Inverse agonist properties of the THBC discriminative stimulus: asymmetrical generalization with FG 7142.

Inverse agonist properties of the THBC discriminative stimulus: asymmetrical generalization with FG 7142.

Leidenheimer N J; Schechter M D

Pharmacology, biochemistry, and behavior

1991

1991-03

Male rats were trained to discriminate the stimulus properties of the beta-carbolines 1,2,3,4-tetrahydro-beta-carboline (THBC) (15.0 mg/kg) or FG 7142 (5.0 mg/kg) from vehicle in a two-lever, food-motivated operant task. Consistent with the serotonergic properties of THBC, administration of the 5HT1B agonists TFMPP and mCPP to THBC-trained rats resulted in THBC-appropriate responding. Norharmane, a beta-carboline metabolite of THBC, also mimicked the THBC discriminative stimulus. In contrast, the benzodiazepine receptor partial inverse agonist FG 7142, the anxiogenic/convulsant pentylenetetrazole (PTZ), two physiological stressors and the alpha 2 adrenergic antagonists yohimbine and idazoxan failed to produce THBC-appropriate responding. In the FG 7142-trained rats, THBC and norharmane dose-dependently mimicked the FG 7142 discriminative stimulus. This generalization was not based upon the serotonergic properties of THBC and norharmane since administration of the serotonin agonist mCPP to FG

Male; Animals; Rats; Discrimination Learning/*drug effects; Avoidance Learning/drug effects; Carbolines/antagonists & inhibitors/*pharmacology; Dose-Response Relationship; Drug; Inbred Strains; Receptors; Generalization; Stimulus/*drug effects; GABA-A/*drug effects

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519–525

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