La noradrenalina modifica la frequenza della scarica spontanea di reti neuronali coinvolte nel controllo del movimento [Nodadrenaline modifies the spontaneous spiking activity of neural networks involved in motor control]

This report summarizes experimental data (cfr.: Licata et al., 1993; Ciranna et al., 1996; Di Mauro et al., 2003) related to investigations we carried out, by microiontophoretic technique, to elucidate the effects of noradrenaline on the excitability of neurons operating in motor control. The aim of these works was to analyze and to compare the effects exerted by NA on neurons belonging to the Red Nucleus (RN), Vestibular Complex (VC) and Cerebellar Nuclei (CN). A secondary goal was to check the specificity of effects exerted by the amine. Results of data analyses indicate that NA application modifies background firing rate of more than 80% of tested neurons. The response recorded in a high majority of neurons is a depression of the background firing rate mediated by noradrenergic alpha2 receptors. An enhancement noradrenergic beta receptors-dependent was recorded in a minority of VC and NR neurons. These findings indicate that various types of motor performances are extensively modulated by the noradrenergic systems. High NA levels (e. g., in the physiological stress) can influence motor activity heavily. Cellular mechanisms mediating these effects are at least partially unknown, but a plausible hypothesis is that NA-induced firing depression is aimed to a selective enhancement of the signal noise ratio, useful to improve the responsiveness to specific inputs.