Immunocytochemical mapping of noradrenergic projections to the rat spinal cord with an antiserum against noradrenaline

Abstract

The mapping of noradrenergic innervation was performed in transverse and longitudinal sections of the adult rat spinal cord using noradrenaline immunocytochemistry. Noradrenergic fibres and terminals were distributed in the dorsal horn (mainly in the superficial part), in the vicinity of the different groups of motoneurons, and concentrated in the intermediolateral cell column and around the central canal. The ultrastructural study showed principally axodendritic synapses in the ventral horn and in the intermediolateral cell column. Fewer axosomatic synapses were detected. In the dorsal horn, noradrenaline-innervation was predominantly non-synaptic. It is hypothesized that the noradrenergic modulation of nociception is not mediated through classical synapses. The concept of 'volume transmission' can explain such an influence. Conversely, noradrenaline may be involved in the control of locomotion and automatic functions through conventional synapses.

Spatial and temporal patterns of serotonin release in the rat’s lumbar spinal cord following electrical stimulation of the nucleus raphe magnus

“…3). This laminar distribution accords with anatomical studies that have demonstrated the greatest density of serotonergic raphe-spinal terminals in dorsal laminae in the rat (Jones and Light, 1992), whereas noradrenergic fibers predominate in intermediate laminae (Rajaofetra et al, 1992).…”

Central noradrenergic control of penile erection

“…17,21,22 By using an antibody raised against noradrenaline, a wide distribution of noradrenergic ®bers at all spinal levels has been described. 23 However, direct evidence of relationships between catecholaminergic ®bers and spinal neurons destined to the pelvic organs is lacking.…”

Theoretical aspects of sensory substitution and of neurotransmission-related reorganization in spinal cord injury

“…There is evidence that the noradrenergic 72 and serotonergic 73 and partly dopaminergic 48 neurotransmission in the dorsal horn is principally nonsynaptic. Some systems in the spinal cord may be highly nonsynaptic.…”

“…They discussed their ®ndings in regard to the role of the descending serotonergic systems in analgesia. Marlier et al 74 also calculated a non-corrected synaptic incidence, while Rajaofetra et al 72 and Ridet et al 49 have determined the synaptic incidence of serotonergic, noradrenergic and dopaminergic innervation of the spinal cord by two procedures: by counting synapses on single sections and then applying the correcting formula established by Beaudet and Sotelo, 75 and by counting synapses on serial ultrathin sections. All of these studies reveal a high nonsynaptic incidence.…”