Compounds of different chemical classes, with affinity for central
benzodiazepine receptors, were investigated for effects on handling-induced ultrasonic cries in rat pups.
Diazepam and
clobazam inhibited ultrasounds and impaired motor performance at higher doses.
Suriclone showed a similar profile to
diazepam but
premazepam clearly separated ultrasound inhibition from motor impairment.
ZK 91296,
CGS 9896, RU 39419 and RU 43028 inhibited ultrasounds with a lower maximal response but induced little or no motor
incoordination.
CL 218872 inconsistently inhibited sounds with no motor impairment and
PK 8165 and
PK 9084 had no consistent effects.
Benzodiazepine antagonists weakly inhibited (RU 40410) or did not affect (
Ro 15-1788 or
CGS 8216) ultrasounds alone but fully (
Ro 15-1788 or
CGS 8216) or partially (RU 40410) antagonised the effects of
benzodiazepines. Inverse agonists
FG 7142, methyl-beta-carboline-3-carboxylate (BCM) and
DMCM tended to increase ultrasounds alone, particularly when less stressful handling stimuli were used, and antagonised
benzodiazepines. This procedure detects the differing behavioural effects of
benzodiazepines receptor
ligands and is proposed as a simple model of anxiety.