Effects of two newly synthetized cholecystokinin tetrapeptides on the activity of single hippocampal and thalamic neurons.
The influence of two iontophoretically administered newly developed cholecystokinin (CCK) tetrapeptides with high selectivity and affinity to CCK-B receptors on the impulse activity of single hippocampal and thalamic neurons were tested in in-vivo experiments, in comparison to the effect of the sulfated octapeptide (CCK8S). A very similar responsiveness to the compared drugs was found. Most neurons responded with an increase of their discharge frequency. Only a few suppressive effects were elicited by each drug and in each of the structures. There was a good correspondence between the compared drugs concerning the direction and relative response amplitude, resulting in a highly significant correlation of the effects of both CCK4s with the CCK8S effects. On a subsample of neurons, the blocking effect of the selective CCK-B receptor blocker PD135 was tested and found to be effective in 16 out of 20 CCK4 responses, including also one inhibition. The results show that the new compounds act as effective CCK agonist binding to the B-type CCK receptor. The few inhibitory effects obtained could be explained by possible indirect effects mediated via inhibitory interneurons which are known to exist in both investigated structures.
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D002766:Cholecystokinin / Q000494:pharmacology*; D004594:Electrophysiology; D006624:Hippocampus / Q000166:cytology*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009479:Neuropeptides / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors; D012844:Sincalide / Q000502:physiology; D013788:Thalamus / Q000166:cytology*
D014151:Anti-Anxiety Agents; D007211:Indoles; D009479:Neuropeptides; D011949:Receptors, Cholecystokinin; C065600:PD 135158; D008536:Meglumine; D002766:Cholecystokinin; D012844:Sincalide