Morphine, but not atropine, blocks nociceptor-driven activity in rat dorsal hippocampal neurones.
Neurones in the CA1 region of the dorsal hippocampus of urethane-anaesthetized rats were recorded extracellularly with microelectrodes, and tested for their response to non-noxious and noxious peripheral stimuli. None of the cells responded to non-noxious stimuli but 91 of 216 cells were excited by noxious stimuli. Morphine (5.0 mg/kg i.v.) increased the background firing rate in 7 of 10 cells tested and blocked the response to noxious heating of the tail in all cases. Naloxone (0.5 mg/kg i.v.) reversed these effects of morphine. Atropine (0.1 plus 0.2 mg/kg i.v.), in another group of animals, produced only transient changes of an inconsistent nature in 7 cells tested.
D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects*; D006358:Hot Temperature; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation; D051381:Rats; D011919:Rats, Inbred Strains
D009270:Naloxone; D009020:Morphine; D001285:Atropine