BEHAVIORAL BIOLOGY 15, 193-205 (1975), Abstract No. 4323

Relations Between Orienting, Pseudoconditioned and Conditioned Responses in the Shuttle-Box-A Pharmacological Analysis by

Means of LSD and Dibenamine

I V A N I Z Q U I E R D O

Departamento de Fisiologia, Escola Paulista de Medicina, Rua Botucatu 862, 04023 S(to Paulo, SP, Brazil

The effect of LSD (0.075 and 0.3 mg/kg, ip) on orienting and on shuttle responses to a buzzer was investigated in rats submitted to three different experimental procedures in a shuttle-box: (a) presentation of 50 buzzers alone (habituation); (b) 50 buzzers interspersed with 25 unpaired footshocks (pseudoconditioning); (c) 50 buzzers paired with footshocks (two-way avoidance). LSD increased orienting response in all three situations in a dose-dependent fashion. Dibenamine (10 mg/kg, ip), which had a similar action of its own, did not antagonize that of LSD. LSD also enhanced performance of pseudoconditioned responses in a dose-dependent fashion, and this effect was potentiated by dibenamine. In the two-way situation, pretrial LSD increased shuttle responses at the lower dose and apparently had no effect at the higher dose, and when given together with dibenamine it was depressant at both doses. Retention, as measured by performance in an avoidance session made 7 days later, was lower in all LSD groups than in water- or dibenamine-treated groups. Since LSD had no effect on retention when given posttrial, it must be concluded that it had a deleterious effect on acquisition of the shuttle response. Dibenamine alone had no effect on either conditioned or pseudoconditioned shuttling. These results indicate that orienting, pseudoconditioned shuttling and conditioned shuttling, while they may occur superimposed, and in spite of the latter two being identical in external appearance, each have a distinct pharmacology of their own, at least in relation to the drugs tested. This is discussed in relation to organization of aversive responses of rats in a shuttle-box depending on the context of the experimental situation.

The typical react ion o f a rat to a buzzer in a shut t le-box consists o f a

b r ie f startle fo l lowed by or ient ing and then by freezing. This react ion

habi tua tes rapidly if the buzzer is repeated alone. However , i f foo tshocks are

presented in the same session, a shutt le response develops to the buzzer .

During several years o f observat ion, the au thor has no t i ced that the shutt le

does no t replace any o f the o ther componen t s o f the response, bu t occurs

instead in te rca la ted be tween the or ient ing and the freezing react ion. I f the

193

Copyright © 1975 by Academic Press, Inc. All rights of reproduction in any form reserved.

194 IVAN IZQUIERDO

shocks are delivered without any temporal pairing to the buzzer, shuttling to the latter will be pseudoconditioned (Vasquez and Izquierdo, 1970; Izquierdo, 1974a, b; Gattoni and Izquierdo, 1974; Izquierdo and Thadddu, 1975). If there is temporal pairing between both stimuli, shuttling responses will be either instrumentally conditioned or classically conditioned (see Katzev and Mills, 1974; and the Discussion of the present paper).

There are several reasons to believe that conditioned and pseudo- conditioned shuttles, in spite of their seemingly identical external appearance, really are two distinctly different events. Each is affected in an opposite way by repetition (conditioned shuttlings increase, and pseudoconditioned ones decrease, Izquierdo, 1974b) and by a number of drugs (Vasquez and Izquierdo, 1970; Izquierdo, 1974a, b; Izquierdo and Thadddu, 1975), and each is accompanied by clearly diverse central biochemical correlates (Gattoni and Izquierdo, 1974). The question of what the relation may be of both types of response to orienting arises, inasmuch as they are invariably preceded by it. Grasty~n and Vereckzei (1974) proposed that in those forms of learning which involve spatial ambiguity and therefore are highly dependent on external cues, orienting may be the only real conditioned response. Pseudo- conditioning, however, is in all probability not a form of learning (Kimble, 1961; Izquierdo, 1974b); and, besides, if the Grasty~n and Vereckzei hypothe- sis were applicable to shuttle behavior, then both conditioned and pseudo- conditioned shuttling would merely be either two forms of dishabituation or two extensions of the orienting response, which is at odds with all existing theories on conditioning, psuedoconditioning or aversive behavior in general (Kimble, 1961; Bolles, 1970; Anisman and Waller, 1973; Izquierdo, 1974b; Katzev and Mills, 1974).

The alternative view is that orienting superimposes on both conditioned and pseudoconditioned shuttling as a result of some link at either the sensory or the motor level. Indeed, a rat which is about to shuttle would need to orient first in order to become aware of its own position relative to that of the midline hole or barrier. If this alternative were true, then it should be possible to find some means to "dissect" orienting from both conditioned and pseudoconditioned shuttling. The present paper attempts such a dissection pharmacologically, by means of LSD and dibenamine.

LSD was chosen because it is widely known to influence orienting behavior in a variety of species (Radulovacki and Adey, 1965; Barratt and Pray, 1965; Hughes, 1973) and to either enhance or depress performance of a wide number of learned responses depending mainly on the dose (Bignami, 1966, 1972; Stoff, Mandel, Gorelick, and Bridger, 1974; Izquierdo, 1975). In the rat, LSD enhances exploration in relatively "open" environments, and depresses it in "enclosed" environments (Hughes, 1973), whereas it may enhance (Bignami, 1972) or depress shuttle avoidance (Bignami, 1972; Stoff et al., 1974) depending on the dose. So far, the effects of LSD on orienting and

LSD ON SHUTTLE AND ORIENTING RESPONSES 195

on shuttle responses have been studied in separate experiments, and neither posttrial administrations (McGaugh, 1973) nor actions on pseudoconditioning have been examined.

The present paper studies the effect of LSD on orienting and on avoidance and pseudoconditioned shuttling to a buzzer in rats. In the avoidance situation, both pre- and posttrial treatments were used, in order to discriminate effects on learning from effects on memory consolidation (McGaugh, 1973). Learning is used here in the sense of "acquisition of a behavioral change as a result of experience" (McGaugh, 1973; Izquierdo, 1975). In all cases two dose levels were used: one that may be considered as "low" (0.075 mg]kg, Hughes, 1973; Izquierdo, 1974c), and one that may be considered as "high" (0.3 mg/kg, Bignami, 1972; Hughes, 1973; Izquierdo, 1974c). Since LSD is known to stimulate sympathetic activity through a central action (Jarvik, 1970), its interaction with dibenamine was also studied. I)ibenamine is a well-known sympathetic blocker which antagonizes the effect of amphetamine and of other drugs on shuttle avoidance (Orsingher and Fulginiti, 1974) and on pseudoconditioning (Izquierdo, 1974a, b), and the behavioral effects of LSD have often been compared with those of ampheta- mine (Bignami, 1966; Izquierdo, 1975).

MATERIAL AND METHODS

Subjects. A total of 198 female Wistar rats (age 72-90 days, weight 110-172 g) were used.

Drugs and injeetT"ons. LSD (Sandoz) and dibenamine (Nordmark) were dissolved in water to appropriate concentrations so that in all cases the doses to be injected were in a volume of 0.1 ml/100 g. Control animals received 0.1 ml/100 g of water. All injections were intraperitoneal.

Apparatus. A 25 × 25 × 50 cm shuttle-box was used. It was made of wood painted in grey except for the two longitudinal walls which were of glass. A 15-W light and a buzzer were at the midline on the lid of the box. The floor consisted of bronze wires of 3 mm diameter spaced 8.5 mm apart. A wood hurdle (25 X 0.5 × 0.5 cm) separated both halves of the grid on the floor. Since rats could cross it without any need to jump, the hurdle served the only purpose of marking the midline on the floor of the box.

Experimental Procedures

"Buzzers alone". Six groups of ten rats each were placed in the box 5 rain after receiving an appropriate injection (Table 1), and after 2 min they were presented with 50 consecutive buzzers of 3-sec duration at intervals ranging randomly from 15 to 45 see. From the 3000 responses recorded in all

196 IVAN IZQUIERDO

groups, only 12 (0.04%) included some motor response which could not be classified as orienting (11 shuttles, 1 jump), and no differences in the incidence of these responses between groups could be detected with a Duncan multiple range test (Bliss, 1967) at the 5% level. Orienting was defined as lateral or upward movement of the head, often with rearing, and with or without accompanying pricking of the ears and sniffing. The mean number of orienting responses per group to the first five buzzers was compared with that to the last five buzzers, and the difference was taken as a measure of habituation in each group.

Pseudoconditioning. Six groups of ten rats each were submitted to this procedure. The animals were placed in the shuttle-box 2 min after receiving an appropriate injection (Table 2) and remained there for 5 rain with no stimulation. After this, they were presented with 50 buzzers of 3-sec duration each interspersed with 35 footshocks (1.5 mA) as follows: 8 shocks among the first 10 buzzers (sessions were always initiated by a shock), 7 among the following 10 buzzers, 5 among the following 10 buzzers, 3 among the next 10 buzzers, and 2 among the last 10 buzzers. As mentioned elsewhere (Izquierdo, 1974b), the reason for this peculiar distribution of the shocks among the buzzers was that this was the average incidence of shocks per block of ten trials in buzzer-shock shuttle avoidance in rats from this laboratory (see control groups of Tables 3 and 4, and Izquierdo and Thadddu, 1975). Buzzer-buzzer intervals varied between 10 and 45 sec, and shock-shock or shock-buzzer intervals between 5 and 15 sec. Interstimulus intervals and the-next-stimulus-to-be-delivered were chosen at random within the limitations stated above. Only animals that responded to all shocks with shuttling were considered. Orienting and shuttle responses to the buzzer were observed. Under these conditions, shuttle responses to the buzzer may be considered as pseudoconditioned for several reasons (Izquierdo, 1974a, b): (a) they develop in the absence of stimulus pairing; (b) they leave no retention (Izquierdo, Salzano, Thomd, and Thadd~u, 1975); (c) they decline with repetition; (d) they are affected by several drugs in a different manner than avoidance responses (Vasquez and Izquierdo, 1970; Izquierdo, 1974a, b; Izquierdo and Thadd~u, 1975); (e) they are accompanied by central biochemical changes which differ from those of true conditioning (Gattoni and Izquierdo, 1974).

Two-way avoidance. Nine groups of rats were submitted to two sessions of shuttle avoidance conditioning with an interval of 1 wk between both sessions. The first or acquisition session consisted of 50 trials, and the second or retention session of 30. Each trial was as follows: the buzzer was set on for 5 sec, after which a 1.5 mA footshock was delivered to the starting side of the box.

Six of the groups (of eight rats each) received an appropriate injection (Table 3) 2 min before each animal was placed in the shuttle-box, where it was left unstimulated for 5 min before the first trial of the acquisition session.

LSD ON SHUTTLE AND ORIENTING RESPONSES 197

This type of treatment was called pretrial treatment (Evangelista and Izquierdo, 1971; McGaugh, 1973; Izquierdo and Thadd~u, 1975). Rats of the other three groups (ten animals per group) received the injections (Table 4) 30 sec after the last trial of the acquisition segsion (posttrial treatment, Evangelista and Izquierdo, 1971; McGaugh, 1973). On the retention test the animals of all groups received no injection whatsoever and were placed in the box 3 rain before the first retention trial.

In order to rule out possible influences of under- or overtraining in the posttrial groups, only animals which fulfilled the following criteria were considered: (a) at least one shuttle response among the first 10 trials; (b) no less than 10 shuttlings during the first 30 trials; (c) no less than 13 shuttlings during the last 20 trials. The results for only four animals had to be discarded; these do not appear in Table 4.

In all cases, only rats who shuttled to all shocks were considered. Statistical Comparisons between groups were by the Duncan multiple

range test (Bliss, 1967). Comparisons within groups (for example, performance in the first five buzzers versus performance in the last five), and others (for example, orienting responses in a group submitted to one treatment versus a group submitted to another) were by the t test.

RESULTS

"Buzzers alone." All animals of the drug-treated groups and all but two of the water group responded to the first buzzer with clear-cut, prominent orienting reactions. The incidence of these movements then declined along the session in all groups except for those treated with 0.3 mg/kg of LSD with or without dibenamine. Except in these two groups, in all others the difference between the number of orienting responses made during the first five buzzers and that made during the last five was significant at least at a P < 0.05 level. Therefore, it can be said that with 0.3 mg/kg of LSD habituation of the orienting response was blocked, and that this effect was not antagonized by dibenamine (Table 1).

The overall incidence of orienting responses to the buzzer was higher in all drug-treated groups than in the water group, and the enhancing effect of LSD on orienting was dose-dependent and unaffected by dibenamine (Table 1).

Pseudoconditioning. For each particular treatment the overall incidence of orienting responses to the buzzer was higher in the groups submitted to the pseudoconditioning routine than in the corresponding groups submitted to the "buzzers alone" situation (significance of the differences ranged between P < 0 . 0 1 and P<0 .0001 ) . In none of the groups submitted to pseudo- conditioning was there any habituation of the orienting response (differences between the first five and the last five buzzers were not significant).

198 IVAN IZQUIERDO

TABLE 1

Effects o f LSD and Dibenamine on Orienting Responses to a Buzzer (50 Buzzers Presented Alone in a Shuttle-Box)

Trea tmen t

Orienting re- sponses to

% Orienting re- first 5 minus Dose sponses per ses- those to last

(mg/kg) sion (50 buzzers) 5 buzzers

Water - 45.0 +- 5.8 2.5 -+ 0.5 LSD 0.075 68.0 +- 5.4 a 1.4 +- 0.5 LSD 0.3 86.3 -+ 3.4 b 0.6 -+ 0.2a Dibenamine 10 57.7 -+ 5.5 c 1.8 -+ 0.6 LSD + dibenamine 0.075 + 10 68.0 +- 6.0 a 1.8 -* 0.4 LSD + dibenamine 0.3 + 10 80.7 -+ 5.1 d 0.6 -+ 0.4a

Each group consists o f 10 rats. In this and following tables, data are expressed as means +- s tandard errors.

aSignificant difference vs water (1% in Duncan test). bSignificant difference vs water (1% in Duncan test) and vs LSD 0.075 mg/kg (1% in

Duncan test). cSignificant difference vs water (5% in Duncan test). dSignificant difference vs water (1% in Duncan test) and vs LSD 0.075 mg/kg +

dibenamine (5% in Duncan test).

TABLE 2

Effects o f LSD and Dibenamine on Orienting and Shutt le Responses to a Buzzer in a Pseudocondi t ioning Situat ion (50 Buzzers and

25 Unpaired Footshocks in a Shuttle-Box)

Dose % Orienting % Shutt le T rea tmen t (mg/kg) responses responses

Water - 76.4 +- 3.9 LSD 0.075 95.0 -+ 1.4 a LSD 0.3 100.0 b Dibenamine 10 95.4 + 1 4 a LSD + dibenamine 0.075 + 10 99.0 -~ 0~1 b LSD + dibenamine 0.3 10 100.0 b

8.4 +- 1.9 18.0 -+ 2.5 a 33.6 -+ 2.9 b

9.2 -+ 2.5 31.3 +- 2.5 b 43.8 -+ 1.7 c

Each group consists o f 10 rats. aSignificant difference vs water (1% in Duncan test). bSignificant difference vs water (1% in Duncan test) and vs LSD 0.075 mg/kg (1% in

Duncan test). cSignificant difference vs water (1% in Duncan test), vs LSD 0.075 mg/kg + dibena-

mine (1% in Duncan test) and vs LSD 0.3 mg/kg (1% in Duncan test).

LSD ON SHUTTLE AND ORIENTING RESPONSES 199

TABLE 3

Effect of Pretrial LSD and Dibenamine on Orienting and Shuttle Responses to a Buzzer During Acquisition and Retention Sessions in a Two-Way Avoidance

Situation (50 Buzzer-Shock Trials for Acquisition, and 30 7 Days Later for Retention; Note that all Treatments Were Made Just Prior to

Acquisition, and that Retention Tests Were Without Drugs)

Dose % Orienting % Shuttle Treatment (mg/kg) responses responses

(A) Acquisition

Water - 92.8 +- 1.4 47.0 +- 4.5 LSD 0.075 97.8 -+ 1.1a 67.5 +- 2.9 a LSD 0.3 100 a 47.5 -+ 5.5 Dibenamine 10 97.0 +- 1.7 a 48.5 +- 4.6 LSD + dibenamine 0.075 + 10 98.0 -+ 1.2a 29.8 -+ 5.1 b LSD + dibenamine 0.3 100 a 26.0 -+ 3.6 b

(B) Retention

Water - 95.0 -+ 3.5 70.8 +- 6.1 LSD 0.075 91.2 -+ 5.7 65.0 +- 9.2 LSD 0.3 88.1 -+ 3.4 32.7 +- 9.5 a Dibenamine 10 97.3 -+ 1.6 62.1 _+ 9.0 LSD + dibenamine 0.075 + 10 94.3 -+ 2.6 31.3 -+ 6.7 b LSD + dib enamine 0.3 + 10 98.7 -+ 0.9 29.2 -+ 5.5 a

Each group consisted of 8 rats. aSignificant difference vs water (1% in Duncan test). bSignificant difference both vs water (1% in Duncan test) and vs the corresponding

dose of LSD alone (1% in Duncan test).

LSD increased b o t h or ient ing and pseudocond i t ioned shuttlings to the

buzzer in a dose-dependen t fashion and, in fact, at the higher dose it caused

all animals to respond to all of the buzzers wi th orienting. Dibenamine on its

own enhanced or ient ing bu t had no effect on shutt l ing, bu t po ten t i a t ed the

e f fec t o f LSD on b o t h types o f responses. In the case o f orient ing, this

po t en t i a t i on was o f course only observable for the low dose o f LSD, since

wi th the higher one there was 100% o f or ient ing responses e i ther wi th or w i thou t d ibenamine (Table 2).

Two-way avoidance. Pretrial treatments. There were more or ient ing

responses to the buzzer in the water group submi t ted to avoidance training

than in the cor responding group submi t ted to pseudocondi t ion ing

(P < 0.0001). This conf i rms a previous repor t ( Izqu ie rdo et aL, 1975), and

may be related to the fact that there were also more shuttl ings in the

avoidance than in the pseudocondi t ion ing s i tuat ion, each shutt le being accompanied by an or ient ing response.

200 IVAN IZQUIERDO

TABLE 4

Effects of the Posttrial Administration of LSD on Retention of a Shuttle Response and on Orienting Responses to a Buzzer in a Two-Way Avoidance Situation (50

Trials for Acquisition and 30 7 Days Later for Retention; Note that all Treatments were 30 sec After the Last Acquisition Trial,

and that Retention Tests Were Without Drugs)

Dose % Orienting % Shuttle Treatment (mg/kg) responses responses

(A) Acquisition (predrug performance)

Water - 92.0 -+ 1.3 50.8 -+ 5.2 LSD 0.075 93.4 -+ 1.2 51.8 -+4.6 LSD 0.3 90.8 -+ 1.0 50.9 -+ 4.1

(B) Retention

Water - 93.3 -+ 3.4 67.0 -+ 8.7 LSD 0.075 94.3 -+ 2.0 60.0 -+ 9.0 LSD 0.3 93.6 -+ 1.6 69.8 -+ 6.9

aEach group consisted of 10 rats. Differences between groups not significant at the 5% level in Duncan test in either session.

LSD increased orienting in the acquisition session in a dose-dependent

fashion and, again, at the higher dose there was 100% of orienting responses to

the buzzer. As happened in the two other experimental situations, dibenamine

also enhanced orienting on its own. Similarly to the "buzzers alone" situation,

but unlike the pseudoconditioning one, dibenamine did not affect the

influence of LSD on orienting in the avoidance paradigm (Table 3). There

were no differences in orienting responses between groups on the retention

test. Neither dibenamine nor the higher dose of LSD had any effect on the

number of shuttle avoidance responses performed on the acquisition session,

but the lower dose of LSD caused a marked increase. However, when either dose of LSD was given together with dibenamine, there was a promounced

depression of shuttle behavior in this session (Table 3). Retention was no different from that of the water group in rats treated

with pretrial dibenamine or with the lower dose of LSD, but it was remarkably lower in all other groups (Table 3). In fact, it was so low that it may be viewed as nonexistent: the mean number of shuttles over the 30 retention trials in these three groups (see Table 3) was not different at a 5% level in a Duncan test from that of the 44 fully naive rats used for posttrial observations (36.4-+ 2.6% shuttle responses) (note that results for four of these rats were later discarded, see Material and Methods).

LSD ON SHUTTLE AND ORIENTING RESPONSES 201

Two-way avoidance. Posttrial treatments. Posttrial LSD had no effect on

performance o f the shuttle responses in the retent ion test (Table 4). Dibena- mine was not investigated since it had been previously found also to be wi thout effect using the same type of rats in the same task (Izquierdo and

Thadddu, unpublished). Intertrial crossings. Rats made no intertrial crossings in the "buzzer

alone" situation, but they made some in the two other tests. However, no significant differences could be detected between groups in any of these two behavioral situations at a 5% level in a Duncan test. Figures for intertrial crossings ranged between 0.3 + 0.2 (LSD, 0.075 mg/kg) and 1.9 + 0.5 per session (LSD 0.3 mg/kg plus dibenamine) in the pseudocondit ioning paradigm, and 0.1 -+ 0.1 (water) and 2.4 + 1.0 (LSD 0.3 mg/kg plus dibenamine) in the

pretrial groups of the avoidance paradigm.

DISCUSSION

A qualitative summary of the results is provided in Table 5, showing that drug-situation interactions were different for each type of response and for each situation. These results point to a clear-cut pharmacological separa- t ion o f the three types of responses, depending on contingencies which can be listed with sufficient precision, at least as concerns rats exposed to buzzers and to shocks in a shutt le-box like the one used here. In fact, animals respond

TABLE 5

"Prof'fles" of Drug Action on Orienting and Shuttling in Each of the Three Experimental Situations (A Qualitative Summary of Tables 1, 2, and 3)a

Situation Treatment

LSD low LSD high Diben- LSD low LSD high amine + diben- + diben-

amine amine

(A) Orienting responses

Buzzers alone + ++ + + ++ Pseudoconditioning + ++ + ++(~) ++ Avoidance + ++ + + ++

(B) Shuttle responses

Buzzers alone 0 0 0 0 0 Pseudoconditioning + ++ 0 ++(') +++(') Avoidance + 0 0 --(") -(")

a+ increase; 0 no effect; - decrease. (') potentiation; (.') inversion.

202 IV,~N IZQUIERDO

tO buzzers by (a)simple orienting, (b) orienting followed by pseudo- conditioned shuttling, and (c) orienting followed by conditioned shuttling. The limiting condition between (a) and the rest is the presence of footshocks, while that between (b) and (c) must be temporarily considered as consisting both of the buzzer-shock contiguity, and of the response-reinforcement relation (i.e., the avoidance contingency). According to some recent work by Katzev and Mills (1974), at least part of the avoidance shuttle responses can be accounted for by classically conditioned effects of the CS-US contiguity, independently of the avoidance contingency. Response plateaus, however, were found to be much lower with a classical than with an avoidance conditioning paradigm (Katzev and Mills, 1974).

This, and previous work on pseudoconditioning (Izquierdo, 1974a, b; Izquierdo and Thadddu, 1975) leads to several questions, such as: are rats inherently more efficient in shuttle avoidance learning than in classically conditioned shuttling? Can the difference between the classical and the avoidance situation be explained by response suppression by the shocks after the first few responses in the classical paradigm? Are the first few shuttlings which occur during classical or avoidance conditioning true conditioned responses, or mere "contaminant" pseudoconditioned responses (Evangelista and Izquierdo, 1971) perhaps due to preparedness phenomena (Bolles, 1970)? What is the relation between the tendency to perform pseudoconditioned shuttlings-which decreases with increasing exposure to the buzzer-and that created by the stimulus-reinforcement and the response-reinforcement relations?

Depending on the answers to these questions, avoidance shuttling might be split into several components related to different underlying processes, ranging from preparedness phenomena (or drive-dependent phenomena, Anisman and Waller, 1973) responsible for pseudoconditioning, to classical conditioning of some components of the motor defensive repertoire (Bolles, 1970), and to selective strengthening of a response which meets reinforcement requirements, according to one or to other of the available avoidance theories (Anisman and Waller, 1973; Katzev and Mills, 1974).

As regards the roles of possible physiological-biochemical mechanisms in each type of response, which were separated from each other by the use of drugs such as LSD and dibenamine, the present data allow few tentative conclusions. It is, in fact, tempting to propose that the effect of LSD on orienting is related to the induction of hippocampal theta rhythm, as has, in fact, been postulated by Radulovacki and Adey (1965) for the cat. Orienting is associated with theta (Grasty~n and Vereckzei, 1974. Izquierdo, 1974c), and LSD stimulates both; furthermore, dibenamine blocks the effect of LSD on neither (Izquierdo and Cavalheir, unpublished). Since the electrophysiology of shuttle behavior is not known, I have no available explanation of a similar type for the effect of LSD on shuttling. As to the effect of dibenamine on its

LSD ON SHUTTLE AND ORIENTING RESPONSES 203

own on orienting, it can not be ascribed to a similar mechanism as that of LSD, since dibenamine does not cause theta (Izquierdo and Cavalheir, unpublished).

Assuming that the influence of dibenamine on LSD-induced response changes depended mainly on sympathetic blockade by the former agent, one could infer that the sympathetic stimulant properties of LSD (Jarvik, 1970) had a different weight in the various situations. This conclusion is possibly strengthened by the tentative finding that the "opt imum" level of sympathetic function required for avoidance is not the same as that for pseudoconditioned shuttling (Izquierdo and Thadd~u, 1975). Therefore, one could affirm that LSD enhancements of orienting and pseudoconditioning were largely indepen- dent of the sympathomimetic action of the drug. The enhancing effect of dibenamine on orienting, and the potentiation of LSD effects on pseudo- conditioned responses by dibenamine, might even suggest that sympathomime- tic and other effects of LSD are in contrast with each other, at least as concerns response changes which are independent of stimulus-reinforcement contiguity and of the response-reinforcement relation. Vice versa, the an- tagonism by dibenamine of LSD effects on avoidance suggests that the sympathomimetic component plays a considerable role in the modulation of conditioned responses (see also Izquierdo and Thadddu, 1975). However, it cannot be decided at this moment whether this must be ascribed to an effect on classically conditioned responding or to an effect on a response- reinforcement event.

The effects of LSD on acquisition of shuttle avoidance deserve some special comment. Bignami (1972) had reported that a low dose of this drug may enhance, and a high one either depress or have no effect on this type of behavior, as has been observed in other learning tasks (Bignami, 1966; Izquierdo, 1975). Superficially, the present results on pretrial LSD support those previous findings. However, the drug cannot be said to have stimulated learning even at the low dose, since shuttle performance did not increase in the retention session in rats treated with this substance as it did with water (P<0 .01 ) . In fact, with the higher dose of LSD there was instead a significant depression of retention, of such magnitude that retention itself was nonexistent. Therefore, it seems likely that LSD had two parallel and opposite effects on shuttling in the avoidance situation, both probably dose-dependent: a stimulant one on performance, and a depressant one on acquisition. It is true that the retention deficit caused by LSD might be ascribed to a dose-dependent dissociation of learning. This, however, seems unlikely since dibenamine "unmasked" a depressant effect of LSD in acquisition sessions as well, which cannot be ascribed to state-dependent learning. (State-dependency seems to be ruled out also by some unpublished observations which show no effect on performance in the retention session of LSD or LSD + dibenamine administered just prior to that session.)Furthermore, posttrial LSD treatments

204 IVtkN IZQUIERDO

had no effect on later performance, which makes it safer to ascribe drug effects on learned responses to an action on acquisition rather than to one on memory consolidation (McGaugh, 1973; Izquierdo, 1974c).

I t may be noted that in the present paper LSD had a depressant influence in two clearly distinct forms o f learning: habi tuat ion of orienting in the "buzzer alone" si tuation," and acquisition of shuttle avoidance.

In conclusion, the present results may be considered to: ( i ) h a v e succeeded in bringing about a pharmacological "dissect ion" o f orienting from pseudocondi t ioned shuttling and from shuttle avoidance; (ii) contr ibute to the individualization o f some of the factors involved in the emission o f one or other response depending on the context of the aversive situation; (iii) illu- strate some aspects of the psychopharmacology o f LSD and o f dibenamine. The several obscure points still await further investigation.

REFERENCES

Anisman, H., and Waller, T. G. (1973). Effects of inescapable shock on subsequent avoidance performance: role of response repertoire changes. Behav. Biol. 9, 331-335.

Barratt, E. S., and Pray, S. L. (1965). Effect of a chemically depressed amygdala on the behavioral manifestations produced in cats by LSD-25. Exp. Neurol. 12, 173-180.

Bignami, G. (1966). Pharmacologic influences on mating behavior in the male rat. Effects of d-amphetamine, LSD-25, strychnine, nicotine and various anticholinergic agents. Psychopharmacologia 10, 44-58.

Bignami, G. (1972). Facilitation of avoidance acquisition by LSD-25. Possible effects on drive-modulating systems. Psychopharmacologia 25, 146-151.

Bliss, C. I. (1967). "Statistics in Biology. Volume 1." New York: McGraw Hill. Bolles, IL C. (1970). Species-specific defense reactions and avoidance learning. Psychol.

Rev. 77, 32-48. Evangelista, A. M., and Izquierdo, I. (1971). The effect of pre- and post-trial ampheta-

mine injections on avoidance responses of rats. Psychopharmacologia 20, 42-47. Gattoni, R. C., and Izquierdo, I. (1974). The effect of conditioning and pseudo-

conditioning on rat hippocampal and neocortical RNA metabolism. Behav. Biol. 12, 67-80.

Grasty~n, E., and Vereckzei, L. (1974). Effects of spatial separation of the conditioned signal from the reinforcement: a demonstration of the conditioned character of the orienting response or the orientational character of conditioning. Behav. Biol. 10, 121-146.

Hughes, R. N. (1973). Effects of LSD on exploratory behavior and locomotion in rats. Behav. Biol. 9, 357-365.

Izquierdo, I. (1974a). Possible peripheral adrenergic and cholinergic mechanisms in pseudoconditioning. Psychopharmaeologia 35, 189-193.

Izquierdo, I. (1974b). Effect on pseudoconditioning of drugs with known central nervous activity. Psychopharmacologia 38, 259-266.

Izquierdo, I. (1975). Pharmacological observations on the role of the hippocampus and of the autonomic nervous system in learning and performance. Current Advan. Psychopharmacol. 1, 65-106.

LSD ON SHUTTLE AND ORIENTING RESPONSES 205

Izquierdo, I., Salzano, F., Thom~, F. S., and Thadd~u, R. (t975). Shuttle behavior in weanling and in adult rats. Behav. BioL 13 (in press).

Izquierdo, I., and Thadd~u, R. (1975). The effect of adrenaline, tyramine and guanethi- dine on two-way avoidance conditioning and on pseudoconditioning. Psycho- pharmacologia (in press).

Jarvik, M° E. (1970). Drugs used in the treatment of psychiatric disorders. In L. S. Goodman and A. Gilman (Eds.), "The Pharmacological Basis of Therapeutics," pp. 151-203. New York: Macmillan.

Katzev, R. D., and Mills, S. K. (1974). Strain differences in avoidance conditioning as a function of the classical CS-US contingency. J. Comp. PhysioL Psychol. 87, 661-671.

McGaugh, J. L. (1973). Drug facilitation of learning and memory. Ann. Rev. Pharmacol. 13, 229-241.

Orsingher, O. A., and Fulginiti, S. (1971). Effects of alpha-methyl-tyrosine and of adrenergic blocking agents on the facilitating action of amphetamine and nicotine on learning. Psychopharmacologia 19, 231-240.

Radulovacki, M., and Adey, W. R. (1965). The hippocampus and the orienting reflex. Exp. Neurol. 12, 68-83.

Stoff, D. M., Mandel, I. J., Gorelick, D. A., and Bridget, W. H. (1974). Acute and chronic effect of LSD and 3,4,-dimethoxyphenylethylamine on shuttle-box escape/avoid- ance in rats. Psychopharmacologia 36, 301-312.