ISSN:
1432-1351
Keywords:
Neurohormone D
;
AKH-neuropeptides
;
Ca2+ resting current
;
Ca2+-activated K+current
;
Cockroach
;
Neuromodulation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract The octapeptide neurohormone D (NHD), a member of the family of adipokinetic hormones (AKH-peptides), increases the frequency of spontaneous activity in dorsal unpaired median (DUM) neurones isolated from the terminal ganglion of the cockroach Periplaneta americana. The increase in spike frequency is accompanied by changes in the shape and the amplitude of the single action potentials, e.g. a more pronounced afterhyperpolarization. Effects of NHD on membrane currents were investigated in these DUM cells with whole-cell voltage-clamp measurements. A voltage-independent Ca2+ current flowing at the resting potential (ICa,R) was found. NHD, at nanomolar concentrations, enhanced this ICa,R in a concentration-dependent manner. 0.1 mM Cd2+markedly reduced ICa,R and in this case ICa,R was hardly potentiated by NHD. In the presence of NHD a fast activating Ca2+-dependent K+current sensitive to charybdotoxin and to low concentrations of tetraethylammonium was augmented. The enhanced afterhyperpolarization of action potentials can be accounted for by the increase in the Ca2+-dependent K+ current. The changes of the membrane currents induced by NHD are discussed with respect to further effects on the spike pattern and in relation to the previously described mode of action of AKH-peptides in other preparations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00191716
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