c-fos mRNA, Fos, and Fos-related antigen induction by hypertonic saline and stress

Abstract

The induction of c-fos mRNA was assessed using Northern blots and in situ hybridization in adult rats administered hypertonic saline (HS) and isotonic saline (IS). HS induced c-fos mRNA in magnocellular paraventricular nucleus (PVNm), parvocellular paraventricular nucleus (PVNp), supraoptic nucleus (SON), and lamina terminalis (LMT). This occurred within 5 min, peaked at 30-60 min, and disappeared by 180 min. Fos protein, detected using a specific monoclonal antibody, was maximal at 1-2 hr and disappeared 4-8 hr after HS administration. This confirms observations showing that the c-fos gene response is transient even in the presence of a continuing stimulus. In contrast, Fos-like immunoreactivity (FLI), detected using two polyclonal antisera, was observed in PVNm, PVNp, SON, and LMT for 1-24 hr during continuous osmotic stimulation. Moreover, FLI was observable in these structures for 7 d in rats administered HS and allowed to drink water ad libitum beginning 24 hr later. At times greater than 8 hr, FLI presumably represents Fos-related antigens (FRA), proteins immunologically and functionally related to Fos, whose expression is much more prolonged than authentic Fos following the osmotic stimulus. In addition to induction of c-fos expression in regions specifically involved in osmotic regulation, HS injections also induced c-fos in many other forebrain regions. In order to assess the induction of c-fos mRNA due to the "stress" of the injections, rats injected with isotonic saline were compared to uninjected controls. Isotonic saline injections induced c-fos mRNA in the PVNp, anterior hypothalamus, suprachiasmatic nucleus, cingulate gyrus, neocortex, ventral lateral septal nucleus, piriform cortex, hippocampal pyramidal and dentate granule neurons, paraventricular and intralaminar thalamic nuclei, bed nuclei of stria terminalis, cortical and medial amygdaloid nuclei, and other structures. In accord with other work, we interpret this pattern of c-fos expression to result from the stress of handling and injections. Since Fos and FRA probably bind to the promoters of target genes and regulate their expression, they likely mediate biochemical changes in the cells activated by the osmotic and stressful stimuli. Whereas the Fos signal is transient, FRA may act on target genes for the duration of the stimulus or longer.

Medial preoptic area afferents to periaqueductal gray medullo-output neurons: a combined Fos and tract tracing study

“…A 1 hr epoch of stimulation was selected because our previous studies of the diagonal band nucleus to piriform cortex projection demonstrated that 45-60 min of electrical stimulation was the minimum necessary to produce a strong, consistent pattern of Fos expression in all animals (Zimmer et al, 1993). This is consistent with findings by others that expression of c-fos mRNA peaks within 30-60 min after increased neuronal activity, whereas Fos-like protein is detectable after 1 hr (Sharp et al, 1991). Animals were perfused 30 min after the termination of MPO stimulation.…”

Ventral pallidum self-stimulation induces stimulus dependent increase in c-fos expression in reward-related brain regions

“…Relevant to this hypothesis is the fact that animals learn to switch-off forced rewarding stimulation if a lever is made available to them 36 and that experimental stress induces measurable Fos-immunoreactivity. 6,10,41 In conclusion, rewarding electrical stimulation of the VP increased Fos immunoreactivity in a frequency-dependent manner in several brain structures known to participate in the regulation of drug and/or brain stimulation reward (PLH, NAC, LSI, VTA and mPFC), and failed to do so in structures devoid of such involvement (SNR and DL-STR). This finding, and the fact that Fos-immunoreactivity correlated with reward magnitude, but not with bar-pressing behaviour, suggests a reward-specific effect.…”

GABA enhancement of maternal defense in mice: Possible neural correlates

“…We previously have found that injections in the absence of light isoflurane impairs maternal aggression (S.C. Gammie, unpublished observations), but injections with light isoflurane could also have a minor negative impact. Previous studies have demonstrated that slight stimuli like injections (Asanuma et al, 1992;Asanuma and Ogawa, 1994;Morgan et al, 1987;Nakajima et al, 1989;Ryabinin et al, 1999;Sharp et al, 1991), anesthesia (Bullitt, 1990;Dragunow et al, 1990;Morgan et al, 1987), and handling ( Asanuma et al, 1992;Asanuma and Ogawa, 1994;Ryabinin et al, 1999) can induce c-Fos mRNA or protein in the male rodent brain. The c-Fos-IR in behaviorally-naïve mice supports the idea that injection with isoflurane itself is a stressor.…”