[Comp-neuro] Query: Calcium Spike

[James Schwaber]

First of all, we need to understand/define
what "calcium spike" means. Is this:
(a) spike in a classical sense - i.e. a change of
membrane  potential (Vm) - i.e an action
potential (AP) with a normal AP amplitude resulted from
temporal depolarization produced by CaT current or
(b) a "hump" or hillock in the intracellular calcium
concentration or membrane potential traces that
finally produce normal rebound spike(s)?

What we had was (b), and the resultant (classical)
rebound spike or series of spikes, if it (or they) occurred,
i.e. spike(s) in (a) sense, was (were) normal, i.e. had a
normal duration about 2 ms.

Normally, rapid Ca accumulation caused by CaT
current can produce a multisecond "hillock"or membrane
depolarization but the resultant spikes (generated
involving Na(fast) and Kdr currents) are normal.

To generate prolonged multisecond AP you need
to do something else with current kinetics, not
just include CaT current.

Ilya

****************************
Ilya A. Rybak, Ph.D.
Professor
Department of Neurobiology and Anatomy
Drexel University College of Medicine
2900 Queen Lane
Philadelphia, PA 19129
USA

Tel.: (215) 991-8596
Fax: (215) 843-9082
E-mail: rybak at drexel.edu
           ilya.rybak at drexelmed.edu
http://neurobio.drexelmed.edu/Rybakweb/rybak.html

----- Original Message ----- From: "Raj Vadigepalli" <raj at mail.dbi.tju.edu>
To: "Harry Erwin" <harry.erwin at sunderland.ac.uk>
Cc: "James Schwaber" <schwaber at mail.dbi.tju.edu>; "Ilya Rybak"
<ilya.rybak at drexelmed.edu>
Sent: Thursday, August 28, 2008 10:00 AM
Subject: Re: [Comp-neuro] Query: Calcium Spike

> Harry,
>
> I believe Ilya's ramp-firing respiratory neuron model (referred to as
> 'type II' in Rybak et al., JNeurophysiol 1997; PubMed 9114250) with
> Ca_T, K_AHP(Ca) and Ca2+ buffer in a 'thin shell' near the membrane,
> exhibits this kind of behavior. Figure 6 in the attached paper shows
> that the Calcium 'spike' lasts over 100-200 ms... not sure if that is
> long enough in your system.
>
> Regards,
> Raj
>