Changes in the Expression of Parvalbumin Immunoreactivity in the Lumbar Spinal Cord of the Rat following Neonatal Nerve Injury

Abstract

Nerve injury in newborn animals results in the loss of motoneurons and dorsal root ganglion neurons and long-term changes in reflex activation of surviving motoneurons. Parvalbumin has been previously shown to be found in large-diameter primary afferent axons and interneurons in the spinal cord, and was used here to study the changes in parvalbumin-immunoreactive appositions onto identified tibialis anterior/extensor digitorum longus (TA/EDL) motoneurons, during both normal development and following neonatal nerve injury in the rat spinal cord. During normal development, there was a decrease in the number of parvalbumin-immunoreactive appositions onto TA/EDL motoneurons. Thus, at postnatal day 7 (P7), there were 72.8 ± 17.5 (mean ± SD) appositions per motoneuron and by P14, it had decreased to 38.8 ± 13.2 (mean ± SD; p > 0.05). Following neonatal nerve injury at P2, there were fewer parvalbumin-positive afferent appositions close to the TA/EDL motoneurons than normal, so that at P7, there were 53.5 ± 17.1 (mean ± SD), and at P14, it further decreased to 25.8 ± 8.6 (mean ± SD; p > 0.05). This injury-induced reduction in the number of parvalbumin-immunoreactive boutons apposing TA/EDL motoneurons may result, at least in part, from the death of dorsal root ganglion cells with the consequent loss of their central projections. The alterations in the number of parvalbumin-positive appositions close to motoneurons observed in this study may contribute to the changes in the pattern of reflex activity observed in the developing spinal cord both during normal development and following neonatal injury.

The Distribution of Primary Nitric Oxide Synthase- and Parvalbumin- Immunoreactive Afferents in the Dorsal Funiculus of the Lumbosacral Spinal Cord in a Dog

“…An interesting finding is that dorsal root nNOS-IR and PV-IR afferents in all lumbosacral segments, shortly before entering the DREZ-one, segregate in such a way that large-diameter nNOS-IR and PV-IR axons enter the MB of the dorsal root, while small-diameter nNOS-IR axons but not PV-IR participate in the formation of the LB which upon entering the DREZ-one tend to proceed in the ventrolateral direction and approach the dorsolateral border of the dorsal horn. Thus, our study based on nNOS-IR and PV-IR immunohistochemistry documents that the MB of the dog, previously well described in man and monkey (Sindou et al, 1974;Snyder, 1977) but absent in cat (Snyder, 1977) and hardly detectable in rat (Willis and Coggeshall, 1991), is a large anatomical entity containing nNOS-IR and PV-IR fibers, the latter being a highly reliable, although not exclusive, marker for fast-conducting Ia proprioceptive muscle afferents originating from muscle spindles (Clowry et al, 2000(Clowry et al, , 2005Dekkers et al, 2002). Once the small-diameter LB and large-diameter MB enters the DREZ-one, the labeling of nNOS-IR is quite apparent in the LB, while PV-IR is strictly limited to the large-diameter axons of the MB.…”

“…Recent developmental and tract-tracing studies strongly support the view that, of the four different classes of sensory fibers that reach the spinal cord (Sherrington, 1906), the large-diameter proprioceptive fibers are strongly PV-IR. The finding that nNOS-IR was found co-localized with PV-IR in the large-diameter, fast-conducting primary proprioceptive fibers providing afferent input to motoneurons suggests that the pattern of motor activity may be, at least at monosynaptic Ia-motoneuron level, under control of PV and nNOS (Dekkers et al, 2002). The potential functional significance of bNOS-IR and PV-IR co-localization may be anticipated on the basis of known facts, that fast-conducting PV-IR proprioceptive Ia afferents coiling around intrafusal muscle fibers (Celio, 1990;Zhang et al, 1990) form the basis of the monosynaptic stretch reflex circuit (Brown and Fyffe, 1981;Kudo and Yamada, 1987).…”

Quantitation of parvalbumin+ neurons and human immunodeficiency virus type 1 (HIV-1) regulatory gene expression in the HIV-1 transgenic rat: effects of vitamin A deficiency and morphine

“…However, parvalbumin, like the other calcium-binding proteins calbindin and calretinin, can regulate levels of free intracellular calcium and therefore cellular functions such as synaptic transmission and apoptosis. These calcium-binding function of the proteins can have important neuroprotective effects during periods of excessive neuronal excitation, as can occur in experimental models of epilepsy (Schwaller et al , 2004), brain ischemia (Gerstein et al , 2005), and trauma (Dekkers et al , 2002). In the setting of HIV infection, elevated levels of parvalbumin expression may potentially provide protection from toxicity that can be induced by HIV proteins with such protective effects potentially enhanced by morphine.…”

Functional Motor Recovery from Motoneuron Axotomy Is Compromised in Mice with Defective Corticospinal Projections

“…During that P0-P10 interval, several changes occur in the spinal cord. Muscle afferent synapses to spinal motoneurons are gradually eliminated [13], [14] and the strength of the monosynaptic stretch reflex decreases [15]. The inner circuitry in the spinal cord is rearranged; the distribution of spinal interneurons is refined and inactivation of the corticospinal system hampers this reorganization [16].…”