Cellular neuroscienceElectrophysiological and morphological heterogeneity of slow firing neurons in medial septal/diagonal band complex as revealed by cluster analysis
Section snippets
Animals and medial septum/diagonal band slices
Experimental protocols were approved by the Institutional Animal Care and Use Committee (IACUC) and experiments were carried out in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publications No. 80-23). Every effort was made to minimize the number of animals used and their suffering. Briefly, slices containing MS/DB were prepared from 15 to 25 day old male Sprague–Dawley rats. Animals were deeply anesthetized with ketamine (10 mg/kg
Electrophysiological variability of intrinsic membrane properties of MS/DB neurons
Neurons were first visually classified as “slow firing neurons” according to described criteria and then electrophysiological variables were analyzed for development of non-supervised cluster analysis. Normal probability plots and Shapiro-Wilcox test for normality revealed that the distribution of several electrophysiological variables deviated from normality (Table 1). Property variability was evident in Table 1 and Fig. 2. The AP half-width was not normally distributed (P=0.048). The AP
Discussion
Unsupervised cluster analysis was used to determine whether the population of MS/DB neurons is composed of highly heterogeneous subgroups of neuronal subtypes or discrete groups of neuronal subtypes displaying a continuum of electrophysiological properties for each firing phenotype (range of individual variations). These methods have recently been used to more objectively characterize neuronal populations in several brain areas such as neocortex and suprachiasmatic nucleus (Azouz et al 1997,
Acknowledgments
We thank Dr. Brian H. Bland (University of Calgary) for graciously reviewing the manuscript and providing us with valuable insights. Grant sponsor: NIH grants: # NS4271 (L. V. Colom); # NSG M068855 (L. V. Colom and E. R. Garrido-Sanabria); # P20MD001091 and # P20MD000161 funded by NIH/NCMHD (RIMI) and also by NIH/NCMHD (EXPORT) (L. V. Colom and E. R. Garrido-Sanabria) as well as MBRS-RISE grant #1R25Gm06592501A1.
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