GENETIC STUDIES OF OPIOID RECEPTOR FUNCTION

Project Details

Description

DESCRIPTION: (Applicant's Abstract)

Endogenous opioid systems play critical roles in analgesia and drug
addiction but numerous questions concerning opioid receptor function remain.
In this project, we will utilize mice harboring targeted mutations in the
DOR1 and MOR1 opioid receptor genes to investigate receptor function in
analgesia, development and immune function. We will complement these
studies with developmental and genetic analysis of the ORL-1 and orphaninFQ
(OFQ) loci that likely interact with classical opioid systems. We will
first investigate the pharmacological and behavioral consequences of MOR1
and DOR1 alteration. We will perform receptor binding studies to determine
whether the mutations are complete nulls, whether residual binding to
morphine, morphine6B-glucuronide (M6G) and receptor subtype-specific ligands
can be detected in either mutant. Analgesic assays will be used to
determine whether morphine and/or M6G analgesia are absent from the mutant
lines, whether pharmacologically-defined subtypes of mu, and delta receptors
are coordinately lost, and whether the opioid component of stress-induced
analgesia is mediated through MOR1 or DOR1. Confocal microscopy and image
analysis will be used to test the hypothesis that receptor alteration leads
to abnormalities in neural cell number and morphology at specific sites of
normal receptor expression. We will next determine whether a potentially
opioid-mediated chemotactic response of macrophages that follows injury to
the developing brain is altered in either or both mutants. The expression
patterns and levels of non-mutated opioid receptor and opioid peptide genes
will be compared in mutant and wild-type mice to establish whether
compensation occurs at the transcriptional level. We will then use GTPgS to
visualize receptor activation in histological sections and thereby determine
when functional receptor coupling begins during development and whether any
changes in opioid receptor mRNA in specific mutants extends to the
functional level. Finally, we will complete ontogenetic studies of ORL-1
and OFQ expression and then genetically ablate both ORL-1 and OFQ to
determine if the early expression of these genes we observe in the nervous
system is critical for neuronal differentiation. The phenotypes of these
mutants will be compared to evaluate possible functional roles for putative
peptides encoded by the OFQ precursor. If viable, these mutants will be
tested to resolve conflicting views of OFQ and ORL-1 action in analgesia.
Taken together, these studies should resolve multiple uncertanties
concerning opioid receptor function in several systems and provide new
animal models to investigate analgesia, tolerance, and withdrawal.
StatusFinished
Effective start/end date9/1/946/30/02

Funding

  • National Institute on Drug Abuse
  • National Institute on Drug Abuse
  • National Institute on Drug Abuse
  • National Institute on Drug Abuse
  • National Institute on Drug Abuse
  • National Institute on Drug Abuse: $412,942.00
  • National Institute on Drug Abuse
  • National Institute on Drug Abuse: $400,916.00
  • National Institute on Drug Abuse

ASJC

  • Genetics
  • Molecular Biology

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