Blockade of alpha2-adrenergic receptors markedly potentiates glutamate-evoked activity of locus coeruleus neurons.

The locus coeruleus (LC) is a small pontine nucleus with widely distributed efferents that supply the majority of norepinephrine in brain. Evidence from our laboratory has implicated alpha2-adrenergic receptors on LC neurons in regulating the magnitude of the bursting response of LC neurons to both sensory stimulation and systemically administered drugs. Sub-stimulation of alpha2-adrenergic receptors in the LC and the resulting hyper-responsiveness of LC neurons is thought to at least partially mediate depression in an animal model. The present study extends previous work in our laboratory by demonstrating that blockade of alpha2-adrenergic receptors also markedly augments the bursting response of LC neurons to locally-via microiontophoresis-applied glutamate.