The role of connexin36 gap junctions in modulating the hypnotic effects of isoflurane and propofol in mice.

Gap junction blockade is a possible mechanism by which general anaesthetic drugs cause unconsciousness. We measured the sensitivity of connexin36 knockout mice to the hypnotic effects of isoflurane and propofol. The experimental endpoint was recovery of the righting reflex of the anaesthetised animals during 0.2% step-reductions in isoflurane concentration, or following intraperitoneal injection of propofol (100 mg.kg(-1) ). Connexin36 knockout animals were more sensitive to the hypnotic effects of isoflurane than 'normal' wild-type animals. The half maximal effective concentration (EC50) for recovery of righting reflex was 0.37% for connexin36 knockout vs 0.49% for wild-type animals (p < 0.001). For propofol, connnexin36 knockout animals showed more rapid loss of righting reflex than wild-type animals (mean (SD) 2.8 (0.13) vs 3.8 (0.27) min); and young (< 60 days) connexin36 knockout animals remained anaesthetised for longer than young wild-type mice (47.2 (2.9) vs 30.5 (1.7) min; p < 0.00001). These findings suggest that the hypnotic effects of anaesthetic drugs may be moderately enhanced by gap junction blockade.

The molecular identification of Streptococcus equi subsp. equi strains isolated within New Zealand.

AIMS: To identify Streptococcus equi subsp. equi (S. equi) by PCR analysis and obtain isolates by culture, in order to investigate the strains of S. equi infecting horses within New Zealand. METHODS: A diagnostic PCR, based on the amplification of the seeI gene for S. equi, was used on 168 samples submitted from horses with and without clinical signs of strangles. Samples were also processed and cultured on selective media for the isolation of ß-haemolytic colonies. In addition, the hypervariable region of the seM gene of S. equi was amplified and then sequenced for strain typing purposes. RESULTS: Of the 168 samples, 35 tested positive for S. equi using PCR. Thirty-two confirmed samples were from horses with a clinical diagnosis of strangles and three were from horses where clinical information was unavailable. Only 22/35 (63%) confirmed S. equi samples were successfully isolated following culture. Strain typing demonstrated that two novel seM alleles of S. equi were found in New Zealand with SeM-99 strains being restricted to the North Island while SeM-100 strains were found in both North and South Islands. CONCLUSIONS: The application of PCR for the laboratory confirmation of strangles allowed for a rapid and sensitive identification of S. equi. Moreover, seM typing revealed that within the samples examined two strains of S. equi co-circulated within the North Island of New Zealand but only one strain in the South Island. CLINICAL RELEVANCE: PCR reduces the time required to obtain laboratory confirmation of strangles compared with culture methods. It also has greater sensitivity in detecting S. equi infections, which is of particular importance in the detection of carrier animals which normally shed low numbers of bacteria. Additionally, seM molecular typing can differentiate between bacterial strains, assisting in the monitoring of local strains of S. equi subsp. equi causing disease.