Anatomical demonstration of the involvement of the substantia nigra in contraversive circling elicited by electrical stimulation of the medial forebrain bundle in the cat: a retrograde transport study using horseradish peroxidase subsequent to an electrolytic lesion

Vestibulo-Cardiorespiratory Responses at the Onset of Chair Rotation in Endurance Runners

Stimulation of the vestibular system has been reported to elicit ventilatory and circulatory changes in humans. The purpose of this study was to clarify the characteristics of vestibular-mediated ventilatory and circulatory responses in male endurance runners at the onset of passive chair rotation, which selectively stimulates the semicircular canals. Fourteen runners and 14 male untrained subjects participated. The vestibular stimulus test, which consists of 180 degrees chair rotations (left or right half-turns on an earth-vertical axis) for a duration of 2 s, was carried out on each subject. Inspiratory minute ventilation, tidal volume, respiratory frequency, heart rate, and blood pressure were measured by breath-by-breath and beat-to-beat techniques before, during, and after the chair rotation for a total of 60 s. It was found in this study that (i) the relative change of minute ventilation response in the endurance runners was significantly (P < 0.05) greater than in the untrained subjects during and after the rotation, and that (ii) no significant group differences were observed in heart rate and mean blood pressure responses during and after the rotation. In conclusion, vestibular-mediated ventilatory response, but not circulatory response, at the onset of the chair rotation in the endurance runners was significantly greater than that in the untrained subjects. The results from the present study suggest that an increase in vestibulo-ventilatory response would be attributed to an adaptation to long-term endurance training.

Behavioral responses induced by electrical stimulation of the caudate nucleus in freely moving cats

The caudate nucleus and adjacent structures of 26 freely moving cats were stimulated through multiwire electrodes chronically implanted. Two main effects here observed with trains of pulses of high frequency (100 Hz) and short duration (1 s): (1) contralateral head turning and (2) arrest reaction, which was associated with crouching and escape behavior. The responses follow a certain topographic distribution. Head turning was elicited with the lowest mean threshold in sites located in the internal two-thirds and caudal region of the caudate nucleus, while the arrest reaction was elicited from the ventromedial region of the caudate and adjacent nucleus accumbens. Stimulation of the corpus callosum and internal capsule produces postural instability, ventral flexion of the head and flexion of the contralateral limb. The extra-caudate responses were accompanied by contralateral head turning when the stimulated points were near of the caudate border. Experimental evidence suggested that striatal responses were not due to current spread to adjacent structures or to activation of corticofugal fibers. The head rotation was suppressed following interruption of the ipsilateral striatal outflow by electrolytic lesion of the globus pallidus and adjacent internal capsule. The chemical lesion of the substantia nigra and the ventral pallidum produced a significant increase in the stimulation threshold for head turning and arrest reaction, respectively. These results suggest a topographic arrangement of the responses evoked by electrical stimulation of the caudate nucleus in the cat, which are mediated by the substantia nigra pars reticulata and the ventral pallidum.

Hypothalamic substrates for brain stimulation-induced grooming, digging and circling in the rat

Despite a great number of studies concerned with the induction of specific behavioural responses from the rat hypothalamus by electrical brain stimulation, hypothalamic response areas and underlying neural substrates have never been determined accurately. In this study the boundaries of the hypothalamic response areas for grooming, digging and circling were delimited using moveable electrodes, an enriched environment containing a variety of goal objects, and an appropriate statistical technique. A total of 641 hypothalamic sites in 71 male CPB/WU Wistar rats were electrically stimulated. Results are plotted on a detailed stereotaxic brain atlas of the rat hypothalamus. Positive sites for any behavioural response cluster into restricted hypothalamic areas. Discriminant analysis of both positive and negative electrode localizations yields areas with high, intermediate or low probabilities of inducing the behavioural response concerned. Each response has its own response area where probabilities are high, although there may be overlap. Even within response areas a distinction can be made between areas in which the response can be induced at relatively high or low threshold current intensities. Lowest threshold sites within electrode tracks are often clustered. In search of neuroanatomical correlates, grooming is related to the distribution of ACTH-immunoreactive neural elements, digging is related to the distribution of efferent fibres from the bed nucleus of the stria terminalis, and circling is related to the distribution of dopaminergic fibres of the nigrostriatal pathway. The results clearly point to the stimulation site being the most important determinant of the evoked behavioural response. Evidently behavioural specificity does exist within the hypothalamus.

Involvement of nigrostriatal dopamine neurons in the contraversive rotational behavior evoked by electrical stimulation of the lateral hypothalamus

This experiment was conducted to determine if nigrostriatal dopamine (DA) neurons are necessary for the contraversive rotational behavior evoked by electrical stimulation in the lateral hypothalamus. Rats were tested daily for electrical stimulation-induced rotational behavior (ESRB) for 5 days, and then given an injection of 6-hydroxydopamine (6-OHDA) or saline into the ipsilateral substantia nigra. The nearly total depletion of striatal DA (greater than 96%) completely abolished contraversive ESRB and resulted in the appearance of ipsiversive ESRB. Partial DA depletion (less than 95%) had no effect on contraversive ESRB. In animals with a partial DA depletion subsequent treatment with a low dose of alpha-methyl-p-tyrosine (40 mg/kg) attenuated contraversive ESRB, while having no effect on control animals, or the ipsiversive turning in animals with greater than 96% DA depletion. We conclude that the nigrostriatal DA system is necessary for contraversive rotational behavior evoked by lateral hypothalamic stimulation, but that only a small percentage of DA fibers are required to maintain apparently 'normal' function--at least as indicated by contraversive ESRB.

Sex differences and estrous cycle dependent variation in rotational behavior elicited by electrical stimulation of the mesostriatal dopamine system

In this study electrical stimulation-induced rotational behavior was used as a behavioral index of mesostriatal dopamine (DA) activity to investigate gender and hormonal influences on the DA system. In female rats we found estrous cycle related variations in electrical stimulation-induced rotational behavior. A constant electrical stimulus produced significantly more turning on the day of estrus, than it did 24 h later, on diestrus 1. Gonadectomy attenuated contraversive rotational behavior in female, but not male rats. In contrast, ovariectomy had no effect on the ipsiversive rotational behavior produced by stimulation of the reticular formation. This evidence supports the idea that endogenous changes in gonadal hormone levels influence the functional activity of the mesostriatal DA system in a sexually dimorphic manner.

Lateralized loss of biting attack-patterned reflexes following induction of contralateral sensory neglect in the cat: a possible role for the striatum in centrally elicited aggressive behaviour

A syndrome of "contralateral sensory neglect' was induced by hypothalamic knife cuts in 6 of 10 cats in which quiet biting attack behaviour could be elicited by lateral hypothalamic stimulation. The contralateral sensory neglect in the 6 affected cats was accompanied by a loss on the "neglected' side of the body of the patterned reflexes which mediate positioning of the head to bite and the jaw-opening component of biting. As a result, when these cats were stimulated in the lateral hypothalamus, although they continued to approach and even make tactile contact with the rat, they generally failed to bite it. Analysis of the histological and behavioural data suggested that damage to the nigrostriatal and/or striato/pallidonigral fibre systems provided the likely basis for both the induction of the contralateral sensory neglect and the lateralized patterned reflex loss. It was suggested, with respect to these specific patterned reflex components of the attack, that an important contribution may be made by the striatum.

Morphological identification of brain stem neurones associated with predatory behaviour elicited by lateral hypothalamic electrical stimulation in the cat: a retrograde transport study using horseradish peroxidase subsequent to an electrolytic lesion

The combination of electrical stimulation of the lateral hypothalamus to elicit predatory behaviour, an electrolytic lesion and a subsequent HRP injection was used to identify brain stem neurones whose axons were affected by such hypothalamic stimulation. In contrast, the injection of HRP into such hypothalamic sites, without a prior lesion, resulted in a significant reduction in the number of labelled neurones. This suggests that an important contribution, namely those neurones which give rise to fibres which pass through the stimulated region, is underestimated by the later procedure.