Temporal patterning of ultrasonic distress calls in the adult rat: effects of morphine and benzodiazepines.
Opioids and benzodiazepines modulate the ultrasounds that rats emit before being presented with aversive stimulation. Mild, intermittent 10 s electrical tail stimulation induces rats to emit 20-30 kHz ultrasounds before and after the stimulation. Analysis of the temporal parameters of the sounds via a customized computer system reveals them to be emitted in bouts of about five sounds, each sound being separated from the next by 0.2-0.35 s pauses. Morphine decreases the per cent time vocalizing during the pre-stimulation period, with 6 mg/kg being fully suppressive. This effect is reversed by 1 mg/kg naloxone pre-treatment. Chlordiazepoxide and morphine have opposite effects on the temporal structure of the pre-stimulation calls; chlordiazepoxide induces longer bouts with more pulses, and morphine dissolves the bout structure into a series of single pulses. These differential and selective effects of morphine and benzodiazepines on the occurrence and temporal structure of ultrasounds may be relevant to characteristics of different affective expressions.
van der Poel
A M
AM
Department of Pharmacology, University of Leiden, The Netherlands.
Noach
E J
EJ
Miczek
K A
KA
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001569:Benzodiazepines; D004305:Dose-Response Relationship, Drug; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D013997:Time Factors; D014828:Vocalization, Animal / Q000187:drug effects*
D014151:Anti-Anxiety Agents; D001569:Benzodiazepines; D009270:Naloxone; D009020:Morphine