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Biomedical subjects

C D Hull

Publications and source records attributed to C D Hull.

At least 37 records · Page 2Linked to original sources
PubMed1986

Basal forebrain neurons have axon collaterals that project to widely divergent cortical areas in the cat.

Basal forebrain neurons with axon collaterals that project to widely divergent cortical areas were identified using retrograde transport of two labels. A proportion of neurons in the basal forebrain have axon collaterals that project to both anterior (precruciate gyrus) and posterior (marginal and suprasylvian gyri) cortical areas or to medial (precruciate gyrus) and lateral (ectosylvian and anterior suprasylvian gyri) cortical areas. These branched fibers originate from cells located predominantly in the basal nucleus of Meynert. The existence of such neurons suggests that individual basal forebrain cells are capable of influencing widespread neocortical zones in the cat.

Afferent Pathways↗
PubMed1986

Neurons of origin of striatonigral axons in the cat: connectivity and Golgi markers of somatodendritic architecture.

We identified adult cat striatonigral neurons and characterized their somatodendritic architecture by single- and double-labeling with connectivity and Golgi markers. Light and electron microscopic observations demonstrated two important structural variations among striatofugal neurons. First, striatonigral axons originate from multiple types of neurons. The principal striatonigral neurons are frequent throughout the caudate nucleus and putamen, have medium spherical or ovoidal cell bodies and form spine-laden distal dendrites. The 'accessory' striatonigral neurons are sparse in limited regions of the caudate nucleus and putamen, have large fusiform cell bodies and lack spinous processes. Second, the medium spiny striatonigral neurons exhibit a range of anatomical specializations. In some cases, these cells have folded nuclear envelopes. Some of these neurons have somatic and/or proximal dendritic as well as distal dendritic spines. We conclude that adult cat striatofugal neurons are morphologically heterogeneous in terms of regional locations, somatodendritic architecture and ultrastructure. These anatomical specializations may affect the origin and processing of synaptic inputs to the neostriatum to provide functionally different routes of neurotransmission through the basal ganglia.

Animals↗
PubMed1986

Branched projections of cat sensorimotor cortex: multiple retrograde labeling via commissural corticocortical, decussated corticostriatal and undecussated corticostriatal axons.

The common origins and interrelationships of commissural corticocortical and descending corticostriatal projections were assessed by multiple retrograde labeling of neurons in the precruciate sensorimotor cortex of the cat. The major finding was that some of these neurons had axons that branched at least twice to send collaterals to contralateral cortical sites and bilateral subcortical sites in the caudate nucleus. Regardless of their collateralization, these axons originated mainly from pyramidal neurons of small-medium size located in cortical laminae III-V. A considerable component of the corticocortical and corticostriatal inputs derived from the same neurons. These fibers subserve both intra- and interhemispheric linkages of the sensorimotor cortex with itself and the basal ganglia.

Animals↗
PubMed1986

The entopeduncular nucleus: Golgi morphometrics of serially reconstructed neurons in adult cats.

Computer-assisted morphometrics were used to characterize mature somatodendritic architecture in Golgi-stained neurons of the entopeduncular nucleus (EN) of the adult cat. Only one form of adult EN neuron was apparent and characterized by common features including: relatively large conical somata, long aspiny and moderately branched dendrites and discoid to spherical dendritic fields oriented randomly within the EN. These results indicate that feline EN neurons have some properties in common with large neurons of the primate medial pallidal segment.

Animals↗
PubMed1986

Axonal branching of basal forebrain projections to the neocortex: a double-labeling study in the cat.

Double-labeling of basal forebrain neurons by retrograde axonal transport demonstrates divergent collateralization among undecussated axonal projections to the neocortex. These branched fibers originate from a considerable complement of large polymorphic cell bodies located mainly in the basal nucleus of Meynert. They terminate in multiple neocortical sites including the precruciate, postcruciate and/or cingulate gyri. This extensive intra- and intergyral axonal branching indicates that neurons in the basal forebrain of the cat have extensive axonal fields innervating adjacent neocortical gyri.

Animals↗
PubMed1986

Postnatal development of identified medium-sized caudate spiny neurons in the cat.

The morphology of intracellularly recorded neurons in the cat caudate nucleus (Cd) was studied during postnatal development. After intracellular recording of evoked responses in these neurons, horseradish peroxidase (HRP) was injected iontophoretically through the recording micropipette. Fifty-eight Cd neurons in cats ranging from 6 days of age through adulthood were identified morphologically. All of the recovered Cd cells were medium-sized spiny neurons. The basic somatodendritic morphology of these neurons was evident in the youngest kittens. The most striking morphological change was the postnatal formation of an extensive local axonal collateral plexus. The development of these local axonal collaterals was also quantified with computer assistance in medium-sized Cd spiny neurons selected from silver-impregnated material. This analysis showed that the major development of the branches of this local plexus occurred between birth and 3-4 months of postnatal age. Data from both the HRP-filled and silver-stained axons indicated that the postnatal growth of the local axonal collaterals of the medium spiny cells was associated with the elaboration and increasing prevalence of evoked inhibitory postsynaptic potentials in Cd neurons.

Age Factors↗
PubMed1986

Postnatal differentiation and growth of cat entopeduncular neurons. A transient spiny period associated with branch elongation.

Qualitative and computer-assisted analyses were performed on Golgi-impregnated neurons which were serially reconstructed in 3 dimensions. Analysis of the temporal pattern of growth indicated that the initial outgrowth, formation of the adult number of dendrites and virtually all dendritic branching occurred in the prenatal period. About 40% of the total growth of the dendrites occurred in the postnatal period. Maturation was completed by 90-120 days. Analyses of the mode of dendritic growth and of the morphological changes associated with growth revealed two significant findings. First, the outward expansion of the dendritic tree was not due to the addition of new branches but resulted from the elongation of terminal and non-terminal branches. Thus, growth occurred between branch points as well as on terminal portions of dendrites. Second, a transient population of spines was found during the period of postnatal growth. These spines may play an integral role in synaptogenesis and dendritic branch elongation. We suggest that developing afferent fibers initially contact spines. As spines retract, axon terminals are brought to the shaft of the dendrites. Further, the dendrites elongated because membrane associated with spines is incorporated into the shafts of dendrites. Striopallidal projections and other afferents may provide an important trophic influence for the normal dendritic differentiation of pallidal neurons by inducing the elaboration or retraction of spines.

Aging↗
PubMed1985

Branched projections of pallidal and peripallidal neurons to neocortex and neostriatum: a double-labeling study in the cat.

Double-labeling of basal forebrain neurons by retrograde axonal transport of different markers demonstrated afferents shared by the neocortex and neostriatum. A considerable double-labeled complement of neurons located in the globus pallidus (lateral pallidal segment) and the adjacent interdigitating basal nucleus of Meynert (peripallidal region) had branched axonal collaterals projecting to the precruciate, cingulate and prorean gyri as well as to the head of the caudate nucleus.

Animals↗
PubMed1985

Behavioral effects of D-amphetamine in developing cats.

The development of the behavioral effects of amphetamine was assessed in kittens of 1-53 days of age. Amphetamine-induced increases in locomotion occurred when animals were beyond 35 days of age. Stereotypic behavior was induced at all ages tested but the predominant type of stereotypy was age-related. From 1 to 14 days amphetamine induced licking. Pendular head movements occurred when animals were under 35 days. At 14 days of age darting, a response consisting of rapid pacing and turning began to occur. Tracking, a series of horizontal and vertical head movements also began to occur after 14 days. The adult response of vertical and horizontal head movements became most prominent after 35 days.

Age Factors↗
PubMed1985

Development of somatosensory responsiveness in the basal ganglia in awake cats.

Single-unit activity was recorded from the caudate nucleus (CD), globus pallidus, and entopeduncular nucleus (GP-ENTO) in awake, partially restrained kittens. The purpose of this experiment was to assess the ability of developing basal ganglia structures to process natural facial somatosensory information and compare this function to that observed in the adult. Somatosensory responsiveness in the CD and GP-ENTO developed slowly during the first three postnatal months. Somatosensory responsiveness had three major developmental trends in these nuclei: 1) The proportion of neurons responding to facial sensory stimulation increased with age; 2) proportionally, the area of face encompassing a receptive field of a neuron was smaller in adults than in young kittens; 3) qualitatively, adultlike responses to sensory stimulation did not appear until approximately three months of age. Units responsive to facial somatosensory stimulation in kittens under three months of age were very limited in the types of information they received. No specific stimuli parameters were encoded by these neurons. At approximately three months of age, units began to respond to varied stimuli (i.e., indentation of the skin as well as to brushing stimuli) and began to encode specific stimulus parameters such as direction of movement and relative location on the face. Kitten units responsive to skin indentation showed no evidence of encoding stimulus magnitude information. This was also true for the majority of adult basal ganglia neurons tested. The present findings suggest that the functions of the basal ganglia may be altered significantly during development. With increasing age, the basal ganglia may change from primarily a relay area for relatively nonspecific sensory information to an active processor of complex afferent information.

Animals↗
PubMed1984

Subcortical crossed axonal projections to the caudate nucleus of the cat: a double-labelling study.

The anatomical organization of the interhemispheric projections of subcortical caudate nucleus (Cd) input neurons in the cat was assessed by the retrograde axonal transport of multiple marker substances. These double-labelling methods indicated the existence of two types of subcortical afferents to the Cd. (1) Uncrossed projections terminating in the ipsilateral Cd (but not the contralateral Cd) originated from the globus pallidus, thalamus, substantia nigra and midbrain raphe nuclei. The uncrossed axons provided the vast bulk of the subcortical Cd inputs. (2) Crossed projections terminating in the contralateral Cd (but not the ipsilateral Cd) originated from the substantia nigra and raphe nuclei. The crossed projections from the midbrain provided a very small Cd input compared to the crossed and divergent corticocaudate projections. Therefore, interhemispheric connections of the Cds may be subserved primarily by arrangement of corticocaudate projections. Monosynaptic interhemispheric subcortical inputs to the Cds are minor. Multisynaptic pathways could provide alternative, but less tightly coupled, interhemispheric linkages of the Cds.

Animals↗
PubMed1984

Interhemispheric organization of corticocaudate projections in the cat: a retrograde double-labelling study.

The organization of interhemispheric corticocaudate projections in the cat was assessed by the retrograde axonal transport of different marker substances. These double-labelling methods indicated the existence of three types of neocortical efferents terminating in the caudate nucleus (Cd): (1) uncrossed axons projecting only to the ipsilateral Cd; (2) crossed axons projecting strictly to the contralateral Cd; and, (3) divergent axons projecting to both Cds. In all cases, the corticocaudate projections originated from small-to-medium sized pyramidal neurons situated in layers III, IV and V of the rostral neocortex. Interhemispheric inputs to the Cd may account, to some extent, for the functional coupling of the right and left basal ganglia.

Animals↗
PubMed1984

Activity of forebrain neurons during alternating movements in cats.

The firing pattern of single units in the precruciate cortex, globus pallidus, entopeduncular nucleus and ventral thalamus of cats was studied before alternating limb movements. Seventy-eight percent of the neurons in these regions of the brain changed their activity more than 500 msec before the movement. No consistent early EMG changes occurred in the proximal or axial muscles which would correlate with the early neuronal activity changes. The data suggest that the sequence of movements required for this alternation task appears to be 'set' well in advance of the activation of the muscles involved in the necessary postural adjustments or the response itself. In addition, the units which showed early activity changes may be involved in the mnemonic processing necessary to discriminate a situational context and make an appropriate response. Over 50% of the movement related units in the globus pallidus, entopeduncular nucleus and ventral thalamus were related to movement of both the contralateral and ipsilateral paws. By contrast, only 33% of cortical units showed this relationship to the movement. Therefore, this 'set' process may be a relatively non-lateralized process. The data support the concept that the basal ganglia are involved in the enabling and sequencing of movements rather than in directly causing them to occur.

Animals↗
PubMed1984

Effects of amphetamine on intracellular responses of caudate neurons in the cat.

The effects of acute administration of amphetamine on membrane potentials and evoked postsynaptic potentials of caudate neurons in cats were assessed using intracellular recording. High doses of amphetamine (0.5 mg/kg, i.v.) produced a reversible depolarization of the cell membrane in 78% of cells tested. Low doses (0.1 mg/kg) had no effect on the resting membrane potential. Long-lasting increases in amplitude of both excitatory and inhibitory components of evoked postsynaptic potential sequences were observed after both high and low doses of amphetamine. These changes were more evident to cortical than to substantia nigra or to intralaminar thalamic stimulation. These results were shown to be independent of the peripheral autonomic actions of amphetamine. These effects appear to be mediated by the ability of amphetamine to alter catecholaminergic mechanisms in the caudate nucleus and suggest that increased dopamine release may have a facilitatory effect on both excitatory and inhibitory synaptic transmission.

Animals↗
PubMed1983

Postnatal development of caudate input neurons in the cat.

Lectin-bound horseradish peroxidase (WG-HRP) was pressure-injected into the caudate nucleus (Cd) of neonatal (less than 24 hours of age) and adult cats in order to assess the postnatal development of monosynaptic Cd input neurons. Tissue was processed for peroxidase activity with a benzidine dihydrochloride chromagen. The injection of WG-HRP produced relatively similar labelled zones of marker uptake in the caudate nuclei of both neonates and adults. Similar axonal projections were also labelled in both age groups. While many characteristics of retrogradely labelled CD input neurons were apparently constant throughout postnatal life, each of these features had a particular developmental modification. (1) Regardless of age, neuronal somata that projected to the CD were located in the neocortex, thalamus, substantia nigra, mesencephalic raphe nuclei, and globus pallidus. In each of these brain sites, labelled CD input neurons appeared to migrate postnatally. (2) The Cd afferent axons originated from the same neuronal lines in neonates and adults--small-to-medium-sized cortical neurons and medium-sized-to-large fusiform cells in all other brain sites. In each of the brain sites, labelled neurons displayed marked postnatal somatic growth. (3) In both age groups, there was a characteristic intrasomatic reaction product density in the labelled neurons located in each brain site (substantia nigra greater than thalamus = raphe = globus pallidus greater than cortex). In each of these brain sites, the intrasomatic reaction product density was less in neonates than in adults.

Afferent Pathways↗
PubMed1983

Intracellular studies of the convergence of sensory input on caudate neurons of cat.

Quantitative analyses of the intracellular responses to peripheral stimuli were made in a 172 neurons recorded in the head of the caudate nucleus (Cd) of cat. Responsiveness of Cd neurons was tested using auditory and somatosensory stimuli which were presented unilaterally. We found that most cells (99%) responded to both auditory and somatosensory stimuli. Excitation followed by inhibition (i.e. E-I response) was the primary pattern of intracellular response occurring approximately 75% of the time. Qualitative and quantitative analyses revealed marked similarities in the amplitudes and time courses of the intracellular responses following supramaximal stimulation of the peripheral stimuli studied. Similarly, analyses of 40 pairs of simultaneously recorded neurons revealed a marked homogeneity in the intracellular responses to the same stimulus even though the recordings were made several mm apart. The most striking feature of the simultaneous recordings was that the peaks of the initial E-I response and the afterpotentials often occurred in register after a peripheral stimulus. Furthermore, changes in the responses of pairs of simultaneously recorded neurons co-varied. Because the striatum typically demonstrates spontaneous rhythmic activity, these data suggest that a peripheral stimulus has the potential of briefly synchronizing Cd's neuronal activity.

Animals↗
PubMed1983

Effects of neonatal destruction of the medial forebrain bundle in the cat: long-term neurochemical, locomotor, and regulatory deficits.

Neonatal kittens (N = 27) 11 to 22 days of age received bilateral electrolytic lesions of the medial forebrain bundle (MFB). These lesions transected the rostral course of the nigrostriatal tract, disrupted other fiber tracts that constitute the MFB, damaged the indigenous neurons of the lateral hypothalamic region, and interrupted striatal output pathways. The behavioral development of these animals was assessed and compared with that of intact littermates (N = 37) and a group of littermates that received lesions that did not encroach upon the MFB (control lesions, N = 16). The MFB lesions produced transient periods of decreased body weight gains. Animals with large MFB lesions had to be tube fed for various periods. Decreased ponderal weight in animals with large MFB lesions occurred throughout the duration of their survival (1 to 2 years of age). Development of locomotor activity was assessed in an open field. At about 6 weeks of age animals with MFB lesions became hyperactive compared with their intact littermates and this hyperactivity was still apparent at 6 months of age when testing was discontinued. Caudate dopamine and tyrosine hydroxylase were measured after the animals were killed. Large MFB lesions produced a marked decrease in concentrations of caudate dopamine (75%) and the activity of tyrosine hydroxylase (62%). These results indicate that early postnatal damage to the MFB in cats produces a constellation of behavioral deficits that differ both quantitatively and qualitatively from the effects of similar lesions produced in the adult animal.

Animals↗