Microinjection of ritanserin into the dorsal hippocampal CA1 and dentate gyrus decrease nociceptive behavior in adult male rat.
Prenatal 5HT depletion causes a significant decrease in the level of nociceptive sensitivity during the second phase of the formalin test behavioral response. These experiments were designed to test whether blocking 5HT2A/2c receptors in the CA1 region of the hippocampus and dentate gyrus would decrease nociceptive behaviors induced by a peripheral noxious stimulus formalin as an animal model of unremitting human being. The 5HT2A/2c receptor antagonist ritanserin (2, 4 and 8 microg/0.5 microl) was injected into the CA1 area and dentate gyrus of behaving rats 5 min before subcutaneous injection of formalin irritant. Nociceptive behaviors in both phases of the formalin test were significantly decreased by ritanserin (4 and 8 microg/0.5 microl) and ritanserin had no effect at 2 microg/0.5 microl. These results support the hypothesis that the hippocampal formation may modify the processing of incoming nociceptive information and that 5HT2A/2c receptor-sensitive mechanisms in the hippocampus may play a role in nociception and/or the expression of related behaviors.
Soleimannejad
E
E
School of Cognitive Sciences, Institute for studies in Theoretical Physics and Mathematics (IPM), Niavaran, P.O. Box 19395-5746, Tehran, Iran.
Semnanian
S
S
Fathollahi
Y
Y
Naghdi
N
N
D000818:Animals; D001522:Behavior, Animal; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects*; D008297:Male; D008845:Microinjections / Q000379:methods; D010146:Pain / Q000188:drug therapy*; D010147:Pain Measurement / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D016713:Ritanserin / Q000008:administration & dosage*; D012702:Serotonin Antagonists / Q000008:administration & dosage*; D013997:Time Factors
D012702:Serotonin Antagonists; D016713:Ritanserin