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Abstract: The pedunculopontine tegmental nucleus (PPTg) is involved in the regulation of thalamocortical transmission and of several functions related to ventral and dorsal striatal circuits. Stimulation of the PPTg in anesthetized animals increases cortical arousal, cortical acetylcholine release, bursting activity of mesopontine dopaminergic cells, and striatal dopamine release. It was hypothetized that PPTg stimulation could improve learning by enhancing cortical arousal and optimizing the activity of striatal circuits. We tested whether electrical stimulation (ES) of the PPTg, applied to freely-moving awake rats previously implanted with a chronic electrode, would improve the acquisition and/or the retention of two-way active avoidance conditioning, and whether this effect would depend on the specific PPTg region stimulated (anterior vs posterior) and on the time of ES: just before (pre-training) or after (post-training) each of three training sessions. The treatment consisted of 20min of ES (0.2ms pulses at 100Hz; current intensity: 40–80μA). The results showed that (1) this stimulation did not induce either any signs of distress nor abnormal behaviors, apart from some motor stereotyped behaviors that disappeared when current intensity was lowered; (2) pre-training ES applied to the anterior PPTg improved the acquisition of two-way active avoidance, (3) no learning improvement was found after either post-training ES of the anterior PPTg, or pre- and post-training ES of the posterior PPTg. The results give support to a role of PPTg in learning-related processes, and point to the existence of functional PPTg regions. [Copyright &y& Elsevier]

Highlights: [•] Voluntary physical exercise improved acquisition in the spatial Barnes maze. [•] The improvement is due to a direct effect of exercise on learning process. [•] Post-training epinephrine only tended to improve learning in the spatial Barnes maze. [•] Both treatments combined did not further enhance acquisition of this task. [ABSTRACT FROM AUTHOR]

Abstract: The present work examined whether post-training systemic epinephrine (EPI) is able to modulate short-term (3h) and long-term (24h and 48h) memory of standard object recognition, as well as long-term (24h) memory of separate “what” (object identity) and “where” (object location) components of object recognition. Although object recognition training is associated to low arousal levels, all the animals received habituation to the training box in order to further reduce emotional arousal. Post-training EPI improved long-term (24h and 48h), but not short-term (3h), memory in the standard object recognition task, as well as 24h memory for both object identity and object location. These data indicate that post-training epinephrine: (1) facilitates long-term memory for standard object recognition; (2) exerts separate facilitatory effects on “what” (object identity) and “where” (object location) components of object recognition; and (3) is capable of improving memory for a low arousing task even in highly habituated rats. [Copyright &y& Elsevier]

A new method of automated sleep–wake staging in the rat is described. Hippocampal electroencephalographic (HPC) and nuchal electromyographic signals were recorded by a digital polygraph. The HPC channel was filtered off-line to obtain the original plus theta and delta waves. Statistics of each of these four channels were obtained every 5 s and exported to a standard spreadsheet. The automated staging consisted of five steps: (1) automatic detection of waking, nonrapid eye movement sleep and rapid eye movement sleep patterns (5-s periods); (2) calculation of statistics for each vigilance state; (3) final classification of 5-s periods; (4) construction of a primary 20-s epoch hypnogram; and (5) automatic refinement of the previous hypnogram. The system includes indices about the accuracy of the staging and was validated with five recordings of 23 h each. The global agreement between human and automatic scoring in the validation recordings was 94.32%. [Copyright &y& Elsevier]

The consequences of traumatic brain injury (TBI) sustained during late adolescence (7 weeks old) on spontaneous object recognition memory and on anxiety-like behaviors in the elevated plus maze were tested in rats during adulthood. Testing took place at 2 different postinjury times, in separate groups: 3 and 6 weeks, when animals were 10 and 13 weeks old, respectively. The rats were either submitted to controlled cortical impact injury, an experimental model of focal TBI with contusion, or were shamoperated. TBI animals failed to remember the familiar object and had a significantly lower performance than sham-operated animals, indicating memory disruption, when the retention delay was 24 hr, but not when it was 3 hr. TBI did not have any significant effect on the main anxiety-related behaviors, but it reduced time in the central platform of the elevated plus maze. The effects of TBI on memory and on anxiety-like behaviors were similar at the 2 postinjury times. In both TBI and sham-operated groups, animals tested 6 weeks after surgery had lower anxiety-related indices than those tested at 3 weeks, an effect that might be indicative of reduced anxiety levels with increasing age. In summary, focal TBI with contusion sustained during late adolescence led to object recognition memory deficits in a 24-hr test during adulthood but did not have a major impact on anxiety-like behaviors. Memory deficits persisted for at least 6 weeks after injury, indicating that spontaneous modifications of these functional disturbances did not take place along this time span. [ABSTRACT FROM AUTHOR]