Author:

Keywords:

Adult, Binding Sites, Brain, Female, Fluorine Radioisotopes, Hot Temperature, Humans, Ketanserin, Male, Pain, Pain Threshold, Positron-Emission Tomography, Protein Binding, Radiopharmaceuticals, Receptor, Serotonin, 5-HT2A, Tissue Distribution, Science & Technology, Life Sciences & Biomedicine, Neurosciences, Neuroimaging, Radiology, Nuclear Medicine & Medical Imaging, Neurosciences & Neurology, SEROTONIN 5-HT2A, NEUROPATHIC PAIN, ACTIVATION, CORTEX, ANTINOCICEPTION, NOCICEPTION, PERCEPTION, MODULATION, INVENTORY, BEHAVIOR, 11 Medical and Health Sciences, 17 Psychology and Cognitive Sciences, Neurology & Neurosurgery, 32 Biomedical and clinical sciences, 42 Health sciences

Abstract:

There is a large body of evidence that serotonin [5-hydroxytryptamine (5-HT)] plays an important role in the transmission and regulation of pain. Here we used positron emission tomography (PET) to study the relationship between baseline 5-HT(2A) binding in the brain and responses to noxious heat stimulation in a group of young healthy volunteers. Twenty-one healthy subjects underwent PET scanning with the 5-HT(2A) antagonist, [(18)F]altanserin. In addition, participants underwent a battery of pain tests using noxious heat stimulation to assess pain threshold, pain tolerance and response to short-lasting phasic and long-lasting (7-minute) tonic painful stimulation. Significant positive correlations were found between tonic pain ratings and [(18)F]altanserin binding in orbitofrontal (r=0.66; p=0.005), medial inferior frontal (r=0.60; p=0.014), primary sensory-motor (r=0.61; p=0.012) and posterior cingulate (r=0.63; p=0.009) cortices. In contrast, measures of regional [(18)F]altanserin binding did not correlate with pain threshold, pain tolerance, or suprathreshold phasic pain responses. These data suggest that cortical 5-HT(2A) receptor availability co-varies with responses to tonic pain. The correlation between [(18)F]altanserin binding in prefrontal cortex and tonic pain suggests a possible role of this brain region in the modulation and/or cognitive-evaluative appreciation of pain.