• canine;
  • dog;
  • dysphoria;
  • opioid receptor;
  • opioid receptor gene;
  • single nucleotide polymorphism


Objective  To determine the presence and frequency of single nucleotide polymorphisms (SNPs) within exon 1 of the canine mu-opioid receptor (MOR) gene.

Study design  Prospective genetic analysis.

Animals  Seventy-five dogs of various breeds.

Methods  DNA was isolated from dog blood. Polymerase chain reaction (PCR) was performed to amplify exon 1 of the canine MOR gene using primers derived from a published sequence. PCR products of anticipated size were identified by gel electrophoresis, isolated and sequenced.

Results  Two SNPs were found within the examined region. One is 15 base pairs (bp) upstream (C-15A) of the protein-coding portion of the gene. The second is at position 207 (C207T); a synonymous mutation predicting unaltered protein sequence. The overall prevalence of the C-15A SNP was 43% (64/150 alleles). The overall prevalence of the C207T SNP was 26% (39/150 alleles).

Conclusions and clinical relevance  Absence of haplotypes containing both an adenosine at position −15 and a thymine at position 207 suggests that these polymorphisms occurred independently from each other. How these SNPs influence variations in responses seen after opioid administration to dogs remain to be determined, however, our data indicates the C-15A SNP may play a role in opioid dysphoria.