Spermine increases paired-pulse facilitation in area CA1 of hippocampus in a calcium-dependent manner.
The effect of spermine on neurotransmission was studied in area CA1 of the hippocampal slice preparation. Paired-pulse stimulation (20 ms interpulse interval) was delivered to stratum radiatum; the evoked field potential responses were recorded simultaneously from stratum radiatum and from stratum pyramidale. At mM and sub-mM concentrations, spermine decreased the slope of pEPSP in stratum radiatum and the area of the conditioning population spike in stratum pyramidale. Short-latency paired-pulse inhibition of the population spike was converted to facilitation by spermine. These effects of spermine resembled those observed at low calcium concentration. In addition, dose-response and input-output curves determined at various Ca2+ concentrations demonstrated that the depressant effects of spermine were larger at low Ca2+ levels. The results support the notion that spermine competitively blocks presynaptic voltage-sensitive Ca2+ channels, thus causing a decreased release of neurotransmitter. Since spermine is present in brain, it is likely that it is a natural modulator of Ca2+ channels.
Ferchmin
P A
PA
Department of Biochemistry, School of Medicine, Universidad Central del Caribe, Bayamón, Puerto Rico 00926-6032, USA.
Eterović
V A
VA
Rivera
E M
EM
Teyler
T J
TJ
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013096:Spermine / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D015220:Calcium Channels; D013096:Spermine; D002118:Calcium