Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2019 Dec;101(Pt A):106547.
doi: 10.1016/j.yebeh.2019.106547. Epub 2019 Nov 4.

Genetic backgrounds have unique seizure response profiles and behavioral outcomes following convulsant administration

Nycole Ashley Copping  1 , Anna Adhikari  1 , Stela Pavlova Petkova  1 , Jill Lynn Silverman  2
Affiliations

Genetic backgrounds have unique seizure response profiles and behavioral outcomes following convulsant administration

Nycole Ashley Copping et al. Epilepsy Behav. 2019 Dec.

Abstract

Three highly utilized strains of mice, common for preclinical genetic studies, were evaluated for seizure susceptibility and behavioral outcomes common to the clinical phenotypes of numerous psychiatric disorders following repeated low-dose treatment with either a gamma-aminobutyric acid (GABA) receptor antagonist (pentylenetetrazole (PTZ)) or a glutamate agonist (kainic acid (KA)). Effects of strain and treatment were evaluated with classic seizure scoring and a tailored behavior battery focused on behavioral domains common in neuropsychiatric research: learning and memory, social behavior, and motor abilities, as well as seizure susceptibility and/or resistance. Seizure response was induced by a single daily treatment of either PTZ (30 mg/kg, intraperitoneally (i.p.)) or KA (5 mg/kg, i.p.) for 10 days. Pentylenetetrazole-treated FVB/NJ and C57BL/6NJ strains of mice showed strong, clear seizure responses. This also resulted in cognitive and social deficits, and increased susceptibility to a high dose of PTZ. Kainic acid-treated FVB/NJ and C57BL/6NJ strains of mice had a robust seizure response, which resulted in hyperactivity. Pentylenetetrazole-treated C57BL/6J mice demonstrated mild hyperactivity, while KA-treated C57BL/6J displayed cognitive deficits and resistance to a high dose of KA but no social deficits. Overall, a uniquely different seizure response profile was detected in the C57BL/6J strain with few observable instances of seizure response despite repeated convulsant administration by two mechanisms. This work illustrated that differing background genetic strains have unique seizure susceptibility profiles and distinct social and cognitive behavior following PTZ and/or KA treatment and that it is, therefore, necessary to consider strain differences before attributing behavioral phenotypes to gene(s) of interest during preclinical evaluations of genetic mouse models, especially when outcome measures are focused on cognitive and/or social behaviors common to the clinical features of numerous neurological disorders.

Keywords: Background strain; Behavior; Cognitive; Genetics; Mouse models; Seizures.

PubMed Disclaimer

Conflict of interest statement

Conflicts: The authors have no conflicts of interest to declare.

Figures

Figure 1:
Figure 1:. Schematic of study design.
Timeline for modified kindling paradigm and subsequent behavioral battery of motor, cognitive, and social domains.
Figure 2:
Figure 2:. Inbred strains exhibit different Racine responses across a 10-day convulsant treatment time.
FVB/NJ and C57BL/6NJ subject mice (A, B and E, F) displayed increased seizure susceptibility to both PTZ and KA while C57BL/6J were only mildly affected by KA. Subjects received an intraperitoneal injection of PTZ, KA, or vehicle and highest Racine score achieved each day was recorded. The Racine score was evaluated for 10-d during a 20-min observation period. Racine scores of 0 indicated no response, 1 immobility, 2 generalized spasm and forelimb clonus, 3 Straub’s tail, 4 loss of righting, 5 running seizure, 6 generalized clonic-tonic seizure, and 7 death. (A-B) PTZ and KA-treated FVB/NJ mice displayed a significant increase in seizure severity score over the 10-day injection period. In subjects that received PTZ, severe Racine score (5–6) were observed while those that were treated with KA did not display scores in the 5–6 level range. (C) PTZ-treated C57BL/6J mice had no significant change in seizure severity score over the 10-d treatment time. (D) KA-treated C57BL/6J mice displayed a significant increase in seizure severity score over the 10-day injection period. No 5–6 Racine score stages were observed in either PTZ or KA-treated group. (E-F) PTZ and KA-treated C57BL/6NJ mice displayed a significant increase in seizure severity score over the 10-day injection period. In subjects that received PTZ severe Racine score (5–6) were observed while those that were treated with KA did not display scores in the 5–6 level range. Both PTZ and KA-treated FVB/NJ and C57BL/6NJ mice spent more time in moderate and severe Racine seizure stages compared to C57BL/6J. *, p < 0.05, linear regression of highest Racine score over convulsant injection days within strain and treatment.
Figure 3:
Figure 3:. PTZ and KA treatment resulted in learning and memory impairments in the novel object recognition assay.
Recognition memory was assessed using a novel object recognition assay. Subjects were habituated to a novel arena, then were given a 10-min familiarization session with two identical objects. After familiarization, subjects were removed from the testing arena and, after a 1-h inter-trial interval, were placed back into the arena with one familiar object and one novel object. Time spent investigating both objects was recorded. (A) PTZ-treated FVB/NJ mice did not spend more time sniffing the novel object over the familiar object. Both vehicle and KA-treated subjects preferred novel object investigation compared to the familiar object. (B) KA-treated C57BL/6J mice did not spend more time sniffing the novel object over the familiar object. Both vehicle and PTZ-treated subjects preferred the novel object compared to the familiar object. (C) KA-treated C57BL/6NJ mice did not spend more time sniffing the novel object over the familiar object. Both vehicle and PTZ-treated subjects did prefer the novel object compared to the familiar object. These data illustrate both convulsant insults can cause disruption in object recognition learning and memory circuitry, however, the cognitive deficits are strain and drug dependent. (D-F) All vehicle, PTZ, and KA-treated subjects of FVB/NJ, C57BL/6J, and C57BL/6N strains showed no preference for either the left or right object during the familiarization phase indicating no innate side bias confounds in the novel object recognition trials. *, p < 0.05, repeated-measures ANOVA within strain and treatment using the familiar versus novel object for comparison.
Figure 4:
Figure 4:. PTZ-treated FVB/NJ and C57BL/6NJ illustrated deficits on sociability parameters while KA-treated C57BL/6NJ showed elevated repetitive behavior during reciprocal social interaction.
Sociability was measured using a male-female reciprocal dyad social interaction assay where parameters such as nose-anogenital sniffing, ultrasonic vocalizations, nose-nose sniffing, and groom time were evaluated. Male subjects were placed in a novel arena with an age-matched, wildtype female in estrous and their interaction was observed for 5-min. (A) PTZ-treated FVB/NJ mice displayed reductions in (i) nose-anogenital sniffing (ii) and ultrasonic vocalizations, compared to vehicle-treated controls. (iii, iv) No differences were observed in nose-nose sniffing and grooming parameters. (i-iv) KA-treated FVB/NJ mice did not differ from the vehicle group on any measured parameter. (B) (i-iv) PTZ and KA-treated C57BL/6J groups did not significantly differ from the vehicle group on any parameter during the reciprocal social interaction assay. (C) (iii) PTZ-treated C57BL/6NJ male subjects exhibited reduced nose-nose sniffing, while KA-treated C57BL/6NJ exhibited increased repetitive behavior, seen as increased grooming. No other significant differences were observed in either PTZ or KA-treated C57BL/6NJ subjects (i-iv). Using the less sensitive but standard measure of 3-chambered social approach, all strains and all treatments groups met the criterion of sociability. (D) Time spent in the novel mouse chamber versus the object chamber (i), as well as, time spent sniffing the novel mouse versus object were statistically significant for both PTZ and KA-treated FVB/NJ. (E, F) C57BL/6J and C57BL/6NJ also spent more time in the chamber with the novel mouse (i) and more time sniffing the novel mouse (ii) compared to the object. No significant difference was identified between vehicle and PTZ, KA-treated FVB/NJ, C57BL/6J, and C57BL/6NJ on the number of transitions between chambers, confirming no locomotor confound (data not shown). *, p < 0.05, Reciprocal social interaction assay: one-way ANOVA comparing vehicle-treated group to either convulsant group by strain factor. 3-Chambered social approach: repeated-measures ANOVA within strain and treatment using the factor of chamber side (novel mouse side vs. novel object side).
Figure 5:
Figure 5:. PTZ and KA treatment elevated motor activity in a novel open field arena on various parameters specific to strain and treatment.
Gross motor abilities were assessed using activity in a novel open field arena by total, horizontal, and vertical activity and time spent in the center across a 30-min session. Data is shown in 5-min bins. (A) Open field parameters for vehicle, PTZ, and KA-treated FVB/NJ mice. KA-treated FVB/NJ animals exhibited (iii) higher total activity and an elevated number of (ii) vertical movements, compared to the PTZ-treated and vehicle controls. No differences were observed by (i) horizontal activity nor (iv) time spent in the center of the arena. (B) Open field parameters for vehicle, PTZ, and KA-treated C57BL/6J mice. (iii) Robust increased total activity was observed in PTZ-treated C57BL/6J mice, but not KA-treated, compared to the vehicle group. (i-ii, iv) No differences detected on horizontal activity, vertical activity, or center time between the PTZ and KA-treated mice and the vehicle treated controls. (C) Open field parameters for vehicle, PTZ, and KA-treated C57BL/6N mice. (iv) Reduced center time was detected in PTZ-treated, but not KA-treated, C57BL/6N mice compared to the vehicle control. Increased activity measured by (i) horizontal, (ii) vertical, and (iii) total activity was detected in KA-treated C57BL/6NJ mice, compared to the PTZ-treated and vehicle controls. *, p < 0.05, repeated-measures ANOVA within strain and treatment using the factor of time across 5-min bins.
Figure 6:
Figure 6:. PTZ-treated FVB/NJ and C57BL/6NJ showed increased susceptibility to a high-dose of PTZ. In contrast, KA-treated C57BL/6J showed seizure resistance to a high-dose of KA.
Response to a high-dose of PTZ (80 mg/kg, i.p.) or KA (30 mg/kg, i.p.) was evaluated in previously treated PTZ (30 mg/kg, i.p.) and KA (5 mg/kg, i.p.) subjects as well as their naïve, vehicle control littermates. Subjects received a high-dose of PTZ or KA and then placed in an empty cage. Latencies to first jerk, loss of righting reflex, clonic-tonic seizure, and death were collected. (A) High-dose administration of PTZ in FVB/NJ mice. (ii-iii) Faster onsets to loss of righting and a trend (p = 0.09) towards faster onset to clonic-tonic seizures were observed in PTZ-treated mice compared to control littermates. (i, iv) No change in latency to onset of first jerk or death after a high-dose treatment of PTZ was observed in PTZ-treated FVB/NJ mice compared to control littermates. (B) High-dose administration of PTZ in C57BL/6J mice. (i-iv) No change in any behavioral seizure metrics following PTZ were observed in PTZ-treated subjects compared to control littermates. (C) High-dose administration of PTZ in C57BL/6NJ mice. (ii-iv) Faster onsets to loss of righting, clonic-tonic seizure, and death were observed in PTZ-treated mice compared to control littermates. (D) High-dose administration of KA in FVB/NJ subjects. (i-iv) No change in any behavioral seizure metrics following KA were observed in KA-treated subjects compared to control littermates. (E) High-dose administration of KA in C57BL/6J subject mice. (ii-iv) Increased latency to loss of righting, clonic-tonic seizure, and death were observed in KA-treated compared to control littermates. (F) High-dose administration of KA in C57BL/6NJ subjects. (i-iv) No change in any behavioral seizure metrics following KA were observed in KA-treated subjects compared to control littermates. *, p < 0.05, one-way ANOVA comparing vehicle-treated group to either convulsant group by strain factor.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Bryda EC. The Mighty Mouse: the impact of rodents on advances in biomedical research. Mo Med 2013;110: 207–11. - PMC - PubMed
    1. Silver L Inbred Strain In: Press A, editor. Encyclopedia of Genetics; 2001, p. 1015–1016.
    1. Sittig LJ, Carbonetto P, Engel KA, Krauss KS, Barrios-Camacho CM, Palmer AA. Genetic Background Limits Generalizability of Genotype-Phenotype Relationships. Neuron 2016;91: 1253–1259. - PMC - PubMed
    1. Butler D Lost in translation. Nature 2007;449: 158–9. - PubMed
    1. Bolivar VJ, Walters SR, Phoenix JL. Assessing autism-like behavior in mice: variations in social interactions among inbred strains. Behav Brain Res 2007;176: 21–6. - PMC - PubMed

Publication types