Chloroquine-induced Itch Response Testing
Objective: Assessment of itch behavior induced by chloroquine in wild-type and mutant mice to evaluate Mrgpr-dependent itch responses and identify itch-selective neurons
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Protocol Steps
Chloroquine-induced itch testing in wild-type mice
Administer chloroquine to wild-type mice and assess itch behavior response
Note: Baseline comparison group for mutant mice lacking Mrgpr genes
View evidence from paper
“Mice lacking a cluster of Mrgpr genes display significant deficits in itch induced by CQ but not histamine”
Chloroquine-induced itch testing in mutant mice
Administer chloroquine to mutant mice lacking Mrgpr gene cluster and assess itch behavior response
Note: Test group to evaluate Mrgpr-dependent itch responses
View evidence from paper
“Mice lacking a cluster of Mrgpr genes display significant deficits in itch induced by CQ but not histamine”
Histamine-induced itch testing
Administer histamine to both wild-type and mutant mice to assess histamine-dependent itch responses
Note: Control to demonstrate that Mrgpr-deficient mice retain normal histamine-induced itch
View evidence from paper
“Mice lacking a cluster of Mrgpr genes display significant deficits in itch induced by CQ but not histamine”
BAM8-22 agonist activation testing
Activate MrgprC11-expressing neurons with BAM8-22 agonist and assess itch induction in wild-type and mutant mice
Note: Demonstrates functional role of MrgprC11 in itch sensation
View evidence from paper
“Activation of these neurons with MrgprC11-specific agonist BAM8-22 induces itch in wild-type but not mutant mice”
Sensory neuron direct excitation assessment
Evaluate direct excitation of sensory neurons by chloroquine in an Mrgpr-dependent manner
Note: Cellular-level assessment of CQ responsiveness
View evidence from paper
“CQ directly excites sensory neurons in an Mrgpr-dependent manner”
MrgprA3 activation specificity testing
Test chloroquine activation of mouse MrgprA3 and human MrgprX1 to establish receptor specificity
Note: Identifies specific Mrgpr isoforms responsible for CQ-induced itch
View evidence from paper
“CQ specifically activates mouse MrgprA3 and human MrgprX1”
Loss-of-function studies
Evaluate MrgprA3 requirement for chloroquine responsiveness using knockout or knockdown approaches
Note: Demonstrates necessity of MrgprA3 for CQ-induced itch
View evidence from paper
“Loss- and gain-of-function studies demonstrate that MrgprA3 is required for CQ responsiveness in mice”
Gain-of-function studies
Evaluate effects of MrgprA3 overexpression or enhanced activation on chloroquine responsiveness
Note: Demonstrates sufficiency of MrgprA3 for CQ-induced itch
View evidence from paper
“Loss- and gain-of-function studies demonstrate that MrgprA3 is required for CQ responsiveness in mice”
Neuronal phenotype characterization
Assess co-expression of histamine responsiveness, Gastrin-Releasing Peptide, and MrgprC11 in MrgprA3-expressing neurons
Note: Characterizes molecular profile of itch-selective neurons
View evidence from paper
“MrgprA3-expressing neurons respond to histamine and co-express Gastrin-Releasing Peptide, a peptide involved in itch sensation, and MrgprC11”