Locomotion produced in mesencephalic cats by injections of putative transmitter substances and antagonists into the medial reticular formation and the pontomedullary locomotor strip

Abstract

The purpose of this study was to determine the distribution of cells in the medial reticular formation (MRF) and the pontomedullary locomotor strip (PLS), which can induce locomotion when activated. Controlled microinjections of neuroactive substances (Goodchild et al., 1982) into the MRF or PLS were made in order to activate cell bodies in those areas. The ability of trigeminal receptive field stimulation to induce locomotion before and after drug infusion into the PLS was also assessed since the PLS and the spinal nucleus of the trigeminal nerve are similar in their anatomical distribution. Experiments were performed on precollicular-postmamillary decerebrate cats walking on a treadmill. Injections of glutamic acid (GA; 500 nmol) into the MRF produced locomotion that was antagonized by infusion of glutamic acid diethyl ester into the same spot. Decreases in the current threshold for locomotion produced by electrical stimulation of the MRF were observed when the MRF was infused with either GA (40–80 nmol), DL- homocysteic acid (DL-HCA; 200 nmol), or picrotoxin (PIC; 15 nmol). Injections of GA (100 nmol), DL-HCA (700 nmol), PIC (10–50 nmol), and substance P (2 nmol) into the PLS also produced locomotion. Locomotion produced by injections of PIC into the PLS was blocked by infusion of equal amounts of muscimol or GABA. Effective PLS injection sites were all confined to the trigeminal spinal nucleus or immediately ventral and medial to this in the adjacent lateral reticular formation. Trigeminal nerve peripheral field stimulation evoked locomotion after microinjection of PIC into the PLS, although this same facial stimulus was not effective prior to drug injection. We conclude that the MRF and PLS regions of the cat brain stem contain cells that produce locomotion when chemically stimulated, and we suggest that the PLS is closely related to or synonymous with the spinal nucleus of the trigeminal nerve. Furthermore, we suggest that stimulation of trigeminal afferents is analogous to stimulation of segmental afferent pathways in the production of locomotion (Sherrington, 1910; Jankowska et al., 1967; Afelt, 1970; Budakova, 1972; Grillner and Zangger, 1979).

Evidence for the Existence of a Functional Polysynaptic Pathway From Trigeminal Afferents to Lumbar Motoneurons in the Neonatal Rat

“…The origin of this inhibition is not yet clear, although GABA-containing cell bodies and terminals have been observed in the spinal trigeminal nucleus (Mugnaini and Oertel, 1985). Similar disinhibition has been observed in the bird (Sholomenko et al, 1991) and the cat (Noga et al, 1988). These authors reported that after injection of picrotoxin into the pontomedullary locomotor strip (i.e.…”

Episodic swimming in the larval zebrafish is generated by a spatially distributed spinal network with modular functional organization

“…The hindbrain acts as an activator (Arrenberg et al 2009;Li et al 2006;Mori et al 1978;Noga et al 1988;Soffe et al 2009) and makes excitatory connections with the spinal episode circuit (Hägglund et al 2010;Li et al 2010). The episode circuit acts as a gating center and makes excitatory connections (Buss and Drapeau 2001;Kyriakatos et al 2011) with the spinal coordination circuit.…”

Descending projections of the posterior nucleus of the hypothalamus:Phaseolus vulgaris leucoagglutinin analysis in the rat

“…A relatively extensive longitudinal zone of the medial pontomedullary RF regulates locomotion presumably through direct action on spinal locomotor networks. It has been shown that 1) electrical or chemical activation of the medial pontomedullary RF (p-mRF) elicits locomotion (Mori et al, 1978;Drew and Rossignol, 1984;Ross and Sinnamon, 1984;Garcia-Rill and Skinner, 1987;Noga et al, 1988); 2) cooling or electrolytic lesions of the p-mRF reversibly or irreversibly abolish spontaneous or MLRinduced locomotion (Shefchyk et al, 1984;Jell et al, 1985;Noga et al, 1991); and 3) the discharge of a large percentage of units of the p-mRF is correlated with locomotion in the decerebrate or intact preparation (Shimamura et al, 1982(Shimamura et al, , 1985Drew et al, 1986;Perreault et al, 1993). The strong PH to p-mRF projections demonstrated here and previously (Bayev et al, 1988) would suggest a relatively pronounced influence of the subthalamic locomotor region on pontomedullary RF locomotor systems.…”