Behavioural brain research
-
Recent studies revealed a causal link between ventral tegmental area (VTA) phasic dopamine (DA) activity and pro-depressive and antidepressant-like behavioral responses in rodent models of depression. Cholinergic activity in the VTA has been demonstrated to regulate phasic DA activity, but the role of VTA cholinergic mechanisms in depression-related behavior is unclear. The goal of this study was to determine whether pharmacological manipulation of VTA cholinergic activity altered behavioral responding in the forced swim test (FST) in rats. ⋯ Finally, the VTA physostigmine-induced increase in immobility was blocked by co-administration with scopolamine, but unaltered by co-administration with mecamylamine. These data show that enhancing VTA cholinergic tone and blocking VTA AChRs has opposing effects in FST. Together, the findings provide evidence for a role of VTA cholinergic mechanisms in behavioral responses in FST.
-
Frontal N30 somatosensory evoked potentials (SEPs) represent early somatosensory input into non-primary motor areas. Importantly, modulations of frontal N30 SEPs can provide insight into the mechanisms involved in sensory processing for movement control. Enhancements of frontal N30 SEPs have been revealed during repetitive but not during the preparation of movements that are contralateral to median nerve (MN) stimulation (i.e. contralateral movements). ⋯ Results revealed that frontal N30 SEPs were significantly enhanced when MN stimulation occurred in the late preparatory and/or early movement execution period (∼750 ms) after the attended VibT stimuli. This result supports that increases in frontal N30 amplitudes during contralateral movements are dependent on the complexity of preparing and executing finger sequences, which is associated with increased activity in several neural areas such as the non-primary motor areas, prefrontal cortex and BG. Furthermore, enhanced N30 SEPs during contralateral movement preparation and execution may be a necessary mechanism to decrease sensory gating to facilitate somatosensory processing in non-primary motor areas when there is a 'noisy' environment.
-
The present study investigated the impact of a spared nerve injury (SNI) on the daily performance of rats tested in two instrumental conditioning procedures: the progressive ratio (PR) schedule of food reinforcement to study motivation for an appetitive stimulus, and the 5-choice serial reaction time task (5-CSRTT), a test of attention and reaction time. Separate groups of male, Sprague-Dawley rats of age 8-10 months were trained to asymptotic performance in either task, before undergoing either SNI or sham surgery. After a recovery period of 3-4 days the animals were run 5 days/week for 3 months in either task. ⋯ This deficit emerged during the second month post-surgery and was characterized by slower response speed, reduced accuracy and increased trial omissions. Both SNI groups showed equivalent hypersensitivity to evoked sensory stimuli compared to controls. Since attention based deficits have been reported in individuals with clinical forms of neuropathic pain, the present studies suggest a novel approach to study this phenomena and a means to study the effect of treatments against this cognitive endpoint.
-
Although attention-deficit hyperactivity disorder (ADHD) is commonly reported after moderate and severe traumatic brain injury (TBI), research is struggling to find a strong link between mild TBI or concussion and ADHD. Epidemiological studies often generate conflicting results which may be related to the difficulty identifying the lingering symptoms of mTBI, the lack of baseline knowledge and the possible exacerbation of pre-existing ADHD symptomology, and/or differential diagnostic criteria for secondary ADHD. The purpose of this study was to determine if a mild TBI/concussion in the juvenile period (postnatal day 30) could induce ADHD-like symptoms in young rodents. ⋯ Significant deficits were identified in sustained attention, response inhibition, and impulsivity. Immediately after the mTBI, all rats were hypoactive in the open field, and while male animals exhibited a trend toward hyperactivity in the long-term, females continued to trend toward hypoactivity for the duration of the experiment. These findings provide a unique platform upon which preventative and therapeutic strategies can be implemented and tested in an effort to improve ADHD-like symptoms following mTBI.
-
Chemokines are a family of cytokines involved in the chemotaxis of leukocytes and other target cells by binding to specific G-protein-coupled receptors on their membranes. As such, the activation of C-C chemokine receptor type 2 (CCR2) is involved in the mobilization of "inflammatory" monocytes from bone marrow and in their recruitment to the brain under inflammatory/pathological conditions. In this study, we investigated whether CCR2 signaling could affect the progression of learning deficits and hippocampal damage in a model of neonatal hypoxic-ischemic (HI) brain injury. ⋯ CCR2 KO mouse pups of both sexes had a lower number of circulating monocytes, although only HI CCR2 KO male mice exhibited reduced numbers of activated macrophages/microglia in the damaged hippocampus, compared to WT mice. However, no differences were observed in hippocampal atrophy between HI CCR2 KO and HI WT mice. These results suggest that CCR2 signaling can protect neonatal mice from developing spatial learning deficits after a HI insult, in a sex-specific fashion.