker neuron R15. 2. Previous work has shown that 5-HT and ELH augment R15s bursting activity by enhancing two ionic currents, an inwardly rectifying K+ current (IR) and a voltage-gated Ca2+ current (ICa), and that the enhancement of the currents is mediated by the intracellular second-messenger adenosine 3',5'-cyclic monophosphate (cAMP). Here we show that both spontaneous action potentials and voltage-clamp depolarizations suppress the modulation by 5-HT and ELH of these currents. Both spontaneous and evoked depolarizations decrease the magnitude and dramatically speed the decay of the modulation of IR and ICa. 3. The depolarization-induced suppression is blocked by intracellular ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N',-tetraacetic acid (EGTA), indicating that the suppression is Ca-dependent. The suppression is specific for responses mediated by cAMP; a non-cyclic AMP-mediated response to acetylcholine is not affected by depolarizing pulses. 4. The Ca-dependent suppression of IR modulation differs from the Ca-dependent suppression of ICa modulation. Ca2+ influx decreases the sensitivity of IR to neuromodulators without reducing the maximal response elicited by high concentrations of neuromodulators. In contrast, Ca2+ not only decreases the sensitivity of ICa but also reduces the maximal effect elicited by high concentrations of neuromodulators. We have shown previously that intracellular Ca2+ also inactivates the basal IR and ICa in neuron R15 by distinct mechanisms. The inactivation of IR is due to an antagonistic action of Ca2+ on cAMP metabolism, whereas the inactivation of the basal ICa is due primarily to a more direct action of Ca2+, perhaps on the Ca channels themselves. 5. We also studied the interaction between action potentials and neuromodulator released onto R15 from an endogenous source: bag cell neurons, which release large amounts of ELH during an intense "afterdischarge." IR and ICa become greatly enhanced during the afterdischarge, even though R15 continually fires action potentials. In addition, Ca-dependent inactivation of IR is suppressed during the afterdischarge. We suggest that the bag cells release an amount of ELH sufficient to temporarily saturate the cAMP-mediated enhancement of IR and that this temporarily prevents the suppressive effects of Ca2+ on IR. 6. The activity-dependent suppression of neuromodulation in neuron R15 is an example of neuronal plasticity that results from interactions between intracellular messengers.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Modulation of electrical activity and ionic currents of isolated neurons by orexin A

2013 ◽  
Vol 11 (4) ◽  
pp. 54-60
Author(s):  
Petr Dmitriyevich Shabanov ◽  
Anatoliy Ivanovich Vislobokov
Keyword(s):  
Membrane Potential ◽  
Lymnaea Stagnalis ◽  
Ionic Currents ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Isolated Neurons ◽  
Orexin A ◽  
High Concentrations ◽  
Kinetics Of ◽  
Dose Dependent

The changes in intracellular potential of resting (PR) and potential of action (PA) of the identified neurons of pedal and visceral ganglia of the CNS mollusk Planorbarius corneus registered by means of intracellular electrodes, and ionic currents of isolated neurons under fixed potential after administration of orexin A in concentrations 1, 10, 100 and 1000 µg/ml were studied by the method of fixation of membrane potential in isolated neurons of the Lymnaea stagnalis mollusk. Dibazol in concentrations of 1 and 10 µM effected slightly on the ionic currents. High concentrations of dibazol (100 and 1000 µM) inhibited all currents in dose dependent manner with maximal effect on potassium currents amplitude. ЕС50 were 7.4 мМ for INa, 4.0 мМ for ICa, 83.9 µM for IKs,1 (one group of neurons) and 2.9 мМ for IKs,2 (the another group of neurons). The voltage-amper membrane characteristics shift was not registered, but the kinetics of currents development was changed. Dibazol was more effective in inhibition of ionic currents compared to its structural analogs.

Multiple, prolonged actions of neuroendocrine bag cells on neurons in Aplysia. II. Effects on beating pacemaker and silent neurons

1979 ◽  
Vol 42 (4) ◽  
pp. 1185-1197 ◽  
Author(s):  
E. Mayeri ◽  
P. Brownell ◽  
W. D. Branton
Keyword(s):  
Spike Activity ◽  
Ganglion Cells ◽  
Direct Action ◽  
Neurosecretory Cells ◽  
Behavioral Pattern ◽  
Egg Laying ◽  
Large Numbers ◽  
The Central Nervous System ◽  
Bag Cells ◽  
Ganglion Neurons

1. A survey of identified cells of the abdominal ganglion of Aplysia was undertaken to determine the extent of bag cell influence in the ganglion. Bursts of bag cell spike activity lasting 5--40 min were elicited by brief, 0.6- to 2 s local stimulation while recording simultaneously from bag cells and other ganglion cells with intracellular electrodes. 2. Slow inhibition occurs in giant cell R2, neurosecretory cells R3-R14, and ink-gland motoneurons, L14A, B, C. The cells remain hyperpolarized for from 15 to 60 min. 3. Transient excitation occurs in mechanoreceptor cells L1 and R1. The cells are strongly depolarized by a slow excitatory potential that lasts for about 10 min and produces spike activity for 3--7 min. 4. Prolonged excitation occurs in some cells of the LB and LC identified cell clusters. The cells are depolarized and spike activity is increased for 3 h or more. 5. A biphasic response occasionally occurs in the command interneuron L10. Inhibition of this cell lasts 10--15 min and is followed by excitation for several hours. Excitation is accompanied by facilitation of synaptic potentials for 40--60 min in cells innervated by L10; the facilitation apparently results from the increase in L10 firing rate. 6. The results indicate that the bag cells have multiple types of actions and affect large numbers of ganglion neurons. All effects have the slowly graded onsets and prolonged durations to be expected of hormonally mediated interactions. 7. Previous studies have indicated that in intact animals the bag cell burst discharge initates a stereotyped egg-laying behavioral pattern that persists for several hours (3, 27). The present data support the hypothesis that certain elements of egg-laying behavior and homeostasis are regulated by a direct action of the bag cells on the central nervous system.

scholarly journals Effect of dibazol and its new derivatives on the mollusk ionic channels

2013 ◽  
Vol 11 (3) ◽  
pp. 26-32
Author(s):  
Anatoliy Ivanovich Vislobokov ◽  
Leonid Vitalyevich Myznikov ◽  
Aleksandr Aleksandrovich Tarasenko ◽  
Petr Dmitriyevich Shabanov
Keyword(s):  
Lymnaea Stagnalis ◽  
Ionic Currents ◽  
Ionic Channels ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Isolated Neurons ◽  
High Concentrations ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Sodium And Potassium

The changes in transmembrane calcium, sodium and potassium ionic currents after extracellular administration of dibazol (2-(phenylmethyl)-1H-benzimidazol hydrochloride) and its two new derivatives in concentrations of 1, 10, 100 and 1000 µM were studied by the method of intracellular dialysis and fixation of membrane potential in isolated neurons of the Lymnaea stagnalis mollusk. Dibazol in concentrations of 1 and 10 µM effected slightly on the ionic currents. High concentrations of dibazol (100 and 1000 µM) inhibited all currents in dose dependent manner with maximal effect on potassium currents amplitude. ЕС50 were 7.4 мМ for INa, 4.0 мМ for ICa, 83.9 µM for IKs,1 (one group of neurons) and 2.9 мМ for IKs,2 (the another group of neurons). The voltage-amper membrane characteristics shift was not registered, but the kinetics of currents development was changed. Dibazol was more effective in inhibition of ionic currents compared to its structural analogs.

Methacholine-induced bronchoconstriction in dogs: effects of lung volume and O3 exposure

1988 ◽  
Vol 65 (6) ◽  
pp. 2679-2686 ◽  
Author(s):  
S. T. Kariya ◽  
S. A. Shore ◽  
W. A. Skornik ◽  
K. Anderson ◽  
R. H. Ingram ◽  
...  
Keyword(s):  
Lung Volume ◽  
Maximal Response ◽  
Maximal Effect ◽  
Response Curves ◽  
Lung Volumes ◽  
Before And After ◽  
Residual Capacity ◽  
Induced Changes ◽  
Conducting Airways ◽  
Concentration Response Curve

The maximal effect induced by methacholine (MCh) aerosols on pulmonary resistance (RL), and the effects of altering lung volume and O3 exposure on these induced changes in RL, was studied in five anesthetized and paralyzed dogs. RL was measured at functional residual capacity (FRC), and lung volumes above and below FRC, after exposure to MCh aerosols generated from solutions of 0.1-300 mg MCh/ml. The relative site of response was examined by magnifying parenchymal [RL with large tidal volume (VT) at fast frequency (RLLS)] or airway effects [RL with small VT at fast frequency (RLSF)]. Measurements were performed on dogs before and after 2 h of exposure to 3 ppm O3. MCh concentration-response curves for both RLLS and RLSF were sigmoid shaped. Alterations in mean lung volume did not alter RLLS; however, RLSF was larger below FRC than at higher lung volumes. Although O3 exposure resulted in small leftward shifts of the concentration-response curve for RLLS, the airway dominated index of RL (RLSF) was not altered by O3 exposure, nor was the maximal response using either index of RL. These data suggest O3 exposure does not affect MCh responses in conducting airways; rather, it affects responses of peripheral contractile elements to MCh, without changing their maximal response.

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