Release properties and functional integration of noradrenergic‐rich tissue grafted to the denervated spinal cord of the adult rat

Abstract

Noradrenaline- (NA-) containing grafts of central (embryonic locus coeruleus, LC) or peripheral (juvenile adrenal medullary, AM, autologous superior cervical ganglionic, SCG) tissue were implanted unilaterally into rat lumbar spinal cord previously depleted of its NA content by 6-hydroxydopamine (6-OHDA) intraventricularly. A microdialysis probe was implanted in the spinal cord 3-4 months after transplantation, and extracellular levels of noradrenaline were monitored in freely moving animals during basal conditions and following administration of pharmacological or behavioural stimuli. Age-matched normal and lesioned animals both served as controls. Morphometric analyses were carried out on horizontal spinal sections processed for dopamine-beta-hydroxylase (DBH) immunocitochemistry, in order to assess lesion- or graft-induced changes in the density of spinal noradrenergic innervation, relative to the normal patterns. In lesioned animals, the entire spinal cord was virtually devoid of DBH-positive fibers, resulting in a dramatic 88% reduction in baseline NA, compared with that in controls, which did not change in response to the various stimuli. LC and SCG grafts reinstated approximately 80% and 50% of normal innervation density, respectively, but they differed strikingly in their release ability. Thus, LC grafts restored baseline NA levels up to 60% of those in controls, and responded with significantly increased NA release to KCl-induced depolarization, neuronal uptake blockade and handling. In contrast, very low NA levels and only poor and inconsistent responses to the various stimuli were observed in the SCG-grafted animals. In AM-grafted animals, spinal extracellular NA levels were restored up to 45% of those in controls, probably as a result of nonsynaptic, endocrine-like release, as grafted AM cells retained the chromaffine phenotype, showed no detectable fibre outgrowth and did not respond to any of the pharmacological or behavioural challenges. Thus, both a regulated, impulse-dependent, and a diffuse, paracrine-like, NA outflow may play roles in the recovery of lesion-induced sensory and/or motor impairments previously reported with these types of grafts following transplantation into the severed spinal cord.

Essential role of hippocampal noradrenaline in the regulation of spatial working memory and TDP‐43 tissue pathology

“…Four weeks later, a noradrenergic‐rich cell suspension was prepared as previously described (Coradazzi et al, ; Leanza, Cataudella, Dimauro, Monaco, & Stanzani, ) following a modified protocol based on the cell suspension technique (Björklund, Stenevi, Schmidt, Dunnett, & Gage, ). Briefly, the developing LC was bilaterally dissected from the dorsolateral pons of 13‐ to 14‐days‐old donor rat foetuses (crown‐to‐rump length, CRL, 9–13 mm) of the same strain as the graft recipients, and collected in cold Dulbecco's Modified Eagle Medium (DMEM, Life Technologies, Italy).…”

Selective lesion of the developing central noradrenergic system: short‐ and long‐term effects and reinnervation by noradrenergic‐rich tissue grafts

“…Four days later (at PD8), a noradrenergic‐rich cell suspension was prepared as previously described (Leanza et al. 1999) following a modified protocol based on the cell suspension technique (Björklund et al.…”

“…As a basis for ongoing studies on the functional integration of monoaminergic neuroblasts implanted into the denervated/depleted rat spinal cord (Leanza et al. 1999; Gulino et al.…”

Neuroplasticity and Repair in Rodent Neurotoxic Models of Spinal Motoneuron Disease

“…Afterwards, functional neuroanatomy studies have relied on the effects of lesions to investigate the function of neural systems, and a large variety of neurotoxins has been used to destroy specific cell populations. For instance, excitotoxins such as kainic acids [ 35 , 36 ] or monoamine toxins including 6-hydroxydopamine [ 37 ] have been used to produce selective lesions based on the neurotransmitter specificity, but these compounds have shown incomplete anatomical and cell-type specificity. A substantial improvement of these methods of “molecular neurosurgery” has been provided by the development of axonally transported toxins such as lectins [ 38 – 41 ], immunotoxins [ 42 – 45 ], tracer-toxins, and neuropeptide-conjugated toxins [ 42 ].…”