title: The action of 5-hydroxytryptamine on neuronal membranes and synaptic transmission in area CA1 of the hippocampus in vitro.
abstract: Cell membrane properties and synaptic transmission were examined by intracellular recording from the CA1 region of hippocampal slices during application of 5-hydroxytryptamine (5-HT). Seventeen cells (50%) showed an inhibitory response to 5-HT. The cells were hyperpolarized with decreased spontaneous activity and increased membrane conductance. The increase may be in potassium or chloride conductance. Synaptic transmission was not involved since Mg2+, Co2+ or Mn2+ did not block the response. 5-HT inhibited dendritic EPSPs by local postsynaptic effect. Four cells (11%) showed an excitatory response. They were depolarized while the spontaneous activity increased and the conductance decreased. The decrease may be in the potassium or chloride conductance. Two cells (6%) showed a mixed type of response with an early excitation and late inhibition. This respons may be a mixture of the two other responses or associated with a third type of 5-HT receptor. Eleven cells (33%) did not respond to 5-HT, but only in 3 of these 5-HT was applied in the soma region. In conclusion, 5-HT may inhibit dendritic excitatory synapses and decrease recurrent inhibition in hippocampus.
mesh_terms: D000818:Animals; D005260:Female; D006168:Guinea Pigs; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology*; D013570:Synaptic Membranes / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D012701:Serotonin