Differential sensitivity of hippocampal interneurons to ethanol in adolescent and adult rats.
Ethanol (EtOH) promotes GABAergic synaptic transmission in the central nervous system. We have shown that EtOH enhances the frequency of GABA(A) receptor-mediated spontaneous inhibitory postsynaptic currents less powerfully in hippocampal CA1 pyramidal neurons from adolescent animals compared with those from adults. However, we have also shown that EtOH promotes the firing of hippocampal interneurons, located in stratum lacunosum moleculare (SLM), from adolescent animals more potently than in those from adults. Thus the latter finding would seem to be inconsistent with the former. To understand this apparent inconsistency, we have now assessed the effects of EtOH on a different subpopulation of hippocampal interneurons, those with somata located in the stratum oriens (SO). We found that EtOH-induced enhancement of the frequency of spontaneous action potentials (sAPs) was less in interneurons from adolescent rats compared with those from adults. In addition, EtOH-induced reduction of the afterhyperpolarization decay time constant (τ(slow)) was less pronounced in interneurons from adolescent rats, as was the EtOH-induced increase in the amplitude of the hyperpolarization-activated cation current, I(h). The effect of EtOH on sAP firing frequency was blocked by application of the I(h) antagonist 4-ethylphenylamino-1,2-dimethyl-6-methylaminopyrimidinium chloride (ZD7288). These results indicate that although EtOH promotes the firing of hippocampal interneurons, through promotion of I(h), the developmental expression of this effect differs between interneurons with somata located in the SO and SLM.
Yan
Haidun
H
Department of Psychiatry, Duke University Medical Center, Durham, North Carolina, USA.
Li
Qiang
Q
Madison
Roger
R
Wilson
Wilkie A
WA
Swartzwelder
H Scott
HS
D000200:Action Potentials / Q000187:drug effects; D000375:Aging / Q000502:physiology*; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004594:Electrophysiology; D000431:Ethanol / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects* / Q000254:growth & development; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects*; D008297:Male; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000187:drug effects; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D002492:Central Nervous System Depressants; D011743:Pyrimidines; C082246:ICI D2788; D000431:Ethanol