Stressor exposure and intraventricular cholecystokinin (CCK-8) administration in the light dark box model of anxiety in CD-1 mice; possible cross-sensitization.

Differential startle reactivity following central CCK-8S and systemic boc CCK-4 administration in mice: Antecedent stressor history and testing condition.

“…The present experiment assessed the immediate and protracted behavioral repercussions attending intraventricular administration of 50 ng CCK-8S (Experiment 1) and systemic administration of the CCK B agonist N-t-Boc-Trp-Met-Asp-Phe-amide (Boc CCK-4; Experiment 2) on acoustic and fear-potentiated startle among independent groups of CD-1 mice. Previous investigations in this laboratory established that central administration of 50 ng CCK-8S in CD-1 mice produced inordinate anxiety in the light-dark task, as evidenced by diminished illuminated chamber occupancy compared with the effects of graded (i.e., 0.5, 5.0 or 25.0 ng) intraventricular CCK-8S doses (MacNeil, 1996; MacNeil, Sela, McIntosh, & Zacharko, 1997), as well as attenuated previously rewarding brain stimulation from the ventral tegmental area (Hebb & Zacharko, 2003a) and reduced exploration in a novel environment (Hebb & Zacharko, 2003b). Moreover, anxiogenic indices accompanying CCK administration were exaggerated if preceded by stressful life events, including uncontrollable footshock, crowded housing, and social isolation (Harro, Vasar, & Bradwejn, 1993; Koks et al, 2000; MacNeil, 1996; MacNeil et al, 1997).…”

“…Previous investigations in this laboratory established that central administration of 50 ng CCK-8S in CD-1 mice produced inordinate anxiety in the light-dark task, as evidenced by diminished illuminated chamber occupancy compared with the effects of graded (i.e., 0.5, 5.0 or 25.0 ng) intraventricular CCK-8S doses (MacNeil, 1996; MacNeil, Sela, McIntosh, & Zacharko, 1997), as well as attenuated previously rewarding brain stimulation from the ventral tegmental area (Hebb & Zacharko, 2003a) and reduced exploration in a novel environment (Hebb & Zacharko, 2003b). Moreover, anxiogenic indices accompanying CCK administration were exaggerated if preceded by stressful life events, including uncontrollable footshock, crowded housing, and social isolation (Harro, Vasar, & Bradwejn, 1993; Koks et al, 2000; MacNeil, 1996; MacNeil et al, 1997). Yet, anxiety expression in the light-dark task or the elevated plus-maze may describe anxiety demonstrably removed from anxiety elicited in the acoustic and fear-potentiated startle paradigms.…”