In an acute study,
cholecystokinin octapeptide sulfate (CCK) in doses of 1, 10 or 100 micrograms/kg
body weight was injected intraperitoneally into rats just prior to the dark cycle. Rats were sacrificed two hours following the CCK injection.
Norepinephrine levels were elevated in the dorsal amygdala of rats injected with 10 micrograms of CCK as well as in the septum of rats injected with 1 and 10 micrograms of CCK. The
dopamine level in the septum of rats injected with 1 microgram of CCK as well as the
gamma-aminobutyric acid (
GABA) level in the lateral hypothalamus of rats injected with 10 micrograms of CCK were also elevated. In a chronic study, CCK (1 microgram/kg
body weight/h) was subcutaneously infused into rats with Alzet osmotic minipump for seven consecutive days. The daily food consumption did not change during the 7 days of CCK infusion. The
dopamine turnover in the striatum accelerated and the
GABA level increased. On the contrary,
dopamine metabolism in the substantia nigra and locus coeruleus decreased. Furthermore, the
serotonin level in the substantia nigra decreased.
Norepinephrine levels decreased in the nucleus paraventricularis, the locus coeruleus and the substantia nigra. The results suggest that peripherally administered CCK may act on the monoaminergic neurons and GABAergic neurons in the brain.