Distribution of Nitrergic Neurons in the Dorsal Root Ganglia of the Bottlenose Dolphin (Tursiops truncatus)

Abstract

Dorsal root ganglia (DRGs) contain the cell bodies of primary afferent neurons that transmit sensory information from the periphery into the spinal cord. Distinct populations of DRG neurons have been characterized by a variety of different immunohistochemical markers. A subpopulation of ganglionic neurons containing neuronal nitric oxide synthase (nNOS), an enzyme known to generate nitric oxide, has been detected in a number of mammalian species. Despite previous studies, no information is known on the presence and exact distribution of nNOS-immunoreactive neurons in the DRGs of the bottlenose dolphin. In this investigation, immunoperoxidase for nNOS was used to determine the distribution and the perikaryal size of nitrergic neurons in the DRGs of this species. Double immunofluorescence protocol was used to determine the percentage of nNOS-immunoreactive (IR) neurons over the total primary afferent neurons. In addition, double immunostaining was used to verify whether there was colocalization of nNOS with substance P (SP). In all DRGs, a subpopulation of small-and medium-sized neurons (about 9%) exhibited nNOS immunoreactivity. Data analysis revealed that the majority of nNOS-IR neurons (81.3%) expressed SP. The density of nNOS-immunoreactive and nNOS/SP-double immunopositive cells was relatively constant throughout the ganglia. However, as observed in others mammals, the number of nitrergic neurons decreased in the caudalmost DRGs. Our results, in conjunction with previous observations, suggest that nNOS-IR neurons may be involved in the afferent transmission of visceral and nociceptive information as well as in the regulation of the vascular tone. Anat Rec, 294:1066Rec, 294: -1073Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.Key words: bottlenose dolphin; dorsal root ganglia; neuronal nitric oxide synthase; substance P Dorsal root ganglia (DRGs) contain the cell bodies of primary afferent neurons that convey somatic and visceral input from the body to the spinal cord. Several studies have indicated that primary afferent neurons of the DRGs can be classified in different populations on the basis of their morphological, physiological, and biochemical features (Lawson, 1992;Willis and Coggeshall, 2004). On the basis of cell body size, the DRG neurons of

Nitrergic Neurons in the Spinal Cord of the Bottlenose Dolphin (Tursiops truncatus)

“…In agreement with the previous data, pharmacological studies revealed that different spinal functional processes, such as nociceptive transmission, central sensibilization, and hyperanalgesia, require the production of NO (Meller et al, 1992;Meller and Gebhart, 1993;McMahon et al, 1993). In the bottlenose dolphin, the involving of NO on nociceptive transmission is also suggested from a recent study indicating that the majority of nitrergic neurons of the spinal ganglia express Substance P (SP) (Bombardi et al, 2011).…”

“…As reported in previous studies, the NADPH-d reaction and the mouse anti-nNOS marked the same neurons (Dawson et al, 1991;Vincent and Kimura, 1992;Giraldi-Guimarães et al, 1999;Bombardi et al, 2006Bombardi et al, , 2011. In the bottlenose dolphin, the laminar distribution of the spinal nitrergic neurons is similar to that reported in mouse, rat, rabbit, dog, cat, and Primates, with somata localized with a high density in Laminae I, II, VII (intermediolateral cell column and nucleus intermediolateralis sacralis of terrestrial Mammals), and X (Br€ uning, 1992;Dun et al, 1992Dun et al, , 1993Valtschanoff et al, 1992a,b;Spike et al, 1993;Terenghi et al, 1993;Saito et al, 1994;Vizzard et al, 1994;Wetts and Vaughn, 1994;Pullen and Humphreys, 1995;Mars ala et al, 1998Mars ala et al, , 1999Kluchov a et al, 2000).…”

“…NADPH-d and nNOS stained axons were seen running across the Lissauers's tract and the dorsal funiculus. Since many nitrergic neurons has been found in the sensory ganglia (Bombardi et al, 2011), these axons may be primary afferent fibers.…”

“…The specificity of monoclonal antibody used in this study has been described previously (Bombardi et al, 2011). Incubation without the substrate NADPH or without the electron acceptor Nitroblue tetrazolium chloride (NBT) drastically reduced the intensity of NADPH-d staining.…”

“…The NO-synthesizing neurons, or nitrergic neurons, can be revealed using both histochemical staining for NADPHdiaphorase (NADPH-d) and immunohistochemical detection of nNOS. The diaphorase activity and consequently its distribution in the CNS is superimposed to nNOS immunoreactivity (Dawson et al, 1991;Vincent and Kimura, 1992;Giraldi-Guimarães et al, 1999;Bombardi et al, 2006Bombardi et al, , 2011. NADPH-d and nNOS containing neurons have been localized in the spinal cord in several mammalian species, including mouse, rat, rabbit, dog, cat, sheep, monkey, and human (Br€ uning, 1992;Valtschanoff et al, 1992a,b;Dun et al, 1992Dun et al, , 1993Spike et al, 1993;Terenghi et al, 1993;Saito et al, 1994;Vizzard et al, 1994;Wetts and Vaughn, 1994;Pullen and Humphreys, 1995;L opez-Figueroa et al, 1996L opez-Figueroa et al, , 1997Mars ala et al, 1998Mars ala et al, , 1999Kluchov a et al, 2000).…”