C-fos Expression In Brain Research Articles

Suppression of cytokine synthesis in spleen and brain and small changes in c-fos expression in rat brain after intranasal administration of single-walled carbon nanotubes

The purpose of this work is to study cytokine synthesis in the brain, blood, spleen, and liver and cfos expression in a rat brain 24 h after the intranasal administration of single-walled carbon nanotubes (SWCNTs) at a low dose (1 μg per rat, or 4 μg/kg). A RT-PCR analysis of cytokine mRNA synthesis has demonstrated that the cytokine profile in the brain does not change significantly under the influence of SWCNTs, but a reduction of the total content of all cytokine mRNA is observed. At the same time, the mRNA content of colony-stimulating factor IL-5 and proinflammatory cytokine IL-18 increases in the liver; only IL-18 mRNA increases in the blood, which indicates a possible activation of Th-2 lymphocytes and macrophages in the liver and only macrophages in the blood. In the spleen, mRNA levels of all cytokines that were detected in the norm were decreased. This indicates a suppression of the transcription of cytokines in the spleen, the main organ of immune system, and hence an immunosuppressive effect of SWCNTs. Administration of SWCNTs does not alter c-fos expression in 35 of 43 brain structures studied compared to the control. The c-fos expression increased only in the olfactory bulb and in the piriform cortex and in six brain structures this index was reduced; i.e., SWCNTs have little effect on the activity of brain structures. It is assumed that the low-dose intranasal administration of SWCNTs can be used in medicine for drug delivery to the brain. In addition, it is not excluded that the immunosuppressive properties of SWCNTs can be applied for the prevention of transplant rejection and treatment of autoimmune disorders. When using SWCNTs for medical and biological purposes it is necessary to take into account the probability of their immunosuppressive effects.

Chlorella vulgaris reduces the impact of stress on hypothalamic–pituitary–adrenal axis and brain c-fos expression

Predominantly emotional stressors activate a wide range of brain areas, as revealed by the expression of immediate early genes, such as c-fos. Chlorella vulgaris (CV) is considered a biological response modifier, as demonstrated by its protective activities against infections, tumors and stress. We evaluated the effect of acute pretreatment with CV on the peripheral and central responses to forced swimming stress in adult male rats. Pretreatment with CV produced a significant reduction of stress-related hypothalamic–pituitary–adrenal activation, demonstrated by decreased corticotrophin releasing factor gene expression in the hypothalamic paraventricular nucleus (PVN) and lower ACTH response. Hyperglycemia induced by the stressor was similarly reduced. This attenuated neuroendocrine response to stress occurred in parallel with a diminished c-fos expression in most evaluated areas, including the PVN. The data presented in this study reinforce the usefulness of CV to diminish the impact of stressors, by reducing the HPA response. Although our results suggest a central effect of CV, further studies are necessary to understand the precise mechanisms underpinning this effect.

Neural correlates of interactions between cannabidiol and Δ(9) -tetrahydrocannabinol in mice: implications for medical cannabis.

It has been proposed that medicinal strains of cannabis and therapeutic preparations would be safer with a more balanced concentration ratio of Δ(9) -tetrahydrocannabinol (THC) to cannabidiol (CBD), as CBD reduces the adverse psychotropic effects of THC. However, our understanding of CBD and THC interactions is limited and the brain circuitry mediating interactions between CBD and THC are unknown. The aim of this study was to investigate whether CBD modulated the functional effects and c-Fos expression induced by THC, using a 1:1 dose ratio that approximates therapeutic strains of cannabis and nabiximols. Male C57BL/6 mice were treated with vehicle, CBD, THC or a combination of CBD and THC (10 mg·kg(-1) i.p. for both cannabinoids) to examine effects on locomotor activity, anxiety-related behaviour, body temperature and brain c-Fos expression (a marker of neuronal activation). CBD potentiated THC-induced locomotor suppression but reduced the hypothermic and anxiogenic effects of THC. CBD alone had no effect on these measures. THC increased brain activation as measured by c-Fos expression in 11 of the 35 brain regions studied. CBD co-administration suppressed THC-induced c-Fos expression in six of these brain regions. This effect was most pronounced in the medial preoptic nucleus and lateral periaqueductal gray. Treatment with CBD alone diminished c-Fos expression only in the central nucleus of the amygdala compared with vehicle. These data confirm that CBD modulated the pharmacological actions of THC and provide new information regarding brain regions involved in the interaction between CBD and THC.

Moderate Peep After Tracheal Lipopolysaccharide Instillation Prevents Inflammation and Modifies the Pattern of Brain Neuronal Activation.

ABSTRACTBackground:Ventilatory strategy and specifically positive end-expiratory pressure (PEEP) can modulate the inflammatory response and pulmonary-to-systemic translocation of lipopolysaccharide (LPS). Both inflammation and ventilatory pattern may modify brain activation, possibly worsening the patient's outcome and resulting in cognitive sequelae.Methods:We prospectively studied Sprague–Dawley rats randomly assigned to undergo 3 h mechanical ventilation with 7 mL/kg tidal ventilation and either 2 cmH2O or 7 cmH2O PEEP after intratracheal instillation of LPS or saline. Healthy nonventilated rats served as baseline. We analyzed lung mechanics, gas exchange, lung and plasma cytokine levels, lung apoptotic cells, and lung neutrophil infiltration. To evaluate brain neuronal activation, we counted c-Fos immunopositive cells in the retrosplenial cortex (RS), thalamus, supraoptic nucleus (SON), nucleus of the solitary tract (NTS), paraventricular nucleus (PVN), and central amygdala (CeA).Results:LPS increased lung neutrophilic infiltration, lung and systemic MCP-1 levels, and neuronal activation in the CeA and NTS. LPS-instilled rats receiving 7 cmH2O PEEP had less lung and systemic inflammation and more c-Fos-immunopositive cells in the RS, SON, and thalamus than those receiving 2 cmH2O PEEP. Applying 7 cmH2O PEEP increased neuronal activation in the CeA and NTS in saline-instilled rats, but not in LPS-instilled rats.Conclusions:Moderate PEEP prevented lung and systemic inflammation secondary to intratracheal LPS instillation. PEEP also modified the neuronal activation pattern in the RS, SON, and thalamus. The relevance of these differential brain c-Fos expression patterns in neurocognitive outcomes should be explored.

Bi-directional effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on fear-related behavior and c-Fos expression after fear conditioning in rats

Pituitary adenylate cyclase-activating polypeptide (PACAP) is implicated in stress regulation and learning and memory. PACAP has neuromodulatory actions on brain structures within the limbic system that could contribute to its acute and persistent effects in animal models of stress and anxiety-like behavior. Here, male Sprague-Dawley rats were implanted with intracerebroventricular (ICV) cannula for infusion of PACAP-38 (0.5, 1, or 1.5μg) or vehicle followed 30min later by fear conditioning. Freezing was measured early (1, 4, and 7 days) or following a delay (7, 10, and 13 days) after conditioning. PACAP (1.5μg) produced a bi-phasic response in freezing behavior across test days: relative to controls, PACAP-treated rats showed a reduction in freezing when tested 1 or 7 days after fear conditioning that evolved into a significant elevation in freezing by the third test session in the early, but not delayed, group. Corticosterone (CORT) levels were significantly elevated in PACAP-treated rats following fear conditioning, but not at the time of testing (Day 1). Brain c-Fos expression revealed PACAP-dependent alterations within, as well as outside of, areas typically implicated in fear conditioning. Our findings raise the possibility that PACAP disrupts fear memory consolidation by altering synaptic plasticity within neurocircuits normally responsible for encoding fear-related cues, producing a type of dissociation or peritraumatic amnesia often seen in people early after exposure to a traumatic event. However, fear memories are retained such that repeated testing and memory reactivation (e.g., re-experiencing) causes the freezing response to emerge and persist at elevated levels. PACAP systems may represent an axis on which stress and exposure to trauma converge to promote maladaptive behavioral responses characteristic of psychiatric illnesses such as post-traumatic stress disorder (PTSD).

Preemptive Analgesia with Acupuncture Monitored by c-Fos Expression in Rats

Pain behavior and awareness are characterized by heightened alertness and anxiety, which begin to disappear as soon as the curative process starts. The present study aimed to quantify c-fos expression in rat spinal cords and brains after a surgical stimulus and with preoperative or postoperative acupuncture. Animals were randomly divided into preoperative and postoperative groups and were then further divided into control, manual acupuncture (MA), or electroacupuncture (EA) groups. Expression of c-fos was quantified using immunohistochemistry. The collected data were analyzed using the t test at a 5% probability level. Presurgery and postsurgery spinal cord c-fos expressions were similar in all of the treatment groups. In the control rats, c-fos expression was higher before surgery than after surgery, contradicting the expected outcome of acupuncture and preemptive analgesia. After treatment, the expression of c-fos in the brains of the rats in the MA and the EA groups was reduced compared with that of the rats in the control group. These findings suggest that acupuncture used as preemptive analgesia in rats is a useful model for studying its application in human treatment.

Medial amygdala lesions selectively block aversive pavlovian-instrumental transfer in rats.

Pavlovian conditioned stimuli (CSs) play an important role in the reinforcement and motivation of instrumental active avoidance (AA). Conditioned threats can also invigorate ongoing AA responding [aversive Pavlovian–instrumental transfer (PIT)]. The neural circuits mediating AA are poorly understood, although lesion studies suggest that lateral, basal, and central amygdala nuclei, as well as infralimbic prefrontal cortex, make key, and sometimes opposing, contributions. We recently completed an extensive analysis of brain c-Fos expression in good vs. poor avoiders following an AA test (Martinez et al., 2013, Learning and Memory). This analysis identified medial amygdala (MeA) as a potentially important region for Pavlovian motivation of instrumental actions. MeA is known to mediate defensive responding to innate threats as well as social behaviors, but its role in mediating aversive Pavlovian–instrumental interactions is unknown. We evaluated the effect of MeA lesions on Pavlovian conditioning, Sidman two-way AA conditioning (shuttling) and aversive PIT in rats. Mild footshocks served as the unconditioned stimulus in all conditioning phases. MeA lesions had no effect on AA but blocked the expression of aversive PIT and 22 kHz ultrasonic vocalizations in the AA context. Interestingly, MeA lesions failed to affect Pavlovian freezing to discrete threats but reduced freezing to contextual threats when assessed outside of the AA chamber. These findings differentiate MeA from lateral and central amygdala, as lesions of these nuclei disrupt Pavlovian freezing and aversive PIT, but have opposite effects on AA performance. Taken together, these results suggest that MeA plays a selective role in the motivation of instrumental avoidance by general or uncertain Pavlovian threats.

C-Fos expression in the paternal mouse brain induced by communicative interaction with maternal mates.

BackgroundAppropriate parental care by fathers greatly facilitates health in human family life. Much less is known from animal studies regarding the factors and neural circuitry that affect paternal behavior compared with those affecting maternal behavior. We recently reported that ICR mouse sires displayed maternal-like retrieval behavior when they were separated from pups and caged with their mates (co-housing) because the sires receive communicative interactions via ultrasonic and pheromone signals from the dams. We investigated the brain structures involved in regulating this activity by quantifying c-Fos-immunoreactive cells as neuronal activation markers in the neural pathway of male parental behavior.Resultsc-Fos expression in the medial preoptic area (mPOA) was significantly higher in sires that exhibited retrieval behavior (retrievers) than those with no such behavior (non-retrievers). Identical increased expression was found in the mPOA region in the retrievers stimulated by ultrasonic vocalizations or pheromones from their mates. Such increases in expression were not observed in the ventral tegmental area (VTA), nucleus accumbens (NAcc) or ventral palladium (VP). On the following day that we identified the families of the retrievers or non-retrievers, c-Fos expression in neuronal subsets in the mPOA, VTA, NAcc and VP was much higher in the retriever sires when they isolated together with their mates in new cages. This difference was not observed in the singly isolated retriever sires in new cages. The non-retriever sires did not display expression changes in the four brain regions that were assessed.ConclusionThe mPOA neurons appeared to be activated by direct communicative interactions with mate dams, including ultrasonic vocalizations and pheromones. The mPOA-VTA-NAcc-VP neural circuit appears to be involved in paternal retrieval behavior.

High doses of the histone deacetylase inhibitor sodium butyrate trigger a stress-like response

The hypothalamic–pituitary–adrenal (HPA) axis is activated by a wide range of stimuli, including drugs. Here we report that in male rats, a dose of sodium butyrate (NaBu) that is typically used to inhibit histone deacetylation (1200 mg/kg) increased the peripheral levels of HPA hormones and glucose. In a further experiment, we compared the effects of two different doses of NaBu (200 and 1200 mg/kg) and equimolar saline solutions on peripheral neuroendocrine markers and brain c-Fos expression to demonstrate a specific stress-like effect of NaBu that is not related to hypertonicity and to localise putatively involved brain areas. Only the high dose of NaBu increased the plasma levels of stress markers. The equimolar (hypertonic) saline solution also activated the HPA axis and the c-Fos expression in the paraventricular nucleus of the hypothalamus (PVN), a key area for the control of the HPA axis, but the effects were of a lower magnitude than those of NaBu. Regarding other brain areas, group differences in c-Fos expression were not observed in the medial prefrontal cortex or the medial amygdala, but they were observed in the central amygdala and the lateral ventral septum. However, only the latter area of the NaBu group showed enhanced c-Fos expression that was significantly higher than that after hypertonic saline. The present data indicate that high doses of NaBu appear to act as a pharmacological stressor, and this fact should be taken into account when using this drug to study the role of epigenetic processes in learning and emotional behaviour.

Abstracts and Commentaries on Key Articles in the Literature

Abstracts and Commentaries on Key Articles in the Literature

Ginsenosides Have a Suppressive Effect on c-Fos Expression in Brain and Reduce Cardiovascular Responses Increased by Noxious Stimulation to the Rat Tooth

The purpose of this study is to investigate the antinociceptive effects of ginsenosides on toothache. c-Fos immunoreactive (IR) neurons were examined after noxious intrapulpal stimulation (NS) by intrapulpal injection of 2 M KCl into upper and lower incisor pulps exposed by bone cutter in Sprague Dawley rats. The number of Fos-IR neurons was increased in the trigeminal subnucleus caudalis (Vc) and the transitional region between Vc and subnucleus interpolaris (Vi) by NS to tooth. The intradental NS raised arterial blood pressure (BP) and heart rate (HR). The number of Fos-IR neurons was also enhanced in thalamic ventral posteromedial nucleus (VPMN) and centrolateral nucleus (CLN) by NS to tooth. The intradental NS increased the number of Fos-IR neurons in the nucleus tractus solitarius (NTS) and rostral ventrolateral medulla (RVLM), hypothalamic supraoptic nucleus (SON) and paraventricular nucleus (PVN), central cardiovascular regulation centers. Ginsenosides reduced the number of c-Fos-IR increased by NS to tooth in the trigeminal Vc and thalamic VPMN and CLN. Naloxone, an opioid antagonist, did not block the effect of ginsenoside on the number of Fos-IR neurons enhanced by NS to tooth in the trigeminal Vc and thalamic VPMN and CLN. Ginsenosides ameliorated arterial BP and HR raised by NS to tooth and reduced the number of Fos-IR neurons increased by NS to tooth in the NTS, RVLM, hypothalamic SON, and PVN. These results suggest that ginsenosides have an antinociceptive effect on toothache through non-opioid system and attenuates BP and HR increased by NS to tooth.

Unique and potent effects of acute ibogaine on zebrafish: The developing utility of novel aquatic models for hallucinogenic drug research

An indole alkaloid, ibogaine is the principal psychoactive component of the iboga plant, used by indigenous peoples in West Africa for centuries. Modulating multiple neurotransmitter systems, the drug is a potent hallucinogen in humans, although its psychotropic effects remain poorly understood. Expanding the range of model species is an important strategy for translational neuroscience research. Here we exposed adult zebrafish (Danio rerio) to 10 and 20mg/L of ibogaine, testing them in the novel tank, light–dark box, open field, mirror stimulation, social preference and shoaling tests. In the novel tank test, the zebrafish natural diving response (geotaxis) was reversed by ibogaine, inducing initial top swimming followed by bottom dwelling. Ibogaine also attenuated the innate preference for dark environments (scototaxis) in the light–dark box test. While it did not exert overt locomotor or thigmotaxic responses in the open field test, the drug altered spatiotemporal exploration of novel environment, inducing clear preference of some areas over others. Ibogaine also promoted ‘mirror’ exploration in the mirror stimulation test, disrupted group cohesion in the shoaling test, and evoked strong coloration responses due to melanophore aggregation, but did not alter brain c-fos expression or whole-body cortisol levels. Overall, our results support the complex pharmacological profile of ibogaine and its high sensitivity in zebrafish models, dose-dependently affecting multiple behavioral domains. While future investigations in zebrafish may help elucidate the mechanisms underlying these unique behavioral effects, our study strongly supports the developing utility of aquatic models in hallucinogenic drug research. High sensitivity of three-dimensional phenotyping approaches applied here to behavioral effects of ibogaine in zebrafish provides further evidence of how 3D reconstructions of zebrafish swimming paths may be useful for high-throughput pharmacological screening.

A test to identify judgement bias in mice

Emotional states are known to affect cognitive processes. For example highly anxious individuals interpret ambiguous stimuli more negatively than low anxious people, an effect called negative judgement bias. Recently, the measurement of judgement bias has been used to try and indicate emotional states in animals. In the present experiment a potential test for judgement bias in mice was examined. Mice were trained with two distinct odour cues (vanilla or apple) predicting either a palatable or an unpalatable almond piece. Subsequently their reaction to mixtures of both odours, the ambiguous stimuli, was investigated. Mice of the BALB/cJ and 129P3/J inbred mouse strains (high initial anxiety and low initial anxiety phenotypes respectively) were tested. While BALB/cJ mice showed odour association learning and showed intermediate reactions to the ambiguous cues, 129P3/J mice did not discriminate between the cues. Additionally BALB/cJ mice that were tested under more aversive white light conditions revealed a higher latency to approach the almond piece than mice tested under less aversive red light conditions. The ambiguous stimulus however was interpreted as negative under both test conditions. Brain c-Fos expression levels (a marker for neuronal activity) differed between the BALB/c/J and 129P3/J in the lateral amygdala and the prelimbic cortex, indicating differences in ambiguous information processing between the strains. The behavioural results suggest that the present judgement bias test might be used to assess emotional states in at least BALB/c mice, however further research on both behaviour and on the involved brain mechanisms is necessary to confirm this idea.

Effects of the hallucinogenic drugs mescaline, phencyclidine and psilocybin on zebrafish behavior and physiology

Mescaline, phencyclidine (PCP) and psilocybin are potent hallucinogenic drugs strongly affecting both human and animal behavior. However, these compounds have not been previously investigated in zebrafish (Danio rerio), rapidly gaining popularity as a model in psychopharmacology research. Here, we examine the effects of mescaline, PCP and psilocybin in multiple behavioral paradigms. Mescaline (10–20 mg/L) generally displayed an anxiolytic effect in the novel tank test, while PCP (1–3 mg/L) reduced freezing behavior and elicited a pattern of erratic swimming. Mescaline‐treated fish markedly increased shoaling behavior and altered movement patterns in the open field test. Additionally, mescaline and PCP disrupted normal zebrafish exploratory behavior, as assessed by ethograms. Psilocybin at doses tested (0.5–3 mg/L) was inactive in all of the behavioral tests. Interestingly, both psilocybin and PCP raised whole‐body cortisol levels without affecting brain c‐fos expression, and mescaline did not alter cortisol or c‐fos levels. Overall, this confirms the high sensitivity of zebrafish models to various hallucinogenic compounds with complex behavioral and physiological profiles. This study was supported by the National Institute on Drug Abuse (NIDA) R03 grant to AVK.

Taste neophobia and c-Fos expression in the rat brain

Taste neophobia refers to a reduction in consumption of a novel taste relative to when it is familiar. To gain more understanding of the neural basis of this phenomenon, the current study examined whether a novel taste (0.5% saccharin) supports a different pattern of c-Fos expression than the same taste when it is familiar. Results revealed that the taste ofthe novel saccharin solution evoked more Fos immunoreactivity than the familiar taste of saccharin in the basolateral region of the amygdala, central nucleus of the amygdala, gustatory portion of the thalamus, and the gustatory insular cortex. No such differential expressionwas found in the other examined areas, including the bed nucleus of stria terminalis,medial amygdala, and medial parabrachial nucleus. The present results are discussed with respect to a forebrain taste neophobia system.

Neuropeptide S promotes wakefulness through activation of the posterior hypothalamic histaminergic and orexinergic neurons

In spite of the initial and pivotal findings that the newly identified neuropeptide S (NPS) promotes arousal associated with locomotor and anxiolytic-like effects, the mechanisms through which NPS acts to modulate sleep-waking states remain unclear. The present study was undertaken to investigate in the rat the effects of i.c.v. injection of NPS on the EEG, sleep-wake cycle, and brain c-Fos expression. NPS at 0.1 and 1 nmol increased significantly wakefulness (W) during the first 2 h (54.7±3.2 and 64.9±2.1 min, respectively, vs. 41.4±2.5 min seen with saline injections, P<0.01 and P<0.001), accompanied by an increase in EEG high frequency activities (14.5–60 Hz). In the meanwhile, slow wave sleep (SWS) and paradoxical sleep (PS) decreased significantly. Ex-vivo Fos immunohistochemistry in the posterior hypothalamus revealed that, as compared with saline-treated rats, NPS enhanced c-Fos expression in histaminergic neurons by 76.0% in the ventral tuberomammillary nucleus (TMN) and 57.8% in the dorsal TMN, and in orexinergic neurons by 28.2% in the perifornical nucleus (PeF), 24.3% in the dorsomedial hypothalamic nucleus (DMH), and 13.7% in the lateral hypothalamic area (LH) of the posterior hypothalamus. The NPS-induced c-Fos expression in histaminergic neurons and orexinergic neurons where NPS receptor (NPSR) mRNA is highly expressed, suggests that NPS activates histaminergic and orexinergic neurons to promote W.

P.1.d.001 The effects of lesions of the raphe nuclei on phencyclidine-induced c-fos expression in the rat brain: implications for schizophrenia

P.1.d.001 The effects of lesions of the raphe nuclei on phencyclidine-induced c-fos expression in the rat brain: implications for schizophrenia

Behavioral and physiological effects of acute ketamine exposure in adult zebrafish

Ketamine is a non-competitive glutamatergic antagonist used to induce sedation and analgesia. In sub-anesthetic doses, it induces hyperlocomotion, impairs memory and evokes stereotypic circling in rodents. Zebrafish ( Danio rerio) emerged as a promising new animal model to screen the effects of psychotropic compounds. Here, we investigated the effects of sub-anesthetic doses of ketamine on anxiety, locomotion, habituation and social behavior of adult zebrafish. Acute 20-min exposure to 20 and 40 mg/L (but not 2 mg/L) of ketamine reduced anxiety, impaired intra-session habituation, evoked circular swimming and disrupted zebrafish shoaling. Additionally, ketamine reduced whole-body cortisol levels and elevated brain c-fos expression in zebrafish. Our findings demonstrate the sensitivity of zebrafish to behavioral and physiological effects of sub-anesthetic doses of ketamine, further supporting the utility of this species as a model for neuropharmacological research, including testing ketamine and related drugs.

Behavioral effects of MDMA (‘ecstasy’) on adult zebrafish

3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') is a potent psychedelic drug inducing euphoria and hypersociability in humans, as well as hyperactivity and anxiety in rodents. Adult zebrafish (Danio rerio) have become a widely used species in neurobehavioral research. Here, we explore the effects of a wide range (0.25-120 mg/l) of acute MDMA doses on zebrafish behavior in the novel tank test. Although MDMA was inactive at lower doses (0.25-10 mg/l), higher doses reduced bottom swimming and immobility (40-120 mg/l) and impaired intrasession habituation (10-120 mg/l). MDMA also elevated brain c-fos expression, collectively confirming the usage of zebrafish models for screening of hallucinogenic compounds.

Chlordiazepoxide and lavender oil alter unconditioned anxiety-induced c-fos expression in the rat brain

Lavender oil has a long history of use for treating anxiety, but only recent research has examined its effects using standard behavioural methods used to test novel drugs. The aim of this study was to investigate the effects of inhaled lavender oil on anxiety related behaviour of rats in the open field and to compare them with the effects of chlordiazepoxide (CDP), a typical anxiolytic drug. Additionally c-fos immunochemistry was used to investigate whether lavender oil produced the same pattern of c-fos expression as CDP in eight different brain areas associated with anxiety. As previously found, lavender oil showed anxiolytic properties in the open field similar to but not as extensive as those of CDP. Immunochemistry results indicated that exposure to the open field increased c-fos expression, while CDP reversed the effects of this behavioural stressor on c-fos expression in all brain regions examined except the central nucleus of the amygdala, where c-fos expression increased. Lavender oil had similar effects to CDP on the paraventricular nucleus of the hypothalamus, the dorsomedial hypothalamic nucleus and the central nucleus of the amygdala. These results strengthen the suggestion that inhaling lavender oil has anxiolytic behavioural effects, but they are weaker than the effects of benzodiazepines, and there is limited evidence that they are mediated by the same neural processes.