Corticosteroids alter the 5-HT1A receptor-mediated response in CA1 hippocampal pyramidal cells

The hippocampus, prolonged excessive corticosterone secretion, and the 5-hy droxytryptamine (5-HT) neurotransmitter system are implicated in the etiolo gy and treatment of psychiatric disorders. Corticosterone regulates CA1 hip pocampal physiology and the 5-HT1A receptor-effector pathway however the ef fect of chronic stress levels of corticosterone is unknown. Bilateral adren alectomy (ADX), adrenalectomy with high dose corticosterone replacement (HC T), or surgical sham (SHAM) treatments were for 2 weeks. Standard intracell ular recording techniques were used in hippocampal slices to measure active and passive cellular properties and 5-HT1A receptor-mediated responses in CAI pyramidal cells. The magnitude and half-decay time of the slow after-hy perpolarization (sAHP) were decreased and the membrane time constant (tau) was increased by HCT treatment. The E-max and EC50, but not the slope, of t he concentration-response curve for 5-HT activation of the 5-HT1A, receptor were reduced in cells recorded from HCT versus SHAM treated vats. The net effect of treatment with stress levels of corticosterone was to increase th e excitability oft he CAI hippocampal pyramidal cell through changes in mem brane properties and 5-HT1A receptor-mediated response. (C) 2000 American C ollege of Neuropsychopharmacology. Published by Elsevier Science Inc.