Distinct neuroplasticity processes are induced by different periods of acrobatic exercise training.

Short and long-term physical exercise induce physiological and structural changes in brain motor areas. The relationship between changes of structural and synaptic proteins in brain motor areas and acrobatic exercise is less understood. Our aim was to evaluate the expression of synapsin I (SYS), synaptophysin (SYP), microtubule-associated protein 2 (MAP2), neurofilament (NF), and a marker for recent neuronal activity (Egr-1) in the motor cortex, striatum and cerebellum of adult rats subjected to acrobatic exercise (AE, for 1-4 weeks). We used adult Wistar rats, divided into 4 groups based on duration of acrobatic training, namely 1 week (AE1, n=15), 2 weeks (AE2, n=15), 4 weeks (AE4, n=15), and sedentary (SED, n=15). In AE groups, the rats covered 5 times a circuit that was composed of obstacles, three times a week. The protein levels were analyzed by immunoblotting and immunohistochemistry. The results revealed that short-term AE (AE1 and AE2) induced MAP2 decreases and NF, SYP and Egr-1 increases in the motor cortex; an increase of MAP2, SYS and SYP in the dorsolateral striatum, whereas the dorsomedial striatum showed increased NF, SYS, SYP and Egr-1. Granular cerebellar layer showed increased NF and Egr-1, with increased NF and SYP in the molecular layer. Long-term AE (AE4) promoted an increase of MAP2, SYP and Egr-1 in motor cortex; MAP2, SYS and SYP in the dorsomedial striatum; and NF and Egr-1 in the cerebellar granular layer. In conclusion, our data suggest that different durations of AE induce distinct plastic responses among distinct cortical and subcortical circuits.

The dorsolateral periaqueductal gray and its role in mediating fear learning to life threatening events.

The dorsolateral column of the periaqueductal gray (dlPAG) integrates aversive emotional experiences and represents an important site responding to life threatening situations, such as hypoxia, cardiac pain and predator threats. Previous studies have shown that the dorsal PAG also supports fear learning; and we have currently explored how the dlPAG influences associative learning. We have first shown that N-methyl-D-aspartate (NMDA) 100 pmol injection in the dlPAG works as a valuable unconditioned stimulus (US) for the acquisition of olfactory fear conditioning (OFC) using amyl acetate odor as conditioned stimulus (CS). Next, we revisited the ascending projections of the dlPAG to the thalamus and hypothalamus to reveal potential paths that could mediate associative learning during OFC. Accordingly, the most important ascending target of the dlPAG is the hypothalamic defensive circuit, and we were able to show that pharmacological inactivation using ß-adrenoceptor blockade of the dorsal premammillary nucleus, the main exit way for the hypothalamic defensive circuit to thalamo-cortical circuits involved in fear learning, impaired the acquisition of the OFC promoted by NMDA stimulation of the dlPAG. Moreover, our tracing study revealed multiple parallel paths from the dlPAG to several thalamic targets linked to cortical-hippocampal-amygdalar circuits involved in fear learning. Overall, the results point to a major role of the dlPAG in the mediation of aversive associative learning via ascending projections to the medial hypothalamic defensive circuit, and perhaps, to other thalamic targets, as well. These results provide interesting perspectives to understand how life threatening events impact on fear learning, and should be useful to understand pathological fear memory encoding in anxiety disorders.

Effects of ventrolateral striatal inactivation on predatory hunting.

Previous studies from our laboratory have shown that insect hunting is associated with a distinct Fos up-regulation in the ventrolateral caudoputamen at intermediate rostro-caudal levels. It is largely known that ventrolateral striatum participates in the control of orofacial movements and forepaw usage accompanying feeding behavior, but there has been no study investigating its possible roles during predatory hunting. We have presently examined the role of the ventrolateral striatum during roach hunting by using the reversible blockade with lidocaine. Accordingly, non-treated and saline-treated animals performed the insect hunting quite well, displaying a rather stereotyped form of motor actions for chasing, capturing and killing the prey. During the bilateral blockade of the ventrolateral striatum, the animals showed a significantly longer latency to start hunting and to capture the first prey. The lidocaine-treated animals captured the prey by using mostly the mouth, with little forepaw assistance, and were less effective in capturing the roaches. Moreover, while handling the prey, animals with ventrolateral striatal inactivation kept biting several parts of the prey, but failed to deliver the killing bite to the head, leaving them alive and moving, more likely to escape. Overall, the present findings suggest that the ventrolateral striatum implements the stereotyped actions seen during prey capture and handling, and may influence the motivational drive to start attacking the roaches, as well.