Interactions between Cholecystokinin and Other Neurotransmitter Systems

Effects of CCK-4 infusion on the acoustic eye-blink startle and psychophysiological measures in healthy volunteers

The acoustic startle response (ASR) and a range of psychophysiological parameters were evaluated during a continuous intravenous administration of cholecystokinin-tetrapeptide (CCK-4) in healthy volunteers. Subjects (n=28) were randomly assigned to double-blind infusion of either CCK-4 (0.5 mg/60 min) or placebo. The ASR sessions were performed prior to infusion and at 20 min and 50 min after the onset of infusion by recording eye-blink response to a series of acoustic stimuli (110 dB, 40 ms). An effect of CCK-4 on the eye-blink startle was observed in the first half of infusion. CCK-4 produced an increase of eye-blink startle amplitude from baseline values in contrast to the decrease observed at this time point with placebo. A mild increase in anxiety and heart rate followed by fatigue was reported with CCK-4. Administration of CCK-4 produced increases in plasma concentrations of adrenocorticotropic hormone, cortisol, prolactin and growth hormone. The results of this study show that a prolonged intravenous administration of CCK-4 may be a useful challenge method for further studies on the role of CCK system in the modulation of human anxiety and stress response.

Inhibition of anxiety in rats by antisense to cholecystokinin precursor protein

BACKGROUND

Cholecystokinin (CCK) and its analogs generates anxiety in humans and measurable anxiety-like behaviors in rats. CCK receptor blockers have had mixed results as a treatment approach for anxiety disorders. Since CCK is a peptide, we explored another strategy to reduce CCK levels in brain by antisense oligodeoxynucleotide inhibition of DNA transcription or messenger RNA (mRNA) translation for CCK precursor protein.

METHODS

Antisense oligodeoxynucleotide complementary to the start coding region of rat CCK-precursor was intracerebroventricularly (icv) infused into rats three times at 24-hour intervals. Control groups received infusions of either a scramble sequence oligodeoxynucleotide or vehicle. On the fourth day, rats were assessed in the elevated plus maze paradigm.

RESULTS

Compared to vehicle and scramble sequence oligodeoxynucleotide control, icv CCK-antisense exogenous administration for 3 days significantly diminished anxiety behavior in rats.

CONCLUSIONS

Antisense inhibition of CCK-mediated anxiety could have therapeutic potential in human anxiety disorders.

Inositol has behavioral effects with adaptation after chronic administration

Inositol is a simple dietary polyol that serves as a precursor in important second messenger systems. Inositol in pharmacological doses has been reported recently to be therapeutic in depression, panic disorder and obsessive compulsive disorder. We hereby report effects of inositol on the elevated plus maze model of anxiety. These results should allow development of new inositol analogs that could expand psychoactive drug development possibilities via second messenger manipulation.