Monday, November 24, 2008

Jing's CC9&10 paper (2008)

They generated rat antibody for 5-HT.
Briefly, the antigen was prepared by coupling 2 mg serotonin oxalate to 10 mg BSA (Sigma-Aldrich) in 1 ml of 50 mM NaH2PO4, pH 7.2, using 100 microL 16% paraformaldehyde (EMS). Followingovernight incubation at 4°C, coupled antigen was purified from the reaction using a Microcon-30 spinning at 13,800 x g for 30 min at 4°C. After washing the retentate four times with 0.4 ml of 50 mM NaH2PO4, it was resuspended in 0.5 ml of the same buffer and transferred to a new tube...
Tissues were fixed in 4% paraformaldehyde, 0.2% picric acid, 25% sucrose, and 0.1MNaH2PO4, pH 7.6, for either 3 h at room temperature or overnight at 4°C.
Washing buffer (WB; 2% Triton X-100, 1% BSA, 154 mM NaCl, 50 mM EDTA, 0.01% thimerosal, and 10mM Na2HPO4, pH 7.4).


Both the dorsal and the ventral surfaces of the cerebral ganglion were desheathed. The cerebral ganglion was then twisted at the commissure to make it possible to access CC9/10 on the dorsal surface and contralateral CBIs on the ventral surface.

Frequent IPSPs are observed simultaneously in both CC9/10 cells (Fig. 2B). Activation of one CC9/10 can induce polysynaptic inhibition in the other CC9/10 (Fig. 2C1).

CC9/10 responds to noxious stimulus by tonic firing.
CC9/10 firing evokes locomotion.
The locomotion can be seen very well from PPCN (para-pedal commissural nerve).
The frequency of the locomotory rhythm is different depending on whether you stimulated P9 or AT4 nerve.

The cycle frequency of locomotor activity reflects the firing frequency of
CC9/10 activity.
CC9 and CC10 may act as locomotion initiators.

One function of CC9/10 is to provide excitation to serotonergic modulatory neurons of the pedal ganglion.
It enhances the induction of the locomotory response.

CC9/10 weakly excites
contralateral MCC and CBI-2. MCC>CBI-2

CC9/10 increase excitability (?) of MCC, but this could be just because of depolarization.

CC9–10 are broadly activated and their responses are not site-specific.

Aplysia locomotes, and then eats.


The Journal of Neuroscience, November 19, 2008 • 28(47):12349 –12361
Neural Analog of Arousal: Persistent Conditional Activation of a Feeding Modulator by Serotonergic Initiators of Locomotion
Jian Jing, Ferdinand S. Vilim, Elizabeth C. Cropper, and Klaudiusz R. Weiss

Xue-Ying Jiang and Tom Abrams' paper (1998)

The first EPSP and the second EPSP in a paired pulse are evoked at distinct loci.

Paired-pulse ratio decreases with repeated testing.

Paired-pulse ratio depends on the size of the initial EPSP size.
The second EPSP size does not do much in determining the PPR.

The decrease in PPR is independent from synaptic depression.
The decrease of PPR occurs even without the depression of the 1st EPSP.
The decrease of PPR develops much faster than the depression of the 1st EPSP.
The PPR is not affected by the depression of the 1st EPSP.

Depresssion reduces EPSP2 along with EPSP1

Does synaptic depression change large synapses into small synapses?
No, they are different.
The paired pulse ratio is independent from the initial synaptic strength.

Use-dependent plasticity of paired-pulse facilitation provides evidence that a separate set of release sites contributes to EPSP2
A dramatic reduction in the 2nd EPSP after a single paired-pulse trial, when there was minimal change in the first.

Post-tetanic potentiation persists through repeated testing
Facilitation is not simply a modest form of PTP.

Interaction of serotonin-induced facilitation with the paired-pulse ratio
Serotonin-induced facilitation persisted only in the 1st EPSP. The 2nd EPSP shows a transient increase.

Contribution of Ca2+ and phosphorylation to paired-pulse facilitation
Facilitation is Ca dependent, but not phosphatase-dependent.

Shakiryanova's vesicle mobility paper (2007)

It has been postulated that vesicle mobility is increased to enhance release of transmitters, its mechanism was unknown.

Ryanodine receptor mediated Ca2+-induced Ca2+ release from ER is necessary for the sustained DCV mobilization.
This RyR-receptor mediated release is short-lived, and triggers activation of CaMKII as a downstream activator.

ryanodine (high purity) and other chemicals were purchased from Calbiochem.

4-bromo-clacimycin is a Ca2+ ionophore.

cytosolic calcium sensor, Cameleon 2.1.

CaMKII activity can be blocked by a membrane-permiable version of AIP-II (Antennapedia peptide fused).

veratridine, a sodium channel opener (that results in an increase of intracellular Ca2+).

Two serotonin blockers in Aplysia

cinanserin, methiothepin, cyproheptadine, spiperone.

10 mM 5-HT stock solutions were made in 0.1 M acetic acid solutions and stored at 4.

methiothepine blocked AC-coupled 5-HT receptors.
spiperone (100microM) blocks PKC-dependent modulatory effects of 5-HT, which is the facilitation from the depressed synapse.
spiperone is a selective antagonist of PLC-coupled 5-HT receptors in Aplysia.

Staurosporine is the PKC blocker.


Serotonin Receptor Antagonists Discriminate Between PKA- and PKC-Mediated Plasticity in Aplysia Sensory Neurons

Bogdan Dumitriu, Jonathan E. Cohen, Qin Wan, Andreea M. Negroiu and Thomas W. Abrams
J Neurophysiol 95: 2713-2720, 2006. First published October 19, 2005; doi:10.1152/jn.00642.2005

Thursday, November 20, 2008

Quantal release of transmitter

The amount of quantal release is determined by both the number of available synaptic vesicles as well as by the probability that an available vesicle is released.

EPSCs can be described as the product of the number of available vesicles (n), release probability of each quanta (Pr) and size of the quantal unit q (mEPSC size):

EPSC = n·Pr·q


If N is the number of release sites (= maximum number of available vesicles), and Pa is the number of available vesicles.

n = N·Pa

EPSC = N·Pa·Po·q


This is the release-site model (Vere-Jones, 1966), assuming that the number of release site is limited.

The value q can be determined by recording mEPSC, sustaining presynaptic neuron depolarized, or stimulating the presynaptic neuron in low-Ca saline.


N can be estimated by giving a depleting stimulus. N is dependent on active zone constituents and mechanisms of vesicle recycling.