Serotoninergic, peptidergic and GABAergic innervation of the ventrolateral and dorsolateral motor nuclei in the cat S1/S2 segments: An immunofluorescence study

Abstract

Indirect single- and double-staining immunofluorescence techniques were used to study the serotoninergic, peptidergic and GABAergic innervation of the ventrolateral (Onuf's nucleus) and dorsolateral (innervating intrinsic foot sole muscles) nuclei, located in the S1/S2 segments of the cat spinal cord. The relative density of 5-hydroxytryptamine-, thyrotropin-releasing hormone-, substance P- and gamma-aminobutyric acid-immunoreactive axonal varicosities was similar in both nuclei. The highest relative density was recorded for varicosities immunoreactive to gamma-aminobutyric acid, while those immunoreactive to 5-hydroxytryptamine or thyrotropin-releasing hormone yielded the lowest values. The density of enkephalin-immunoreactive varicosities was higher in the ventrolateral than in the dorsolateral nucleus. Calcitonin gene-related peptide-like immunoreactivity could be seen in neurons of the ventrolateral and dorsolateral nuclei. Occasionally, calcitonin gene-related peptide-immunoreactive axonal fibers were also encountered in these nuclei. Virtually all thyrotropin-releasing hormone-immunoreactive varicosities in the ventrolateral and dorsolateral nuclei also contained 5-hydroxytryptamine-like immunoreactivity, while a somewhat smaller number of them were co-localized with substance P. About 5-10% of the 5-hydroxytryptamine-immunoreactive varicosities were devoid of peptide-like immunoreactivity, and the number of 5-hydroxytryptamine-immunoreactive varicosities lacking thyrotropin-releasing hormone-like immunoreactivity was higher in the dorsolateral than in the ventrolateral nucleus. Finally, the free fraction of substance P-immunoreactive varicosities, i.e., those lacking both 5-hydroxytryptamine and thyrotropin-releasing hormone, was about 39% in the ventrolateral and 26% in the dorsolateral nucleus. Spinal cord transection at the lower thoracic level induced a depletion of 5-hydroxytryptamine and thyrotropin-releasing hormone-immunoreactive fibers from the ventrolateral and dorsolateral nuclei, indicating an exclusive supraspinal origin for these fibers. A reduction in substance P-like immunoreactivity following spinal cord transection alone or spinal cord transection combined with unilateral dorsal rhizotomy was also detected in both nuclei, suggesting a dual origin for substance P-immunoreactive fibers, i.e., both supra- and intraspinal. The decrease in number of substance P-immunoreactive fibers was however smaller than expected from the analysis of the fraction of substance P-immunoreactive fibers co-localized with 5-hydroxytryptamine, indicating thus that the experimental lesions may have triggered a sprouting of substance P-immunoreactive axons originating from spinal cord sources. The distribution of gamma-aminobutyric acid in the ventrolateral and dorsolateral nuclei was not affected by the different lesion paradigms. It is therefore assumed that these inputs are intrinsic to the spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Anatomical distribution of serotonin‐containing neurons and axons in the central nervous system of the cat

“…1d, L1, 8C) (Krukoff et al, 1985). 8D) Arvidsson et al, 1990;Ramirez-Leon et al, 1994). At all levels of the spinal cord, dense networks of immunolabeled fibers, a number of which were large varicose, were visualized in layer I (marginal zone; Fig.…”

Two pontine micturition centers in the cat are not interconnected directly: Implications for the central organization of micturition

“…The majority of them make contact with ␥-amino butyric acid (GABA)-immunoreactive dendrites or somata (Blok et al, 1997a). Other studies have indicated that many of the local neurons projecting to the Onuf 's nucleus are located in the sacral DGC (Konishi et al, 1985;Nadelhaft and Vera, 1996) and that Onuf 's nucleus receives a substantial afferent input from GABAimmunoreactive neurons in the caudal lumbar and sacral cord (Ramirez-Léon et al, 1994). Electrical stimulation in the sacral DGC results in a sharp decrease in the intraurethral pressure indicating a relaxation of the external urethral sphincter (Blok et al, 1998b).…”

Coordination of the Bladder Detrusor and the External Urethral Sphincter in a Rat Model of Spinal Cord Injury: Effect of Injury Severity

“…We, therefore, used serotonin as a marker of direct supraspinal projections to DL (Ramirez-Leon et al, 1994;Tang et al, 1998). Previous studies in our laboratory and the work of others have established that serotonin immunoreactivity distal to the injury site is a good indicator of both SCI severity and the degree of recovery of somatic sensorimotor function (Faden et al, 1988;Wrathall et al, 1994;Teng and Wrathall, 1997).…”