Three-dimensional analysis of cerebellar terminals and their postsynaptic components in the ventral lateral nucleus of the cat thalamus

Abstract

Relationships among cerebellar terminals (CTs), dendrites of thalamocortical projection neurons (TCNs), and dendrites of local circuit neurons in the ventral lateral nucleus of the cat thalamus were analyzed quantitatively by observing several series of serial ultrathin sections and by using a computer-assisted program for the three-dimensional reconstruction from serial ultrathin sections. In pentobarbital-anesthetized cats, CTs were labeled either by injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the cerebellar nuclei or by intra-axonal injection of HRP after electrophysiological identification. By using two series of 133 and 73 serial sections, mutual relationships between 43 WGA-HRP-labeled CTs and their postsynaptic structures were analyzed based on their synaptic specializations and shapes of synaptic vesicles. Thirty-nine of these CTs formed a synapse with one TCN dendrite, whereas only four CTs formed synapses with two TCN dendrites. These CTs also synapsed on dendrites containing pleomorphic synaptic vesicles (presynaptic dendrites). Single CTs synapsed on 0-6 presynaptic dendrites (2.2 +/- 1.5, N = 43) through their whole extents, and about 40% of these presynaptic dendrites that were contacted by CTs established synaptic contacts with the same TCN dendrites on which the CTs synapsed. Thus, a CT, a presynaptic dendrite, and a TCN dendrite formed a triadic arrangement. Triadic arrangements were identified in approximately 60% of these 43 CTs. However, they rarely had a glomerulus-like appearance, as described previously in the ventral lateral nucleus and other main thalamic relay nuclei. In another series of 83 and 43 serial sections along dendrites of TCNs, observations were focused on the triadic arrangement. Triadic arrangements were located evenly on the primary and secondary dendrites of TCNs. Computer-assisted three-dimensional reconstructions were made on one WGA-HRP-labeled CT and two intra-axonally labeled CTs (a bouton en passant and a bouton terminal) with their surrounding neuronal elements, and complex spatial arrangement of neuronal processes became obvious. These results provide the quantitative assessment of synaptic arrangements among CTs, presynaptic dendrites, and TCN dendrites and reveal their spatial interrelations in the cat ventral lateral nucleus.

Neural origin of evoked potentials during thalamic deep brain stimulation

“…Alternatively, the effect of CNQX/ APV on experimentally recorded primary phases could have been generated by antagonism of the thalamic triad in the VL thalamus. In this thalamic triad, a CER afferent makes synaptic connections to both a postsynaptic TC dendrite and a presynaptic input from a local interneuron, and the latter establishes synaptic contact with the same TC dendrite (Sato et al 1996). There is evidence for AMPA and NMDA receptors on the presynaptic inputs from local interneurons in a similar triad arrangement within the LGN of cats (Sherman 2004).…”

Lagged cells in alert monkey lateral geniculate nucleus

“…The projections of these cells to cortex also should be traced, especially in the case of the P cells. Finally, generalization of these results to other thalamic nuclei (Kultas-Ilinsky et al, 1985; Kuroda et al, 1993; Ralston and Ralston, 1994; Balercia et al, 1996; Sato et al, 1996) and other species may show that temporal transformation is a common function of thalamus. If mediodorsal thalamus contains neurons that shift their input by about a quarter cycle, prefrontal cortex might use the range of timing provided to sequence behavior appropriately over long periods of time.…”

Retrograde and anterograde labeling of cerebellar afferent projection by the injection of recombinant adenoviral vectors into the mouse cerebellar cortex

“…For detailed morphological characterization of axons and their collaterals, intracellular staining of single neurons in vivo is the best among a variety of neuronal tracing methods (Shinoda et al 1992;Sato et al 1996). However, this technique requires skill and electrophysiological equipment.…”