Induction of immediate early gene encoded proteins in the rat hippocampus after bicuculline-induced seizures: differential expression of KROX-24, FOS and JUN proteins

Immunocytochemistry with specific antisera was used to assess regional levels of six immediate early gene encoded proteins (KROX-24, c-FOS, FOS B, c-JUN, JUN B and JUN D) in the rat hippocampus after 15 min of bicuculline-induced seizures. Serial sections of the dorsal hippocampus were examined at various postictal recovery periods up to 24 h. The results demonstrate a complex temporal and spatial pattern of immediate early gene synthesis and accumulation. Three major categories of immediate early gene products could best be distinguished in the dentate gyrus: KROX-24 and c-FOS showed a concurrent rapid rise with peak levels at 2 h and a return to baseline levels within 8 h after seizure termination. FOS B, c-JUN and JUN B levels increased more gradually with peak intensities in the dentate gyrus reached at 4 h. These immediate early gene products showed above normal levels in various hippocampal subpopulations up to 24 h. JUN D exhibited the most delayed onset combined with a prolonged increase of seizure-induced immunoreactivity. Irrespective of this differential temporal expression profile of individual transcription factors, the sequence of induction in the hippocampal subpopulations was identical for all immediate early gene-encoded proteins examined: first in the dentate gyrus granule cells followed by CA1 and CA3 neurons, respectively. Our data indicate an asynchronous synthesis of several immediate early gene-encoded proteins in the brain after status epilepticus. FOS and JUN proteins act via homo- or heterodimer complexes at the AP-1 and other DNA binding sites. The different time-courses for individual immediate early gene products strongly suggest, that at different time-points after status epilepticus, different AP-1 complexes are effective. In vitro studies have shown that different AP-1 complexes possess different DNA binding affinities as well as different transcriptional regulatory effects. Our results suggest that these molecular mechanisms are also effective in vivo.

Selective expression of Jun proteins following axotomy and axonal transport block in peripheral nerves in the rat: evidence for a role in the regeneration process

Expression of the protein products of the immediate-early genes (IEGs), members of the fos, jun and krox families (Jun, Fos, and Krox, resp.) was investigated in the spinal cord and sensory ganglia (DRG) of normal rats; and following transection of, block of axonal transport in, or electrical stimulation of their peripheral axons. The nuclei of many moto- and DRG neurons showed a faint basal immunoreactivity (IR) for Jun proteins, but not for Fos or Krox proteins. There was a strong and selective induction of Jun-IR in moto- and DRG neurons after peripheral nerve transection or crush, or colchicine- or vinblastine-induced block of axonal transport. The Jun-IR induced by nerve transection disappeared after nerve regeneration. In contrast, Jun, Fos and Krox proteins were all induced transynaptically in spinal dorsal horn neurons following electrical stimulation of the C-fibers in the afferent nerves. Thus in differentiated neurons in vivo these IEG proteins can be expressed either independently or concomitantly depending on the type of stimulus.

Specific temporal and spatial distribution of JUN, FOS, and KROX-24 proteins in spinal neurons following noxious transsynaptic stimulation

We present the first comparative investigation of the basal and transsynaptically induced expression of c-JUN, JUN B, JUN D, c-FOS, FOS B, and KROX-24 proteins in the spinal cord, using immunocytochemistry with specific antibodies. We demonstrate that electrical stimulation of the sciatic nerve at A delta/C-fiber (not A alpha/beta-fiber) intensity strongly induces the expression of these immediate-early gene-encoded proteins. Basal immunoreactivity was found for c-JUN in motoneurons, for JUN D in almost every cell of the gray matter, and for KROX-24 in the superficial dorsal horn. One hour after electrical stimulation of the sciatic nerve at A delta/C-fiber intensity, expression of all proteins except JUN D reached its maximum. Initially immunoreactivity was restricted to the ipsilateral dorsal horn, but after 4 hours appeared contralaterally. Expression of JUN D was increased only after 4 hours. Within the dorsal horn, the expression of c-JUN, JUN B, FOS B, and KROX-24 was mainly restricted to the superficial layers. Immunoreactivity decreased to basal levels between 8 and 16 hours. c-FOS and JUN D were expressed in both the superficial and deep dorsal horn; in the latter, c-FOS and JUN D persisted longer. Induced JUN D was present the longest and was still visible after 32 hours. In motoneurons of the ipsilateral ventral horn, c-JUN, JUN D, and c-FOS appeared after 8 hours. Surgical exposure of the sciatic nerve evoked a strikingly prolonged expression of all proteins compared to that following electrical stimulation of the sciatic nerve. Our results demonstrate that stimulation of nociceptive A delta- and C-fibers induces early and late expression of proteins encoded by immediate-early genes with a specific temporal and spatial distribution of the expression of each protein. Furthermore, the extent of protein expression reflects the intensity of noxious stimulation.

Sequential expression of JUN B, JUN D and FOS B proteins in rat spinal neurons: cascade of transcriptional operations during nociception

Expression of the immediate-early gene encoded proteins JUN B, JUN D and FOS B was investigated by immunocytochemistry in rat L5 spinal cord up to 24 h following stimulation of hind limb somatosensory nociceptors by noxious heat or injection of formalin. In both experimental protocols, JUN B, which did not show basal expression, reached maximum expression after 2 h and thereafter slowly decreased. In contrast, the expression of JUN D, which was present before stimulation in many spinal neurons, was increased after 4 h, reached its maximum after 8 h and thereafter remained elevated. FOS B which was absent under basal conditions reached its maximum between 4 h and 8 h and thereafter declined but was still present after 24 h. All immunoreactivities were restricted to the ipsilateral dorsal horn except JUN D which was also induced in the contralateral side after 8 h. The results are discussed in respect to their meaning for transcriptional operations of JUN and FOS proteins.

c-FOS-like immunoreactivity in rat brainstem neurons following noxious chemical stimulation of the nasal mucosa

It has previously been shown that noxious and non-noxious peripheral stimuli induce c-fos expression in spinal dorsal horn neurons. In the present study we have examined the expression of c-fos in brainstem neurons following noxious chemical stimulation of the respiratory region of the nasal mucosa. In urethane-anaesthetized rats we injected mustard oil or applied CO2 pulses to the right nasal cavity. In control animals we applied paraffin oil or a continuous flow of air. A further group of control animals was anaesthetized and not subjected to any experimental treatment. Two hours after the first stimulus the rats were perfused with 4% phosphate-buffered paraformaldehyde. Brainstem sections were incubated with primary antiserum against the FOS protein and processed according to the ABC method. Only the mustard oil-treated rats had obvious signs of rhinitis and displayed FOS-positive cells in laminae I and II of the subnucleus caudalis and in the subnucleus interpolaris of the trigeminal brainstem nuclear complex as well as in the medullary lateral reticular nucleus. These areas are known to be involved in the processing of nociceptive information. Although CO2 pulses applied to the nasal mucosa are known to evoke pain sensations in man we did not observe any FOS-positive neurons in trigeminal and reticular brainstem areas of CO2-treated rats. This lack of c-fos expression probably results from the fact that unlike mustard oil, CO2 did not induce any apparent inflammatory reactions. In all animals c-fos expression was found in the nucleus of the solitary tract and in the area postrema. Staining in these areas might partly result from factors related to anaesthesia, changed respiration parameters and stress. Since the mustard oil-treated rats displayed the highest levels of immunoreactivity in the nucleus of the solitary tract and in the area postrema, additional effects specifically related to nociceptive input are very likely.

Expression of c-JUN, JUN B and JUN D proteins in rat nervous system following transection of vagus nerve and cervical sympathetic trunk

Expression of c-JUN, JUN B and JUN D proteins was investigated in axotomized neurons following transection of the vagus nerve and the cervical sympathetic trunk in the rat. Vagotomy induced the expression of c-JUN and JUN D in the nodose ganglion, dorsal motor nucleus of the vagus nerve and nucleus ambiguus, whereas JUN B was not expressed in these areas, c-JUN and JUN D appeared after 10 h in the nodose ganglion and after 24 h in the dorsal motor nucleus of the vagus nerve with a maximum of immunoreactivity after 48 h. The c-JUN protein remained expressed at an increased level up to 100 days, whereas the immunoreactivity of JUN D declined after five days. Crush of the vagus nerve initially evoked an intense expression of c-JUN and JUN D, but in the course of regeneration the expression of c-JUN and JUN D had returned to more basal levels after 100 days. Similar to vagotomy, application of colchicine and vinblastine on to the intact vagus nerve induced expression of c-JUN and JUN D. On the other hand, application of lidocaine prior to vagotomy did not prevent the expression of these proteins. Transection of the cervical sympathetic trunk induced expression of c-JUN and JUN D, but not of JUN B, in the preganglionic sympathetic neurons of thoracic spinal cord. In these neurons, expression of c-JUN was still enhanced after 60 days whereas JUN D had returned to basal level. One hour after vagotomy, c-JUN and JUN B were transynaptically expressed in the area of central termination of sensory vagal neurons and declined within 10 h to basal levels. JUN D showed a late onset of expression, it appeared after 5 h and persisted for 60 days in this area. We postulate that the expression of c-JUN and JUN D in axotomized neurons is induced by deprivation of a target-derived suppressor.

c-JUN-like immunoreactivity in the CNS of the adult rat: basal and transynaptically induced expression of an immediate-early gene

An immunocytochemical study of dorsal root ganglia, spinal cord and medulla oblongata was performed with antisera against the c-jun proto-oncogene encoded protein. The c-JUN-like immunoreactivity was restricted to the cell nucleus. In the CNS of untreated rats a basal c-JUN-like immunoreactivity was present in the nuclei of two types of neurons: motor and autonomic. Labelled nuclei could be seen in many motoneurons of the ventral horn of the entire length of spinal cord and the lower medulla oblongata, as well as in the area of the nucleus hypoglossus, the dorsal motor nucleus of nucleus vagus, nucleus ambiguus, nucleus facialis, nucleus abducens and motor nucleus of nucleus trigeminus. Additionally, labelled nuclei were found in the preganglionic sympathetic and preganglionic parasympathetic cells of the nucleus intermediolateralis and nucleus intercalatus in the spinal cord. In the medulla oblongata we found a cluster of cells with c-JUN-like immunoreactivity in an area between the dorsomedial part of the oral nucleus spinalis trigeminalis and the lateral border of the knee of facial nerve. Additionally, a second cluster of c-JUN-like immunoreactivity cells was visible between the ventromedial part of the oral nucleus spinalis trigeminalis and the lateral border of the rostral nucleus facialis. Examination of the characteristics of all cell groups with a basal c-JUN-like immunoreactivity in the spinal cord and lower brainstem revealed an overlapping distribution with cholinergic cell groups. Basal c-JUN-like immunoreactivity was also seen in the dorsal root ganglion cells. We examined the factors which can effect the expression of the c-JUN protein. Maximal expression of c-JUN-like immunoreactivity was observed after electrical stimulation of primary afferents. Stimulation of sciatic nerve at a strength sufficient to recruit A delta- and C-fibres produced c-JUN-like immunoreactivity in many nuclei of the ipsilateral dorsal horn of the lumbar spinal cord. c-JUN-like immunoreactivity was first detectable at 30 min following the end of stimulation, reached a maximum after 1 h, remained unchanged for another 1 h and declined to the basal level after 16 h. The distribution of c-JUN-like immunoreactivity in the lumbar cord coincided with the region of termination of sciatic nociceptive afferents. Contralateral c-JUN-like immunoreactivity appeared after 4 h. After noxious mechanical stimulation of the plantar hindpaw c-JUN-like immunoreactivity occurred in the spinal area of termination of nociceptive afferents of the tibial nerve. Noxious stimulation did not provoke additional c-JUN-like immunoreactivity in dorsal root ganglia.(ABSTRACT TRUNCATED AT 400 WORDS)

The KROX-24 protein, a new transcription regulating factor: expression in the rat central nervous system following afferent somatosensory stimulation

The expression of the protein product encoded by the Krox-24 gene was investigated immunocytochemically in the central nervous system of adult rats. Immunoreactivity (IR) of the KROX-24 protein which is a nuclear transacting transcription factor, showed a pattern of nuclear staining. Basal KROX-24-IR was visible in the superficial layers of spinal dorsal horn and trigeminal nucleus, and in many areas of the brain including the cerebellum, nucleus raphe magnus, colliculi, periaqueductal gray, hypothalamus, geniculate nuclei, caudate putamen, amygdala, hippocampus, lateral septal nucleus, olfactory tubercle and cerebral cortex. Electrical stimulation of sciatic nerve A- and C-fibers, but not of A alpha- and A beta-fibers alone, induced transient expression of KROX-24 in numerous spinal neurons in the termination area of the stimulated nerve. One hour following the onset of this stimulation of the sciatic nerve the distribution of KROX-24-IR was investigated in the brain and compared to untreated rats. In stimulated animals, the KROX-24-IR was induced in many areas including the lateral reticular nucleus, parabrachial nucleus, periaqueductal gray, hypothalamus, amygdala and lateral habenular nucleus.