Spontaneous activity and responses of reticular neurones in monoamine-depleted rats.

Depletion of rat brain serotonin by p-chlorophenylalanine (PCPA) pretreatment, or of monoamines by reserpine pretreatment, was associated with reduced spontaneous firing rates of bulbar reticular neurones. Administration of 5-hydroxytryptophan to PCPA-treated rats reversed the reduction of neuronal activity. It is suggested that the results indicate a tonic excitatory serotoninergic input to a significant proportion of these neurones, which is abolished by serotonin depletion. Responses to serotonin and noradrenaline were greater in PCPA-treated and reserpire-treated rats respectively, indicating the development of supersensitivity.