Direct spinal projections to limbic and striatal areas: Anterograde transport studies from the upper cervical spinal cord and the cervical enlargement in squirrel monkey and rat

Abstract

With the anterograde tracers Phaseolus vulgaris-leucoagglutinin (PHA-L) and biotinylated dextranamine (BD), direct spinal connections from the upper cervical spinal cord (UC; C1 and C2) and the cervical enlargement (CE; C5-T1) were demonstrated in various striatal and limbic nuclei in both squirrel monkey and rat. Within each species and from each spinal level, the total number of terminals seen in the limbic and striatal areas was approximately 50-80% of the number seen within the thalamus. Labeled terminal structures were seen in the hypothalamic nuclei, ventral striatum, globus pallidus, amygdala, preoptic area, and septal nuclei. In both species, the number of labeled terminals in limbic and striatal regions was larger from UC than from CE, although the distributions to each nucleus varied with the specific lamina injected. In both species and from both UC and CE, approximately one-half of the projections to striatal and limbic areas terminated in the hypothalamus. The only region that demonstrated a topographical organization was the globus pallidus, where terminals from the CE were located dorsomedially to those from the UC. In the rat, UC and CE injections into the lateral dorsal horn and pericentral laminae resulted in the largest number of limbic and striatal terminations. The proportion of ipsilateral terminations was greatest when the medial laminae in the UC or the lateral dorsal horn in the CE received injections. Analysis of the morphology of these spinohypothalamic and spinotelencephalic terminals showed that, in the squirrel monkey, terminals from CE injections were larger than terminals from UC injections; no such size difference was evident in the rat. However, limbic and striatal terminals in the rat were generally larger than those in the squirrel monkey following injections into the UC or CE. The exact function of these direct spinal projections to various striatal and limbic areas in primates and in rodents remains to be determined. These findings, however, support recent imaging studies that suggest that the limbic system plays an important role in the mediation of chest pain, perhaps directly through these spinolimbic and spinostriatal pathways.

Brain stem afferent connections of the amygdala in the rat with special references to a projection from the parabigeminal nucleus: a fluorescent retrograde tracing study

“…On another hand, the labeled neurons in the first cervical segment of the spinal cord confirm an already well known, although sparce connection (Menetrey and De Pommery 1991;Cliffer et al 1991;Burstein and Potrebic 1993;Newman et al 1996;Wang et al 1999;Gauriau and Bernard 2004). Our finding are in agreement with the authors cited above: we found the neurons bilaterally very deep, almost in the ventral horn, as well as in the lateral spinal neurons.…”

Adenosine A2A receptors in ventral striatum, hypothalamus and nociceptive circuitry

“…It might be easy to be dismissive of a central role for A 2A receptors in pain processing as autoradiographic mapping of the receptor with highly selective ligands in both rat (Johansson et al, 1997;Svenningsson et al, 1999) and mouse (Bailey et al, 2002;Bailey et al, 2004;Kelly et al, 2004) as well as in humans (Svenningsson et al, 1997b;Ishiwata et al, 2005) shows predominantly a localization to the dorsal and ventral striatum, structures with no major recognized role in pain circuitry. However, there is some evidence that both the dorsal and ventral striatum are directly accessed by nociceptive neurones (Newman et al, 1996) and that the ventral striatum, like many parts of the limbic system, modulates pain processing (see Millan, 1999). Using immunohistochemical techniques, most of the receptor expression is also seen in the basal ganglia (Rosin et al, 1998).…”

Striatal Inhibition of Nociceptive Responses Evoked in Trigeminal Sensory Neurons by Tooth Pulp Stimulation

“…rior colliculus, raphe nuclei, amygdala, and probably from direct spinal projections (Bernard et al 1992;Corvaja et al 1993;Grunwerg et al 1992;Lapper and Bolam 1992;McGeorge and Faull 1989;Newman et al 1996;Shinonaga et al 1992;Yasui et al 1987). Indeed, experiments performed in cats have shown that the striatal neurons were activated by stimulation of the inferior dental nerve only with a stimulus intensity that elicited the jaw opening reflex (Lidsky et al 1978).…”