Conditioning of amphetamine-induced behaviour in the albino rat

12 male albino rats were injected with amphetamine, 5 mg/kg, every 4th to 5th day, 30 times/rat in all, and their behaviour recorded 10–31 min after injection. During the observation period 4 rats, the stereotypy-group, were electro-stimulated when they did not demonstrate stereotypy, which is a well-defined, constantly and spontaneously occurring amphetamine-induced behaviour. 4 rats non-stereotypy-group, were stimulated when demonstrating stereotypy. 4 rats acted as control group and were not stimulated.Whereas there was no difference between the groups during the first experiments, their behaviour differed in a statistically significant was during the experiments with stimulation, and the differences remained during control experiments without stimulation. The groups differed in the following way: the stereotypy-group demonstrated a high percentage of stereotypy per experiment, the non-stereotypy-group a low percentage, while the results of the control group lay between those of the stimulated groups.It is concluded that stereotypy can be subjected to conditioning.     

A possible caudate-cholinergic mechanism in two instrumental conditioned responses

Two series of experiments were performed in cats in which 80 Μg of atropine in 5 Μl were injected into the head of both caudate nuclei. In order to obtain a reward (a constant amount of milk) the first group of Ss learned to walk a distance of 75 cm after the delivery of 4 flashes, while the second group learned to press a lever. Both tasks were significantly impaired (P<0.05) after atropine injection. The motor reflex response as well as hunger motivation were not modified by the substance. A caudate-cholinergic mechanism involved in the maintenance of motor conditioned responses is proposed.     

THE DIFFERENTIAL CONDITIONABILITY OF TWO COMPONENTS OF THE SKIN CONDUCTANCE RESPONSE

The dual effector basis of the skin conductance response (SCR) was investigated in an experiment in which responses from both the dorsal and palmar surfaces of the hand were classically conditioned using a delayed, discrimination conditioning paradigm. Orienting (OR), anticipatory (AR) and unconditional responses (UCR) were distinguished on the basis of latency. Both the anticipatory response and the response which occurred when the unconditional stimulus (UCS) was omitted (CR) were conditional. The magnitude of the response from the dorsal and palmar placements was similar for the ORs, UCRs, and CRs, but the palmar ARs were significantly greater than the dorsal. A conditioning index which took into account the magnitude of the UCR, revealed that the palmar AR differentiated between reinforced and non-reinforced conditional stimuli to a greater degree than the dorsal response. These results are consistent with the hypothesis that the epidermal component of the SCR, reflected in measurements from the dorsum of the hand, accompanies the alerting or orienting response of the organism, whereas the sweat gland component of the SCR, represented largely in measurements from palmar sites, is primarily associated with a defensive, anxiety-like response.     

Morphine and naloxone: effects on conditioned fear as measured with the potentiated startle paradigm.

Morphine (0.6 to 10 mg/kg) produced a dose-dependent reduction of the potentiated startle effect where acoustic startle amplitude is normally increased in the presence of a light previously paired with a shock. The effect was selective since the same doses did not appreciably depress baseline levels of startle. Naloxone (2 mg/kg) did not significantly affect potentiated startle, but antagonized the ability of morphine (10 mg/kg) to block potentiated startle. Morphine did not block potentiated startle by accelerating extinction. The advantages of this paradigm for studying fear or anxiety were discussed.     

Asymmetrical dissociation of learning between scopolamine and Wy 4036, a new benzodiazepine tranquilizer

Summary Hungry rats, trained to drink milk rapidly in a small test chamber, received a single electric shock 30 min after injections of either scopolamine, a new benzodiazepine tranquilizer (Wy 4036), or saline. One week later, subgroups were tested for conditioned suppression of the drinking response under all drug conditions, according to a factorial design. Conditioned suppression transferred from saline to both drugs, across the same drug, and from scopolamine to Wy 4036, but not from the drugs to saline or from Wy 4036 to scopolamine. All groups tested under Wy 4036 showed supernormal suppression. The pattern of asymmetrical transfer was explained by a hypothetical neural conditioning model. The supernormal suppression caused by Wy 4036 was attributed to enhanced retrieval of the memory of the shock experience.     

Expectancy and Magnitude of Reaction to a Noxious UCS

The relationship between expectancy and magnitude of reaction to a noxious UCS was examined in studies using a classical conditioning paradigm, in habituation studies, and in studies using a count-up to stimulus presentation. An initial hypothesis that accurate expectancy reduces reactivity was found inadequate, and replaced by one that stated that accurate expectancy facilitates habituation. Although this hypothesis was consistent with the data reviewed, it was concluded that it, too, requires modification. The final hypothesis proffered was that accurate expectancy facilitates habituation when it fosters appropriate modulation of attention, which, for highly threatening stimulation, consists of a degree of restriction of attention to begin with, followed by increasing attention to new elements of the stimulus complex as reactivity to old elements is reduced.     

CLASSICAL CONDITIONING OF THE PERIPHERAL VASOMOTOR ORIENTING RESPONSE

The present study demonstrates that the peripheral vasomotor response is conditionable. The paradigm used involved a delayed, differential conditioning procedure and utilized both a conditioning and sensitization control group. The results demonstrate that the vasomotor orienting response can be differentially conditioned.     

Effect of number of conditioning trials on the development of associative tolerance to morphine

The acquisition of associative tolerance to the analgesic effects of morphine was investigated by giving independent groups of rats 1, 3, 5, 8, 14, 20, or 30 administrations of drug either explicitly paired or unpaired with a distinctive context. Tolerance, assessed on a tail-flick device using dose-response curve (DRC) methodology, developed more rapidly and reached greater magnitude when morphine and the distinctive context were explicitly paired rather than explicitly unpaired. Tolerance magnitude in both conditions reached a maximum at eight conditioning sessions. It is argued that the tolerance found in both treatment groups was associatively controlled. The function of handling and injection cues as conditioned stimuli, and the deleterious effects of latent inhibition and partial reinforcement on conditioned excitation and conditioned inhibition are discussed.     

Conditioning and place-specific sensitization of increases in activity induced by morphine in the VTA

The conditionability of increases in locomotor activity induced by morphine administration into the ventral tegmental area was studied in rats. Morphine produced a clear increase in locomotor activity that was reversed by the opiate receptor blocker, naloxone, and blocked by the neuroleptic, pimozide, suggesting the mediation of this effect by the ascending mesolimbic dopamine system. The increase in locomotor activity showed sensitization with repeated morphine administrations and this sensitization was found to be specific to the environment in which morphine was administered. Conditioning tests also revealed that, in the absence of morphine, increased locomotor activity was elicited by the administration environment. Pimozide blocked the development of the conditioned sensitization. These data demonstrate that a learned association developed between this excitatory action of morphine and the administration environment. These results have important implications for the role of conditioning factors in relapse to drug use and may provide an explanation for conditioning data obtained when morphine is administered systemically.     

Conditioned ejaculatory preference in male rats paired with haloperidol-treated females

We have shown that males trained to copulate with the same almond-scented female in environments that restrict access to the female during copulation develop a conditioned ejaculation preference (CEP) for their familiar female over a novel one. These findings suggest that copulation in environments in which the female spends more time away from the male and in which the male anticipates female copulatory contact facilitates the development of CEP. However, conditioned place and partner preference studies have shown that males prefer easy over obstructed access to the female partners during copulation. The objective of this study was to attempt to understand the discrepancy between the findings by examining the importance of female proceptive behavior and genital stimulation in the development of CEP while keeping the environment constant. Experiment 1 investigated the effect of administering a range of doses of haloperidol, a dopamine D2-receptor antagonist, to females, on female and male sexual behavior. Haloperidol treatment significantly reduced female proceptive behaviors in a dose-dependent manner. Experiment 2 examined the importance of female proceptive behaviors in the development of CEP by inhibiting those behaviors with haloperidol. Following alternating copulatory trials with scented or unscented haloperidol- or saline-treated females, males were given a partner preference test. Males displayed a preference to copulate with females bearing cues predictive of prior copulation with haloperidol-treated females, suggesting that males do not require female proceptive behaviors for the development of CEP. We conclude that copulation to ejaculation at a male's preferred rate is essential for the development of CEP, as it is for the development of a sexually-conditioned place preference.