544778 research-article2014
JOP0010.1177/0269881114544778Journal of Psychopharmacology 0(0)McKibben et al.
Original Paper
Analysis of sociability and preference for social novelty in the acute and subchronic phencyclidine rat Claire E McKibben1, Gavin P Reynolds1,2 and Trisha A Jenkins1,3
Journal of Psychopharmacology 2014, Vol. 28(10) 955–963 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0269881114544778 jop.sagepub.com
Abstract Both acute and sub-chronic phencyclidine administration produce behavioural and pathophysiological changes that resemble some features of schizophrenia. The present study aimed to determine if acute and sub-chronic phencyclidine treatment in male rats produces deficits in sociability and social novelty preference, which may reflect aspects of the negative symptomatology observed in schizophrenia. Rats were treated with phencyclidine acutely (2 or 5 mg/kg) or subchronically (2 or 5 mg/kg bi-daily for one week followed by a one week wash-out period) or vehicle. Social affiliative behaviour was assessed using the sociability and preference for social novelty paradigm where social interaction time was measured in (a) a chamber containing an unfamiliar conspecific vs an empty chamber (sociability), or (b) a chamber containing an unfamiliar conspecific vs a chamber containing a familiar conspecific (preference for social novelty). Results showed that acute administration of phencyclidine produced a reduction in measures of sociability but had no effect on preference for social novelty while sub-chronic administration of phencyclidine had no effect on sociability or social novelty. This study provides further evidence for the usefulness of phencyclidine models in modelling the symptomatology of schizophrenia.
Keywords Social interaction, social withdrawal, phencyclidine, schizophrenia, negative symptoms
Introduction The delineation of schizophrenia into positive and negative symptoms has been described since the early observations of Kraeplin and Bleuler (Hanson et al., 2010). Recently, the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Development Conference on Negative Symptoms agreed on a set of relevant dimensions of negative symptomatology including blunted affect, alogia, anhedonia, avolition and asociality (Blanchard et al., 2011). Negative symptoms often begin to manifest themselves before the patient experiences their first psychotic episode (Milev et al., 2005), and are associated with poor psychosocial functioning and reduced quality of life (Ho et al., 1998). Currently available treatments for schizophrenia have little to no effect on negative symptoms (Foussias and Remington, 2010; Hanson et al., 2010), with the result that these symptoms continue to disproportionately limit patient recovery. Asociality, which can be considered as a combination of social withdrawal, and lack of social drive, is considered to be one of the most problematic symptoms of schizophrenia. It is present at the premorbid stages of the illness, and persists throughout the entire course of the disease, even during psychosis remission periods (Bellack et al., 1990), and remains inadequately addressed by current pharmacotherapy (Murphy et al., 2006). The development of better animal models and tests to imitate schizophrenia-like asocial behaviour will provide a means for examining potential different pharmacologic approaches.
Social interaction, where an experimental rodent is placed with a novel con-specific rodent of the same species and interactionbehaviour measured (File and Seth, 2003), is one of the most used paradigms to measure social withdrawal in animal models. Administration of the N-methyl-d-aspartate (NMDA) receptor antagonist, phencyclidine (PCP), disrupts social behaviour in rodents using a variety of different methodologies (Gururajan et al., 2010; Jentsch and Roth, 1999; Neill et al., 2010, 2013). Acute exposure to PCP, 45 min after injection, showed a reduction in social interaction in adult male rats (Bruins Slot et al., 2005; SamsDodd, 1996, 1998), while less affiliation to a novel cage-mate and more aggressive interaction was observed 20 h after PCP injection using a sub-chronic PCP treatment regime (Audet et al., 2009). Subchronic regimes followed by a larger washout period, however, provide conflicting results. No deficits in social interaction after sub-chronic PCP with a drug-free period of three and nine days
1Division
of Psychiatry and Neuroscience, Queen’s University Belfast, Belfast, UK 2Biomedical Research Centre, Sheffield Hallam University, Sheffield, UK 3School of Medical Sciences, Health Innovations Research Institute, RMIT University, Bundoora, VIC, Australia Corresponding author: Trisha Jenkins, RMIT University, Plenty Road, Bundoora, VIC 3083, Australia. Email: [email protected]
956
Journal of Psychopharmacology 28(10)
was observed in male rats (Egerton et al., 2005; Sams-Dodd, 2004), while in adult female rats impaired social interaction was observed after a one to six week washout period. Within our laboratory we showed no deficit in social interaction 24 h until six weeks after the final PCP injection, but observed social disinhibited behaviour within a male PCP group (Jenkins et al., 2008). Crawley and colleagues have recently developed an updated test of social interaction (Moy et al., 2004). Designed initially to assess autistic-like behaviour in mice, it allows for a focus on a more narrowly defined set of parameters such as reduced social approach, avoidance of unfamiliar social partners and diminished interest in novelty. Although schizophrenia and autism are two clearly individual disorders, they share a significant number of common clinical characteristics including behavioural phenotypes, comorbid symptoms, genetics, epidemiology and neuroimaging findings (Cheung et al., 2010; De Lacy and King, 2013). Furthermore, studies comparing social cognition in autism and schizophrenia have reported highly similar deficits and underlying neural substrates (Couture et al., 2010; Pinkham et al., 2008). Until 2007, no studies had investigated the use of the sociability and social novelty preference paradigm in an animal model of schizophrenia. Using the paradigm, O’Tuathaigh et al. (2007) reported deficits in social interaction behaviours in NRG1 mutant mice, concluding that the paradigm is relevant for assessing processes similar to those known to be disrupted in schizophrenia. To date, no studies using this paradigm have been conducted in rats, despite the fact that they are a highly social species and their social behaviours have been investigated in a range of other models using alternative social interaction paradigms. Thus the present study was designed to ascertain if acute and sub-chronic PCP treatment in male rats produces deficits in sociability and social novelty preference, which may reflect aspects of the negative symptomatology observed in schizophrenia.
behavioural testing began six weeks after the last PCP or saline injection.
Materials and methods
Stage 2: Sociability. Following habituation, an unfamiliar (tar-
Animals
get) rat (stranger1), that had no prior contact with the experimental rat, was placed in one of the side chambers enclosed in an internal wire cage (20 cm×20 cm×15 cm) that allowed nose contact between the bars. An empty, but otherwise identical, wire cage was placed in the opposite chamber. Both doors to the side chambers were then unblocked and the experimental rat was allowed to explore the entire arena for a period of 10 min.
Male Lister Hooded rats, obtained from Harlan, UK, and weighing on average 256 g at the time of first drug administration were used for the behavioural analysis. Animals were housed in groups of 4–5 same treated rats per cage under a 12 h light/dark cycle (lights on at 08:00) with food and water available ad libitum. All behavioural testing was carried out during the light phase. Room temperature (21±2°C) and humidity (45–55%) were kept constant throughout.
Drug administration Rats were assigned to weight-matched groups: Control (n=20) and PCP (n=40). PCP HCl (Sigma, USA) was dissolved in 0.9% saline and administered either acutely intraperitoneally; (i.p.) at doses of 2 mg/kg (n=10) and 5 mg/kg (n=10) or bi-daily (i.p.) (09:00–10:00 and 16:00–17:00), for seven days at doses of 2 mg/ kg (n=10) or 5 mg/kg (n=10). Control animals received vehicle solution (0.9% saline) with the same dosing and volume/weight regime (n=10 for acute study, n=10 for subchronic study). In the acute PCP study, behavioural testing began 30 min after injection of either PCP or saline. For the sub-chronic PCP study,
Behavioural apparatus Testing took place in a room (185 cm×305 cm×285 cm) under 360 lux lighting. The apparatus consisted of a solid, 3 chambered black plastic box (each chamber 21 cm×63 cm×45 cm; total size 63 cm×63 cm×45 cm) which was placed on the floor. Dividing walls were made of clear Plexiglas, with rectangular openings (11 cm×13 cm) allowing access from the centre chamber into the left and right chambers. A DVD camcorder (Samsung, South Korea) was positioned on a moveable trolley directly above the box in order to record behaviour. Between each test, the arena was cleaned with 70% alcohol and fresh sawdust was put down to remove any remaining olfactory cues.
Behavioural protocol The sociability and social novelty preference procedure and analysis method were adapted from those described by (Moy et al., 2004; O’Tuathaigh et al., 2007). The test involves a three-stage procedure consisting of stage 1: habituation, stage 2: sociability and stage 3: social novelty preference. Stranger or ‘target’ rats (n=26) were weight matched to the experimental rats and had each been habituated for 5 min to placement in the wire cage 24 h before testing. The rats serving as strangers and their location in the left vs right side chamber were alternated between trials.
Stage 1: Habituation. The test rat was placed in the middle chamber and allowed to explore this chamber for 5 min. The doorways into each side chamber were obstructed by plastic boxes during this habituation phase.
Stage 3: Social novelty preference. Following stage 2, the experimental rat was immediately returned to the centre chamber and the doors to the side chambers re-blocked. With stranger1 (now familiar) retained in its original chamber, a second, unfamiliar (novel target) rat (stranger2) was placed in the previously empty wire cage in the opposite chamber. Both doors to the side chambers were unblocked and the experimental rat was allowed to explore the entire arena again for a further period of 10 min.
Data collection Each stage of the test was DVD recorded and all DVDs were subsequently analysed by an observer blind to the treatment groups. In both stage 2 and stage 3, time spent in each compartment was measured along with time within nose contact (
JOP0010.1177/0269881114544778Journal of Psychopharmacology 0(0)McKibben et al.
Original Paper
Analysis of sociability and preference for social novelty in the acute and subchronic phencyclidine rat Claire E McKibben1, Gavin P Reynolds1,2 and Trisha A Jenkins1,3
Journal of Psychopharmacology 2014, Vol. 28(10) 955–963 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0269881114544778 jop.sagepub.com
Abstract Both acute and sub-chronic phencyclidine administration produce behavioural and pathophysiological changes that resemble some features of schizophrenia. The present study aimed to determine if acute and sub-chronic phencyclidine treatment in male rats produces deficits in sociability and social novelty preference, which may reflect aspects of the negative symptomatology observed in schizophrenia. Rats were treated with phencyclidine acutely (2 or 5 mg/kg) or subchronically (2 or 5 mg/kg bi-daily for one week followed by a one week wash-out period) or vehicle. Social affiliative behaviour was assessed using the sociability and preference for social novelty paradigm where social interaction time was measured in (a) a chamber containing an unfamiliar conspecific vs an empty chamber (sociability), or (b) a chamber containing an unfamiliar conspecific vs a chamber containing a familiar conspecific (preference for social novelty). Results showed that acute administration of phencyclidine produced a reduction in measures of sociability but had no effect on preference for social novelty while sub-chronic administration of phencyclidine had no effect on sociability or social novelty. This study provides further evidence for the usefulness of phencyclidine models in modelling the symptomatology of schizophrenia.
Keywords Social interaction, social withdrawal, phencyclidine, schizophrenia, negative symptoms
Introduction The delineation of schizophrenia into positive and negative symptoms has been described since the early observations of Kraeplin and Bleuler (Hanson et al., 2010). Recently, the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Development Conference on Negative Symptoms agreed on a set of relevant dimensions of negative symptomatology including blunted affect, alogia, anhedonia, avolition and asociality (Blanchard et al., 2011). Negative symptoms often begin to manifest themselves before the patient experiences their first psychotic episode (Milev et al., 2005), and are associated with poor psychosocial functioning and reduced quality of life (Ho et al., 1998). Currently available treatments for schizophrenia have little to no effect on negative symptoms (Foussias and Remington, 2010; Hanson et al., 2010), with the result that these symptoms continue to disproportionately limit patient recovery. Asociality, which can be considered as a combination of social withdrawal, and lack of social drive, is considered to be one of the most problematic symptoms of schizophrenia. It is present at the premorbid stages of the illness, and persists throughout the entire course of the disease, even during psychosis remission periods (Bellack et al., 1990), and remains inadequately addressed by current pharmacotherapy (Murphy et al., 2006). The development of better animal models and tests to imitate schizophrenia-like asocial behaviour will provide a means for examining potential different pharmacologic approaches.
Social interaction, where an experimental rodent is placed with a novel con-specific rodent of the same species and interactionbehaviour measured (File and Seth, 2003), is one of the most used paradigms to measure social withdrawal in animal models. Administration of the N-methyl-d-aspartate (NMDA) receptor antagonist, phencyclidine (PCP), disrupts social behaviour in rodents using a variety of different methodologies (Gururajan et al., 2010; Jentsch and Roth, 1999; Neill et al., 2010, 2013). Acute exposure to PCP, 45 min after injection, showed a reduction in social interaction in adult male rats (Bruins Slot et al., 2005; SamsDodd, 1996, 1998), while less affiliation to a novel cage-mate and more aggressive interaction was observed 20 h after PCP injection using a sub-chronic PCP treatment regime (Audet et al., 2009). Subchronic regimes followed by a larger washout period, however, provide conflicting results. No deficits in social interaction after sub-chronic PCP with a drug-free period of three and nine days
1Division
of Psychiatry and Neuroscience, Queen’s University Belfast, Belfast, UK 2Biomedical Research Centre, Sheffield Hallam University, Sheffield, UK 3School of Medical Sciences, Health Innovations Research Institute, RMIT University, Bundoora, VIC, Australia Corresponding author: Trisha Jenkins, RMIT University, Plenty Road, Bundoora, VIC 3083, Australia. Email: [email protected]
956
Journal of Psychopharmacology 28(10)
was observed in male rats (Egerton et al., 2005; Sams-Dodd, 2004), while in adult female rats impaired social interaction was observed after a one to six week washout period. Within our laboratory we showed no deficit in social interaction 24 h until six weeks after the final PCP injection, but observed social disinhibited behaviour within a male PCP group (Jenkins et al., 2008). Crawley and colleagues have recently developed an updated test of social interaction (Moy et al., 2004). Designed initially to assess autistic-like behaviour in mice, it allows for a focus on a more narrowly defined set of parameters such as reduced social approach, avoidance of unfamiliar social partners and diminished interest in novelty. Although schizophrenia and autism are two clearly individual disorders, they share a significant number of common clinical characteristics including behavioural phenotypes, comorbid symptoms, genetics, epidemiology and neuroimaging findings (Cheung et al., 2010; De Lacy and King, 2013). Furthermore, studies comparing social cognition in autism and schizophrenia have reported highly similar deficits and underlying neural substrates (Couture et al., 2010; Pinkham et al., 2008). Until 2007, no studies had investigated the use of the sociability and social novelty preference paradigm in an animal model of schizophrenia. Using the paradigm, O’Tuathaigh et al. (2007) reported deficits in social interaction behaviours in NRG1 mutant mice, concluding that the paradigm is relevant for assessing processes similar to those known to be disrupted in schizophrenia. To date, no studies using this paradigm have been conducted in rats, despite the fact that they are a highly social species and their social behaviours have been investigated in a range of other models using alternative social interaction paradigms. Thus the present study was designed to ascertain if acute and sub-chronic PCP treatment in male rats produces deficits in sociability and social novelty preference, which may reflect aspects of the negative symptomatology observed in schizophrenia.
behavioural testing began six weeks after the last PCP or saline injection.
Materials and methods
Stage 2: Sociability. Following habituation, an unfamiliar (tar-
Animals
get) rat (stranger1), that had no prior contact with the experimental rat, was placed in one of the side chambers enclosed in an internal wire cage (20 cm×20 cm×15 cm) that allowed nose contact between the bars. An empty, but otherwise identical, wire cage was placed in the opposite chamber. Both doors to the side chambers were then unblocked and the experimental rat was allowed to explore the entire arena for a period of 10 min.
Male Lister Hooded rats, obtained from Harlan, UK, and weighing on average 256 g at the time of first drug administration were used for the behavioural analysis. Animals were housed in groups of 4–5 same treated rats per cage under a 12 h light/dark cycle (lights on at 08:00) with food and water available ad libitum. All behavioural testing was carried out during the light phase. Room temperature (21±2°C) and humidity (45–55%) were kept constant throughout.
Drug administration Rats were assigned to weight-matched groups: Control (n=20) and PCP (n=40). PCP HCl (Sigma, USA) was dissolved in 0.9% saline and administered either acutely intraperitoneally; (i.p.) at doses of 2 mg/kg (n=10) and 5 mg/kg (n=10) or bi-daily (i.p.) (09:00–10:00 and 16:00–17:00), for seven days at doses of 2 mg/ kg (n=10) or 5 mg/kg (n=10). Control animals received vehicle solution (0.9% saline) with the same dosing and volume/weight regime (n=10 for acute study, n=10 for subchronic study). In the acute PCP study, behavioural testing began 30 min after injection of either PCP or saline. For the sub-chronic PCP study,
Behavioural apparatus Testing took place in a room (185 cm×305 cm×285 cm) under 360 lux lighting. The apparatus consisted of a solid, 3 chambered black plastic box (each chamber 21 cm×63 cm×45 cm; total size 63 cm×63 cm×45 cm) which was placed on the floor. Dividing walls were made of clear Plexiglas, with rectangular openings (11 cm×13 cm) allowing access from the centre chamber into the left and right chambers. A DVD camcorder (Samsung, South Korea) was positioned on a moveable trolley directly above the box in order to record behaviour. Between each test, the arena was cleaned with 70% alcohol and fresh sawdust was put down to remove any remaining olfactory cues.
Behavioural protocol The sociability and social novelty preference procedure and analysis method were adapted from those described by (Moy et al., 2004; O’Tuathaigh et al., 2007). The test involves a three-stage procedure consisting of stage 1: habituation, stage 2: sociability and stage 3: social novelty preference. Stranger or ‘target’ rats (n=26) were weight matched to the experimental rats and had each been habituated for 5 min to placement in the wire cage 24 h before testing. The rats serving as strangers and their location in the left vs right side chamber were alternated between trials.
Stage 1: Habituation. The test rat was placed in the middle chamber and allowed to explore this chamber for 5 min. The doorways into each side chamber were obstructed by plastic boxes during this habituation phase.
Stage 3: Social novelty preference. Following stage 2, the experimental rat was immediately returned to the centre chamber and the doors to the side chambers re-blocked. With stranger1 (now familiar) retained in its original chamber, a second, unfamiliar (novel target) rat (stranger2) was placed in the previously empty wire cage in the opposite chamber. Both doors to the side chambers were unblocked and the experimental rat was allowed to explore the entire arena again for a further period of 10 min.
Data collection Each stage of the test was DVD recorded and all DVDs were subsequently analysed by an observer blind to the treatment groups. In both stage 2 and stage 3, time spent in each compartment was measured along with time within nose contact (
