Periaqueductal grey

In further support of a pro-nociceptive role of CX3CL1 are data showing that the direct injection of CX3CL1 in the periaqueductal grey, a brain region mostly involved with analgesic responses, albeit un-effective by itself, results in inhibition of the antinociceptive effects induced by p, 5, and k opioid agonists (Chen et al. 2(X)7). 

Chen X, Geller EB, Rogers TJ, Adler MW (2007) The chemokine CX3CLl/fractaUdne interferes with the antinociceptive effect induced by opioid agonists in the periaqueductal grey of rats. Brain Res 1153 52-57... 

One final mechanism that has recently shown promise for antidepressant effects appears distinct from all of the monoamine systems. A study published in 1998 demonstrated that a substance P antagonist (MK-869) had antidepressant effects in humans (Kramer et al. 1998). Substance P is localized to many areas of the brain that are involved in emotional processing, including the amygdala, dentate gyrus, subiculum, nucleus accumbens, striatum, locus coeruleus and periaqueductal grey (Kramer... 

Bergquist J, Vona MJ, Stiller CO, O Connor WT, Falkenberg T, et al. 1996. Capillary electrophoresis with laser-induced fluorescence detection a sensitive method for monitoring extracellular concentrations of amino acids in the periaqueductal grey matter. J Neurosci Methods 65( 1) 33-42. 

GABA is one of the most widely distributed transmitters in the brain and it has been calculated that it occurs in over 40% of all s)mapses. Nevertheless, its distribution is quite heterogeneous, with the highest concentrations being present in the basal ganglia, followed by the hypothalamus, the periaqueductal grey matter and the hippocampus approximately equal concentrations are present in the cortex, amygdala and... 

Midhrain and brainstem ventral tegmental area raphe nuclei superior cerebellar peduncle mesencephalic nucleus of trigeminal nerve substantia nigra nucleus coeruleus periaqueductal grey... 

Behbehani, M. M. and Fields, H. L. Evidence that an excitatory connection between the periaqueductal grey and nucleus raphe magnus mediated stimulation produced analgesia, Brain Res. 1979, 170, 85-93. 

Vaughan CW, Bagley EE, Drew GM, et al. Cellular actions of opioids on periaqueductal grey neurons from C57B16/J mice and mutant mice lacking MOR-1. Br J Pharmacol. 2003 139 362-367. 

The highest concentration of opioid receptors appears to be in the sensory, limbic and hypothalamic regions of the brain, with particularly high concentrations being found in the amygdala and the periaqueductal grey... 

Griffiths, J. L., and Lovick, T. A. (2005). GABAergic neurones in the rat periaqueductal grey matter express alpha4, betal and delta GABAA receptor subunits Plasticity of expression during the estrous cycle. Neuroscience 136, 457-466. 

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