title: Effects of intra-hippocampal microinjection of vitamin B12on the orofacial pain and memory impairments induced by scopolamine and orofacial pain in rats.
abstract: In the present study, we investigated the effects of microinjection of vitamin B12into the hippocampus on the orofacial pain and memory impairments induced by scopolamine and orofacial pain. In ketamine-xylazine anesthetized rats, the right and left sides of the dorsal hippocampus (CA1) were implanted with two guide cannulas. Orofacial pain was induced by subcutaneous injection of formalin (1.5%, 50μl) into the right vibrissa pad, and the durations of face rubbing were recorded at 3-min blocks for 45min. Morris water maze (MWM) was used for evaluation of learning and memory. Finally, locomotor activity was assessed using an open-field test. Vitamin B12attenuated both phases of formalin-induced orofacial pain. Prior administration of naloxone and naloxonazine, but not naltrindole and nor-binaltorphimine, prevented this effect. Vitamin B12and physostigmine decreased latency time as well as traveled distance in Morris water maze. In addition, these chemicals improved scopolamine-induced memory impairment. The memory impairment induced by orofacial pain was improved by vitamin B12and physostigmine used alone. Naloxone prevented, whereas physostigmine enhanced the memory improving effect of vitamin B12in the pain-induced memory impairment. All the above-mentioned chemicals did not alter locomotor activity. The results of the present study showed that at the level of the dorsal hippocampus, vitamin B12modulated orofacial pain through a mu-opioid receptor mechanism. In addition, vitamin B12contributed to hippocampal cholinergic system in processing of memory. Moreover, cholinergic and opioid systems may be involved in improving effect of vitamin B12on pain-induced memory impairment.
authors.affiliation: Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia 57153-1177, Iran. Electronic address: erfanparast@gmail.com.
authors.forename: Amir
authors.initials: A
authors.lastname: Erfanparast
authors.affiliation: Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia 57153-1177, Iran.
authors.forename: Esmaeal
authors.initials: E
authors.lastname: Tamaddonfard
authors.affiliation: Division of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Urmia University, Urmia 57153-1177, Iran.
authors.forename: Shaghayegh
authors.initials: S
authors.lastname: Nemati
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000503:physiopathology; D002408:Catheters, Indwelling; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005157:Facial Pain / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D005557:Formaldehyde; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D008569:Memory Disorders / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018697:Nootropic Agents / Q000494:pharmacology*; D017208:Rats, Wistar; D012601:Scopolamine; D014738:Vibrissae; D014805:Vitamin B 12 / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D000700:Analgesics; D009292:Narcotic Antagonists; D018697:Nootropic Agents; D005557:Formaldehyde; D009270:Naloxone; C019476:mecobalamin; D012601:Scopolamine; D014805:Vitamin B 12
keywords: Hippocampus; Memory impairment; Orofacial pain; Rats; Vitamin B(12)