Effects of typical and atypical antipsychotic drugs on maternal behavior in postpartum female rats

Schizophrenia Research 70 (2004) 69 – 80 www.elsevier.com/locate/schres

Effects of typical and atypical antipsychotic drugs on maternal behavior in postpartum female rats Ming Li a, Patty Davidson b, Radek Budin b, Shitij Kapur a,c,*, Alison S. Fleming b a

Centre for Addiction and Mental Health, The Clarke Division of CAMH, PET Centre, Clarke Site, 250 College Street, Toronto, Ontario, Canada M5T 1T8 b Department of Psychology, University of Toronto, Canada c Department of Psychiatry, University of Toronto, Canada Received 1 August 2003; received in revised form 15 September 2003; accepted 28 September 2003 Available online 1 December 2003

Abstract Understanding the effects of antipsychotic drugs (APDs) on social behaviors such as maternal behavior is valuable for understanding the complete spectrum of therapeutic and side-effects of antipsychotics. Although previous studies have suggested that typical antipsychotics impair maternal behavior, the effects of the atypical antipsychotics have not been systematically explored. The purpose of the present report was to examine the effects of typical (haloperidol, HAL) and several atypical (clozapine, CLZ; risperidone, RIS; quetiapine, QUE) antipsychotics on maternal behavior in female rats. Maternal behaviors were examined repeatedly over a period of 24 h after a single injection of a range of doses of HAL, CLZ, RIS or QUE on Day 6 postpartum. All antipsychotic drugs, typical or atypical, elicited a qualitatively similar disruptive effect on the active components of maternal behavior such as pup approach, pup retrieval and nest building at clinically relevant doses. However, HAL caused a prolonged disruption, whereas CLZ, RIS and QUE induced an early onset but shorter duration disruption. In addition, only the atypical antipsychotics showed some inhibitory effects on nursing behavior, possibly due to sedative sideeffects shared by all atypical antipsychotics. The current generation of atypical antipsychotics shows a disruptive influence on maternal behavior similar to that of the typical antipsychotics. This effect may be intrinsic to antipsychotic activity or may be reflective of a side-effect. Since the latter is more likely, this may be an effect to avoid in the design of future antipsychotics. D 2003 Published by Elsevier B.V. Keywords: Haloperidol; Clozapine; Risperidone; Quetiapine; Maternal behavior; Rat

1. Introduction Animal models are extensively used to investigate behavioral effects of antipsychotic drugs (APDs). The * Corresponding author. Centre for Addiction and Mental Health, The Clarke Division of CAMH, PET Centre, Clarke Site, 250 College Street, Toronto, Ontario, Canada M5T 1T8. Tel.: +1416-535-8501x4361; fax: +1-416-979-4656. E-mail address: [email protected] (S. Kapur). 0920-9964/$ - see front matter D 2003 Published by Elsevier B.V. doi:10.1016/j.schres.2003.09.013

most commonly used animal models, such as conditioned avoidance response, prepulse inhibition or latent inhibition, are simple and have a high predictive validity, yet, they are ethologically artificial mechanistic behaviors and may not well reflect the complex and multi-dimensional actions of APDs on affective, cognitive and social functions. Thus, there is a need to move the study of antipsychotic effects in animals to encompass the analysis of more complex and natural

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social behaviors. In fact, such a line of research has captured some attention recently as social behavior deficits induced by phencyclidine treatment have been proposed to be a valid model of positive and negative symptoms of schizophrenia and can be used to evaluate the efficacies of APDs (Sams-Dodd, 1998a,b, 1999). Maternal behavior provides another valuable social interaction model with high ecological validity for the study of APDs. In the past, studies have examined the effects of typical APDs like haloperidol (HAL) and raclopride on the expression of maternal behavior, mainly from the point of view of elucidating the role of the dopamine system in maternal behavior. Giordano et al. (1990) found that HAL dose-dependently inhibited pup retrieval and nest building, but not nursing and pup licking. Hansen et al. (1991) showed that raclopride administered to postpartum female mothers also significantly inhibited pup retrieval but not nursing. A similar effect of HAL on pup retrieval was reported by Stern and Taylor (1991). The primary purpose of the present study was to further investigate the behavioral effects of various APDs on maternal behavior in postpartum female rats using several recently developed atypical APDs and to compare their effects with the typical APD haloperidol. The effects of clozapine (CLZ) and other atypical APDs on rat maternal behavior have not been systematically explored and whether they would show similar effects as haloperidol is not known. However, this issue is of considerable importance because (a) atypical APDs have replaced typical APDs in terms of being agents of choice for the treatment of schizophrenia; (b) atypical APDs (except at extremely high doses) do not give rise to catalepsy in rats (Kapur et al., 2003; Nielsen et al., 1997) and this correlates with a lack of extrapyramidal symptoms (EPS, Parkinsonlike motor impairment) in patients (Hoffman and Donovan, 1995), therefore, it is a possibility that atypical APDs are devoid of a disruptive influence on maternal behavior; (c) the receptor pharmacology of the atypicals differs from that of typical APDs (Jibson and Tandon, 1998; Kapur and Remington, 2001), especially haloperidol, which primarily binds to DA D2 receptors. Most of atypical APDs, however, are high 5-HT2A and low D2 antagonists (Jibson and Tandon, 1998). Because this has been suggested to reduce EPS and negative symptoms (Meltzer et al.,

1989)—it could provide a basis for differential effects on maternal behavior. Besides its importance in providing insights on the basic behavioral functions of APDs, studying behavioral effects of APDs on maternal behavior may have a direct and immediate implication. With the new generation of APDs, which do not produce sustained hyperprolactinemia, there has been an increase in the trend of schizophrenic women becoming first-time mothers. Clinical observations show that schizophrenic mothers exhibit more negative emotional responses and less social contact toward their infants than do healthy mothers (McNeil et al., 1985; Naslund et al., 1985; Persson-Blennow et al., 1984, 1986). Since it is hard to conduct systematic clinical trials in this population, little is known about whether APDs help or exacerbate these deficits. Because maternal behavior shares many direct features across species (Fleming and Corter, 1988; Rosenblatt, 1989), the study of the effects of atypical APDs on maternal behaviors may help generate some ideas regarding this clinical situation.

2. Materials and methods 2.1. Subjects and housing Subjects were 60- to 100-day-old virgin female Sprague – Dawley rats, weighing 250 – 380 g. They were reared and mated at Department of Psychology, University of Toronto at Mississauga, from a stock originally obtained from Charles River, St. Denis, Quebec, Canada. The animals were housed individually in opaque plastic cages (47 L  26 W  20 H cm) with food (Purina Rat Chow) and tap water ad lib. Wood shavings were provided for bedding. Subjects were maintained on a day– night cycle of 12:12 (lights on at 8:00 am) and room temperature was kept at 22 jC and humidity was controlled at 45 – 55%. All procedures were approved by the animal care committee at University of Toronto at Mississauga. 2.2. Groups and choice of doses In an antipsychotic comparison study, dose selection is absolutely crucial. Inappropriate dose choices can lead to misinterpretation of the data and wrong

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conclusions (Kapur et al., 2000a). Therefore, we chose our doses based on the following considerations: (i) chosen doses must provide in animals receptor occupancies comparable to those observed in patients (Kapur et al., 2003); (ii) doses of HAL, CLZ, risperidone (RIS) and quetiapine (QUE) must be active in the conditioned avoidance response model—a model which has high predictive validity for APDs’ clinical potencies (Wadenberg et al., 2000); (iii) the range of doses must cover subclinical, as well as supra-therapeutic doses. PET studies in human patients have suggested that a reliable antipsychotic effect of any APDs requires at least 65% of D2 occupancy, whereas the EPS begins when D2 occupancy reaches 80% (Farde et al., 1992; Kapur et al., 1999, 2000b). Animal research has also found that D2 occupancy at around 70% elicits conditioned avoidance responding deficits (an indication of an antipsychotic effect), whereas D2 occupancy greater than 80% leads to catalepsy (Wadenberg et al., 2000), suggesting the thresholds for the clinical potency (65 – 70%) and for EPS (greater than 80%) in humans are comparable to those in animals. Guided by these two thresholds, we selected the doses of 0.02, 0.1 and 0.2 mg/kg of HAL, 2, 10, and 20 mg/kg of CLZ, 0.2, 0.8, and 2 mg/kg of RIS, and 5, 25, and 50 mg/kg of QUE; this reflects the subclinical through to the high-end of clinical doses (Kapur et al., 2003), and this selection also enables us to evaluate different drugs on a common ground. One hundred and two female rats were assigned to 13 groups: HAL-0.2 mg/kg (n = 12), HAL-0.1 mg/kg (n = 8), HAL-0.02 mg/kg (n = 8), CLZ-20 mg/kg (n = 8), CLZ-10 mg/kg (n = 12), CLZ-2 mg/kg (n = 8), RIS-2.0 mg/kg (n = 8), RIS-0.8 mg/kg (n = 8), RIS-0.2 mg/kg (n = 8), QUE-50 mg/kg (n = 8), QUE25 mg/kg (n = 8), QUE-5 mg/kg (n = 8) and vehicle (n = 28, in which 18 were injected with 0.9% saline as controls for HAL, RIS and QUE groups, and 10 were injected with a 1% of glacial acetic acid saline as CLZ controls). The subjects were run in five batches, and each batch contained at least one vehicle control group (n z 4) and two drug groups (n z 8). The effects of HAL and CLZ on maternal behavior were assessed first, followed by tests on RIS and QUE. During each test day, a maximum of three subjects were tested. They were randomly assigned to either the drug or vehicle groups. Since there were no statistically reliable differences, on any measure between saline-trea-

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ted and 1% acetic-acid saline controls, and between vehicle groups in each batch, we chose to combine all vehicle groups for added statistical power in our analysis. 2.3. Drug injections HAL (0.02, 0.1, and 0.2 mg/kg/sc), CLZ (2, 10 and 20 mg/kg/sc), RIS (0.2, 0.8, and 2 mg/kg/sc) and QUE (5, 25, and 50 mg/kg/ip) were dissolved in 0.4 ml of vehicle. Solutions of HAL (5 mg/ml, Sabex, Boucherville, Canada), RIS (Sigma, St. Louis, USA) and QUE (ICI 204,636) (Zeneca Pharmaceuticals, Macclesfield, Cheshire, England) were obtained by diluting the stock with 0.9% of saline. Solution of CLZ (Anawa Biomedical Services and Products, Zurich, Switzerland) was obtained by dissolving the drug powder with 1% glacial acetic acid of saline solution. 2.4. Procedure All subjects were placed into the cage of a proven stud male for a week to ensure the pregnancy. Starting 2 or 3 days before first possible expected parturition date, the parturition was monitored every morning. Once the dam was found with pups in the morning (that day was designated as Day 1 postpartum), she was transferred into a large translucent maternal observation cage (51 L  40.5 W  21 H cm) with wood shavings for bedding. Two shredded paper towels were also provided for nesting material. The litter size was culled to six pups (the ones that had most visible milk bands were retained in the litter). On Day 4 postpartum, all subjects were changed to clean observation cages with their litters. Two shredded paper towels were also added. On Day 6 postpartum, nursing and pup retrieval behavior tests were conducted six times throughout the day, with the first one beginning at 0.5 h before the drug injections, and the rest being carried out at 0.5, 1, 2, 4 and 6 h after the drug injections. The last nursing and pup retrieval behavior tests were conducted at 24 h after the drug injections (Day 7 postpartum). 2.5. Maternal behavior tests On Day 6 or 7 (for 24-h time point) postpartum, maternal behavior tests were conducted. Each test

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consisted of two phases. The first one was a 5-min nursing behavior observation. Using a 0/1 manual time sampling procedure, the frequency of nursing behavior (a rat positioned herself over the pups with a pronounced dorsal arch and with legs splayed to accommodate the pups, including high and low crouching over postures) was recorded every 5 s for 5 min with ‘‘1’’ indicating the presence of nursing and ‘‘0’’ indicating the absence. The quality of the nest was also rated according to the following scale: 0: no nest, paper remains scattered over the floor of the cage; 1: little nest, only a couple of paper strips are used; 2: poor nest, not all the paper is used, and the nest consists of a flat pad of paper strips; 3: fair nest, all paper is used but a flat nest is built; 4: good nest, all paper is used and the nest has low walls; 5: excellent nest, all paper is used and the nest has high walls. The second phase was a 5-min pup retrieval behavior test starting immediately after the nursing behavior test. It was initiated by taking the pups away from the subject, and disrupting the nest. Ten seconds later, all six pups were placed at one corner of the cage diagonally opposite to the test female’s nest site, and the latencies of approaching the pups were recorded. When a subject picked a pup up in her mouth carried it to a different ‘‘quadrant’’ of the large observation cage, it was referred as a successful ‘‘pup retrieval’’ (The 300 s was assigned to non-responders who did not approach or retrieve the testing pups). The total number of pups retrieved was recorded. The occurrence of following behaviors was also recorded on a 0/ 1 time sampling sheet with 5-s intervals for a continuous 5 min (60 intervals in total): sniffing pups (a rat poked her snout close to or touch on pups), grooming (self-licking any part of the body), and nest building (a rat picked up nesting material in her mouth and transported back to the nest site or pushed the material with her forepaws toward the nest site). After each retrieval test, unretrieved pups were returned to the nest site. 2.6. Statistical analysis As many of the behaviors were non-normally distributed, the frequency data of various maternal activities and the latency to display various maternal behaviors between drug-treated and vehicle-treated groups were analyzed using the nonparametric Krus-

kall – Wallis Test. Once the overall significant effects were found, two group comparisons between the drug group and vehicle group were performed using Mann – Whitney U-test. Statistical significance was accepted at p < 0.05, two-tailed. All animals were entered in the analyses for the pup approach, pup retrieval, nest building and nursing behaviors except that five animals from the HAL-0.2 and CLZ-10 mg/ kg groups and seven from the vehicle group were not recorded for the nest building behaviors. Thus, for the nest building, the numbers of animals in these groups were: HAL-0.2 mg/kg (n = 7), CLZ-10 mg/kg (n = 7) and vehicle (n = 21).

3. Results 3.1. Latency to approach pups Table 1 illustrates the effects of various doses of HAL, CLZ, RIS and QUE on pup approach latency in postpartum 6 – 7-day lactating rats. Pup approach was inhibited in all drug-treated animals in a dose-dependent and time-dependent manner (all p < 0.001). In comparison to the vehicle treatment, HAL at the lowest dose (0.02 mg/kg) had little effect on the pup approach latency (all p’s>0.08, except at the 2-h point, when the vehicle rats approached pups slower than the 0.02 HAL rats, p = 0.044). At the 0.1 mg/kg, its effect started at 2 h (U = 41.5, p = 0.006), then lasted for another 2 h (U = 39.0, p = 0.004). At the highest dose (0.2 mg/kg), its inhibitory effects started even earlier (at 0.5 h after drug injection, U = 90.0, p = 0.021) and lasted much longer (up to 6 h) (U = 4.0, p < 0.001). Atypical APDs as a group, on the other hand, showed an early-onset and short-lasting effect on pup approach. For example, the medium doses of CLZ (10 mg/kg), RIS (0.8 mg/kg) and QUE (25 mg/ kg) exhibited an inhibitory effect as early as 0.5 h after drug injection and this effect lasted about 4 h (for QUE, this only lasted about 2 h). However, unlike the high dose of HAL (0.2 mg/kg), high doses of all atypicals except RIS all lost their suppressive effects on pup approach at the 6-h point. RIS at the high dosage level only slightly increased the pup approach latency at the 6-h point, although this effect was still significantly less severe than that of HAL (0.2 mg/kg) ( p < 0.004).

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Table 1 Effects of HAL, CLZ, RIS and QUE on the pup approach latency in postpartum female rats Groups

N

Pup approach latency (median + interquartile range) 0.5 h

HAL-0.20 HAL-0.10 HAL-0.02 CLZ-20.0 CLZ-10.0 CLZ-2.0 RIS-2.0 RIS-0.8 RIS-0.2 QUE-50.0 QUE-25.0 QUE-5.0 VEHICLE

12 8 8 12 8 8 8 8 8 8 8 8 28

1.0 (3.3) 9.0 (18.8) 3.5 (27.8) 4.5 (7.3) 4.0 (5.3) 3.0 (3.8) 5.5 (10.3) 5.5 (9.0) 6.0 (8.5) 13.0 (42.3) 5.0 (12.8) 0.0 (4.5) 4.36 (14.5)

0.5 h

1h

2h

4h

6h

24 h

10.0* (16.8) 1.5 (24.3) 0.0 (3.3) 189.5* (291.5) 204.0* (279.0) 14.5* (227.8) 300* (300.0) 59.5* (244.3) 28.5 (245.8) 300* (0.0) 300* (280.0) 0.0 (16.5) 1.5 (6.8)

51.5* (78.3) 2.0 (23.8) 1.0 (9.5) 300* (204) 275.0* (272.3) 5.0* (33.3) 300* (0.0) 188.5* (263.3) 46.0 (245.8) 300* (0.0) 300* (0.0) 7.0 (23.0) 1.0 (1.8)

132.5* (275.5) 35.5* (275) 0.0 (0.8) 300* (296.8) 265.5 (299.5) 3.5 (19.8) 300* (211.5) 117.5* (235.8) 5.0 (9.0) 64.0* (285.0) 72.5* (85.8) 0.5 (8.0) 2.0 (5.5)

270.0* (274.3) 31.5* (294.8) 0.0 (0.8) 18.0* (83.8) 6.5* (53.8) 2.0 (12.8) 47.0* (101.8) 12.5* (39.3) 3.5 (12.8) 8.5 (48.5) 3.0 (10.5) 0.0 (9.5) 1.0 (2.0)

201.0* (229.5) 43.0 (250.5) 0.0 (1.8) 5.5 (11.3) 2.5 (16.0) 1.5 (3.5) 11.5* (31.8) 5.0 (14.5) 5.0 (11) 6.5 (3.5) 1.0 (14.3) 0.0 (6.8) 2.5 (5.8)

1.0 1.5 0.5 1.5 2.0 0.0 2.0 4.0 2.0 3.0 3.0 0.0 2.0

(6.8) (7.0) (4.0) (5.0) (7.5) (3.8) (2) (9.3) (2.0) (26.0) (13.0) (4.8) (7.8)

Behavior was evaluated in the 6- to 7-day postpartum lactating female rats. Data are reported as median frequency + interquartile range. * Significantly different compared to the vehicle group ( p < 0.05) using Mann±Whitney U-test.

Statistical comparisons between drugs are only meaningful when different drugs are compared at an ‘‘equivalent’’ effective dosage level. Our dose selective criteria enabled us to achieve this in the present study. We selectively compared the effects of the medium dose of each drug (HAL-0.1 mg/kg, CLZ-10 mg/kg, RIS-0.8 mg/kg and QUE-20 mg/kg), which represents a clinically relevant dosage level in animal research (Kapur et al., 2000a, 2003), on maternal behavior. Statistical results revealed a similar temporal difference between typical HAL and atypicals CLZ, RIS and QUE. First of all, no significant difference on pup approach latency was found between CLZ, RIS and QUE ( p < 0.05). Second, HAL differed from each of the atypical APDs (CLZ, RIS and QUE) at the 0.5- and 1-h testing points ( p>0.05), with HAL rats showing a much faster pup approach response than the atypicaltreated rats at these two time points, suggesting that at the early stages of testing, atypicals had a stronger inhibitory effect on pup approach than did HAL. 3.2. Retrieval of pups As shown in Fig. 1, pup retrieval was significantly impaired in animals treated with the medium and high doses of APDs, but not the low doses (for the high and medium doses, all p < 0.001; for the low doses, all p>0.428). Mother rats injected with 0.1 and 0.2 mg/kg of HAL retrieved fewer pups at 1 h, 2 h, 4 h and 6

h after drug injection (all p < 0.006), but not at 24 h after injection (all p>0.4). A total of 10 and 20, but not 2 mg/kg CLZ, significantly inhibited the number of pups retrieved at 0.5, 1, and 2 h after drug injection (all p < 0.05). The inhibitory effect of 10 mg/kg CLZ was still apparent 4 h after drug injection (U = 84.0, p = 0.012), but not at 6 h after injection (U = 140.00, p = 0.422). RIS and QUE, like CLZ, showed a transient disruptive effect on pup retrieval. Their inhibition on pup retrieval lasted no more than 4 h even at the high doses. This was in contrast to the HAL’s prolonged effect (more than 6 h) ( p < 0.001). This prolonged effect was also apparent when between drug comparisons were conducted. HAL’s (0.1 mg/kg) disruption on pup retrieval persisted up to 6 h, differing significantly from CLZ (10 mg/kg) at the 6-h point, and from RIS (0.8 mg/kg) and QUE (25 mg/kg) at the 4- and 6-h points. However, at the 0.5and 1-h points, CLZ and QUE-induced pup retrieval deficits were more severe than that of HAL, suggesting that an early-onset effect is exhibited by atypical APDs. No significant difference was found between CLZ and RIS, and the differences between CLZ and QUE and between RIS and QUE were only found at one testing point (2 and 0.5 h, respectively), indicating that as a group, atypicals generally do not differ from one another with regards to their disruptive effects on pup retrieval when they are compared at a clinically comparable dosage level.

74 M. Li et al. / Schizophrenia Research 70 (2003) 69–80 Fig. 1. The number of pups retrieved (median + interquartile range) during the 5-min testing period in various doses of HAL (A), CLZ (B), RIS (C) and QUE (D) treated groups. *p < 0.05 versus VEH group (Mann – Whitney U-test).

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Fig. 2. Effects of various doses of HAL (A), CLZ (B), RIS (C) and QUE (D) on nest building activity (median + interquartile range) in postpartum 6 – 7-day lactating rats. All antipsychotics dose-dependently decreased the time spent on nest building. *p < 0.05 versus VEH group (Mann – Whitney U-test).

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3.3. Nest building The maternal behavior that was most severely impaired by the action of ADPs was nest building. Both typical and atypicals (except for RIS) produced a dose-dependent decrease on nest building activity (Fig. 2) and impaired the quality of the nest (data not shown, all p < 0.001). The effects of HAL were seen with the 0.1 mg/kg dose, at which dosage level, the treated animals spent less time on nest building up to 6 h after injection ( p < 0.001). The highest dose of HAL (0.2 mg/kg) had such profound and depressing effect on nest building activity, even 24 h after drug injection, this activity remained low (U = 15.00, p = 0.001). The three doses of CLZ and RIS employed here all showed significant impairment effects on nest building behavior at 0.5, 1, 2 and 4 h after drug injection (all p < 0.05). Animals treated with 20 mg/kg CLZ and 2.0 mg/kg RIS exhibited less nest building even 6 h after drug injection (for CLZ, U = 29.5, p = 0.006; for RIS, U = 21.5, p = 0.001). QUE, on the other hand, showed less of a disruptive effect compared to comparable doses of CLZ and RIS. The time range of QUE’s inhibitory action appeared at 0.5 h after drug injection and lasted about 2 h ( p < 0.009). This occurred for all three doses. Between drugs comparisons also indicated that the nest building impairment induced by QUE (25 mg/kg)

was less severe compared to those induced by the corresponding HAL (0.1 mg/kg), CLZ (10 mg/kg) and RIS (0.8 mg/kg) (all p < 0.05) injections. For instance, at the 4-h point, QUE differed significantly from all other antipsychotics (all p < 0.015). The differences between typical HAL and atypicals mainly occurred at the 6-h point, when the effects from CLZ, RIS and QUE were returned to the control levels, whereas HAL continued to significantly suppressed nest building activity, indicative of a prolonged effect. 3.4. Nursing behavior As shown in Table 2, there were no consistent effects among the different drug conditions on nursing behavior; some drugs produced effects, others did not. For example, none of the HAL groups showed an effect, while CLZ (10 mg/kg) suppressed nursing at 0.5 h (U = 95.5, p = 0.031) and RIS (2.0 mg/kg) suppressed nursing at 1 h (U = 45.0, p = 0.009). All doses of QUE showed similar transiently inhibitory effects on nursing duration in a dose-independent fashion, at 0.5 and 1 h after drug injection ( p < 0.037). Among all of these APDs, QUE (25 mg/kg) seems to be the most potent. It differed from other APDs at the 0.5- and 1h points (all p < 0.039), whereas the other APDs did not differ from each other with the exception of a difference between HAL (0.1 mg/kg) and CLZ (10 mg/kg) at the 0.5-h point ( p = 0.025).

Table 2 Effects of HAL, CLZ, RIS and QUE on the frequency of nursing behavior in postpartum female rats Groups

N

Frequency of nursing behavior (median + interquartile range)

HAL-0.20 HAL-0.10 HAL-0.02 CLZ-20.0 CLZ-10.0 CLZ-2.0 RIS-2.0 RIS-0.8 RIS-0.2 QUE-50.0 QUE-25.0 QUE-5.0 VEHICLE

12 8 8 12 8 8 8 8 8 8 8 8 28

60.0 57.5 53.0 54.5 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0

0.5 h (0) (50.5) (41.8) (52.8) (0) (0) (0) (0) (45.8) (11.3) (0) (3.8) (0)

0.5 h

1h

2h

60.0 (0) 60.0 (0) 60.0 (30.8) 49.0 (60) 17.5* 60.0 (45) 60.0 (60) 60.0 (60) 41.5 (60) 0.0* (0) 0.0* (0) 36.5* (54.3) 60.0 (23.8)

60.0 (0) 60.0 (41.8) 59.0 (40.3) 7.5 (60) 56.5 (29.5) 30.0 (60) 0.0* (45) 60.0 (0) 52.0 (54.3) 0.0* (32.8) 0.0* (25.5) 29.5* (48.3) 60.0 (20)

60.0 60.0 60.0 0.0 45.5 60.0 0.0 60.0 60.0 60.0 52.0 60.0 60.0

4h (0) (0) (27) (60) (45.8) (0) (60) (0) (33) (60) (50.5) (48.3) (39.5)

60.0 60.0 60.0 60.0 60.0 60.0 30.0 60.0 60.0 60.0 60.0 60.0 60.0

6h (60) (0) (0) (46.8) (13.5) (7.5) (60) (55.8) (60) (46) (45) (0) (12)

60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0

24 h (0) (0) (0) (45) (21) (0) (0) (0) (0) (0) (0) (0) (0)

60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 60.0 56.5 60.0 60.0 60.0

(0) (0) (5.3) (45) (0) (0) (0) (0) (0) (29.3) (3.8) (3) (0)

Behavior was evaluated in the 6- to 7-day postpartum lactating female rats. Data are reported as median frequency + interquartile range. * Significantly different compared to the vehicle group ( p < 0.05) using Mann – Whitney U-test.

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4. Discussion The present study demonstrates that both typical and atypical APDs have a qualitatively similar, though temporally distinct, disruptive effect on active components of maternal behavior such as pup approach, pup retrieval and nest building at clinically relevant doses. Our results are consistent with those of earlier investigations on the disruptive effects of dopamine antagonists on maternal behavior (Giordano et al., 1990; Hansen et al., 1991; Silva et al., 2001; Stern and Taylor, 1991). However, with regard to the durations of this disruption, no consensus has been reached. For example, Giordano et al. (1990) found that 0.1 mg/kg haloperidol inhibited pup retrieving for 1.5 h, whereas Silva et al. (2001) found the same dose of HAL inhibited pup retrieving for more than 3 h. In the current study, we found that this inhibition lasted about 6 h. The difference could be at least partially attributed to the fact that different pup retrieval measures were used in these studies. The previous studies used ‘‘the number of subjects retrieved pups’’ as the measure of pup retrieving. In our study, we used ‘‘the number of pups retrieved’’. It seems that this measurement was more sensitive than others. This is the first report that examined the newer atypical APDs risperidone and quetiapine on maternal behavior. It is also the first one which allows one to effectively evaluate and compare different APDs’ as they were administered in dose ranges that are representative of their clinical doses (Kapur et al., 1999, 2000a, 2003; Wadenberg et al., 2000). We reported that all APDs examined in this study disrupt maternal behavior. Another important finding was that the temporal characteristics of the action of HAL (a typical antipsychotic) and RIS/QUE/CLZ (all atypical antipsychotics) were different. Since we had only one typical antipsychotic, it is unclear if this is a class difference (i.e. typical vs. atypical) or whether it is a peculiarity of haloperidol. In all likelihood, this difference may reflect the distinct temporal binding profiles of D2 receptor binding between haloperidol and the other drugs, rather than some other fundamental differences (Kapur and Seeman, 2000; Meltzer et al., 1989; Seeman, 2000). It has been shown that after an acute administration (in non-pregnant animals), haloperidol shows prolonged D2-related thera-

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peutic effects and side-effects, whereas the effects of RIS/QUE/CLZ tend to be more transient (Burki, 1986; Campbell and Baldessarini, 1985; Saller and Salama, 1993). On the other hand, the 5-HT2A property of the atypicals is credited as being responsible for diminishing the motor side-effects of these atypicals (Lucas et al., 1997; Neal-Beliveau et al., 1993)— thus, it is conceivable that the combined 5-HT2A/D2 blockade may provide some protection from the disruption of maternal behavior. However, the latter explanation seems unlikely because (1) the magnitude of the disruption at peak was similar for typical versus atypical APDs, although HAL has a low affinity for the 5-HT2A receptor systems; (2) the serotonin systems in general are found to be not critical for maternal behavior (Brunner et al., 1999; Lonstein et al., 2003). Prepartum and postpartum depletions of 5HT were without effect on maternal behavior per se, but might affect the expression of this behavior by interfering with suckling-induced prolactin release (Barofsky and Harney, 1978; Barofsky et al., 1983; Rowland et al., 1978). An alternative explanation for these early onset and transient disruptive effect of acute administration of the atypical APDs is that they may have fast-onset short-lasting sedative side-effects (in contrast to haloperidol), due to their actions on histamine H1 receptors and/or adrenergic receptors. However, risperidone, at least in clinical trials, does not show more sedation than haloperidol, yet it too had early disruptive effects on maternal behavior. Nonetheless, since sedation was not specifically and independently measured, we cannot rule out this possibility and this issue will be addressed in future studies. One way to resolve this issue may be to compare atypicals’ effects on maternal behavior to those of other sedative-hypnotic agents at the doses which produce the same degree of sedation as CLZ/RIS/QUE. Since maternal behavior has motivational as well as motor components, and given that APDs (at least the typical APDs) are known to produce motor deficits, it raises the question of whether the findings presented here are merely motor deficits. Several findings suggest that the effect we observed is not just a motor deficit: First, postpartum mother rats treated with even 0.2 mg/kg HAL are able to pick up food pellets and carry them back to the nest (Giordano et al., 1990), suggesting that pup retrieval

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and nest building deficits are observed in the presence of preserved motor and oral-manipulation behaviors (Giordano et al., 1990). Second, in our hands and those of others, HAL at 0.10 mg/kg does not produce catalepsy (De Ryck et al., 1982; Wadenberg et al., 2000), but it did produce maternal deficits, suggesting that this measure is not merely another manifestation of catalepsy. Third, atypicals such as CLZ, RIS and QUE are well known for their lack of effect on catalepsy, especially at the doses employed in our study (Kapur et al., 2003). Yet, in the current study, CLZ, RIS, and QUE-treated rats approached pups more slowly, retrieved fewer pups, and displayed less nest-building activity than vehicle rats. While we think it is unlikely that the observed deficits are just another manifestation of catalepsy-like extrapyramidal motor deficits, a more subtle form of motor dysfunction may be a contributory mechanism for these effects. Studies employing special measures of subtle motor dysfunction will be needed to resolve this question. It has been shown that DA deficiencies induced by either 6-OHDA lesions of the mesolimbic DA systems or DA antagonists infused into the nucleus accumbens give rise to deficits specifically in maternal motivation, but not maternal performance (Hansen, 1994; Stern and Keer, 1999). These findings are consistent with the hypothesis that the mesolimbic DA system is critical for the translation of ‘‘motivational-emotional’’ commands of behavior into ‘‘actions’’ (Mogenson et al., 1980). Based on these findings, we propose that the disruptive influence of APDs on maternal behavior may arise from their effects on the mesolimbic dopamine system which inhibit the translation of motivation-into-action. Since even atypical APDs block dopamine D2 receptors, and it has been shown that the clinical doses of even atypical APDs are best predicted by their D2 binding affinities (rather than 5HT2 or any other receptor activity) (Kapur and Seeman, 2001), it is possible that atypicals produce maternal behavior deficits through blocking D2 receptors in the nucleus accumbens. In fact, Keer and Stern (1999) have already shown cis-flupenthixol (a mixed DA D1 and D2 receptor antagonist) infused directly into the nucleus accumbens disrupts pup retrieval. Further studies should examine whether atypicals infused into the nucleus accumbens would also disrupt maternal behavior.

The current study has implications for our thinking about the effects of APDs on maternal motivation in humans. Schizophrenic mothers (usually treated with APDs) show less positive emotional responses, and less social contact toward their infants than do healthy mothers (McNeil et al., 1985; Naslund et al., 1985; Persson-Blennow et al., 1984, 1986). The current findings raise the question whether these clinically observed deficits are, at least partly, due to the APDs disruptive effects on maternal behavior. Of course, more studies are needed in order to tease apart the influences of schizophrenic symptoms and the intrinsic effects of APDs on human maternal behavior. At a more general level, APDs are often implicated in the induction of a ‘‘neuroleptic-induced deficit syndrome’’ (NIDS) or the so-called neuroleptic-induced negative symptoms (Awad, 1993; Awad and Hogan, 1994) which manifests itself as poverty of speech, flattened affect, loss of drive, social withdrawal, etc. (Lewander, 1994; Schooler, 1994). NIDS has been linked to poor compliance and less favored outcome, and is a major factor affecting patients’ quality of life (Gerlach, 2002; Karow and Naber, 2002; Van Putten et al., 1981). NIDS may reflect the dampening effects of APDs on motivational drive related to the effect of the drugs on the dopamine system (Heinz et al., 1994; Kapur, 2003). The current model of drug-induced disruption of maternal behavior towards the pups bears similarities to the NIDS as it is clearly antipsychotic-induced, and it likely reflects the consequence of a dopamine blockade and seems to reflect a disruption in motivational drive. While our understanding of how these deficits relate to the human condition continues to evolve, it is safe to presume that this attribute of current APDs is unlikely to have positive consequences for patients. Therefore, maternal behavior studies may serve as a model of deficits that should be avoided in future APDs. Since closely modeling mothering behaviors of human schizophrenic mothers requires a chronic APDs treated animal model, the present study should be viewed as the first step towards understanding the intrinsic effects of APDs on mothering behaviors in schizophrenic patients. We are currently undertaking a series of experiments to look into this issue. The fact that no studies have ever investigated the chronic effects of APDs on maternal behavior in animals further provides a strong incentive to this effort.

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Acknowledgements This study was funded by an Independent Investigator Award from NARSAD to SK and the Ontario Mental Health Foundation Postdoc Fellowship to ML and by NSERC to AF. We thank AstraZeneca Canada for the partial financial support for initiating this work. We thank Zeneca Pharmaceuticals (Macclesfield, Cheshire, England) for the gift of quetiapine. We also thank an anonymous reviewer for pointing out the importance of studying the effects of chronic treatment with antipsychotic drugs on maternal behavior.

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