Identification of Alpha and Gamma Trigeminal Motoneurons by the Vibratome Paraplast Technique for HRP Histochemistry

Abstract

A morphometric analysis of the masseteric motoneuron pool of the trigeminal motor nucleus was performed in the rat using horseradish peroxidase as a marker. Thick (40 µm) cryosections and thin (7 µm) Paraplast sections were compared. Two types of motoneurons related to the masseter muscle were observed. Small motoneurons, which had a high nuclear index, were found interspersed between large motoneurons, which had more cytoplasm. Evidence is provided that the small trigeminal motoneurons are gamma neurons that innervate the intrafusal muscle fibers of the masseteric muscle spindles.

Quantitative ultrastructural analysis of glycine‐ and γ‐aminobutyric acid‐immunoreactive terminals on trigeminal α‐ and γ‐motoneuron somata in the rat

“…The present finding indicating that a bimodal size distribution of masseter motoneurons allows distinction of large α‐ from small γ‐motoneurons is in accordance with data on cat spinal motoneurons (Burke et al, 1977; Johnson, 1986; Horcholle‐Bossavit et al, 1988; Hoover and Burkovic, 1991) and rat trigeminal JC motoneurons (Limwongse and De Santis, 1977; Rokx et al, 1987). The observation of a higher density of synapses on α‐ than on γ‐motoneurons is similarly consistent with data from cat (see Lagerbäck, 1985; Johnson, 1986; Lagerbäck et al, 1986; Destombes et al, 1992a,b).…”

“…In the present study, we examined immunoreactivity for glycine and/or GABA in boutons covering the somata of trigeminal motoneurons and compared their distribution patterns between JC and JO α‐motoneurons and JC γ‐motoneurons. In contrast to the case for JC motoneurons in the cat (see Yoshida et al, 2001), soma diameters of rat JC motoneurons have been reported to show a clear bimodal distribution (Limwongse and De Santis, 1977; Rokx et al, 1987), so we examined the size distribution of horseradish peroxidase (HRP)‐labeled JC and JO motoneurons to distinguish α‐ from γ‐motoneurons.…”

Ultrastructural anatomy of physiologically identified jaw-muscle spindle afferent terminations onto retrogradely labeled jaw-elevator motoneurons in the rat

“…The size, shape, and ultrastructural characteristics of these neurons are consistent with previous descriptions of cells in the trigeminal motor nucleus (Hamos and King, 1980;Limwongse and DeSantis, 1980;Moody and Meszler, 1980b;Card et al, 1986;Hemmendinger and Moore, 1986;Rokx et al, 1987;Saha et al, 1991a;Mogoseanu et al, 1993). Card et al (1986) reported two major classes of neuron within the rat trigeminal motor nucleus.…”

“…Several previous studies have described the fine structure of the trigeminal motor nucleus (Hamos and King, 1980;Moody and Meszler, 1980a;Yew et al, 1991), but only a few ultrastructural studies of this nucleus have positively identified trigeminal motoneurons by retrograde neuroanatomical labeling (Moody and Meszler, 1980b;Mizuno et al, 1981;Rokx et al, 1987). Ultrastructural studies have also provided evidence that boutons within the trigeminal motor nucleus (Vmo) contain a variety of putative neurotransmitters (Takeuchi et al, 1983;Card et al, 1986;Saha et al, 1991b), and other studies (Saha et al, 1991a;Yang et al, 1997a,b) have shown that ␥-aminobutyric acid-and glycine-immunoreactive boutons contact retrogradely labeled jaw-elevator motoneurons.…”

Development of γ‐aminobutyric acid‐, glycine‐, and glutamate‐immunopositive boutons on rat jaw‐opening motoneurons

“…At variance with the JC motoneurons, which showed a developmental change from unimodal to bimodal size distribution (Limwongse and DeSantis, 1977;Rokx et al, 1987;Kubota et al, 1988;Paik et al, 2007), JO motoneurons (anterior digastric motoneurons) showed unimodal size distribution during development. In addition, the sizes of both small and large JO motoneurons increased uniformly with maturation, including the diameter of the cell body and the length of dendrites, whereas JC motoneurons from the lower end of the size distribution spectrum did not exhibit an increase in size or any prominent morphological change with maturation, consistent with the developmental features of c motoneurons (Miyata et al, 1996;Paik et al, 2007).…”