Cortical and brain stem projections to the spinal cord of the hedgehog (Erinaceus europaeus). A horseradish peroxidase study

Summary Cortical and brain stem neurons projecting to the spinal cord in the hedgehog were studied by means of the horseradish peroxidase (HRP) tracing method. HRP injections were placed in the first cervical segments, in the cervical enlargement (C₅-T₃) and in the lumbar enlargement. Following injections in the first cervical segments and in the cervical enlargement labelled neurons were observed in the somatic motor and somatic sensory cortices, the paraventricular and the dorsomedial hypothalamic nucleus, the lateral hypothalamic area, the nuclei of field H of Forel, the red nucleus, the mesencephalic reticular formation, the deep layers of the superior colliculus, the Edinger-Westphal nucleus, the periaqueductal grey, the mesencephalic trigeminal nucleus, the loci coeruleus and subcoeruleus, the nuclei raphe dorsalis, centralis superior, raphe magnus, raphe pallidus, and raphe obscurus, the rhombencephalic reticular formation, the lateral, medial and caudal vestibular nuclei, the nucleus ambiguus, the nucleus of the solitary tract and the gracile nucleus. After HRP injections in the lumbar enlargement, labelled neurons were not found in the cortex, the dorsomedial hypothalamic nucleus, the nuclei of field H of Forel, the superior colliculus and the mesencephalic trigeminal nucleus. These results show that cortical and brain stem projection to the spinal cord are comparable to those described in other species.Abbreviations ac anterior commissure - Am nucleus ambiguus - Aq cerebral aqueduct - cc corpus callosum - Cd caudate nucleus - CE cervical enlargement - CeS nucleus centralis superior - CG periaqueductal grey - ci capsula interna - Cq cochlear nuclei - cp cerebral peduncle - Cu cuneiform nucleus - CV caudal vestibular nucleus - DM dorsomedial hypothalamic nucleus - DX dorsal motor nucleus of vagus - EC external cuneate nucleus - EW Edinger-Westphal nucleus - F nuclei of field H of Forel - G gracile nucleus - H nippocampus - IC inferior colliculus - IP interpeduncular nucleus - LC locus coeruleus - LE lumbar enlargement - LH lateral hypothalamic area - LL nucleus of lateral lemniscus - lo lateral olfactory tract - LV lateral vestibular nucleus - MC medial cuneate nucleus - MesV mesencephalic trigeminal nucleus - MG medial geniculate nucleus - MM medial mammillary nucleus - MV medial vestibular nucleus - oc optic chiasm - PH nucleus praepositus - Pn pontine nuclei - Put putamen - PV paraventricular hypothalamic nucleus - R red nucleus - Rd nucleus raphe dorsalis - RGc gigantocellular reticular nucleus - Rl lateral reticular nucleus - Rm nucleus raphe magnus - Rmes mesencephalic reticular formation - Ro nucleus raphe obscurus - Rpa nucleus raphe pallidus - Rpc caudal reticular nucleus of the pons - Rpo rostral reticular nucleus of the pons - Rv ventral reticular nucleus - s solitary tract - SC superior colliculus - SN substantia nigra - SO supraoptic nucleus - SR sulcus rhinalis - STh subthalamic nucleus - siV spinal tract of trigeminal nerve - STV nucleus of spinal tract of trigeminal nerve - subC locus subcoeruleus - SuM supramammillary nucleus - Th thalamus - TS nucleus of solitary tract - VM ventromedial hypothalamic nucleus - ZI zona incerta - 3V third ventricle - 4V fourth ventricle - IV layer IV of the cortex - V layer V of the cortex - VI layer VI of the cortex - 7 facial nucleus - 12 hypoglossal nucleus