The AC sends

descending projections to the IC that terminate most densely upon the dorsal, lateral and rostral IC cortices – areas where strong SSA has been reported. To investigate whether SSA in the IC is dependent upon the AC for its generation, we recorded the response from single IC neurons to stimuli presented in an oddball paradigm before, during and after reversibly deactivating the ipsilateral AC with a cryoloop. While Pexidartinib chemical structure changes in the basic response properties of the IC neurons were widespread (89%), changes in SSA sensitivity were less common; approximately half of the neurons recorded showed a significant change in SSA, while the other half remained unchanged. Changes in SSA could be in either direction: 18% enhanced their SSA sensitivity, while 34% showed reduced SSA sensitivity. For the majority

of this latter group, cortical deactivation reduced, but did not eliminate, significant SSA levels. Only eight neurons seemed to inherit SSA from the AC, as their pre-existing significant level of SSA became non-significant during cortical deactivation. Thus, the presence of SSA in the IC is generally not dependent upon the corticocollicular projection, suggesting the AC is not essential for the generation of subcortical SSA; however, the AC may play a role in the modulation of subcortical SSA. “
“How external stimuli prevent the onset of Selleckchem Stem Cell Compound Library sleep has been little studied. This is usually considered to be a non-specific type of phenomenon. However, the hypnotic drug dexmedetomidine, an agonist at α2 adrenergic receptors, has unusual properties that make it useful for investigating this question. Dexmedetomidine is considered to produce very an ‘arousable’ sleep-like state, so that patients or animals given dexmedetomidine become alert following modest stimulation. We hypothesized that it might be more difficult to make mice

unconscious with dexmedetomidine if there was a sufficient external stimulus. Employing a motorized rotating cylinder, which provided a continuous and controlled arousal stimulus, we quantitatively measured the ability of such a stimulus to prevent dexmedetomidine loss of righting reflex in two inbred strains of mice (C57BL/6 and 129X1). We found that whereas the C57BL/6 strain required a strong stimulus to prevent dexmedetomidine-induced hypnosis, the 129X1 strain stayed awake even with minimal stimuli. Remarkably, this could be calibrated as a simple threshold trait, i.e. a binary ‘yes–no’ response, which after crossing the two mouse strains behaved as a dominant-like trait. We carried out a genome-wide linkage analysis on the F2 progeny to determine if the ability of a stimulus to prevent dexmedetomidine hypnosis could be mapped to one or more chromosomal regions. We identified a locus on chromosome 4 with an associated Logarithm of Odds score exceeding the pre-established threshold level.