Afferents to the zona incerta in the rat: A combined retrograde and anterograde study

Abstract

In a first set of experiments, the retrograde transport of horseradish peroxidase (HRP) was utilized to investigate the afferent projections to the zona incerta (ZI) in the hooded rat. HRP was introduced in its crystalline form into various sectors of the ZI of seven subjects. The largest contingent of afferents arises from the following centers: the cingulate and somatosensory cortices, central amygdaloid nucleus, ventromedial hypothalamic nucleus, posterior thalamic nucleus, anterior pretectal nucleus, peripeduncular area, deep and intermediate layers of the superior colliculus, dorsal and ventral parabrachial nuclei, principal and interpolar trigeminal subnuclei, and cuneate nucleus. Other centers less systematically or more sparsely labeled were the lateral hypothalamic area, ventrobasal complex, lateral geniculate nucleus pars ventralis, medial geniculate nucleus, interstitial nucleus of Cajal, Darkschewitsch nucleus, perirubral fields, cuneiform, tegmental pedunculopontine, and deep mesencephalic reticular nuclei, pontine reticular nucleus pars oralis, lateral and interpositus cerebellar nuclei, and gracile nucleus. In a second set of experiments, an anterograde tracer (WGA-HRP) was injected in several centers projecting to the ZI in order to localize their terminal fields within this structure. It has been thus possible to distinguish a ventral zone (ventral sector of pars caudalis and pars ventralis) in which the somesthetic (somatosensory cortex, trigeminal complex, and dorsal column nuclei (DCN), collicular, and cerebellar projections terminate, from a dorsal zone (pars dorsalis) to which a limbic input (cingulate cortex and ventromedial hypothalamic nucleus) is directed. In most cases, the labeled terminal fields consisted of well-delimited, narrow bands disposed obliquely, parallel to the cerebral peduncle or the internal capsule. The contingent of somatosensory afferents is relatively large and there is a high degree of overlapping between the different somatosensory terminal fields within the ventral ZI. This suggests a participation of this structure in the treatment of somesthetic information and/or in the transmission of noxious stimuli.

Single- and Multi-Whisker Channels in the Ascending Projections from the Principal Trigeminal Nucleus in the Rat

“…In addition to the V Pm, the Pr5 was found to project to Po (Smith, 1975;Chiaia et al, 1991;Williams et al, 1993), MGm (Peschanski, 1984), superior colliculus (Erzurumlu et al, 1980;K illackey and Erzurumlu, 1981;Huerta et al, 1983;Bruce et al, 1987), the ventral part of the zona incerta (Smith, 1975;Roger and C adesseau, 1983;Peschanski, 1984;ShammahLagnado et al, 1985;Nicolelis et al, 1992), and the anterior pretectal nucleus (Yoshida et al, 1992). The same projection sites were found in the present study, which shows how these multiple projections are generated at a single-cell level.…”

Functional Metabolic Mapping of the Rat Brain during Unilateral Electrical Stimulation of the Subthalamic Nucleus

“…The fact that the STH stimulation did not induce any metabolic changes in sensory and reticular regions indicates further that the electrical current did not spread in the adjacent zona incerta, which is known to be a major reticular and somato sensory relay area in the rat (Roger and Cadusseau, 1985;Shammah-Lagnado et aI., 1985;Nikoledis et aI., 1992).…”

Organization of the zona incerta in the macaque: An electron microscopic study

“…It has been asserted that this may be a characteristic of ''projection neurons'' of the somatosensory system (Maxwell et al, 1995). The ZI receives direct projections from the dorsal column and trigeminal nuclei in a number of species (Ricardo, 1981;Roger and Cadusseau, 1985;Carstens et al, 1990), but not in the macaque (unpublished results). Likewise, the ZI in the macaque does not possess this characteristic of having larger numbers of asymmetrical contacts on their somata.…”