Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 1996
Publication Date: N/A
Technical Abstract: An opioid-like receptor (ORL-1) has been described in the rodent central nervous system that is structurally similar to the family of opioid receptors. The presence of this receptor in the hypothalamus, limbic areas, and spinal cord suggests that it may be involved in neuroendocrine regulation, learning and memory, and sensory perception. This receptor does not bind any of the known endogenous opioid peptides; however, activation of this receptor with the heptadecapeptide Nociceptin results in increased pain sensitivity and locomotor changes in rats. Such a receptor-ligand neural pathway, if present in food animals, would likely influence these animals' behavior and well-being. The objective of this experiment was to determine if the genes for ORL-1 and nociceptin are expressed in the hypothalamus of the pig. Total RNA was extracted from the hypothalamic and preoptic area (HYP/POA) regions of mature boars (n=10), was reverse transcribed, then subjected to polymerase chain reaction (PCR) PCR primers were designed to amplify a 506 bp fragment of ORL-1 gene and a 199 bp fragment of the nociceptin gene. The amplified products were later subjected to restriction endonuclease digestion. Agarose gel electrophoresis showed that appropriately-sized PCR products, reflecting the ORL-1 and nociceptin mRNAs, were produced in all ten of the porcine HYP/POA RNA samples. In addition, enzyme digestion produced products that were identical in size to those predicted for the rodent genes. These results are consistent with the theory that this opioid-like receptor (ORL-1) and an endogenous ligand are produced in the pig brain. Since this neural pathway is now identified in the pig, we can begin to evaluate its implied role in the physiological and psychological well-being of the pig.