CCK-A and CCK-B receptors enhance olfactory recognition via distinct neuronal pathways.
We have previously reported that CCK-A receptor agonists and CCK-B receptor antagonists both enhance memory in an olfactory recognition test. Here, we report that the memory-enhancing effect of the CCK-B receptor antagonist L-365,260 (1 mg/kg i.p.), but not that of the CCK-A receptor agonist caerulein (0.03 mg/kg i.p.), was dramatically decreased following a bilateral transection of the perforant path, a principal source of input to the hippocampal formation. We further confirmed that a significant memory deficit occurred subsequent to this deafferentation of the hippocampus in untreated animals. In contrast, the effect of caerulein, but not that of L-365,260, was abolished following a bilateral subdiaphragmatic vagotomy. These results demonstrate that the hippocampal system plays a role in olfactory recognition and indicate that distinct neuronal pathways underlie the memory-enhancing effects of CCK-A and CCK-B drugs observed in the olfactory recognition test. The former effects (CCK-A) appear to involve a peripheral relay to the brain via the vagus nerve, whereas the latter (CCK-B) are directly central and involve, at least in part, the hippocampal system.
Lemaire
M
M
Rhône-Poulenc Rorer S.A., Centre de Recherches de Vitry-Alfortville, Vitry-sur-Seine, France.
Barnéoud
P
P
Böhme
G A
GA
Piot
O
O
Haun
F
F
Roques
B P
BP
Blanchard
J C
JC
D000818:Animals; D003071:Cognition / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009833:Olfactory Pathways / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D043886:Receptor, Cholecystokinin A; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin / Q000819:agonists / Q000502:physiology*; D012903:Smell / Q000187:drug effects / Q000502:physiology*; D013268:Stimulation, Chemical; D014628:Vagotomy
D043886:Receptor, Cholecystokinin A; D043887:Receptor, Cholecystokinin B; D011949:Receptors, Cholecystokinin