The behavioural response to picrotoxin (25-500 ng) injected into the colliculus superior (CS) of freely moving cats was investigated. The maximal response to unilateral injections of picrotoxin (greater than or equal to 200 ng) was characterized by the following sequence of behavioural events. During the first 5 min after the injection the cat executed retroflexions of the contralateral ear. After 1-5 min these contralateral ear movements were followed by short, contralateral head movements. As time progressed the front part of the body, including the forelimbs, became involved in the movements resulting in contralateral torso movements. Finally, as the response was maximal, the whole body became involved in the movements resulting in contralateral body movements. Data are shown indicating that most of these behavioural phenomena were dose-dependent, locus-specific, and GABA-specific. Bilateral injections of picrotoxin resulted in similar characteristic movements, but now directed towards both sides and/or directed 'ventrocaudally'. Finally, it was found that blindfolding the animals did not change the response to unilaterally injected picrotoxin. As the behavioural phenomena described here are dissimilar to the effects observed after disturbing the GABAergic activity in the substantia nigra, pars reticulata (SNR), it is concluded that the CS, being an output station of the SNR, transforms its input signals into new output signals. Finally, it is suggested that picrotoxin resulted in a fixed code at the level of the CS, forcing the animal to execute characteristic motor patterns.

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PubMedDate not supplied

Locus coeruleus and substantia nigra: involvement in morphine-induced behavior.

Cats pretreated with morphine (5 mg/kg, IP) received naloxone into the area of the locus coeruleus (LC) or the area of the substantia nigra (SN). The LC-treated animals stopped the morphine-induced stereotyped behavior and showed normal but hyperactive behavior. The SN-treated animals, however, ceased their movements of the head and the forelegs, adopted a rigid posture with extended forelegs and became hypoactive. It is concluded that both the LC area, which contains noradrenergic cell bodies, and the SN area, which contains dopaminergic cell bodies, are sites of action of morphine on behavior.

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PubMedDate not supplied

Asymmetrical spotting and direction of circling in the varitint-waddler mouse.

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Animals↗

PubMedDate not supplied

Use of high and low responders to novelty in rat studies on the role of the ventral striatum in radial maze performance: effects of intra-accumbens injections of sulpiride.

High and low responders to novelty (Wistar rats) were selected with the help of an open-field test and then equipped with intra-accumbens cannulae. They were then tested in a simple four-arm radial maze during 5 successive days, three trials per day, following intra-accumbens injections of distilled water or the dopaminergic D2 antagonist (+/-)-sulpiride. The injections were given 15 min before the first trial on each day. Both types of drug-naive rats reached the same level of performance on day 5. However, high responders made more visits, more revisits, and needed less time to make the first visit than low responders. Moreover, high responders showed their greatest increase in learning 2 days earlier than low responders. It is discussed that these differences between high and low responders are not due simply to differences in locomotor activity, but are due to a subtle, but important, difference in the mode of learning between both types. Sulpiride significantly attenuated the learning in both rat types; however, its effect in high responders was much less than that in low responders. It is suggested that the effects of sulpiride are not due to changes in locomotor activity, motivation, or perception, but are due to a learning deficit. The data are discussed in view of the genetic variation in the neurochemical and neurobiological makeup of the nucleus accumbens in both types.

Animals↗