UNLABELLED: The opioid and serotonergic systems are closely involved in pain processing and mood disorders. The aim of this study was to assess the influence of systemic morphine on cerebral serotonin 2A receptor (5-HT(2A)) binding in dogs using SPECT with the 5-HT(2A) radioligand (123)I-5I-R91150. METHODS: 5-HT(2A) binding was estimated with and without morphine pretreatment in 8 dogs. The 5-HT(2A) binding indices in the frontal, parietal, temporal, and occipital cortex and in the subcortical region were obtained by semiquantification. RESULTS: A significantly decreased 5-HT(2A) binding index was found in the morphine group for the right (morphine, 1.41 ± 0.06; control, 1.52 ± 0.10) and left (morphine, 1.44 ± 0.08; control, 1.55 ± 0.11) frontal cortices, with P = 0.012 and P = 0.040, respectively. No significant differences were noted for the other regions. CONCLUSION: Morphine decreased the frontocortical 5-HT(2A) availability, confirming an interaction between the 5-HTergic and the opioid systems. Whether this interaction is caused by decreased receptor density due to direct internalization or is the result of indirect actions, such as increased endogenous serotonin release, remains to be elucidated.
UNLABELLED: The opioid and serotonergic systems are closely involved in pain processing and mood disorders. The aim of this study was to assess the influence of systemic morphine on cerebral serotonin 2A receptor (5-HT(2A)) binding in dogs using SPECT with the 5-HT(2A) radioligand (123)I-5I-R91150. METHODS: 5-HT(2A) binding was estimated with and without morphine pretreatment in 8 dogs. The 5-HT(2A) binding indices in the frontal, parietal, temporal, and occipital cortex and in the subcortical region were obtained by semiquantification. RESULTS: A significantly decreased 5-HT(2A) binding index was found in the morphine group for the right (morphine, 1.41 ± 0.06; control, 1.52 ± 0.10) and left (morphine, 1.44 ± 0.08; control, 1.55 ± 0.11) frontal cortices, with P = 0.012 and P = 0.040, respectively. No significant differences were noted for the other regions. CONCLUSION:Morphine decreased the frontocortical 5-HT(2A) availability, confirming an interaction between the 5-HTergic and the opioid systems. Whether this interaction is caused by decreased receptor density due to direct internalization or is the result of indirect actions, such as increased endogenous serotonin release, remains to be elucidated.
Authors: Antita Adriaens; Kathelijne Peremans; Tim Waelbers; Eva Vandermeulen; Siska Croubels; Luc Duchateau; André Dobbeleir; Kurt Audenaert; Jos Eersels; Simon Vermeire; Bart De Spiegeleer; Ingeborgh Polis Journal: PLoS One Date: 2014-10-08 Impact factor: 3.240