Evidence for serotonin as a possible inhibitory transmitter in some limbic structures

It is concluded that serotonin may be an inhibitory synaptic transmitter in these limbic structures and used for microelectrode recording from single cells in the amygdaloid complex.

Abstract

Cats were used for microelectrode recording from single cells in the amygdaloid complex, and for fluorescence histochemical demonstration of monoamines. It was found that the firing rate of amygdaloid neurones decreased sharply following the administration of 5-HTP, the precursor of serotonin. Conversely, it increased after the administration of L-DOPA, the precursor of dopamine and norepinephrine. The fluorescence microscopy studies, after formaldehyde condensation, showed the presence of what appear to be axosomatic synapses containing serotonin on amygdaloid and hippocampal neurones. We conclude that serotonin may be an inhibitory synaptic transmitter in these limbic structures.