Biomedical subjects

S M Pellis

Publications and source records attributed to S M Pellis.

61 records · Page 4Linked to original sources

PubMed1986

Bandage backfall: labyrinthine and non-labyrinthine components.

A cataleptic animal clings in a vertical position, unmoving, for abnormally long periods by supporting some of its weight on its hindlegs, grasping with the forepaws, flexing its forelimbs, and holding the head horizontal. When the head is snugly wrapped with a bandage, the head slowly falls backward, the neck hyperextends, the forelimbs extend and the grasp is released, resulting in the animal falling backward to the ground. It was earlier suggested that in cataleptic animals, the bandage inhibits vestibular and kinesthetic mechanisms of head support, yielding the backfall sequence [35]. However, preliminary experiments showed that labyrinthectomized rats made cataleptic by haloperidol fall backwards when placed in a vertical clinging position, even without a bandage, suggesting that in the rat the bandage-backfall reaction depends only on the vestibular system. In the present paper, this result is verified but, by additional experiments, the latter conclusion is shown to be incorrect. In labyrinthectomized rats made cataleptic by other means (lateral hypothalamic damage, or bulbocapnine), backfall from clinging did not occur unless a bandage was applied. Therefore, the bandage does indeed appear to inhibit the kinesthetic mechanisms that maintain head support in labyrinthectomized cataleptic rats. Haloperidol, particularly in high doses, greatly weakens postural support in labyrinthectomized rats (causing the animal to sag down and fall back when clinging), although the effect is not detectable in rats with labyrinths intact. However, labyrinthectomy reveals that the bandage can trigger an active dorsiflexion of the neck which in itself appears to inhibit clinging and righting. Bandage-induced dorsiflexion is present to a much lesser degree in intact animals, indicating that labyrinthine mechanisms inhibit the dorsiflexion reflex. Therefore, in the intact, cataleptic rat the bandage backfall reaction appears to be produced by the combined effects of a passive component (inhibition of kinesthetic support mechanisms), and an active component (elicitation of dorsiflexion of the neck).

Animals↗

PubMed1986

Morphine subtracts subcomponents of haloperidol-isolated postural support reflexes to reveal gradients of their integration.

Although cataleptic rats do not spontaneously orient, scan, or walk, they will cling, stand, right themselves in the air, and resist being displaced from a stable position (Schallert, Whishaw, De Ryck, & Teitelbaum, 1978). Morphine produces a state of immobility in which all reflexes used for stable static support (e.g., standing, righting, clinging, and bracing) appear to be inhibited (De Ryck, Schallert, & Teitelbaum, 1980). Addition of morphine to haloperidol abolished or reduced those reflexes used to defend against slow postural displacements (e.g., bracing) but left intact those used to protect against fast postural displacements (e.g., righting in the air). However, although intact, these responses to fast postural displacements were completely abolished by labyrinthectomy, showing that they were controlled only by vestibular inputs. During recovery from morphine's effects, the responses to slow postural displacements reemerged, revealing fractional subcomponents. Furthermore, the reorganization of the subcomponents proceeded along specific body gradients; for example, bracing and standing reemerged caudorostrally, while at the same time, righting and clinging reemerged rostrocaudally.

Animals↗

PubMed1985

Fractionation of the cataleptic bracing response in rats.

In haloperidol-treated rats, bracing, i.e., resistance to displacement along a horizontal surface, was found to involve four components: gripping by the digits, extension by the limbs, stiffening of the body axis and arching the vertebral column towards the displacing force. Labyrinthectomy weakened the bracing of the forequarters as did application of a head bandage. Labyrinthectomy, when combined with head bandage, completely abolished all forequarter bracing responses. Neither manipulation affected the bracing responses of the hindquarters. The hindquarter bracing reaction was abolished by application of an abdominal bandage, which left most of the forequarter responses intact. Isolation of fore- and hindquarter bracing responses revealed that whereas gripping by the digits and extension by the limbs could occur independently in either part of the body, stiffening of the body axis and arching of the vertebral column originated in the hindquarters. However, although these latter components of bracing originate in the hindquarters, as evidenced by their abolition with application of an abdominal bandage, their recruitment into the anterior of the body only occurred when the bracing of the forequarters was unimpaired. Either labyrinthectomy or head bandage prevented stiffening and arching of the vertebral column from occurring in the forequarters, even though these procedures had no effect on the hindquarters. Labyrinthectomy, head bandage and abdominal bandage all fractionated the bracing response over a wide range of haloperidol dosages (0.5, 1.0, 2,5, 5,0 and 7.5 mg/kg).

Animals↗

PubMed1985

Head displacement and bracing in haloperidol-treated rats compared to rats with lateral hypothalamic damage.

A characteristic of catecholamine-depletion-induced catalepsy is that such animals resist horizontal displacement, forward, backward or sideward, by bracing, i.e., pushing against the displacing force rather than stepping away as do normal animals. In this report the bracing responses of two cataleptic preparations were compared: (1) intact rats given haloperidol, a dopamine antagonist, and (2) rats with large lesions of the lateral hypothalamus (LH). Although both preparations exhibited exaggerated bracing responses when pushed, the LH rats acted in a non-cataleptic manner when pushed backward by the head; they retreated backward. The backward walking was a head-elicited response, because pushing the body backwards by the shoulders elicited bracing, not walking. Other forms of head displacement elicited body bracing if the body's stability was challenged: as when the head (and thus the body) was pulled forward; or no strong bracing responses if the head was displaced without affecting the body's stability, i.e., when as the head was pushed laterally. Therefore, retreating rather than bracing was elicited by one specific form of head displacement: backward. In contrast, haloperidol-treated rats braced whenever the body's stability was challenged, including when the head was pushed backward.

Animals↗

PubMed1985

Previous experience disrupts atropine-induced stereotyped "trapping" in rats.

Three experiments were conducted to investigate the phenomenon of atropine-induced stereotypic trapping in rats reported by Schallert, De Ryck, and Teitelbaum (1980). The first two showed that such trapping was disrupted by previous experience with the specific trapping task or the test context alone. The third showed that, in response to the test context, specific behaviors were altered in rats experienced with the context. Inexperienced atropine-treated animals moved slowly and showed a strong thigmotaxis to surfaces with the body and particularly the snout. The hindquarters did not cooperate well with the movements of the forequarters. In contrast, atropine-treated animals familiar with the context moved with medium-speed, coordinated movements, were independent of surface contact with body and snout, and the hindquarters cooperated fully with forequarter movements. These reactions of drugged animals were exaggerated forms of those of undrugged animals to the unfamiliar and familiar context, respectively. Thus, atropine enhances the reactions of the rat to both a novel and a familiar environment. The enhanced reactions to a novel environment appear as stereotyped behaviors that trap the animal in particular configurations of surfaces. The enhanced reactions to a familiar environment abolish the stereotypic trapping normally produced by atropine. This pattern of results indicates that it is not atropine per se that leads to trapping. Rather, stereotypic trapping develops as a consequence of an interaction between the adaptive responses of the rat to a novel environment and atropine.

Animals↗

PubMed1983

Locomotor-rotational movements in the ontogeny and play of the laboratory rat Rattus norvegicus.

During postnatal development, young laboratory rats, Rattus norvegicus, exhibit a variety of locomotor-rotational movements, that is, runs and jerk-jumps, in both playful and nonplayful contexts. The frequency of movement types differed between contexts. Some contexts, such as exploration and sleeping, contained spontaneously (i.e., possible eliciting stimuli were not observed) occurring jerk-jumps which varied with increasing age. In some contexts, such as social play, in which locomotor-rotational movements were elicited by observed stimuli, the frequency of jerk-jumps remained similar throughout ontogeny. During social play some locomotor-rotational movements were found to have immediate functions, such as achieving advantage over the partner during play-fighting, and as a means of terminating sensory input from the partner at the end of social contact.

Age Factors↗

PubMedDate not supplied

Uses of vision by rats in play fighting and other close-quarter social interactions.

Enucleated juvenile rats were compared to sighted juveniles, and tested over six trials. In some of these trials, the vibrissae were clipped and the test chamber was flooded with white noise. Even though the enucleated rats played, they did so in an atypical manner. They tended to initiate more playful and other social contacts, and were more likely to defend themselves if contacted. When they did defend themselves, they adopted behavior patterns that were more likely to evade the partner's attack. In addition, the enucleated rats were hypersensitive to the partner, being more likely to respond defensively when contacted further from the nape (the main play target). All these changes in play fighting by nonsighted rats suggest that the loss of vision leads to motivational changes in activity and reactivity, and so has an indirect effect on play behavior. In addition, direct evidence is also provided to show that vision is used to orient attacks to the nape. When the vibrissae were closely clipped, the sighted rats continued to make direct attacks on the partner's napes, whereas the nonsighted rats did not. Rather, they first contacted some other part of the partner's body and then oriented to the nape. Another test paradigm was used to determine whether vision is used to trigger defensive responses. The rats were partially food deprived as adults and were filmed in a food wrenching and dodging situation where one rat was given a food pellet and the other allowed to steal it. Measurement of the distance at initiation of the lateral swerve away from the approaching partner (i.e., dodge) showed that when the vibrissae are clipped, the sighted rats continued to initiate dodges at the same distance, whereas the nonsighted rats could not. Therefore, vision appears to have an active role in organizing movement sequences of attack and defense in play fighting and other close-quarter interactions.

Aggression↗