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Keywords:

  • Odor reactivity;
  • Epilepsy;
  • Stress;
  • CRF;
  • Seizure;
  • Tail suspension handling

Abstract

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES

Summary: Purpose: The present study explored the causal relationship between stressor exposure/stress neuropeptide activation and avoidant exploratory phenotype/enhanced seizure susceptibility in an animal model of epilepsy.

Methods: The olfactory detection and investigation phenotype of seizure susceptible El (epilepsy) strain and nonsusceptible ddY control mice was first evaluated in untreated mice. In a second series of experiments, the olfactory exploration phenotype, food intake/body weight regulation, circadian locomotor activity, and seizure susceptibility were assessed over a 14-day period following central administration of the neurotoxin saporin alone or a conjugate of the stress neuropeptide, corticotropin releasing factor (CRF), and saporin (CRF-SAP) which impairs CRF system function following central administration.

Results: In support of the main experimental hypothesis, administration of CRF-SAP in El mice reduced handling-induced seizure susceptibility by 75% for up to 2 weeks following treatment. Similarly, El mice were slow to detect a cache of buried food pellets relative to ddY controls and this exploratory deficit was reversed 3 days following administration of CRF-SAP. Efficacy of CRF-SAP treatment was confirmed using CRF immunohistochemistry, which revealed suppression of brain CRF content in El mice treated with CRF-SAP relative to El controls. Other functional and persistent effects of CRF-SAP included increased locomotor activity and hyperphagia.

Conclusions: Taken together, these results support strongly the possibility that activated brain stress neuropeptide systems are necessary for the expression of motivational and neurological perturbations in seizure susceptible El mice.

Olfaction is the primary sense for the recognition of social cues pertinent to reproduction and territorial defense in rodents (Leon, 1992; Ferguson et al., 2000). In support of a link between olfaction and seizures, neurotransmitter deficiencies have been detected in the olfactory bulb of seizure susceptible GEPR rats (Dailey et al., 1991) and olfactory stimulation is capable of altering seizure threshold in amygdala-kindled rats (Ebert and Loscher, 2000). Consistent with these findings, clinical studies have assessed the identification of common smells in patients with epileptogenic foci in the left temporal lobe, the right temporal lobe, or other brain regions relative to normal control subjects (Carroll et al., 1993; Kohler et al., 2001); these studies found that all three patient groups were substantially impaired in verbal labeling of odor cues. Thus, olfactory recognition performance is one component of behavioral phenotyping in animal models of epilepsy that may provide insight into the neural mechanisms of seizure induction.

The seizure susceptible El mouse is an animal model of idiopathic simple reflex epilepsy arising from the interaction of genetic predisposition and lifetime exposure to seizure triggers such as tail suspension handling (Todorova et al., 1999). Two aspects of the known El phenotype suggest the need to assess olfactory performance in this strain of mouse. First, El dams exhibit poor maternal care following parturition when separation from pups typically elicits a vigorous retrieval response in the caregiver (Fleming et al., 1992); this retrieval response is an unlearned maternal behavior that is critically dependent on the sense of smell. Second, El mice are deficient in social recognition, an unlearned form of working memory for conspecifics (Lim et al., 2007), which is also critically dependent upon olfactory discrimination performance (Sawyer et al., 1984). In order to detect potential olfactory recognition impairment in El mice in a nonsocial testing context, the present study assessed the ability of seizure susceptible adults to perform olfactory food pellet detection and inanimate olfactory stimulus exploration tasks.

The second aim of the present study was to assess the dependence of olfactory performance and seizure susceptibility in El mice on stress-related brain activation. Several pieces of evidence suggest that El mice have intrinsically elevated levels of arousal. First, tail suspension handling is an explicit stressor in laboratory rodents (Balcombe et al., 2004), which facilitates seizure onset and frequency in El mice (Todorova et al., 1999; Leussis and Heinrichs, 2006). Second, behavioral, pituitary-adrenocortical and electrophysiological indices of stressor exposure reveal heightened activation in El mice relative to ddY controls whereby activation of the stress neuropeptide, corticotropin releasing factor (CRF), acts as one component of the coping response to environmental challenge (Forcelli et al., in press). Elevation of CRF by pharmacological (Ehlers et al., 1983) or genetic (Jinde et al., 1999) means is known to promote seizures in the rodent brain. Thus, the present study was designed to assess a potential causal link between stressor exposure via brain CRF activation on the one hand and olfactory discrimination/seizure susceptibility phenotypes on the other. In particular, a targeted toxin, CRF + saporin conjugate (CRF-SAP), which is reported to impair CRF system function (Maciejewski-Lenoir et al., 2000; Chance et al., 2006) was administered to mice prior to olfactory or seizure susceptibility assessments. Antiseizure efficacy of CRF-SAP in El mice can be predicted from prior studies employing CRF receptor antagonist drugs as anticonvulsants (Baram et al., 1999). Since the consequences of CRF system activation in the brain also extend to other response modalities such as locomotor activity and food intake regulation, these forms of motivated behavior were also quantified in the present studies.

METHODS

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES

Animals

Equal proportions of male and female ddY (n = 26) and El (n = 52) strain mice served as experimental subjects. Experimental mice were group-housed in standard polypropylene cage in a reverse light–dark cycle colony (lights off at 10:00, lights on at 22:00) at 21°C and 48% humidity. Water and standard lab chow (ProLab3000, LabDiets, Richmond, IN, U.S.A.) were available ad libitum throughout the duration of the experiment. The Institutional Animal Care and Use Committee of Boston College approved all experimental procedures described herein.

Pellet detection and odor reactivity tests

Mice were tested using two olfactory tests: (1) food pellet detection and (2) novel odor exploration. In the 5-min food pellet detection test, four 45 mg food pellets (P.J. Noyes) of the type used for operant box dispensers were buried in the bedding of one corner of a clean test cage. The amount of time it took for the mouse to discover the pellets following placement in the cage was recorded using a stopwatch. Pellet discovery was characterized by sniffing the area, sticking the nose into the bedding immediately over the pellets, and digging into the bedding with the front paws to uncover the pellets. Mice that failed to detect the pellets within 300 s were assigned this maximum latency score. Mice were not likely to recognize the pellets as food or be motivated by hunger since the pellets were novel at the time of presentation. The pellets were formulated using a sugar-based recipe distinct from the laboratory chow recipe, and the pellets were presented to mice immediately following a period of ad libitum access to food in the home cage.

In the novel odor exploration test, a 0.1 ml volume of lemon extract (Schilling) was squirted onto a gauze pad and inserted into a small tube with a wire mesh opening at one end. The tube was placed in one corner of a clean testing cage and the amount of time spent exploring the odor chamber over a 5-min period was recorded using a stopwatch following placement of a test mouse into the cage. Chamber exploration was characterized by sniffing, biting, burying, or placing front paws on the tube. Two replications of both the pellet detection and odor exploration tests were performed using separate sets of naive mice.

Intracerebroventricular freehand injection of CRF-SAP

Mice were anesthetized with isoflurane (Aerrane, Baxter Healthcare Corporation, Deerfield, IL, U.S.A.) and a disinfectant (Betadine) was applied to the top of the scalp. The ddY and half of the El mice were injected with a 2 μg/5 μl dose of unconjugated saporin (Advanced Targeting Systems, La Jolla, CA, U.S.A.) into the lateral ventricle (2 mm right of bregma and 3.5 mm below skull surface). Intracerebroventricular injections are known to spread very quickly throughout the ventricular space, including the contralateral cerebroventricles, following unilateral injection (Proescholdt et al., 2000). The remaining El strain mice were similarly injected with either 1 or 2 μg/5 μl doses of CRF-SAP (Advanced Targeting Systems). There is little guidance in the literature regarding in vivo efficacy of CRF-SAP although the dosage used in the present studies has been reported to reduced hypermetabolism resulting from burn trauma (Chance et al., 2006). Note that all three injection groups were administered a form of saporin in order to control for potential nonspecific actions of the neurotoxin whereas ddY mice were not injected with CRF-SAP since this treatment group was not necessary to test any of the a priori hypotheses.

The olfactory exploration test was performed 72 h after the injection had taken place. On Days 7 and 14 post-injection, seizure likelihood was tested using the handling-induced seizure susceptibility (HISS) protocol to reproduce the repetitive handling stress associated with routine cage changes. Each mouse was picked up by the tail and suspended 10–15 cm above the home cage floor for 30 s and then placed in a clean cage for 120 s. The mouse was then suspended for an additional 15 s before being returned to its home cage. Generalized seizures were identified by a loss of postural equilibrium, an erect forward-arching Straub tail, and head, limb, or chewing automatisms. Mice that displayed other signs of seizures such as vocalizations or twitching, but that did not progress to a generalized seizure were not considered seizure susceptible. Regular husbandry was discontinued for the week prior to HISS testing in order to insure a high frequency of seizures in El mice. Two hours after HISS testing on Day 14, one cohort of mice was euthanized with an overdose of isoflurane and perfused transcardially. Two replications of the olfactory exploration/CRF-SAP administration procedure were performed using separate sets of naive mice.

Locomotor activity test

Two groups of El mice were single housed, administered saporin alone or CRF-SAP as described previously, and placed immediately afterwards in a home cage photocell activity monitor. The locomotor apparatus (San Diego Instruments, San Diego, CA, U.S.A.) consisted of photocell grids, each measuring 25 × 48 cm, positioned around the perimeter of a standard mouse cage. Four infrared photocell beams located along the long axis and eight beams across the width were positioned 2 cm above the bedding at 16-cm intervals. Mice were tested in the locomotor apparatus for seven consecutive days and remaining food and drinking water were measured daily at 10:00 without handling the mouse. Two replications of the locomotor/CRF-SAP administration procedure were performed using separate sets of naive mice.

Perfusion and tissue sectioning

Mice were anesthetized with isoflurane (Aerrane, Baxter Healthcare Corporation, Deerfield, IL, USA) prior to intracardial perfusion with 0.1 M phosphate-buffered saline (PBS, pH 7.4), followed by 4% paraformaldehyde in 0.9% saline. Brains were removed immediately and post-fixed overnight at 4°C and then placed in a 30% sucrose solution at 4° C until sinking (48–72 h). Free-floating sections (40 μm) were cut with a cryostat, and stored in cryoprotectant (pH 7.2) at –20°C until histological and immunocytochemical analyses were performed.

Nissl staining

Tissue sections were mounted onto gelatinized slides, rinsed in ethanol and distilled water and then stained using 0.13% cresyl violet in an acetic acid buffer. Stained slides were rinsed in ethanol, cleared in xylene, and coverslipped.

CRF immunocytochemistry

Immunocytochemical detection of r/h CRF (1–41) peptide was performed using a kit (Peninsula Laboratories, San Carlos, CA, U.S.A.). After rinsing in 50% ethanol and quenching of endogenous peroxidase activity with a 3% hydrogen peroxide solution, tissue sections were placed in a 0.15% normal goat serum blocking solution. Sections were incubated with the rabbit anti-CRF antibody (1:1000) overnight at 4°C. On the second day, sections were incubated with a goat, anti-rabbit secondary antibody (1:1000) for 1 h and then a streptavidin-HRP conjugate for 30 min. Sections were stained using a DAB chromagen and a hematoxylin counterstain.

Brain mapping by microscopy

Sections were photographed using an RT color Spot camera (Diagnostic Instruments Inc, Sterling Heights, MI, U.S.A.) mounted on a Zeiss bright-field microscope. Nissl positive and CRF immunoreactive cells were counted using IP Lab image analysis software (Scanalytics, Fairfax, VA, U.S.A.). In order to avoid potential experimenter and laterality biases, analyses were completed without knowledge of strain or treatment condition using brain tissue from both sides of the sagittal plane. Nissl stained and CRF-labeled cells were counted in the striatal fundus, paraventricular nucleus of the hypothalamus, hippocampus, basolateral nucleus of the amygdala, and paraventricular nucleus of the thalamus. Sites were selected for the analysis based upon a series of cFos mapping studies performed previously in El and ddY strain mice (McFadyen-Leussis and Heinrichs, 2004), by coarse examination for areas of intense staining by a treatment-blind observer, and by the known distribution of CRF-containing nuclei in rodent seizure models (Piekut and Phipps, 1998). Moreover, the diencephalic and basal forebrain regions of interest in the present studies are reported to constitute brain sites for seizure facilitation and interactivity with other brain seizure substrates (Eells et al., 2004). Specific brain regions and nuclei of interest were identified using a mouse brain atlas (Paxinos and Franklin, 2001).

Statistical analysis

For experiment 1 (olfactory phenotyping), a one-way analysis of variance (ANOVA) for detection latency and investigation time was performed with strain as a between subjects factor. For experiment 2 (olfactory/CRF-SAP), two-way ANOVAs for detection latency and body weight were performed with strain and treatment as between subjects factors. For experiment 3 (locomotor/CRF-SAP), two-way mixed ANOVAs were performed with treatment as a between subjects factor and time as a within subjects factor. Simple main effect analyses were conducted when appropriate to determine individual group differences, and comparisons were considered significant when p < 0.05.

RESULTS

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES

Analysis of the time spent in investigating a novel odor cue did not reveal any main or interaction effects of strain or gender with El mice exploring the object for the same duration (110 ± 15 s) as ddY controls (115 ± 15 s). In contrast, there was a significant [F(1,28) = 4.2, p < 0.05] main effect of strain on pellet detection latency with El mice taking more time to excavate the buried food relative to ddY controls (Fig. 1). Examination of ddY and El mice following administration of saporin alone or CRF-SAP revealed a significant [F(1,18) = 3.5, p < 0.05] effect of strain on pellet detection latency with saporin alone-treated El mice again taking more time to excavate the buried food relative to saporin alone-treated ddY controls (Fig. 1). Moreover, administration of the high dose, but not the low dose, of CRF-SAP in El mice significantly [F(1,14) = 4.2, p < 0.05] reduced pellet detection latency relative to saporin alone-treated El controls (Fig. 1). These results suggest that the impaired pellet detection latency phenotype of El mice was normalized to ddY control levels by central administration of CRF-SAP.

image

Figure 1. Latency to detect buried pellets (mean ± SEM) among ddY (n = 16) and El mice (n = 16) which were untreated or administered saporin alone (control) or 1–2 μg doses of CRF + saporin conjugate (CRF-SAP) 3 days prior to testing. * p < 0.05 relative to the ddY control group, † p < 0.05 relative to the El control group

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Evaluation of body weight at the beginning and end of the 14-day trial revealed significant main effects of strain [ddY > El; F(1,22) = 25.1, p < 0.001] and gender [male > female; F(1,22) = 4.4, p < 0.05] but no main or interaction effect of treatment. Evaluation of seizure susceptibility in El mice 7 and 14 days after administration of saporin alone or CRF-SAP revealed a significant [χ2(1) = 3.5, p < 0.05] difference in frequency with saporin alone-treated El controls seizing 44% of the time (8 of 18) versus 10% of the time (1 of 10) for mice treated with the high dose of CRF-SAP. Mice treated with the low dose of CRF-SAP exhibited a seizure frequency of 50% (4 of 8) which is comparable to the 44% value of saporin alone-treated El controls. Thus, CRF-SAP treatment dose-dependently attenuated handling-induced seizures in susceptible El mice.

Examination of cell density via Nissl staining of brains harvested from ddY and El mice 14 days after saporin alone or CRF-SAP administration revealed no significant main or interaction effects of strain or treatment factors (Fig. 2). However, examination of CRF immunohistochemistry in ddY and El mice treated 14 days previously with saporin alone or CRF-SAP revealed a significant [F(1,19) = 14.7, p < 0.001] main effect of strain for the striatal fundus with El mice exhibiting higher CRF content in this basal forebrain, accumbal region relative to ddY controls (Fig. 3). There were also significant main effects of treatment on CRF content in both the striatal fundus [F(1,19) = 4.4, p < 0.05] and lateral septum [F(1,19) = 14.3, p < 0.01] with saporin alone-treated El mice exhibiting higher CRF content than El mice treated with CRF-SAP (Fig. 3).

image

Figure 2. Region of interest cell density (mean ± SEM) assessed by Nissl staining in ddY and El mice treated 2 weeks previously with saporin alone (control) or a 2 μg dose of CRF-SAP (n = 6/group). Amyg,basolateral nucleus of amygdala; PVN, paraventricular nucleus of hypothalamus; PVT, paraventricular nucleus of thalamus; FS, fundus of the striatum; Sept, lateral septum.

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image

Figure 3. Corticotropin releasing factor (CRF) content (mean ± SEM) assessed immunohistochemically in ddY and El mice exposed 14 days previously to saporin alone (control) or a 2 μg dose of CRF-SAP (top panel, n = 6/group). Representative sections of lateral septum are provided for El mice in the control (left) and CRF-SAP (right) treatment groups (bottom panels). Amyg, basolateral amygdalar nucleus; FS, fundus of the striatum; LS, lateral septum; LV, lateral ventricle; PVN, paraventricular nucleus of hypothalamus; PVT, paraventricular nucleus of thalamus; Sept, lateral septum. * p < 0.05 relative to the ddY control group, † p < 0.05 relative to the El control group

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Analysis of the locomotor trials revealed a significant [F(23,322) = 6.7, p < 0.001] effect of time as mice exhibited a typical pattern of circadian activity: ascending during the nocturnal phase and descending during the diurnal phase of the cycle (Fig. 4). There was also a significant [F(23,322) = 1.8, p < 0.01] time by treatment interaction effect whereby mice in the CRF-SAP group were more active during most hours of the day, with the exception of the light-to-dark phase transition (Fig. 4). There was a significant [F(1,14) = 5.4, p < 0.05] main effect of treatment on food intake with saporin alone-treated mice eating a daily average of 5 ± 1 g of chow versus 8 ± 1 g for the CRF-SAP group (Fig. 5). There was no significant effect of treatment on fluid intake with saporin alone-treated mice drinking a daily average of 7 ± 1 ml of water versus 9 ± 1 ml for the CRF-SAP group. Assessment of body weights 14 days after administration of saporin alone or CRF-SAP revealed no effect of treatment in mice that had been body weight matched at the beginning of the study (saporin alone El—37 ± 2 g; CRF-SAP El—37 ± 3 g). HISS testing of El mice at the conclusion of the locomotor trials revealed that 2 of 7 mice (28%) in the saporin alone-treated group seized relative to 0 of 8 mice (0%) in the CRF-SAP-treated group.

image

Figure 4. Hourly locomotor activity (mean ± SEM) averaged over 7 consecutive 24-h periods in El mice treated with saporin alone (control) or a 2 μg dose of CRF-SAP (n = 8/group). The black shaded bar reflects the nocturnal phase of the circadian cycle, and the white shaded bar the diurnal phase.

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image

Figure 5. Daily food intake (mean ± SEM) in El mice treated with saporin alone (control) or a 2 μg dose of CRF-SAP immediately prior to the 1-week test (n = 8/group).

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DISCUSSION

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES

The key finding of the present studies is that deficits in olfactory detection latency and seizure-related pathology were both dependent upon intact brain CRF systems in El mice. In the first experiment, El mice exhibited a delay in locating a buried food pellet cache relative to ddY control mice. This increase in detection latency was probably not due to motivation to explore a novel olfactory stimulus that was investigated for an equivalent amount of time by both mouse strains. In the second experiment, impairment of brain CRF systems by central injection of CRF-SAP antagonized the olfactory detection deficit and reduced the frequency of handling-induced seizures in El mice. The neurobiological consequences of CRF-SAP administration were selective since no change in overall cell density was detected in several brain regions of interest whereas CRF-SAP suppressed CRF content in multiple brain sites in El mice. While it is certainly true that CRF-SAP has neurotoxic potential in vitro (Maciejewski-Lenoir et al. 2000), there was no evidence in the present studies of comparable neural loss following in vivo administration of CRF-SAP and thus the emphasis should be on diminished CRF system function based upon reduced CRF neuropeptide content detected using immunoassay. In the final experiment exploring daily activity and intake patterns, CRF-SAP-treated El mice exhibited both persistent locomotor hyperactivity and increased food intake for the duration of a one week post-treatment monitoring period. These findings suggest that while functional impairment of brain stress neuropeptide systems is an effective strategy for normalization of olfactory exploration and seizure susceptibility phenotypes in El mice, long-term dysregulation of motor activity and ingestive behavior also result from CRF-SAP treatment.

The present study provides strong evidence in support of the hypothesized role of excess brain CRF activation in triggering and maintaining seizures in genetically susceptible animals (Jobe, 2003). In the present studies, CRF was increased in the striatal fundus of El mice and this elevation was significantly attenuated by administration of CRF-SAP. Although there is no causal link between activation of this brain nucleus and any of the behavioral-dependent measures employed in the present study, the fact that CRF-SAP administration normalized olfactory exploration and attenuated seizure frequency of El mice suggests a strong positive association between brain CRF activation and these functional phenotypes. On the other hand, CRF-SAP administration also engendered hyperactivity and hyperphagia responses continuously over a 7-day period following administration. The hyperphagic effect of CRF-SAP is potentially troubling since it is well known that clinically relevant dietary restriction or feeding of low carbohydrate diets are effective anticonvulsive treatments in animal models of epilepsy including the El mouse (Stafstrom and Bough, 2003; Mantis et al., 2004; Seyfried et al., 2004). Similarly, the El mouse is already known to exhibit locomotor hyperactivity (Drage and Heinrichs, 2005) such that the present augmentation of locomotor activity would presumably exaggerate, rather than attenuate, this behavioral phenotype. The increased caloric intake produced by hyperphagia seems to have been counterbalanced by the increased energy expenditure necessary for motor hyperactivity such that the body weights of CRF-SAP mice did not differ 7 days post-treatment from saporin alone controls. Future studies will be required to determine if the present motoric and appetitive side effects of CRF-SAP treatment generalize to other testing contexts.

While several investigators implicate hypothalamic and amygdalar subdivisions as potential seizure-trigger zones responsive to stressor exposure (Jobe, 2003), the present results also implicate regions of the pole of the basal forebrain such as the striatal fundus and the lateral septum as potential zones of seizure modulation. The term “striatal fundus” describes the ventral portion of the rostral striatum, which includes the nucleus accumbens and substantia innominata in both rodent and human species and subserves motor and cognitive output functions of the striatum (Heimer, 2003). For example, one study examined the induction of CRF in extrahypothalamic brain sites following generalized clonic seizures induced by kainic acid and observed a marked increase of CRF immunolabeled cells in select brain areas such as the striatal fundus (Piekut and Phipps, 1998). Moreover, in the present study CRF in the striatal fundus was elevated as a function of strain in El mice and the CRF-SAP neurotoxin was effective in attenuating this increase. While the functional neuroanatomy of this brain site in the context of the present studies is unclear, the striatal fundus receives a dense projection from the amygdala, another brain area reported to be dysregulated in El mice (Forcelli et al., in press). Moreover, the amygdalostriatal pathway is an anatomical circuit implicated in feeding and social behavior regulation (Petrovich et al., 1996), which would certainly be consistent with the present CRF-SAP treatment effect on daily chow intake. The lateral septum is another brain area in which CRF levels are increased by kainic acid administration (Piekut and Phipps, 1998) and this brain area is well known to mediate fear learning and other stress coping responses (Radulovic et al. 2000; Price et al. 2002). Future studies could extend these positive correlations between striatal/septal CRF activation and seizure/affective phenomena using local site injection of tools such as CRF-SAP capable of inactivating specific neural circuits presumed to underlie the El phenotype.

The present results provide support for the hypothesized comorbidity of affective and seizure-related disorders (Jobe, 2003; 2004; Jobe and Browning, 2005). In particular, El mice exhibit both high emotionality and seizure susceptibility. Emotionality in El mice is documented by exaggerated pituitary-adrenocortical, neural, and electroencephalographic responses to explicit stressors such as foot shock and tail suspension handling (Drage and Heinrichs, 2005; Forcelli et al., in press). El seizure susceptibility reflects a heritable characteristic that is quite plastic and can be enhanced by systematic exposure to repeated handling stressors, for example (Todorova et al., 1999; Leussis and Heinrichs, 2006), or alternatively by separation from the dam during a critical developmental period (McFadyen-Leussis and Heinrichs, 2005). Moreover, the present delay in detection of an olfactory cue can also be considered evidence of increased emotionality since the cue and the means by which it was presented were both unfamiliar, a circumstance that has an anxiogenic-like consequence for rodent exploratory behavior (File and Seth, 2003). The fact that CRF-SAP exerted dual efficacy in attenuating both affective and seizure phenotypes in El mice further strengthens the evidence in favor of affective/seizure comorbidity. If in fact brain CRF neurotransmission acts as a seizure-triggering mechanism in response to environmental challenge, then CRF receptor antagonist drugs would be expected to attenuate both heightened emotionality and seizure susceptibility in comorbid animal models of epilepsy (Brunson et al., 2001; Jobe, 2004).

Acknowledgments

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES

Acknowledgments:  We thank Alyssa Richman, Chem Lim, and Laura Turner for technical assistance. This research was supported by C.U.R.E and a Boston College Research Incentive Grant (SCH).

REFERENCES

  1. Top of page
  2. Abstract
  3. METHODS
  4. RESULTS
  5. DISCUSSION
  6. Acknowledgments
  7. REFERENCES
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