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. Author manuscript; available in PMC: 2012 Jul 6.
Published in final edited form as: Annu Rev Neurosci. 2011;34:601–628. doi: 10.1146/annurev-neuro-060909-153200

Table 4. Summary of the behaviors, physiological responses, and neural circuits for the actions of alpha receptor agonistsa.

Drugs Behavioral and physiological responses Possible neural circuit mechanisms Receptors
Dexmedetomidine Sedation mimicking non-REM sleep Hyperpolarization of LC reducing inhibitory output to POA, allowing POA to inhibit multiple ascending arousal systems (PPT/LDT, vPAG, TMN, Raphe, LC) by GABA and galanin projectionsReduction of NE-mediated activation of the cortex, the ILN of the thalamus, and the BF α2 adrenergic
Clonidine Analgesia Inhibition of descending pain facilitation pathway achieved by blocking presynaptic NE release in excitatory interneuron in the spinal cord
a

Abbreviations: BF, basal forebrain; GABAA, gamma aminobutyric acid type A; ILN, intralaminar nucleus; LC, locus coeruleus; LDT, laterodorsal tegmental area; NE, norepinephrine; PPT, pedunculopontine tegmental area; TMN, tuberomamillary nucleus; POA preoptic area; vPAG, ventral periaquaductal gray.