Bilateral 6-OHDA lesions to the hippocampus attenuate the facilitatory effect of CCK-8 us and caerulein on memory in rats.
The involvement of dopaminergic projection to the hippocampus in the facilitatory effect of cholecystokinin-unsulphated octapeptide (CCK-8 us) and caerulein (CER) on memory motivated affectively was investigated in male rats. CCK-8 us and CER were given subcutaneously at the doses of 10 microg kg(-1)and 0.5 microg kg(-1), respectively, immediately after a single learning trial in a passive avoidance situation, after bilateral 6-OHDA lesions to the dentate gyrus of the hippocampus. In order to protect noradrenergic neurones against destruction by neurotoxin, 30 min before surgery rats were pre-treated intraperitoneally with 25 mg kg(-1)of desmethylimipramine, an inhibitor of noradrenaline uptake. Bilateral 6-OHDA lesions to the hippocampus significantly attenuate the facilitatory effect of CCK-8 us and CER on retention of passive avoidance behaviour evaluated 24 h after the learning trial. Neither, destruction of dopaminergic endings in the hippocampus, nor application of CCK-8 us and CER changed the spontaneous psychomotor activity of rats estimated in an 'open field' test. These results may indicate that the facilitatory effect of CCK-8 us and CER on memory motivated affectively is, in part, mediated by dopaminergic projection from the ventral tegmental area to the dentate gyrus of the hippocampus.
Winnicka
M M
MM
Department of Pharmacology, Medical Academy of Bia*ylystok, Mickiewicza 2c, Biaylystok, 15-222, Poland.
Wisniewski
K
K
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D002108:Ceruletide / Q000494:pharmacology*; D018891:Dentate Gyrus / Q000187:drug effects* / Q000502:physiology; D004357:Drug Synergism; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects; D016627:Oxidopamine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012844:Sincalide / Q000494:pharmacology*
D002108:Ceruletide; D016627:Oxidopamine; D012844:Sincalide