Brain potassium channels

This peptide itself has no selectivity for the two CCK receptors, CCK-A and B, which have so far been established to stimulate IP3/DAG while, like substance P, can close potassium channels to increase neuronal activity. The CCK-B receptor is thought to predominate in the CNS but species differences may make this interpretation difficult. It has a wide distribution in the CNS but is also found in the gut whereas the CCK-A receptor is more restricted but is found in the hypothalamus, hippocampus and in the brainstem. There are high levels of the natural peptide, CCK-8 in cortex, hippocampus, hypothalamus, ventral tegmentum, substantia nigra, brainstem and spinal cord. CCK is one of the most abundant peptides in the brain and CCK co-exists with dopamine, substance P, 5-HT and vasopressin. Interestingly, in the dopamine areas, CCK co-exists in the mesolimbic pathways but in the nigrostriatal projections, the peptide and... 

H receptor activation induces depolarizing responses in many brain areas, notably hypothalamus, thalamus and cerebral cortex. In vertebrate brain, many of these effects are mediated by opening cation channels. H,-induced excitation can also occur by blockade of KUak conductances [ 1 ]. In other cases, however, H, receptors can attenuate neuronal excitation by activating certain voltagegated potassium channels. Most of the H, receptor-induced conductance changes are mediated by the IP3-Ca2+ cascade. 

Boettger, M. K., Till, S., Chen, M. X., Anand, U., Otto, W. R., Plumpton, C., Trezise, D. J., Tate, S. N., Bountra, C., Coward, K., Birch, R., Anand, P. Calcium-activated potassium channel SK1-and IK1-like immunoreactivity in injured human sensory neurones and its regulation by neurotrophic factors, Brain 2002, 125, 252-260. 

Kang, Y., Zhang, C., Qiao, J. Involvement of endogenous opioids and ATP-sensitive potassium channels in the mediation of carbachol-induced antinociception at the spinal level a behavioral study in rats, Brain Research 1997, 761, 342-346. 

Narita, M., Suzuki, T., Misawa, M., Nagase, H., Nabeshima, A., Ashizawa, T., Ozawa, H., Saito, T., Takahata, N. Role of central ATP-sensitive potassium channels in the analgesic effect and spinal noradrenaline turnover-enhancing effect of intracerebroventricularly injected morphine in mice, Brain Research 1992, 596, 209-214. 

Kohler, M., Hirschberg, B., Bond, C. T., Kinzie, J. M., Manion, N. V., Maylie, J., and Adelman, J. P. 1996. Small-conductance,calcium-activated potassium channels from mammalian brain. Science 273 1709-1714. 

Hawkins, R.A., Jessy, J., Mans, A.M., De Joseph, M.R. (1993). Effect of reducing brain glutamine synthesis on metabolic symptoms of hepatic encephalopathy. J. Neurochem. 60, 1000-1006. Henderson, R.M., Graf, J., Boyer, J.L. (1989). Inward-rectifying potassium channels in rat hepatocytes. Am. J. Physiol. 256, G1028-G1035. 

Vincent A, Buckley C, Schott JM, Baker I, Dewar BK, Detert N, et al. Potassium channel antibody-associated encephalopathy A potentially immunotherapy-responsive form of limbic encephalitis. Brain 2004 127(Pt. 3) 701—712. 

Cooper EC, Aldape KD, Abosch A et al. (2000) Colocalization and coassembly of two human brain M-type potassium channel subunits that are mutated in epilepsy. Proc Nat Acad Sci USA 97(9) 4914-4919... 

Altemus KL, Levine MS (1996) Potassium channel blockade does not alter the modulatory effects of dopamine in neostriatal slices. Brain Res 718 212-216. 

A class of cardiac potassium channels operates in smooth and skeletal muscle, brain, and pancreatic cells. Potassium channels are activated when intracellular ATP levels decrease, and are an important link between the cellular excitability and the metabolic status of the cell. The ratio of ATP/ADP, pH, lactate, and divalent cations determines and modulates the channel activity. The opening of the potassium channels leads to membrane hyperpolarization and a potential decrease as the potassium ions flow out of the cell. Since phosphorylation changes the activity of potassium channels, it modulates cellular excitability. 

---