Effects of yohimbine and idazoxan on motor behaviors in male rats.
Yohimbine, an alpha 2 adrenergic antagonist, facilitates copulatory behaviors in male rats. This facilitation may reflect nonspecific activation of behavior rather than a more selective activation of copulatory behaviors. The present experiments assessed the effects of yohimbine on locomotor behaviors at a dose (2.0 mg/kg) known to facilitate sexual behaviors. Experiment 1 used a computer pattern-recognition system to classify motor behaviors into specific acts and act groups. Male albino rats were tested in three conspecific conditions: estrous female, anestrous female, or no conspecific. Yohimbine decreased locomotor activity in all three conspecific conditions. Experiment 2 examined the effects of yohimbine (2.0 mg/kg) and amphetamine (1.0 mg/kg) on locomotor behavior in a photocell-equipped activity measurement system. Amphetamine increased and yohimbine decreased locomotor activity. Experiment 3 used the computer pattern-recognition system to compare the effects of yohimbine and idazoxan, another alpha 2 adrenergic antagonist, on motor behaviors. Yohimbine and idazoxan both decreased activity but produced different patterns of behavioral change. The facilitatory effects of yohimbine on copulatory behaviors at a dose of 2.0 mg/kg are apparently not mediated by nonspecific activation of behavior.
Department of Neurosciences, University of California, San Diego, La Jolla 92093-0624.
M P
MP
Bowes
R H
RH
Peters
W J
WJ
Kernan
D L
DL
Hopper
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004146:Dioxanes / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D019329:Idazoxan; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D015016:Yohimbine / Q000008:administration & dosage / Q000494:pharmacology*
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D015016:Yohimbine; D019329:Idazoxan