The bag cell neurons ofAplysia

1989 ◽  
Vol 3 (4) ◽  
pp. 237-273 ◽  
Author(s):  
P. Jeffrey Conn ◽  
Leonard K. Kaczmarek
Keyword(s):  
Bag Cell Neurons

Ca2+ entry through a non-selective cation channel in Aplysia bag cell neurons

Neuroscience ◽  
2009 ◽  
Vol 162 (4) ◽  
pp. 1023-1038 ◽  
Author(s):  
J.E. Geiger ◽  
C.M. Hickey ◽  
N.S. Magoski
Keyword(s):  
Cation Channel ◽  
Bag Cell Neurons

Imaging Free Calcium in Cultured Aplysia Bag Cell Neurons

1991 ◽  
Vol 181 (2) ◽  
pp. 325-325 ◽  
Author(s):  
A. L. Miller ◽  
P. J. S. Smith ◽  
C. A. Rainville ◽  
O. Shimomura ◽  
F. Strumwasser ◽  
...  
Keyword(s):  
Free Calcium ◽  
Bag Cell Neurons

Transient changes in intracellular calcium associated with a prolonged increase in excitability in neurons of Aplysia californica

1994 ◽  
Vol 71 (3) ◽  
pp. 1254-1257 ◽  
Author(s):  
T. E. Fisher ◽  
S. Levy ◽  
L. K. Kaczmarek
Keyword(s):  
Intracellular Calcium ◽  
Action Potentials ◽  
Calcium Release ◽  
External Medium ◽  
Aplysia Californica ◽  
Spontaneous Firing ◽  
Barium Ions ◽  
Transient Elevation ◽  
Bag Cell Neurons ◽  
Stimulation Of

1. Transient stimulation of an afferent input to the bag cell neurons of Aplysia californica triggers a 30-min period of spontaneous firing termed the afterdischarge. Measurement of free calcium ion concentrations using calcium-sensitive electrodes revealed a biphasic pattern of elevation of intracellular calcium levels during the afterdischarge. Basal calcium levels at the soma were found to rise rapidly during afferent stimulation and then to decline before the onset of spontaneous firing. This early peak in intracellular calcium was followed by a slower, transient elevation of calcium levels during the period of rapid firing that occurs in the first few minutes of afterdischarge. Stimulation of clusters of bag cell neurons in a calcium-free external medium failed to trigger afterdischarge and produced no changes in basal intracellular calcium levels. 2. When calcium ions in the external medium were replaced by barium ions, stimulation of clusters of bag cell neurons triggered afterdischarges that were characterized by long-duration action potentials. Intracellular calcium levels during these afterdischarges rose slowly over the first few minutes of spontaneous firing. Because calcium-sensitive microelectrodes do not respond to barium ions, these data suggest that stimulation of afterdischarge triggers calcium release from an intracellular compartment. 3. During afterdischarges in barium-containing external media, each broadened action potential produced a discrete transient elevation of intracellular calcium levels. A similar effect was observed in isolated bag cell neurons in primary culture when action potentials were stimulated by depolarizing current pulses in a barium-containing medium. These data suggest that, under these conditions, individual action potentials trigger the release of intracellular calcium from some intracellular pool.

A voltage-clamp analysis of currents underlying cyclic AMP-induced membrane modulation in isolated peptidergic neurons of Aplysia

1984 ◽  
Vol 52 (2) ◽  
pp. 340-349 ◽  
Author(s):  
L. K. Kaczmarek ◽  
F. Strumwasser
Keyword(s):  
Cell Culture ◽  
Cyclic Amp ◽  
Voltage Clamp ◽  
Cultured Cells ◽  
Sodium Current ◽  
Negative Slope ◽  
Spontaneous Discharge ◽  
Inward Current ◽  
Outward Currents ◽  
Bag Cell Neurons

A variety of chemical and electrophysiological evidence indicates that the onset of afterdischarge and the subsequent profound enhancement of spike broadening that occur in the bag cell neurons of Aplysia are related to an increase in adenosine 3',5'-monophosphate-(cAMP) dependent protein phosphorylation. We have now used a two-electrode voltage clamp to study the properties of isolated bag cell neurons in cell culture and their response to 8 benzylthio-cAMP (8BTcAMP) and N6-n-butyl 8BTcAMP. These membrane-permeant and phosphodiesterase-resistant cAMP analogs induce spontaneous discharge and spike broadening in both the intact bag cell cluster and isolated bag cell neurons in cell culture. The dominant inward current in these cultured cells was found to be the calcium current, Ica, which was abolished by Co2+ (20 mM) or Ni2+ (10 mM) and could be observed in Na+-free media. In a minority of cells (2 of 12), in normal ionic media, a transient inward current was observed that was unaffected by Co2+ and Ni2+ and probably represents a sodium current. The three characterized potassium currents, the delayed rectifying current IK, the calcium-dependent current IC, and the early transient current IA, distinguished by their differing pharmacological and voltage-activation properties, were present in all healthy cells. Three effects of the cyclic AMP analogs (0.5 mM) on the electrical properties of these cells were 1) the emergence of a region of negative slope resistance in the steady-state I-V relations, 2) a depression of the net sustained outward currents due to depolarizing commands, and 3) a marked reduction in IA. When outward currents had been largely suppressed using high concentrations of tetraethylammonium (TEA) ions (100-460 mM) no effects of the cyclic AMP analogs could be observed on peak inward currents using NA+ and Ca2+ or Ba2+ as carriers of inward current. At least part of these electrical effects of the cyclic AMP analogs could be accounted for by a depression of a delayed potassium current and the A current.

Progressive potentiation of peptide release during a neuronal discharge

1990 ◽  
Vol 63 (4) ◽  
pp. 738-744 ◽  
Author(s):  
K. J. Loechner ◽  
E. M. Azhderian ◽  
R. Dreyer ◽  
L. K. Kaczmarek
Keyword(s):  
Time Course ◽  
External Medium ◽  
Egg Laying ◽  
Maximal Rate ◽  
Peptide Release ◽  
Acidic Peptide ◽  
Neuroactive Peptides ◽  
Connective Tissue Sheath ◽  
Bag Cell Neurons ◽  
Stimulation Of

1. In response to electrical stimulation, the bag cell neurons of Aplysia generate an afterdischarge that lasts 20-40 min. During this afterdischarge several neuroactive peptides are released. We have now studied the time course of release of two of these peptides, egg-laying hormone (ELH) and acidic peptide (AP). For the collection of released peptides, the artery to the bag cell clusters was perfused. The medium surrounding the clusters (artificial seawater, ASW) was completely exchanged at 5-min intervals before, during, and after stimulation of an afterdischarge. Peptides released into the external medium were analyzed with the use of high-pressure liquid chromatography. 2. Before stimulation, no detectable ELH and AP were found in the external medium. After the onset of an afterdischarge, the amount of ELH and AP released increased progressively until 15-20 min of firing. Toward the conclusion of an afterdischarge, the release of ELH and AP returned to control levels. 3. In contrast to the pattern of release of the peptides, the firing rate of the bag cell neurons is maximal within the first minute of afterdischarge and thereafter declines. 4. Release of the peptides from axonal varicosities occurs within the vascularized connective-tissue sheath that covers the clusters of bag cell neurons. Experiments were therefore carried out to establish whether the observed time course of release is affected by diffusion of the peptides through the vasculature into the external medium and, in particular, to determine whether the maximal rate of release at 15-20 min into the afterdischarge could be accounted for by a delay in transport of peptides from the neurites.(ABSTRACT TRUNCATED AT 250 WORDS)

Aplysia Bag Cells Function as a Distributed Neurosecretory Network

2008 ◽  
Vol 99 (1) ◽  
pp. 333-343 ◽  
Author(s):  
Nathan G. Hatcher ◽  
Jonathan V. Sweedler
Keyword(s):  
Single Gene ◽  
Egg Laying ◽  
Site Specific ◽  
Cell Clusters ◽  
Cell Network ◽  
Flight Mass Spectrometry ◽  
Bag Cells ◽  
And Behavior ◽  
Bag Cell Neurons ◽  
Neuroendocrine Systems

The anatomical organization of many neuroendocrine systems implies multiple sites of hormone release in areas mediating multiple aspects of physiology and behavior, yet this neurosecretory complexity has not often been verified. Here we probe the well-characterized hormonal model, the reproductive bag cell neuroendocrine system of the sea slug Aplysia californica. The bag cell neurons of Aplysia mediate egg-laying behavior through the coordinated secretion of a suite of peptides derived from a single gene product, the egg-laying prohormone (proELH). Although the majority of bag cell neurons are located within two major abdominal bag cell clusters, smaller groups of egg-laying hormone-expressing cells have been observed in specific pleural and cerebral ganglia regions, some of which have been reported to be electrically connected to the abdominal bag cell clusters. Releasates are sampled from discrete locations within the Aplysia CNS before and during stimulation of afterdischarge activity and subsequently analyzed with matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Site-specific release profiles are observed at bag cell cluster, pleural, and genital ganglion sites after site-specific electrophysiological activation of bag cell afterdischarges. These data demonstrate that the bag cell network has multiple neurohemal release sites, exhibits descending activation that travels from the cerebral and pleural ganglia down to the abdominal bag cell clusters, and releases spatially distinct profiles of proELH-derived peptides within the Aplysia nervous system. Such distributed neurosecretory organization may be a common feature of neuroendocrine systems across higher order organisms linking multiple behavioral aspects to a single neuronal network.

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