Journal of Neuroscience, Vol 8, 1-11, Copyright © 1988 by Society for Neuroscience
Buspirone attenuates synaptic activation of hippocampal pyramidal cells
MD Mauk, SJ Peroutka and JD Kocsis
Department of Neurology, Stanford University School of Medicine, California 94305.
The actions of 5-hydroxytryptamine (5-HT) and buspirone, an anxiolytic
agent that displays high and selective affinity for 5-HT1A receptor sites,
on synaptic activation of hippocampal CA1 pyramidal cells were studied in
vitro. Whereas 5-HT application leads to a rapid hyperpolarization and
decreased input resistance in pyramidal cells, buspirone has no measurable
effects on membrane potential and input resistance. However, unlike 5-HT,
buspirone application leads to a gradual and reversible reduction in
excitatory postsynaptic potentials (EPSPs) elicited by stimulation of
afferents in the stratum radiatum. Concurrent with this attenuation of the
EPSP, buspirone decreases the excitability of afferent fibers in the
stratum radiatum as evidenced by conduction slowing, increased refractory
period, and decreased ability to generate repetitive impulses. 5-HT has no
measurable effect on the afferent fibers. The attenuation of the EPSPs and
the decrease in afferent fiber excitability appear to be independent of
5-HT receptors as 5-HT neither shares nor antagonizes the effects of
buspirone. Thus, both 5-HT and buspirone can contribute to reduced spike
activity in pyramidal cells, but they do so via different mechanisms: 5-HT
hyperpolarizes pyramidal cells whereas buspirone attenuates their synaptic
activation, possibly via action on the presynaptic fibers in the stratum
radiatum.