Possible neural mechanisms involved in footshock stress-induced enhancement of exploratory behavior in mice

The effect of inescapable footshock stress on open-held activity, as measur ed by the number of ambulations, was studied in male mice. Ambulations sign ificantly increased after footshock stress, the most significant effect app eared after 20 min-stimulation and the effect decreased as footshock time l engthened. The footshock stress-induced enhancement of ambulation was inhib ited by haloperidol (0.2, 0.5 and 1 mg/kg), phentolamine (5 and 10 mg/kg), mianserin (20 mg/kg), atropine (0.5, 1 and 2 mg/kg), naltrexone (10 mg/kg) and MK-801 (0.05, 0.1 and 0.2 mg/kg), but was not influenced by propranolol (5, 10 and 20 mg/kg) or diazepam (1, 2 and 5 mg/kg). Haloperidol (0.5 and 1 mg/kg) and mianserin (5, 10 and 20 mg/kg) also exerted an inhibitory effe ct on non-stressed normal mice. These results suggest that dopaminergic, al pha-adrenergic, cholinergic, opioidergic and N-methyl-D-aspartate (NMDA) re ceptor-mediated neurotransmission systems are involved in the footshock str ess-induced ambulatory activation.