ACTIONS OF GABA AND ETHYLENEDIAMINE ON CA1 PYRAMIDAL NEURONES OF THE RAT HIPPOCAMPUS

¹ Addiction Research Foundation, 33 Russell Street, Toronto, Ontario M5S 2S1, Canada
² Department of Physiology and Pharmacology, University of St Andrews, St Andrews, Fife KY16 9TS

The effects of locally applied -aminobutyric acid (GABA) and ethylenediamine were examined and compared on CA1 pyramidal neurones in slice preparations of rat hippocampus using intracellular voltage recording techniques. Each substance produced both depolarization and hyperpolarization of the dendrites; the cell body responded with hyperpolarization alone. Ion substitution experiments suggest that the depolarizing responses of the dendrites were Cl^- dependent and the hyperpolarizing responses of the cell body were dependent on Cl^-, which suggests that the Cl^- potential (E_Cl) is different in the dendrites compared with the cell body. The hyperpolarizing responses of the dendrites were dependent on K⁺. Dendritic depolarizing responses to GABA and ethylenediamine were antagonized by bicuculline and picrotoxin whereas the dendritic hyperpolarizing response was unaffected. The hyperpolarizing responses of the cell body were more difficult to study but it appeared that they were reduced by both bicuculline and picrotoxin. The benzodiazepines flurazepam and diazepam potentiated the dendritic depolarizing responses to GABA and ethylenediamine. It also had this effect on the hyperpolarizing response of the cell body but not on the hyperpolarizing response of the dendrites.