Buspirone antagonizes the expression of conditioned taste aversion in rats

5-Hydroxytryptamine-interacting drugs in animal models of anxiety disorders: more than 30 years of research

An overview of the behavioral data arising from the vast literature concerning the involvement of 5-hydroxytryptamine (5-HT) neurotransmission in the regulation of anxiety is presented. More than 1300 experiments were carried out in this area and they provide evidence that: (1) results obtained in ethologically based animal models of anxiety with drugs stimulating 5-HT transmission are most consistent with the classic 5-HT hypothesis of anxiety in that they show an increase in animals' emotional reactivity; (2) no category of anti-anxiety models are selectively sensitive to the anxiolytic-like effects of drugs targetting 5-HT1A, 5-HT2A or 5-HT2C receptor subtypes; (3) anxiolytic-like effects of 5-HT3 receptor antagonists, in the great part, are revealed by models based on spontaneous behaviors. Taken together, these observations lead to the conclusion that different 5-HT mechanisms, mediated by different receptor subtypes, are involved in the genesis of anxiety.

Assessment of the stimulus properties of anxiolytic drugs by means of the conditioned taste aversion procedure

The conditioned taste aversion (CTA) procedure has recently been described as a more rapid alternative to two-lever operant procedures in drug discrimination research. We trained different groups of rats to discriminate the benzodiazepine chlordiazepoxide (CDP, 20 mg/kg) or the 5-hydroxytryptamine1A (5-HT1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (0.4 mg/kg) from saline by means of the CTA procedure. The results were in agreement with findings from two-lever operant drug discrimination procedures. However, discrimination training took 40 sessions in the case of CDP and 72 sessions for 8-OH-DPAT, which is comparable to results obtained with two-lever operant procedures. Dose-response curves were determined and generalization tests were performed for different benzodiazepine and nonbenzodiazepine anxiolytics. Baseline behavior deteriorated in the course of generalization and substitution testing, thus preventing further generalization testing. Our experience is that the use of the CTA procedure in drug discrimination research does not have sufficient advantages over traditionally used procedures to replace the latter.

Footshock-induced freezing behavior in rats as a model for assessing anxiolytics

A number of chemically distinct anxiolytics were examined for effects on defensive behavior (foot-shock-induced freezing) in rats. Central nervous system acting drugs which are not anxiolytics were also studied. Animals were injected with a drug or vehicle (IP) prior to being placed in a chamber with a grid floor through which two footshocks were delivered. Behavior was observed during the pre-shock period (2 min) and for 4 min after the second footshock. The effects of the following drugs on the duration of footshock-induced freezing were studied: diazepam (DZP); 2-amino-4,5-(1,2-cyclohexyl)-7 phosphonoheptonic acid (NPC 12626); 3-((+/-)-2-carboxypiperazine-4-yl)-propyl-l-phosphonic acid (CPP); [(+)-5-methyl-10-11,dihydroxy-5H-dibenzo(a,d)cyclohepten-5,10- imine (MK-801); buspirone hydrochloride (BUS); DL-amphetamine sulfate (AMP); haloperidol (HAL); ethyl-beta-carboline-3 carboxylate (beta-CCE). Compounds which reduced the duration of footshock-induced freezing included DZP, BUS, and the competitive NMDA antagonists NPC 12626 and CPP. The non-competitive NMDA antagonist, MK-801, had no effect on the response. The highest dose of amphetamine tested also reduced footshock-induced freezing. However, amphetamine-treated animals did not locomote or rear after footshock, suggesting fear of the environment. Animals injected with DZP, NPC 12626, CPP or buspirone spent at least 1.4 of the 4 post shock minutes locomoting. Haloperidol had no effect on freezing at the doses tested. beta-CCE tended to increase the duration of footshock-induced freezing.(ABSTRACT TRUNCATED AT 250 WORDS)