Greater Number Of Neurons Research Articles

Evidence for co-existence of thyrotropin-releasing hormone, substance P and serotonin in ventral medullary neurons that project to the intermediolateral cell column in the rat

The present study was conducted to determine if substance P-, thyrotropin-releasing hormone and/or serotonin-immunoreactivities coexist in ventral medullary neurons that project to the intermediolateral cell column in the rat. Neurons that projected to the intermediolateral cell column were identified by the presence of retrogradely transported rhodamine bead-labeled microspheres in the cell body after an injection of the microspheres into the intermediolateral cell column of the third thoracic spinal cord segment. Co-existence was determined by using a combination of dual color immunohistochemistry and serial 4-μm sections that were immunostained with different antibodies. Antibodies to substance P, serotonin, and pre-pro-thyrotropin releasing hormone 160–169 were used to identify substance P, serotonin and thyrotropin-releasing hormone, respectively. Neurons that contained substance P-, thyrotropin-releasing hormone- and/or serotonin-immunoreactivities and that projected to the intermediolateral cell column were present in the nucleus raphe magnus, the nucleus raphe pallidus, the nucleus reticularis magnocellularis pars alpha, the paragigantocellular reticular nucleus and the parapyramidal region. Neurons that projected to the intermediolateral cell column, in each of these regions, were found to contain each of the following combinations of immunoreactive neurochemicals: substance P and thyrotropin-releasing hormone; substance P and serotonin; thyrotropin-releasing hormone and serotonin; or substance P, thyrotropin-releasing hormone and serotonin. In addition, most of the regions also contained neurons that appeared to contain only one of the neurochemicals and that also projected to the intermediolateral cell column. The greatest number of neurons that projected to the intermediolateral cell column and that also contained two or more co-existing neurochemicals was present in the midline regions. This study demonstrates the presence of neurons in the ventral medulla that project to the intermediolateral cell column and contain three co-existing neurochemicals. This study also demonstrates the use of a new method for the localization of three neurochemicals in single projection-specific neurons.

Influence of laminin on the responsiveness of early chick embryo neural tube neurons to nerve growth factor.

Dissociated neurons from the neural tube containing the trigeminal motor nucleus from early chick embryos were cultured on laminin or collagen-polyornithine substrates, with and without nerve growth factor (NGF). Control cultures were grown in similar conditions with cytochrome-C. It was found that neuronal survival was not affected by NGF or cytochrome-C, but it was enhanced by laminin. The expression of neuritic processes, however, was significantly enhanced in the presence of NGF on both laminin and collagen-polyornithine surfaces, with the greatest number of neurons producing processes seen in the laminin-plus-NGF group. The length of processes was similarly enhanced by laminin and by NGF. Cytochrome-C did not influence any of these measures. The results indicate that while laminin potentiates the NGF effect on these early neuronal populations, NGF in conjunction with other substrata can have similar, though less dramatic, effects. These results, together with prior evidence of NGF receptors and specific NGF retrograde transport, suggest that this growth factor may play a significant role in the normal ontogeny of early motoneuron populations.

Human neuroethology of emotion

Ploog, Detlev: Human Neuroethology of Emotion. Prog. Neuro-Psychopharma-col. & Biol. Psychiat. 1989, 13 (Suppl):S15–S22 1. 1. Based on ethological theory, the question of what is the difference between human and nonhuman primate emotionality is investigated. 2. 2. The anatomical basis for this difference is the greater number of neurons in the anterior thalamic nuclei in humans than in monkeys and apes. This may represent an increased differentiation of the limbic message being sent to the cortex. 3. 3. Only humans can report about experiences and subjective feelings in certain motivational states. The two most general states are wakefulness and sleep. The subjective aspect of (desynchronized) sleep is dreaming. The causal relationship between dreaming and certain lower brain stem mechanisms is analysed. 4. 4. Whereas the motor system is usually blocked during desynchronized sleep, there are individuals who voice their emotions and speak while sleeping. As there are essential differences in the substrates for the voluntary control of the voice in the human and nonhuman primates there are essential differences in the voluntary control of emotions. 5. 5. Similar to the motor matching theory of speech perception a motor matching process of affect perception is suggested. 6. 6. The evolutionary change in the human motivational system is thought to be one of several prerequisites for the evolution of language.

Dopamine release at behaviorally relevant parameters of nigrostriatal stimulation: effects of current and frequency

Released dopamine was monitored voltammetrically in the rat striatum in response to electrical stimulation of the nigrostriatal bundle. Stimulation parameters encompassed those typically used in behavioral studies. Dopamine released during intracranial self-stimulation (ICSS)-like stimulation reached a maximum within the first minute of stimulation, then rapidly decreased. The pattern of release obtained with continuous stimulation as a function of current and frequency supports the view that as the stimulation current is increased, a greater number of neurons are stimulated, while increasing the frequency of stimulation results in a fixed population of neurons being stimulated more intensely. Computer modeling of stimulated release from a population of dopaminergic nerve terminals was used to interpret effects of current and frequency and to predict ICSS release patterns as a function of schedule of reinforcement.

Clinical, pathological, and neurochemical changes in dementia: a subgroup with preserved mental status and numerous neocortical plaques.

Postmortem examination was performed on 137 residents (average age 85.5 years) of a skilled nursing facility whose mental status, memory, and functional status had been evaluated during life. Seventy-eight percent were demented using conservative criteria; 55% had characteristic Alzheimer's disease. Choline acetyltransferase and somatostatin were significantly reduced in the brains of patients with Alzheimer's disease as compared with age-matched nursing home control subjects, although the degree of the reduction was less severe than found in subjects less than 80 years of age. Ten subjects whose functional and cognitive performance was in the upper quintile of the nursing home residents, as good as or better than the performance of the upper quintile of residents without brain pathology (control subjects), showed the pathological features of mild Alzheimer's disease, with many neocortical plaques. Plaque counts were 80% of those of demented patients with Alzheimer's disease. Choline acetyltransferase and somatostatin levels were intermediate between controls and demented patients with Alzheimer's disease. The unexpected findings in these subjects were higher brain weights and greater number of neurons (greater than 90 micron 2 in a cross-sectional area in cerebral cortex) as compared to age-matched nursing home control subjects. These people may have had incipient Alzheimer's disease but escaped loss of large neurons, or alternatively, started with larger brains and more large neurons and thus might be said to have had a greater reserve.

Evidence for the existence of a lateral cervical nucleus in mice, guinea pigs, and rabbits.

The lateral cervical nucleus of carnivores is large and is thought to play a prominent role in somatosensory processing. In contrast, early studies indicated that rats, mice, guinea pigs, and rabbits did not have a lateral cervical nucleus. However, we reported the existence of a lateral cervical nucleus in rats as a result of studies using retrograde transport techniques. In the present study, similar techniques were used to examine the possibility that early studies also overlooked the lateral cervical nucleus in mice, guinea pigs, and rabbits. In each of these species, a retrograde tracer was injected into the thalamus. These injections labeled a small number of neurons contralaterally in the dorsal part of the lateral funiculi of rostral cervical segments. Mice had the greatest number of neurons projecting from the lateral cervical nucleus to the thalamus, and rabbits had the fewest.

Development of adenosine deaminase-immunoreactive neurons in the rat brain

It has previously been demonstrated that neurons immunoreactive for the enzyme adenosine deaminase (ADA) have a highly restricted distribution pattern in the adult rat brain. In order to determine whether the pattern of ADA expression is equally limited during the period of brain development, the localization of ADA was investigated immunohistochemically in brains of embryonic, early postnatal and young adult rats. No immunostaining for ADA was detected on the 12th embryonic day. On embryonic day 15, ADA-immunoreactive cells were first observed in the hypoglossal motor nucleus, and on day 18 in cingulate, retrosplenial and visual cortex, in the posterior basal hypothalamus, and in the facial motor nucleus. On the 20th embryonic day ADA-immunoreactive neurons appeared in various olfactory and related systems and in the superior colliculus. On the 1st postnatal day, immunoreactivity was intensified in all structures in which it was observed at preceeding ages and, in addition, appeared in several brainstem regions. On postnatal day 10 and 15, immunostained neurons appeared in several subcortical structures whereas the number of these decreased in the anterior olfactory nucleus and some related cortical areas. In animals 25 days of age the intensity of immunostaining continued to increase, essentially producing the adult pattern in all except olfactory areas where there was a dramatic loss of ADA-immunoreactive cells. These results show that the restricted pattern of ADA-immunostaining observed in adult rat brain is generated over a protracted period of development, various stages of which are characterized predominantly by the expression of ADA in greater abundance, at least to the extent this can be gleaned immunohistochemically, in greater numbers of neurons and to a minor degree by a decreased capacity to express this enzyme.

Projections from the paratrigeminal nucleus and the medullary and spinal dorsal horns to the peribrachial area in the cat

The projections from the medullary and spinal dorsal horns to the dorsolateral pons were investigated in the cat utilizing both the retrograde and anterograde transport of a wheat germ agglutinin-horseradish peroxidase complex and the retrograde transport of the fluorescent dyes Fast Blue and Nuclear Yellow. After injections of wheat germ agglutinin-horseradish peroxidase into the area surrouncling the brachium conjunctivum, numerous neurons were labeled ipsilaterally near levels of the obex in the paratrigeminal nucleus. Such neurons were located in connected pockets of neuropil located within the spinal trigeminal tract and along its medial edge. Most of the neurons labeled in the dorsal horns after such injections were found in lamina I. Those found in the medullary dorsal horn were mostly ipsilateral to the injection while those in the spinal dorsal horn were found bilaterally. Some labeled neurons were also found in lamina V of both the medullary and spinal dorsal horns bilaterally. When the injection was centered in either the medial parabrachial nucleus or the Kolliker-Fuse nucleus, a greater number of neurons were labeled ipsilaterally in lamina V of the medullary dorsal horn. Since neurons in lamina I of the medullary dorsal horn also project to the medial thalamus, fluorescent dyes were used to determine if the same neuron might project to both targets. Fast Blue was first injected into either the peribrachial area or the medial thalamus. After an appropriate period. Nuclear Yellow was injected into that target not injected first with Fast Blue. The injection of Nuclear Yellow was always placed on the side of the brain opposite to the first injection. Both dyes were transported retrogradely and were found in neurons located in lamina I of the medullary dorsal horn. However, no double-labeled neurons were seen. In general those labeled after injections of the medial thalamus were more superficial than those labeled after injections of the dorsolateral pons. The anterograde transport of wheat germ agglutinin-horseradish peroxidase was used to determine the termination of the projections from neurons in the medullary dorsal horn and the cervical spinal cord to the peribrachial area. After injections into these areas a moderate to sparse labeling of the lateral parabrachial nucleus and the Kolliker-Fuse nucleus was seen. It was mostly ipsilateral in cases with injections of the medullary dorsal horn but was bilateral following injections into the cervical enlargement. Dense labeling was noted in the medial parabrachial nucleus and the Kolliker-Fuse nucleus ipsilaterally but only after injections into the rostral parts of the medullary dorsal horn.

A comparison of the number of neurons in individual laminae of cortical areas 17, 18 and posteromedial suprasylvian (PMLS) area in the cat

The binocular region of area 17 (17B) has a greater number of neurons under a given unit of cortical surface (N C, number per column) than either the monocular region of area 17 (17M), area 18 or the posteromedial suprasylvian area (PMLS). The latter three areas follow the general principle of basic uniformity in the number of neurons under given units of cortical surface formulated by Rockel et al. 13. This basic uniformity is maintained in layers I and II. The N C of other layers varies. The greatest differences are found in layer IV where the N C of each area is significantly different from that of each other area. Though the difference between layer IV of 17M and of either 18 and PMLS is largely offset by changes in the third layer, layers V (PMLS) and VI (18 and PMLS) also contribute to the compensation. The compensation between 18 and PMLS is due entirely to changes in layer IV. It is important to note that there are statistically demonstrable interindividual differences in the neuronal N C of the cats used in the present study. We suggest that these may be due to age, breeding, or rearing conditions, probably the latter.

NEURAL CIRCUITS FOR GENERATING RHYTHMIC MOVEMENTS

Inasmuch as the identified neural circuits discussed in this review pertain only to the nervous systems of two invertebrate species, one may ask whether or not these findings are generally applicable to central nervous oscillators that generate rhythmic movements in animals of other species and phyla, particularly in the vertebrates. This question is not easy to answer at this time, because detailed cellular network analyses thus far have been possible only in a very few neurophysiologically favorable preparations, such as those presented by the cardiac and stomatogastric ganglia of the lobster and the segmental ganglion of the leech. Nevertheless it is significant that the mechanisms according to which these invertebrate circuits are now thought to generate their oscillations--endogenous rhythmic polarization, reciprocal inhibition, and recurrent cyclic inhibition--were all first proposed to account for generation of rhythmic movements in vertebrate animals (7-9, 51, 71, 79). Moreover, the pattern of motor neuron activity in rhythmic movements of vertebrates is not necessarily more complex than the corresponding pattern in analogous movements of invertebrates. Therefore, the very much greater number of neurons in the central nervous system of vertebrates does not necessarily imply a greater complexity of the central oscillators that generate their rhythmic movements; it may only place greater obstacles in the way of identifying the underlying neuronal circuitry. In any case, it is worthy of note that the current list of fundamentally different and theoretically plausible types of neuronal oscillators is not only quite short but also of long standing. Thus, on these grounds, it seems reasonable to expect that the identified circuits discussed here will prove to be of general applicability to the generation of rhythmic movements in the whole animal kingdom.