Modulation of carbon monoxide production and enhanced spatial learning by tin protoporphyrin.
Endogenous carbon monoxide (CO), produced by haem oxygenase (HO), may play a role in hippocampal long-term potentiation (LTP). Its role in learning and memory in intact animals is less well known. Tin protoporphyrin (Sn-PP; 25 mg kg-1, i.p.) effectively but transiently inhibited HO activity in brain homogenates, and improved acquisition in the Morris water maze. Locomotor activity was unaffected, indicating a behavioural specificity of the learning effect. The analogue zinc protoporphyrin (25 mg kg-1, i.p.), which does not pass the blood-brain barrier, did not affect learning. If the observed memory effect is related to inhibition of HO, the role of CO in spatial learning may be different from that suggested by LTP studies.
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D002248:Carbon Monoxide / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017774:Long-Term Potentiation / Q000187:drug effects; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008665:Metalloporphyrins / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D011524:Protoporphyrins / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D004791:Enzyme Inhibitors; D008665:Metalloporphyrins; D011524:Protoporphyrins; D002248:Carbon Monoxide; C032628:tin protoporphyrin IX; D006419:Heme Oxygenase (Decyclizing)