Cholecystokinin conditioning in rats: ontogenetic determinants

Area of Science:

• Neuroscience
• Developmental Biology
• Behavioral Science

Background:

• Cholecystokinin octapeptide (CCK) is a peptide hormone involved in various physiological processes.
• CCK's role in learning and memory, particularly in early development, is not fully understood.
• Investigating CCK's influence on olfactory learning can provide insights into developmental neurobiology.

Purpose of the Study:

• To determine the effect of CCK on conditioned odor preference formation in rats at different developmental stages.
• To identify the age at which CCK loses its efficacy in supporting olfactory conditioning.
• To explore potential links between CCK's effectiveness and developmental milestones like weaning.

Main Methods:

• Neonatal and weanling rats (5, 11, 22, and 28 days old) and adult rats were used.
• Rats were exposed to a novel odor paired with low-dose intraperitoneal CCK injection or vehicle.
• Olfactory preferences were assessed 24 hours later by measuring choices between the conditioned odor and a neutral odor.

Main Results:

• Rats at 5, 11, and 22 days of age showed a significant preference for the odor associated with CCK.
• CCK failed to support conditioned odor preference in 28-day-old rats (weaned, suckling, or milk-fed) and adult rats.
• The effectiveness of CCK in olfactory conditioning ceased around the 4th postnatal week.

Conclusions:

• CCK administration supports the development of conditioned odor preference in young rats.
• CCK's ability to facilitate olfactory learning diminishes significantly around the 4th postnatal week.
• This developmental shift in CCK's function may be linked to maturational changes during weaning.