Behavioral rating scales for assessing phencyclidine-induced locomotor activity, stereotypes behavior and ataxia in rats

European Journal o f Pharmacology, 59 (1979) 169--179 © Elsevier/North-Holland Biomedical Press

169

BEHAVIORAL RATING SCALES FOR ASSESSING PHENCYCLIDINE-INDUCED LOCOMOTOR ACTIVITY, STEREOTYPED BEHAVIOR AND ATAXIA IN RATS R. DAVID S T U R G E O N *, RICHARD G. FESSLER *,** and HERBERT Y. MELTZER *,***

* Laboratory of Biological Psychiatry, Illinois State Psychiatric Institute, and ** Department of Pharmacological and PhysiologicalSciences, University of Chicago Pritzker School of Medicine, and *** Department of Psychiatry, University o f Chicago Pritzker School of Medicine, Chicago, Ill., U.S.A. Received 27 February 1979, revised MS received 27 June 1979, accepted 3 August 1979

R.D. STURGEON, R.G. FESSLER and H.Y. MELTZER, Behavioral rating scales for assessing phencyclidineinduced locomotor activity, stereotyped behavior and ataxia in rats, European J. Pharmacol. 59 (1979) 169--179. Behavioral rating scales were developed for quantification of phencyclidine (PCP)-induced locomotor activity, stereotyped behavior and ataxia in rats. The dose-response relationship for PCP-induced l o co m o t o r activity was found to be an inverted U-shaped function over the first 25 min after injection while over the last 30 rain of the experiment the function was highly linear. A linear dose-response relationship was found for ratings of stereotyped behavior and ataxia throughout the 90 rain period of observation. The ratings of these two behaviors were found to be closely parallel. The effects of PCP on locomotor activity were found to be greatest during those intervals when stereotyped behavior and ataxia were at moderate levels. Ratings of locomotor activity may be confounded by ataxia when PCP is administered alone or in combination with other drugs. Stereotyped behavior

L o c o m o t o r activity

Phencyclidine

1. Introduction

Phencyclidine (1-(phenylcyclohexyl) piperidine hydrochloride) (PCP) is a potent psychotomimetic agent (Luby et al., 1960; Meltzer et al., 1972; Rosenbaum et at., 1959) which has become a major drug of abuse as well as a "drug of choice" among substance abusers in a number of countries during the past decade (Lundberg et al., 1976). Current widespread abuse of this psychotomimetic drug and the resultant increase in the reported number of PCP-induced psychoses (Showalter and Thornton, 1977; Slavney et al., 1977), as well as speculation regarding the possible relevance of PCP as a neurochemical model for schizophrenia (Meltzer and 8tahl, 1976), have been major stimuli for research into behavioral effects of this drug in animals. In rodents, PCP produces increased locomotor activity, stereotyped behavior patterns

Behavior

Ataxia

and ataxia (Chen et al., 1959; Kanner et al., 1975; Tonge and Leonard, 1972). There have been no published studies in which the effects of PCP have been assessed on all three of these dimensions of behavior, concurrently. Therefore, comprehensive dose-response and time-course relationships of the pattern, amount, and interaction of PCP-induced locomotor activity, stereotyped behaviors and ataxia, have not been described. In behavioral experiments, investigators have, typically, quantified effects within only one or two of these behavioral parameters, resulting in a piecemeal description of the behavioral effects of PCP (Balster and Chait, 1978; Chen et al., 1959; Johnson et al., 1978; Kanner et al., 1975; Murray and Horita, 1978; Pinchasi et al., 1978). With the large number of studies currently being conducted in an attempt to elucidate the mechanisms of action of PCP, it is clear

170

that there is a need for a broad spectrum rating scale or scales for quantifying PCPinduced behaviors in rats, similar to those used for quantifying amphetamine-induced behaviors (e.g., Ellinwood and Balster, 1974; Iversen, 1977; Kelly, 1977; Randrup and Munkvad, 1970). The availability of suitable instruments for quantitating the behavioral effects of PCP should facilitate studies of pharmacological, neurochemical and neuroanatomical mechanisms which mediate PCPinduced behaviors. Data are presented in this paper of the dose-response and time-course of the locomotor activity, stereotyped behaviors and ataxia induced b y PCP in rats derived from studies which utilized scales specifically developed for each parameter of behavior.

2. Materials and methods

2.1. Rating scales Separate rating scales were developed for quantifying PCP-induced locomotor activity, stereotyped behaviors and ataxia so that these behaviors could be assessed independently. Items for each of the scales were developed from observations of the qualitative and quantitative differences in behaviors induced in groups of rats injected with saline or various doses of PCP. These behaviors were imposed along continua which described, as accurately as possible, the dose-response appearance of PCP-induced locomotor activity, stereotyped behaviors and ataxia with the first item of behavior (rating = 0) in each category indicating no drug effect (see t a b l e 1 ) . We attempted to avoid overlap between the times of consecutive rating levels within and between the three dimensions of behavior. The appearance of PCP-induced gagging, head weaving and sniffing together with the more complex stereotyped behaviors is, however, reflected in the between-time overlap in the stereotyped behavior rating scale (Table 1 B). The most critical (i.e., the criterion) behaviors for determining a sub-

R.D. S T U R G E O N ET AL.

ject's stereotyped behavior rating are therefore hierarchically arranged within the items of the scale for convenience to the rater.

2.1.1. Locomotor activity L o c o m o t o r activity was operationally defined as the amount and pattern of movement of the animal over the surface of the floor of the observation cage. The l o c o m o t o r activity rating scale (table 1 A ) is of the ordinal type in that each item represents a progressively greater amount of locomotion over the area of the floor of the cage. The format of items used in construction of this scale allows the observer to rate l o c o m o t o r activity according to the amount of activity displayed and the area of the cage over which the activity occurred. An activity rating of 1 was defined as movement within a circumscribed area of the cage, typically with the hindlimbs remaining relatively stationary. Intermittent l o c o m o t o r activity occurring at a low-moderate rate within 50% of the cage was assigned a rating of 2; continuous activity over a similar area, emitted at a moderaterapid rate, was assigned a rating of 3. Locomotor activity over greater than 50% of the area of the surface of the cage, which occurred intermittently and at a low-moderate rate, was assigned a rating of 4; locomotion over an area of this size, which occurred continuously and at a moderate-rapid rate, was assigned a rating of 5. 2.1.2. Stereotyped behaviors Stereotyped behavior was operationally defined as isolated motor acts or partial sequences of more complex behavioral patterns from the repertoire of a species which occur o u t of the normal behavioral context and with an abnormally high frequency (Iversen, 1977). The items comprising this scale (table l B) describe the ordinal, dose-response, progression of PCP-induced stereotyped behaviors. The least intense of the PCP stereotypic behaviors are locomotor activity and sniffing (exploratory behavior)

RATING SCALES F O R ASSESSING PHENCYCLIDINE-INDUCED BEHAVIORS

171

TABLE 1 PCP behavior rating scales. Behavioral scales for quantifying PCP-induced lo c o m ot o r activity, stereotyped behavior and ataxia. Ratings were made in a single-blind fashion by trained observers who evaluated the behavior of each rat for 1 min and recorded ratings during the next 15-20 sec. Behavioral ratings for each o f the three scales were repeated once every 10 rain throughout the experimental session. Rating

Description of behavior

A. L o c o m o t o r activity 0 Stationary, with little or no movement 1 Movement within localized area of cage, intermittent activity emitted at a low rate 2 Movement over a small area of cage, intermittent activity emitted at a low-moderate rate 3 Movement over small area of cage, activity emitted continuously and at a moderate-rapid rate 4 Movement over large area of cage, activity is intermittent and emitted at a low-moderate rate 5 Movement over large area of cage, activity is emitted continuously and at a moderate-rapid rate B. Stereotyped behaviors 0 Inactive or in-place activity of a non-repetitive nature 1 L o c o m o t o r activity, sniffing, and grooming more frequent than observed for control 2 Gagging, weaving, nondirected movements, occasional reciprocal forepaw treading (RFT), higher frequency of rearing or sniffing than in 1 3 Moderate rate and intermittent turning, backpeddling, praying, RFT, nondirected movements, sniffing, weaving, gagging 4 Rapid rate and continuous turning, backpeddling, praying, sniffing, weaving, gagging 5 Dyskinetic extension and flexion of limbs, head and neck, gagging and weaving C. Ataxia 0 1 2 3 4

Inactive or in-place activity, coordinated movement Unusual, awkward or jerky movement, loss of balance during rearing, occasional falling on side Awkward-jerky movements, moderate rate of falling on side while rearing or moving about Frequent falling on back and/or side while moving, partial impairment of antigravity reflexes Cannot move beyond a restricted area, antigravity reflexes greatly impaired, may support weight on haunches or abdomen Unable to move except for twitching/convulsive movements, occasional rolling on side or raising head

and grooming, which are observed soon after injecting a low dose of PCP (2-3 mg/kg) and typically occur in conjunction with more complex stereotyped behaviors subsequent to injecting larger dose (5.0-15.0 mg/kg). The appearance o f these stereotyped behaviors observed after injecting the smallest effective dose of PCP are not unlike those observed after injection o f amphetamine-like drugs while the appearance of these behaviors is somewhat distorted at higher doses of PCP. From a dose-response ordering of stereotyped behaviors, "gagging, weaving, nondirected movements and reciprocal forepaw treading" are the next stereotypic behaviors emitted

(rating = 2). Gagging is an exaggerated opening of the m o u t h with protrusion of the tongue during dorsoventral flexion of the neck. The appearance of this behavior is not unlike that in humans. Weaving refers to slow, side to side or lateral, head movements. Nondirected movements appear to be a component of grooming where the forelimbs are directed toward, b u t seldom make contact with, the snout. Reciprocal forepaw treading is the rhythmic, alternating, dorsoventral movement of forelimbs and is similar to a response seen with some serotonin agonists (Jacobs, 1974). A moderate rate and intermittent display of stereotyped turning, back-

172

R.D. S T U R G E O N ET AL.

peddling and praying was assigned a rating of 3. Turning refers to lateral circling to the left or right over 360 ° within a relatively small area with animals typically displaying this behavior while moving in a forward direction. Backpeddling refers to vigorous backward locomotion. Praying refers to the simultaneous ventromedial flexion of the forelimbs while the neck is flexed dorsoventrally. This behavior looks very much like a praying posture in humans. A continuous display of these stereotyped behaviors at a very rapid rate was given a rating of 4 along the stereot y p y behavioral continuum. The most intense form of stereotyped behaviors, which consisted of dyskinetic extension and flexion of the fore- and hindlimbs and the head and neck, with a low frequency of gagging and head weaving, was assigned a rating of 5. These stereotypic responses occur during periods of extreme ataxia while the animal is lying on its abdomen.

of movement within the environment. This level of ataxia is typically observed soon after injecting 7.5-10.0 mg/kg PCP. A still greater degree of impairment is produced after injection o f dosages in the range of 12.5-15.0 mg/ kg PCP where the animal is able to move only within a small area of the environment while making "swimming-like" movements with pronounced abduction or splaying of foreand hindlimbs (rating = 4). At this level of impairment, animals may also shift into a " s l u m p e d " sitting posture where the body weight is supported on haunches and tail. The greatest impairment (assigned a rating of 5) is characterized by complete cessation of locomotion about the cage. At this level of ataxia and animal may occasionally roll onto its side or raise its head and display small twitching or convulsive movements with total abduction of fore- and hindlimbs.

2.1.3. Ataxia We defined ataxia as impairment in the ability of the animal to execute coordinated m o t o r responses leading, in the extreme, to incapacitation of the animal. The scale items for assessing PCP-induced ataxia were chosen to reflect ordinal increases in impairment of motor behaviors (table 1 C). At the lowest level of impairment animals appear somewhat awkward and exhibit " j e r k y " , uncoordinated, m o t o r movements with only occasional loss of equilibrium during rearing or while changing direction of movement (rating = 1). A greater degree of impairment results in a greater frequency of falling while the animal is rearing or changing direction of movement and is given a rating of 2. This level of ataxia usually results after injection of 5.0-7.5 mg/kg PCP. The next level of ataxia (rating = 3), is distinguishable from the previous level as a result of a greater degree of impairment of antigravity reflexes indicated by partial abduction (splaying) of hindlimbs which results in frequent falling on side and/ or back while rearing or changing direction

The subjects were 56 experimentally naive, male, Sprague-Dawley rats (Sprague-Dawley, Inc., Madison, Wisconsin) whose average weight was 238 g at the time of the experiment. Prior to the experiment rats were grouphoused (10 per cage) in a temperature controlled (26°C) colony where lights were on from 7 a.m. to 7 p.m. and Purina Rat Chow and water were available ad libitum. On the day of the experiment seven rats were removed to a sound attenuated room and placed in individual clear plastic cages with inside dimensions of 42 cm × 21 cm × 19 cm with a wire mesh top and containing wood chips at approximately 1 cm depth as bedding. Rats were allowed a minimum of 1 h to habituate to the environment before intraperitoneal (i.p.) injection of saline (1 ml/kg) or PCP {2.5, 5.0, 7.5, 10.0, 12.5. or 15.0 mg/ kg). Eight rats were used for each treatment level (dosage) with one subject at each of the seven dosages being tested during each experimental session. Treatments were administered to individual rats in a random, single-blind, fashion. Behavioral ratings were made by one

2.2. Subjects and procedures

RATING

SCALES FOR ASSESSING PHENCYCLIDINE-INDUCED

or two of the authors, beginning 5 min after drug injection and every 10 min thereafter for 90 min. Each subject was observed for 1 min and ratings were recorded during the next 15-20 sec for each of the three behavioral rating scales. When heterogeneous criterion behaviors were displayed within a behavioral category, raters scored those behaviors which predominated during the observation interval. Interrater reliability was calculated from those simultaneous ratings made by two of the authors using the Pearson product-moment correlation (r). Interrater reliabilities for locomotor activity, stereotyped behavior and ataxia scales were found to be 0.97, 0.97 and 0.96, respectively, indicating a high degree of interrater agreement. Dose-response data for PCP-induced locomotor activity, stereotyped behavior and ataxia were analyzed with linear regression and multiple linear regression (Snedecor and Cochran, 1967). While the legitimacy of regression analysis of ordinal data may be questioned, this type of analysis has been shown (Bock, 1975) to be valid for demonstrating dose-response differences in data of the type reported here. Fresh solutions of PCP (Sernylan®) (BioCeutic Laboratories, St. Joseph, Mo.) were prepared every 2 or 3 days by dilution of the stock solution with sterile physiological saline to the appropriate concentration (2.5, 5.0, 7.5, 10.0, 12.5, 15.0 mg/ml). Drug dosages refer to the hydrochloride (HC1) salt. Drug solutions were refrigerated when not in use but were allowed to warm to room temperature prior to injection.

3. Results

3.1. L o c o m o t o r activity

The behavioral ratings of PCP-induced locomotor activity were averaged within treatment level for each 10 min interval and are presented in fig. 1. It may be observed that after injection of PCP, ratings of locomotor activity were consistently greater for the 5.0

5,

BEHAVIORS

173

iii 5

[5

25

55 45 55 Minutee after PCP

65

"?5

85

95

Fig. 1. Time-course and dose-response o f PCP-induced l o c o m o t o r activity. Data points are averages (n = 8) w i t h i n treatment level for each t i m e period. PCP, rag/ kg: 0 (saline) o o; 2.5 • . . . . . . D; 5.0 ~, A_; 7.5 •

o...... •.

o; 1 0 . 0 v.

v.; 1 2 . 5 • . . . . . .

m; 1 5 . 0

mg/kg dosage than for the 2.5 mg/kg dosage at all time points. Ratings for locomotor activity during the first 25 min, for groups which received 7.5, 10.0, 12.5 or 15.0 mg/kg PCP, were within the range of ratings for groups which received 2.5 or 5.0 mg/kg. Thus, during this time, a dose-response relationship for PCP-induced locomotor activity was found only up to 5.0 mg/kg. The locomotor activating effects of 7.5-15.0mg/kg PCP peaked between 45 and 75 min after injection and by 75 min after administration, ratings of locomotor activity were ordered in a doseresponse manner. For each animal, behavioral ratings were obtained at ten time points over the experimental session. A single response measure was obtained by averaging ratings within each dose over the entire session so that independent measures could be determined for each subject for the purpose of performing regression analysis of response on dose. This analysis indicated that there was a significant linear component in the relationship (/3= 0.166 + 0.024, P < 0.001). However, the relationship began to move away from linearity at the higher dosage levels. A multiple regression analysis resulted in significant linear (fl~ =

174

R.D. S T U R G E O N ET AL.

0.439 +- 0.079, P < 0.001) and quadratic (/32 = --0.018 -+ 0.005, P < 0.001) terms, providing an equation which more adequately described the relationship between dosage and PCP-induced l o c o m o t o r activity. These findings indicate that the dose-response relationship for PCP-induced l o c o m o t o r activity contained linear as well as nonlinear components. By averaging data over only the first 3 behavioral ratings it was found that the simple linear regression model provided a rather poor fit to the data (/3 = 0.042 +- 0.30, P > 0.05) whereas multiple regression resulted in a quadratic equation that fit these data fairly well (/]1 = 0.460 + 0.091, P < 0.001; /32 = - 0 . 0 2 8 +- 0.006, P < 0.001), indicating the presence of a significant nonlinear relationship between dose and PCP-induced l o c o m o t o r activity during the first 25 min after injection. These data are plotted in fig. 2 where it may be seen that the relationship closely approximates an inverted U-shaped function. When a similar analysis was performed on data averaged over the last 3 ratings on the experimental session, a significant linear term was found (/3 = 0.271 + 0.026, P < 0.001) and the addition of a quadratic term was not significant, indicating that a highly significant linear dose-response relationship was obtained for PCP-induced l o c o m o t o r activity during the last 30 min of the session (fig. 2).

0 Fig. 2. activity t h e first periods;

2.5

5.0 7.5 I0.0 12.5 Dose PCP m g / k g

15.0

Dose-response of PCP-induced l o c o m o t o r for data averaged within t r e a t m e n t level over and last three rating periods. • First 3 rating • last 3 rating periods,

3.2. Stereotyped behavior The ratings of PCP-induced stereotyped behaviors were averaged within treatment level of each 10 min interval and are presented in fig. 3. It is apparent that a much different relationship exists for the stereotyped behaviors compared to the locomotor activity induced by PCP. The peak stereotypy-inducing effects of PCP, at all dosages tested, occurred within the first 25 min after injection. Regression analysis of the dose-response relationship for PCP-induced stereotyped behaviors resulted in a significant linear term (/3 = 0.219 -+ 0.015, P < 0.001) while the quadratic term was found not to be significant. These findings indicate that the relationship between dose and PCP-induced stereotyped behaviors closely approximates a linear function. It may be observed from the data in fig. 3 that b y the end of the experimental session, rats which were injected with dosages between 2.5 and 7.5 mg/kg were predominately exhibiting locomotor activity, sniffing (exploration) and grooming while those that received dosages in the range of 10.0 to 15.0 mg/kg were still exhibiting the more complex stereotypic behaviors including turning, backpeddling and praying.

t

;,

~

2'5

~:5

45

5's

6'5

T'5

e'~

Mi..t. after PCP Fig. 3. Time-course and dose-response of PCP-induced s t e r e o t y p e d behaviors. Data points were obtained by averaging ratings within t r e a t m e n t level (n = 8) for each t i m e period. F o r details see legend to fig. 1.

RATING SCALES FOR ASSESSING PHENCYCLIDINE-INDUCED BEHAVIORS

dosages of 7.5 mg/kg and higher resulted in marked ataxia (ratings> 3) which greatly impaired locomotion (fig. l ) . Very little ataxia was evident at the end of the experimental session for animals which had been given dosages of 5.0 mg/kg or less, while ataxia was still significant at this time in animals that received 7 . 5 - - 1 5 . 0 m g / k g PCP. Regression analysis of PCP-induced ataxia resulted in a highly significant linear term (13 = 0.228 -+ 0.014, P < 0.001) while again a significant quadratic term was not found. These data indicate that the relationship between dosage and PCP-induced ataxia is highly linear. It is important to note that the relationship observed between dosage and PCPinduced ataxia and stereotyped behaviors are highly similar. Additionally, there is an approximate inverse relationship between ataxia and l o c o m o t o r activity in that we found that when ataxia was at its highest levels, l o c o m o t o r behaviors were greatly

I

o

g

,'5

2'5

~

4'~

15

i~

15

~'5

85

175

Minutes after PCP

Fig. 4. Time-course and dose-response of PCP-induced ataxia. Again, data points are average ratings within treatment level for each time period. For details see legend to fig. 1.

3.3. Ataxia

The ratings of PCP-induced ataxia are plotted in fig. 4. A consistent dose-response relationship for ataxia was observed over the entire observation period. Ataxia appeared to peak between 5-15 min after injection of PCP; A. Locomotor Activity

[ ~

0 Rating $ G a l e l O t COtegor y

I 2 34

B. S t e r e o t y p e d

5

0 I 23

4 5

0 I 23

4 5

0 I 2 3 4 S

r--I 0 I 2 3 4 5

0 I 2 34

~)

0 I 2 34

5

5

Behavior

0

~

fl

i i

H

n

i

Rating Scale 1 0 Category f

I 2 345

0 I 2 34

S

0 I 23

45

0 I 2345

0 I 2 34

5

0 I 23

45

0 I 234

5

0 I 23

45

0 I 2 345

C. Ataxla

0

Category PC P (Mg/Kg)

~

{

Rating Scale 1 0

I 2 s$ 4 5

0 I 2 345

i

0 I 2345

0 I 234

5

1

i

0 I 234

f

0.0 (Saline).

2.5

5.0

7.5

I0.0

12.5

15.0

Fig. 5. Bar graphs of the distribution of the locomotor activity (A), stereotyped behavior (B) and ataxia (C) induced by PCP (0.0-15.0 mg/kg) 15 min after administration.

176

impaired. L o c o m o t o r activating effects of PCP appeared to be greatest during those periods when ataxia was at a moderate level.

3.4. Heterogeneity of behaviors The data of fig. 5A-C show that there was significant variability in the l o c o m o t o r activity, stereotyped behavior and ataxia displayed among rats given the same dose of PCP. The distribution of ratings at 15 min after administration of PCP (0.0-15.0 mg/kg) presented in this figure is typical of the behavioral variability observed throughout the experiment. These data nonetheless show dose-related increases in PCP-induced stereotyped behavior and ataxia and the inverse relationship between ataxia and l o c o m o t o r activity at dosages of PCP between 7.5 and 15.0 mg/kg 15 min after administration.

4. Discussion Behavioral rating scales were developed for concurrent quantification of PCP-induced l o c o m o t o r activity, stereotyped behavior and ataxia. The rating scale technique is the method of choice for quantifying PCP-induced behaviors since there is, at present, no generally accepted mechanical or electronic apparatus available for quantifying the stereot y p e d behaviors and ataxia produced b y this drug. The data presented here permit an assessment of the reliability and validity of the rating scales. The high interrater reliability obtained in the present study suggests that the rating scales are composed of items of behavior which are readily observable and are defined in operational terms. The behavioral scales are sensitive to time-course and doseresponse effects and shifts to the left or right can be assessed. These findings indicate that these scales may be used to develop valid animal models for studying the physiological mechanisms mediating PCP-induced behavioral phenomena. Data from the present paper are useful for

R.D. S T U R G E O N ET AL.

the selection of appropriate dosage, timecourse and behavior parameters when designing studies with PCP. For a study of the effect of putative antagonists of PCP-induced locomotor activity, within 1 h of drug administration, a dose of 7.5 mg/kg or less should be utilized since, in the present study, the administration of 7.5 mg/kg PCP produced the greatest l o c o m o t o r activity with the least interference from ataxia, during this time. If a study is designed to investigate the neurophysiological or neuropharmacological mechanisms of PCP-induced sniffing behavior a dose of PCP between 2.5 and 5.0 mg/kg would be useful since the greatest frequency o f this behavior is found in this dosage range. A dose between 5.0 and 7.5 mg/kg should be employed for studies of neurologic mechanisms underlying the more complex stereot y p e d behaviors. Research into mechanisms underlying PCP-induced ataxia might best be conducted with dosages above 10.0 mg/kg. It should also be noted that the selection of a 90 min experimental session was somewhat arbitrary and that the sensitivity of the scales to gradual changes within the three dimensions of behavior indicate that these scales are equally as valid for experiments utilizing a different time course. Additionally, the size of the test environment has been found to affect PCP-induced locomotor activity and stereotyped behaviors. Specifically, in a large circular "open field" test environment, l o c o m o t o r activity was greater and rats displayed bouts or episodes of stereotyped turning and backpeddling of greater frequency and duration than occured in the test environment utilized in the present study (see Subjects and Procedures). These observations suggest that experiments utilizing a test environment significantly different in size from that of the present study may obtain slightly different behavioral results. The variability of behavioral ratings depicted in fig. 5 A and B is partially accounted for b y the episodic nature of PCP-induced l o c o m o t o r activity and stereotyped behavior after injec-

RATING SCALES FOR ASSESSINGPHENCYCLIDINE-INDUCEDBEHAVIORS tion of low-moderate dosages. During a relatively long (1 min) observation interval, rats may exhibit criterion behaviors satisfying one or more rating levels within a category of behavior while only the predominant behavior occurring within the observation interval is scored. Therefore, the predominant criterion behaviors displayed by respective subjects observed at the same time after administration of the same dosage of PCP may vary significantly. We have found in pilot studies that the frequency of heterogeneous behavioral displays is reduced when observation intervals of shorter duration (30 sec) are employed. The 1 min observation interval of the present study allowed the raters sufficient time to accurately score PCP-induced behaviors in their initial experience with the rating scales. We also observed significant variability in behaviors of rats tested with a given dose of PCP which could not be accounted for by the episodic nature of PCPinduced behaviors. This type of variability is perhaps most readily observed in the ataxia data (fig. 5C) but also occurred with locomotor activity and stereotyped behaviors. Elucidation of those variables affecting this type of behavioral variability after PCP will be the subject of future investigation. Rating scales for quantifying amphetamineinduced behaviors have been utilized in developing animal models for studies in which the pharmacological, neurochemical and neuroanatomical mechanisms of action of drugs of the amphetamine class have been elucidated (Kelly, 1977; Randrup and Munkvad, 1970). Comparison of the PCP behavioral rating scales and data of the present study with amphetamine scales and data derived in studies with these scales (Costall et al., 1972; Ellinwood and Balster, 1974; Kelly et al., 1975) reinforces the contention of Balster and Chait (1978) that amphetamine scales are inappropriate for rating PCP-induced behaviors. The first facet of this inappropriateness results from the different topography of stereotyped behaviors induced by the two drugs. As indicated, amphetamine stereotypies

177

begin with sniffing and progress to licking and biting as dosage is increased, while PCPinduced stereotypies begin with sniffing and exploration and progress in a dose-related manner through gagging, head weaving, reciprocal forepaw treading, turning, backpeddling, and praying, ending with dyskinetic extension and flexion of limbs, head and neck. Head weaving, reciprocal forepaw treading, turning and backpeddling stereotyped behaviors are induced in rats by amphetamine only after injection of very large dosages (1580 mg/kg) (Sloviter et al., 1978; Lees et al., 1979). Additionally, data presented above show a linear dose-response increase in PCPinduced ataxia which impairs locomotor behaviors. It is apparent, then, that ataxia which results after injection of PCP would confound interpretation of behavioral ratings from scales designed for quantifying amphetamine-induced behaviors. Data of the present study allow the opportunity to reconcile seemingly discrepant findings from previous studies. Johnson et al. (1978) described an inverted U-shaped function for PCP-induced locomotor activity in guinea pigs during 1 h after injection while Kanner et al. (1975) and Chen et al., (1959) found linear dose-response increases in PCPinduced locomotion in rats and mice. Kanner et al. (1975), however, recorded activity over a 1 h period on automated apparatus, a procedure which apparently obscures the initial impairment of locomotor activity resulting from ataxia after injection of PCP in dosages greater than 7.5 mg/kg. This suggestion is consistent with data of the present study in that we found an inverted U-shaped dose-response function for locomotor activity during the first 25 min after injection but showed a linear relationship at a dose-related point in time after injection of PCP when impairment from ataxia was at a low-moderate level (rating = 2-3). The 1 and 2 hr observation periods and the low-moderate dosage of PCP (0.0-8.0 mg/kg) utilized by Chen et al. (1959) would also be expected, on the basis of data presented here, to reflect a linear relationship

178

for l o c o m o t o r activity. It is therefore likely that, at least for rodents, moderate-high dosages of PCP induce a species dependent, dose-related increase in l o c o m o t o r activity which is impaired b y ataxia in a dose- and time-related manner. A linear dose-response relationship is found over periods when impairment due to ataxia is lessened or when the initial impairment is obscured by cumulative data collection procedures. Data reported here provide the first description of the dose-response and time-course of PCP-induced stereotyped behaviors and ataxia in rats. Previous studies of ataxia were conducted with mice utilizing the rotarod procedure (Chen et al., 1959; Pinchasi et al., 1978), a method which precludes concurrent assessment of stereotyped behavior and l o c o m o t o r activity induced b y this drug. However, data of the present study, showing nearly parallel dose-response functions for the time~ourse of PCP-induced stereotyped behavior and ataxia, suggest that c o m m o n or overlapping physiological mechanisms m a y mediate these effects. The rating scales described here provide a means b y which this question may be investigated. The relationship between PCP-induced ataxia and l o c o m o t o r activity is demonstrated b y data presented above where it was found that l o c o m o t o r activity was significantly impaired when ataxia was at a moderate to high level. Significant impairment of locomotion occurred at dosages of PCP of 7.5-15.0 mg/kg, resulting in an inverted Ushaped dose-response relationship for PCPinduced l o c o m o t o r activity. Impairment due to ataxia was still evident 1 h after injection of dosages of PCP of 10.0 to 15.0 mg/kg. The importance of being able to quantify PCPinduced ataxia is further illustrated when data collected with the PCP behavioral rating scales were compared with data which were collected on a u t o m a t e d activity monitoring apparatus (Kanner et al., 1975). In the latter study, it was found that PCP-induced l o c o m o t o r activity was antagonized b y cholinomimetics, arecoline or physostigmine. However, recent

R.D. STURGEON ET AL.

data collected with the rating scales indicate that the apparent antagonism of PCP-induced l o c o m o t o r activity b y cholinomimetics may have been due to increased ataxia resulting from an additive interaction when these t w o ataxia-producing drugs are administered together (Sturgeon and Meltzer, unpublished observation). These data, as well as the d a t a presented above, show that ataxia produced b y PCP impairs the ability of animals to execute motor behaviors and demonstrate that studies relying exclusively on automated activity monitoring apparatus may result in misleading conclusions. Data such as these underscore the validity of the "observation technique" in conjunction with other types of experimental instrumentation in behavioral studies (Robbins, 1977) and suggest that rating scales such as those presented here will play an important role in studies designed to elucidate the physiological mechanisms of action of PCP.

Acknowledgements The authors express their gratitude to Mr. Theodore Karrison and Ms. Mary-Dichtel for assistance with statistical analyses. This research was supported, in part, by USPHS DA 02081, USPHS MHCRC 30,938 and the State of Illinois Department of Mental Health and Developmental Disabilities. RGF is recipient of 5 T32 GM 07151 and HYM is recipient of USPHS RCSA MH 47,808.

References Balster, R.L. and L.D. Chait, 1978, The effects of phencyclidine on amphetamine stereotypy in rats, European J. Pharmacol. 4 8 , 4 4 5 . Bock, R.D., 1975, Multivariate Statistical Methods in Behavioral Research (Mc Graw-Hill Book Co., New York} p. 208. Chen, G., C.R. Ensor, D. Russell and B. Bohner, 1959, The pharmacology of ( 1 -(phenylcyclohexyl) piperidine HC1, J. Pharmacol Exp. Therap. 127,241. Costall, B., R.J. Naylor and J.E. Olley, 1972, Stereotypic and anticataleptic activities of amphetamine after intracerebral injections, European J. Pharmacol. 18, 83.

RATING SCALES FOR ASSESSING PHENCYCLIDINE-INDUCED BEHAVIORS Ellinwood, E.H., Jr. and R.L. Balster, 1974, Rating the behavioral effects of amphetamine, European J. Pharmacol. 28, 35. Iversen, S.D., 1977, Brain dopamine systems and behavior, in: Handbook of Psychopharmacology, Vol. VIII: Drugs, Neurotransmitters and Behavior, eds. L.L. Iversen, S.D. Iversen and S.H. Snyder (Plenum Press, New York) p. 333. Jacobs, B.L., 1974, Evidence for the functional interaction of two central neurotransmitters, Psychopharmacologia, 39, 81. Johnson, K.M., M.B. Gordon and M.G. Ziegler, 1978, Phencyclidine: Effects on motor activity and brain biogenic amines in the guinea pig, Pharmacol. Biochem. Beh. 9,563. Kanner, M., H.Y. Meltzer and J.M. Davis, 1975, Pharmacologic aspects of the locomotor stimulation produced by phencyclidine in the rat, Neurosci. Abstracts 1, No. 366. Kelly, P.H., 1977, Drug-induced motor behavior, in: Handbook of Psychopharmacology, Vol. VIII: Drugs, Neurotransmitters and Behavior, eds. L.L. Iversen, S.D. Iversen and S.H. Snyder (Plenum Press, New York) p. 295. Kelly, P.H., P.W. Seviour and S.D. Iversen, 1975, Amphetamine and apomorphine responses in the rat following 6-OHDA lesions of the nucleus accumbens septi and corpus striatum, Brain Res. 94,507. Lees, A.J., J.C.R. Fernando and G. Curzon, 1979, Serotonergic involvement in behavioural responses to amphetamine at high dosage, Neuropharmacology 18,153. Luby, E.D., J.S. Gottlieb, D.D. Cohen, G. Rosenbaum and E.F. Domino, 1960, Model psychoses and schizophrenia, Amer. J. Psychiat. 119, 61. Lundberg, G.D., R.C. Gupta and S.H. Montgomery, 1976, Phencyclidine: Patterns seen in street drug analysis, Clin. Tox. 9,503. Meltzer, H.Y., P.S. Holzman, S.Z. Hassan and A. Guschwan, 1972, Effects of phencyclidine and stress on plasma creatine phosphokinase (CPK) and aldolase activities in man, Psychopharmacologia 26, 44. Meltzer, H.Y. and S.M. Stahl, 1976, The dopamine

179

hypothesis of schizophrenia: A review, Schizophrenia Bull. 2, 19. Murray, T.F. and A. Horita, 1978, Dose response effects of phencyclidine on stereotyped behavior, Neurosci. Abstracts 4, 1594. Pinchasi, I., S. Maayani and M. Sokolovsky, 1978, On the interaction of drugs with the cholinergic nervous system. I. Tolerance to phencyclidine derivatives in mice: Pharmacological characterization, Psychopharmacology 56, 27. Randrup, A. and I. Munkvad, 1970, Biochemical, anatomical and psychological investigations of stereotyped behavior induced by amphetamine, in: Amphetamines and Related Compounds, eds. E. Costa and S. Garattini (Raven Press, New York) p. 695. Robbins, R.W., 1977, A critique of the methods available for the measurement of spontaneous motor activity, in: Handbook of Pscyhopharmacology, Vol. VII: Principles of Behavioral Pharmacology, eds. L.L. Iversen, S.D. Iversen and S.H. Snyder (Plenum Press, New York) p. 37. Rosenbaum, G., B.D. Cohen, E.D. Luby, J.S. Gottlieb and D. Yelen, 1959, Comparison of Sernyl with other drugs: Simulation of schizophrenic performance with Sernyl, LSD-25, and amobarbital (Amytal) sodium; I. Attention, motor function and proprioception, Arch. Gen. Psychiat. 1,651. Showalter, C.V. and W.E. Thornton, 1977, Clinical pharmacology of phencyclidine toxicity, Amer. J. Psychiat. 134, 1234. Slavney, P.R., G.B. Rich, G.D. Pearlson and P.R. McHugh, 1977, Phencyclidine abuse and symptomatic mania, Biol. Psychiat. 12,697. Sloviter, R.S., E.G. Drust and J.D. Connor, 1978, Evidence that serotonin mediates some behavioral effects of amphetamine, J. Pharm. Exp. Therap. 206,348. Snedecor, G.W. and W.G. Cochran, 1967, Statistical Methods, 6th edn. (Iowa State University Press, Ames, Iowa). Tonge, S.R. and B.E. Leonard, 1972, Partial antagonism of the behavioral and neurochemical effects of phencyclidine by drugs affecting monoamine metabolism, Psychoph armacologia 14, 516.