The effects of IP midazolam (1.0-3.0 mg/kg), pentobarbital (10-20 mg/kg), ethanol (500-2000 mg/kg), scopolamine (0.05-1.25 mg/kg), chlorpromazine (0.5-5.0 mg/kg), yohimbine (0.5-2.0 mg/kg), and pentylene-tetrazol (5.0-20.0 mg/kg) were compared in the shock-probe/burying test. Consistent with results found previously for chlordiazepoxide and buspirone, the anxiolytic agents midazolam and pentobarbital decreased rats' burying behavior toward a continuously electrified (2 mA) shock-probe, and increased the number of contact-induced probe-shocks rats received. A concurrent decrease in probe-burying and increase in probe-shocks was not reliably observed after ethanol, scopolamine, chlorpromazine, yohimbine, or pentylenetetrazol. Although most of these nonanxiolytic agents produced some suppression of burying behavior at high doses, none of these drugs induced a significant increase in probe-shocks. In fact, pentylenetetrazol, which is believed to be anxiogenic, produced a significant reduction in probe-shocks. Yohimbine, another putative anxiogenic agent, was not active in the present test. In summary, concurrent increases in probe-shocks and decreases in probe-burying seem to be characteristic effects of clinically useful anxiolytic agents, which distinguish them from nonanxiolytic agents.
Animals Anti-Anxiety Agents