Lack of cross-desensitization of somatostatin-14 and somatostatin-28 receptors coupled to potassium channels in rat neocortical neurons.
The effects of somatostatin-14 (SOM-14) and somatostatin-28 (SOM-28) on the delayed rectifier K+ current (IK) in rat neocortical neurons in culture were measured by using whole-cell patch clamp techniques. SOM-14 stimulated IK in a reversible manner. Continuous application of SOM-14 to the neocortical neurons led to a gradual desensitization of the SOM-14 response. Many cells became completely densensitized to SOM-14. SOM-28 also modulated IK in neocortical cells. However, SOM-28 reduced IK. This response was also reversible. Continuous application of SOM-28 to neocortical neurons led to a desensitization of the SOM-28 inhibition of IK. Many of the neurons that responded to SOM-28 became completely refractory to the peptide following prolonged SOM-28 pretreatment. While most neocortical neurons responded either to SOM-14 or to SOM-28, a population of neurons responded to both peptides. Chronic application of SOM-14 to these neurons completely desensitized the SOM-14 stimulation of IK but did not affect SOM-28 inhibition of this potassium current. Similarly, complete desensitization of SOM-28 responses in these cells was not associated with a modification of SOM-14 stimulation of IK. The lack of cross-desensitization between SOM-14 and SOM-28 induced responses suggests that these peptides act through different receptors to regulate IK.
Wang
H L
HL
Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia.
Dichter
M
M
Reisine
T
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D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000187:drug effects*; D017481:Receptors, Somatostatin; D013004:Somatostatin / Q000494:pharmacology*; D053561:Somatostatin-28
D015221:Potassium Channels; D017981:Receptors, Neurotransmitter; D017481:Receptors, Somatostatin; D013004:Somatostatin; D053561:Somatostatin-28; D019204:GTP-Binding Proteins