Descending supraspinal pathways in amphibians. II. Distribution and origin of the catecholaminergic innervation of the spinal cord

Abstract

Immunohistochemical studies with antibodies against tyrosine hydroxylase, dopamine, and noradrenaline have revealed that the spinal cord of anuran, urodele, and gymnophionan (apodan) amphibians is abundantly innervated by catecholaminergic (CA) fibers and terminals. Because intraspinal cells occur in all three orders of amphibians CA, it is unclear to what extent the CA innervation of the spinal cord is of supraspinal origin. In a previous study, we showed that many cell groups throughout the forebrain and brainstem project to the spinal cord of two anurans (the green frog, Rana perezi, and the clawed toad, Xenopus laevis), a urodele (the Iberian ribbed newt, Pleurodeles waltl), and a gymnophionan (the Mexican caecilian, Dermophis mexicanus). To determine the exact site of origin of the supraspinal CA innervation of the amphibian spinal cord, retrograde tracing techniques were combined with immunohistochemistry for tyrosine hydroxylase in the same sections. The double-labeling experiments demonstrated that four brain centers provide CA innervation to the amphibian spinal cord: 1.) the ventrolateral component of the posterior tubercle in the mammillary region, 2.) the periventricular nucleus of the zona incerta in the ventral thalamus, 3.) the locus coeruleus, and 4.) the nucleus of the solitary tract. This pattern holds for all three orders of amphibians, except for the CA projection from the nucleus of the solitary tract in gymnophionans. There are differences in the strength of the projections (based on the number of double-labeled cells), but in general, spinal functions in amphibians are controlled by CA innervation from brain centers that can easily be compared with their counterparts in amniotes. The organization of the CA input to the spinal cord of amphibians is largely similar to that described for mammals. Nevertheless, by using a segmental approach of the CNS, a remarkable difference was observed with respect to the diencephalic CA projections.

Catecholaminergic innervation of the septum in the frog: A combined immunohistochemical and tract‐tracing study

“…Because in this location only DA neurons are located in amphibians (Gonzá lez and Smeets, 1994a), the neurons in the region of the zona incerta of Rana perezi would provide DA innervation to the septum, as in mammals. This observation strengthens the homology between the amphibian catecholaminergic groups in the ventral thalamus and their counterparts in mammals, as was proposed on the basis of their descending projections (Sá nchez-Camacho et al, 2001b).…”

“…The nomenclature is the same as that used in our previous studies on the connections of the CA cell groups in the brain of amphibians (Marín et al, 1997b;Sá nchez-Camacho et al, 2001b, 2002a.…”

Midbrain dopaminergic neurogenesis and behavioural recovery in a salamander lesion-induced regeneration model

“…Development 134 (15) DEVELOPMENT affected by our regimen of 6-OHDA administration because the cell groups we lesion do not project to the spinal cord in salamanders (Sanchez-Camacho et al, 2001). Movies 1 and 2 (see Movies 1 and 2 in the supplementary material) show sham-and 6-OHDA-injected newts with or without an amphetamine challenge.…”

Neuroanatomical Distribution of Cannabinoid Receptor Gene Expression in the Brain of the Rough-Skinned Newt, <i>Taricha granulosa</i>

“…Nomenclature used to refer to neuroanatomical regions was based on the work of Herrick [1927], Northcutt and Kicliter [1980], Roth [1987], Schmidt and Roth [1990], Marin et al [1997a, b], Sanchez-Camacho et al [2001], and Stuesse et al [2001].…”

“…Specifi cally, in the rostral area of the hindbrain, CB1 ISH labeling occurred in cells of the stratum griseum [Herrick, 1914]. However, this labeling was only in the very medial region of the raphe nucleus [Sanchez-Camacho et al, 2001], more specifi cally, at the location of the raphe magnus, just dorso-medial to the griseum centrale rhombencephali [Stuesse et al, 2001], and medial to the locus coeruleus [Marin et al, 1997a, b]. At a slightly more caudal level of the rostral medulla, CB1 ISH labeling extended through cells of the stratum griseum, with the exception of the area acousticolateralis.…”