Abstract
The neurons in the inferior olive express subthreshold oscillations in their membrane potential. This oscillatory activity is known to drive synchronous activity in the cerebellar cortex and plays a role in motor learning and motor timing. In the past years, it was commonly thought that olivary neurons belonged to a unique population of oscillating units and that oscillation properties were exclusively dependent on network settings and/or synaptic inputs. The origin of olivary oscillations is now known to be a local phenomenon and is generated by a combination of conductances. In the present work, we show the existence of at least two neuronal populations that can be distinguished on the basis of the presence or absence of low-voltage activated Ca2+ channels. The expression of this channel determines the oscillatory behavior of olivary neurons. Furthermore, the number of cells that express this channel is different between sub nuclei of the inferior olive. These findings clearly indicate the functional variability within and between olivary sub nuclei.
Highlights
The inferior olive (IO) receives both motor and sensory information from the cerebellar nuclei and the body and provides one of the major afferents to the cerebellum: the climbing fiber (Desclin, 1974; Courville and Faraco-Cantin, 1978)
Our results reveal that olivary neurons can be distinguished in two populations based on the presence or absence of CaV3.1 channels in their membranes and their capability of generating spontaneous subthreshold oscillations in their membrane potentials
The first series of electrophysiological experiments were performed in Voltage Clamp mode and allowed us to identify two distinct populations of olivary neurons based on the presence of LowVoltage Activated Ca2+ channels (LVA) Ca2+ currents
Summary
The inferior olive (IO) receives both motor and sensory information from the cerebellar nuclei and the body and provides one of the major afferents to the cerebellum: the climbing fiber (Desclin, 1974; Courville and Faraco-Cantin, 1978). During an hyperpolarizing event LVA Ca2+ channels will be de-inactivated and after termination of the hyperpolarization (i.e., anodal break), all available LVA Ca2+ channels can be activated to induce a Low-Threshold Ca2+ Spike (LTS; Crunelli et al, 1989; Perez-Reyes, 2003) These channels are involved in the generation of neuronal oscillations, resonance, and pacemaker activities (Huguenard, 1996; McCormick and Bal, 1997; Kim et al, 2001) and they are highly expressed in the olivo-cerebellar system (Talley et al, 1999), including neurons of the. Our results reveal that olivary neurons can be distinguished in two populations based on the presence or absence of CaV3.1 channels in their membranes and their capability of generating spontaneous (or induced) subthreshold oscillations in their membrane potentials These novel observations provide the experimental ground both for previous model studies (Manor et al, 1997) and for the design of future virtual networks of the Olivo Cerebellar system
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