| Summary: | It has been established that 5-HT(1A) receptors are expressed both presynaptically as autoreceptors by 5-HT containing neurones, and postsynaptically by a variety of other neurones. Activation of either somatodendritic 5-HT(1A) autoreceptors or postsynaptic 5-HT(1A) receptors induces hyperpolarisation and inhibition of action potential discharge of the neurones, but it is unclear whether 5-HT(1A) receptors are under a general tonic influence by 5-HT. In the present study, using single unit recordings from both anesthetized and non-anesthetized rats, we show that the activity of neurones in the medial prefrontal cortex is not altered by systemic administration of the selective 5-HT(1A) receptor antagonist, WAY 100635. In contrast, WAY 100635 increased the firing rate of 5-HT neurones in the dorsal raphe nucleus. Our findings indicate a tonic activation of presynaptic somatodendritic but not postsynaptic cortical 5-HT(1A) receptors.
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