In the present series of studies, we have investigated the effects of antagonists selective for the 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors on motor and 'impulsive'-type behaviours elicited by the non-competitive N-methyl- d-aspartate (NMDA) antagonist dizocilpine. The selective 5-HT(2A) receptor antagonist M100,907 (0.5 mg/kg) attenuated the hyperlocomotion and stereotypy produced by dizocilpine (0.1-0.3 mg/kg). The selective 5-HT(2B) receptor antagonist SB215,505 (3 mg/kg) and the selective 5-HT(2C) receptor antagonist SB242,084 (0.5 mg/kg) had no effect against either measure, except that SB242,084 produced a small potentiation of the hyperactivity response. Dizocilpine (0.03 mg/kg) increased premature responding in rats performing the 5-choice serial reaction time task (5-CSRTT), and increased response frequency consequently reducing the mean inter-response time (IRT) and efficiency of responding in a DRL24 task. M100,907 (0.5 mg/kg) attenuated each of these effects, as well as the increased premature responding produced by the NMDA NR2B selective antagonist Ro 63-1908 (1 mg/kg) in the 5-CSRTT. In contrast SB242,084 (0.5 mg/kg) did not attenuate the dizocilpine-induced premature responding or increased responding in the DRL24 task. Rather, SB242,084 (0.05-0.5 mg/kg) produced qualitatively similar effects to dizocilpine, increasing premature responding and reducing IRT. The results suggest that 5-HT(2A) receptor antagonists may normalise certain 'impulsive' behaviours produced by NMDA receptor hypofunction. The 5-HT(2C) receptor antagonist SB242,084 failed to exert equivalent effects, rather a trend toward exacerbation of the behavioural changes produced by dizocilpine was apparent.

bClostridium difficile is a leading cause of health care-associated diarrhea with significant morbidity and mortality, and new options for the treatment of C. difficile-associated diarrhea (CDAD) are needed. Cadazolid is a new oxazolidinone-type antibiotic that is currently in clinical development for treatment of CDAD. Here, we report the in vitro and in vivo antibacterial evaluation of cadazolid against C. difficile. Cadazolid showed potent in vitro activity against C. difficile with a MIC range of 0.125 to 0.5 g/ml, including strains resistant to linezolid and fluoroquinolones. In time-kill kinetics experiments, cadazolid showed a bactericidal effect against C. difficile isolates, with >99.9% killing in 24 h, and was more bactericidal than vancomycin. In contrast to metronidazole and vancomycin, cadazolid strongly inhibited de novo toxin A and B formation in stationary-phase cultures of toxigenic C. difficile. Cadazolid also inhibited C. difficile spore formation substantially at growth-inhibitory concentrations. In the hamster and mouse models for CDAD, cadazolid was active, conferring full protection from diarrhea and death with a potency similar to that of vancomycin. These findings support further investigations of cadazolid for the treatment of CDAD.C lostridium difficile infection (CDI), or CDAD for C. difficileassociated diarrhea, is a major health care problem and a leading cause of morbidity and mortality in elderly hospitalized patients (1, 2). During the past decade, there has been a renewed interest in CDAD triggered by an increase in both frequency and severity of the disease in the Western world and the discovery of new hypervirulent strains (3-6), as well as an increased incidence of CDAD in the community (7). CDAD results from overgrowth of toxin-producing strains in the colon, typically following disturbances of the normal protective enteric flora. Clinical symptoms range from asymptomatic colonization to diarrhea, severe pseudomembranous colitis, sepsis, and death. The main virulence factors of C. difficile are two high-molecular-weight toxins, the enterotoxin toxin A (TcdA) and the cytotoxin toxin B (TcdB), while the contribution of the binary toxin remains unclear (8). Toxin A and toxin B cause damage to the intestinal epithelial barrier and promote mucosal inflammation. In fact, the main clinical symptoms of CDAD (secretory diarrhea and inflammation of the colonic mucosa) can be explained by the action of toxins A and B (8). Moreover, C. difficile produces endospores that are resistant to antibiotic treatment and routine disinfection (9). Spores surviving in the gut of patients and in the hospital environment may play a major role in reinfection and relapse of CDAD. Current antibiotic therapy for CDAD includes vancomycin and metronidazole, which have limited treatment success in severe disease, and high recurrence rates of up to 30% have been observed with these treatments (10). Only one new antibiotic, fidaxomicin (11, 12), has been approved in the last 30 years for this indication. In c...

The present studies support the view that selective NR2B NMDA antagonists promote impulsive-type responding in the 5-CSRTT; however, under certain test conditions, drugs of this class-notably traxoprodil-may also improve task performance.

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The purpose of these studies were threefold. Firstly, to further characterize the effect of perforant path transection on a test of short-term memory: delayed matching (or nonmatching)-to-position [D(N)MTP]. Secondly, to evaluate the effect of a transient cerebral ischaemia in the same task. Both surgical procedures were chosen as they produce a CNS lesion similar to that described in Alzheimer's Disease (AD). Thirdly, the effect of the acetylcholinesterase inhibitor, donepezil (Aricept(R), E2020), on the resulting cognitive impairment was studied. Perforant path transection produced a robust, delay-dependent impairment of choice accuracy in rats performing either a delayed matching- or nonmatching-to-position task. Sample latency was also reduced following lesion, yet the lesion-induced impairment was not affected by increasing the response requirement at the sample stage. An 11-min period of transient ischaemia (two-vessel occlusion model) resulted in almost complete loss of hippocampal CA1 pyramidal cells and a delay-dependent impairment in DMTP performance. However, unlike perforant path lesions, this deficit was unstable and declined in magnitude over the experimental period. Increasing the delay interval restored this deficit. Donepezil, at doses that robustly attenuated a scopolamine (0.06 mg/kg s.c.)-induced DMTP accuracy impairment in naïve, unoperated rats, had no effect against either lesion-induced impairment. The results are considered in terms of the effectiveness of acetylcholinesterase inhibitors in noncholinergic-based preclinical cognitive models.