Biomedical subjects

S E Brauth

Publications and source records attributed to S E Brauth.

13 recordsLinked to original sources

PubMed1992

Effects of yohimbine as a reversing agent for ketamine-xylazine anesthesia in budgerigars.

Fourteen adult budgerigars (Melopsittacus undulatus) were anesthetized with a combination of ketamine hydrochloride (40 mg/kg) and xylazine hydrochloride (10 mg/kg) intramuscularly. Forty-five minutes after ketamine-xylazine injection, one of four yohimbine hydrochloride doses (0.0, 0.11, 0.275, or 0.44 mg/kg, IM) was administered in a 0.7% saline vehicle. Latencies were recorded in minutes from yohimbine injection until subjects' behavior indicated three different points of recovery: 1) lifting the head, 2) standing unaided without ataxia, and 3) perching. Means for all three recovery point latencies were significantly reduced by 0.275 mg/kg of yohimbine compared with saline vehicle alone. Mean latencies among treatment groups for each of the three recovery points were not significantly different, other than control versus treated groups. Based on these results, we recommend a yohimbine dose of 0.275 mg/kg as an effective reversing agent for ketamine-xylazine anesthesia in budgerigars.

Anesthesia↗

PubMed1991

Calcitonin-gene related peptide is an evolutionarily conserved marker within the amniote thalamo-telencephalic auditory pathway.

The distribution of neurons and fibers containing calcitonin-gene-related peptide (CGRP) was mapped in the thalamo-telencephalic auditory pathways of four amniote species, rats, pigeons (Columba livia), caiman (Caiman crocodilus), and turtles (Pseudemys scripta). In colchicine-treated turtles and pigeons, numerous CGRP+ perikarya were observed in the auditory relay nucleus of the thalamus (n. reuniens of reptiles, and n. ovoidalis of birds). In pigeons, these neurons were most abundant in the outer circumference of the nucleus and were not observed without colchicine pretreatment. In the telencephalon of turtles, caiman, and pigeons, CGRP+ fibers were observed within portions of the dorsal ventricular ridge previously shown to receive projections from the auditory thalamus, thus implying that the thalamic CGRP+ neurons observed here in fact project to these telencephalic areas. In colchicine treated rats, numerous CGRP+ perikarya were observed along the ventral margin of the medial geniculate nucleus extending into the posterior intralaminar and peripeduncular nuclei, as well as occasionally within the ventral subdivision of the medial geniculate nucleus. Injections of fluorogold into the auditory cortex combined with immunofluorescence labeling for CGRP revealed that CGRP+ cells in these areas do, in fact, project to the auditory cortices. The present results are interpreted as providing strong support for the theory, advanced previously, that the medial geniculate nucleus of mammals, nucleus ovoidalis of birds, and nucleus reuniens of reptiles contain at least some homologous cell populations. Although the data are consistent with the theory that the telencephalic projection fields are homologous, other interpretations are also consistent with the data presented here. These include the possibility that auditory thalamic projections to the telencephalon arose independently in the lines of evolution leading to mammals and sauropsids.

Alligators and Crocodiles↗

PubMed1990

Investigation of central auditory nuclei in the budgerigar with cytochrome oxidase histochemistry.

Cytochrome oxidase (CO) histochemistry was used to study the organization of central auditory structures in the budgerigar (Melopsittacus undulatus). In contrast to prior studies in birds showing that acetylcholinesterase staining is most intense within hindbrain auditory structures CO staining was prominent at all levels of the auditory pathway including the thalamus (i.e. nucleus ovoidalis) and primary telencephalic auditory area (Field 'L'). Furthermore, CO staining clearly distinguishes the boundaries of Field 'L' from adjacent portions of the neostriatum intermedium pars dorsolateralis which do not receive input from the auditory thalamus. Thus CO staining can be used as a marker for distinguishing auditory and non-auditory portions of the avian telencephalon.

Animals↗

PubMed1990

Histochemical strategies in the study of neural evolution.

The use of histochemical methods, including enzyme histochemical, immunohistochemical and pathway tracing methods, as tools for testing hypotheses about the mechanism of neural evolution is reviewed. Many hypotheses have been proposed to explain aspects of neural evolution, including the occurrence of encephalization, quantitative changes in homologous cell populations, changes in the alignment, orientation and parcellation of neuronal populations into cytoarchitectonic units, and the appearance of new neuronal phenotypes. It is argued here that neural evolution must be viewed as a set of coordinated changes in neural circuits, rather than as a set of discrete events. For illustrative purposes the present discussion focuses on the use of histochemical methods in testings hypotheses about neural evolution in the basal ganglia system of amniotes. Three problem areas are considered: the bases for (1) differences in the alignment and organization of catecholaminergic and noncatecholaminergic neurons into cytoarchitectonic fields within the substantia nigra; (2) differences in the relative size and neurotransmitter organization of the caudal nigral cell groups and (3) differences in the organization of pallidal efferent systems, including the organization of pallidal-pretectal and pallidal-thalamic projection systems. Furthermore, the role of comparative data in framing hypotheses concerning the adaptive significance of such changes is also considered.

Alligators and Crocodiles↗

PubMed1989

Distribution of mu, delta, and kappa opiate receptor types in the forebrain and midbrain of pigeons.

Ligands that are highly specific for the mu, delta, and kappa opiate receptor binding sites in mammalian brains have been identified and used to map the distribution of these receptor types in the brains of various mammalian species. In the present study, the selectivity and binding characteristics in the pigeon brain of three such ligands were examined by in vitro receptor binding techniques and found to be similar to those reported in previous studies on mammalian species. These ligands were then used in conjunction with autoradiographic receptor binding techniques to study the distribution of mu, delta, and kappa opiate receptor binding sites in the forebrain and midbrain of pigeons. The autoradiographic results indicated that the three opiate receptor types showed similar but not identical distributions. For example, mu, delta, and kappa receptors were all abundant within several parts of the cortical-equivalent region of the telencephalon, particularly the hyperstriatum ventrale and the medial neostriatum. In contrast, in other parts of the cortical-equivalent region of the avian telencephalon, such as the dorsal archistriatum and caudal neostriatum, only kappa receptors appeared to be abundant. Within the basal ganglia, all three types of opiate receptors were abundant in the striatum and low in the pallidum. Within the diencephalon, kappa and delta binding was high in the dorsal and dorsomedial thalamic nuclei, but the levels of all three receptor types were generally low in the specific sensory relay nuclei of the thalamus. Kappa binding and delta binding were high, but mu was low in the hypothalamus. Within the midbrain, all three receptor types were abundant in both the superficial and deep tectal layers, in periventricular areas, and in the tegmental dopaminergic cell groups. In many cases, the distribution of opiate receptors in the pigeon forebrain generally showed considerable overlap with the distribution of opioid peptide-containing fiber systems (for example, in the striatal portion of the basal ganglia), but there were some clear examples of receptor-ligand mismatch. For example, although all three receptor types are very abundant in the hyperstriatum ventrale, opioid peptide-containing fibers are sparse in this region. Conversely, within the pallidal portion of the basal ganglia, opioid peptide-containing fibers are abundant, but the levels of opiate receptors appear to be considerably lower than would be expected. Thus, receptor-ligand mismatches are not restricted to the mammalian brain, since they are a prominent feature of the organization of the brain opiate systems in pigeons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Catecholamine neurons in the brainstem of the reptile Caiman crocodilus.

Immunohistochemical methods were used to map the distribution of neurons exhibiting tyrosine hydroxylase-like immunoreactivity (TH) in the brainstem of the reptile Caiman crocodilus. The results reveal that many catecholamine systems previously described in mammalian and avian species are present in the brainstem of the caiman. Within the medulla, many immunoreactive neurons surround the central canal. This neuronal field extends rostrally to the level of the dorsal motor nucleus of the vagus. Many TH neurons overlap the region of the solitary nucleus, and an extensive system of fibers derived from these neurons extends ventrally and laterally into the region immediately bordering the descending nucleus of the trigeminal nerve. Some TH neurons are also present in the ventrolateral tegmentum of the medulla at this level. A large number of TH cells are present in the pons and midbrain. These include the locus coeruleus, nucleus subcoeruleus ventralis, nucleus subcoeruleus dorsalis, substantia nigra (Brauth et al., '83), and area ventralis of Tsai. The subcoeruleus nuclei are considerably larger in the caiman than in other reptilian species including turtles and lizards and closely resemble the subcoeruleus nuclei of birds in terms of position and anterior-posterior extent. Within the diencephalon, numerous small, intensely staining, TH-immunoreactive and CSF-contacting neurons were observed within the preoptic recess and in close proximity to the ventricular wall at rostral hypothalamic and preoptic levels. Many intensely stained, immunoreactive cell bodies were observed in the medial hypothalamus similar in position to the A13 cell group of mammals. In the subthalamus, TH neurons completely surround the ventral peduncle of the forebrain bundle (which contains fibers of the ansa lenticularis) and extend into the ventromedial and ventrolateral thalamic areas. A rich plexus of TH-positive axons and terminals invests the external layer of the median eminence.

Alligators and Crocodiles↗

PubMed1986

Telencephalic projections from midbrain and isthmal cell groups in the pigeon. I. Locus coeruleus and subcoeruleus.

Horseradish peroxidase (HRP) and amino acid autoradiography were used in pigeon to determine the trajectories and projection patterns of neurons within the locus coeruleus and subcoeruleus nuclei upon the cerebral hemispheres. The specific cell groups investigated include the locus coeruleus (LoC), nucleus subcoeruleus dorsalis, and nucleus subcoeruleus ventralis. Efferents from each of these nuclei ascend to the telencephalon via the medial and lateral forebrain bundles, ansa lenticularis, and the quintofrontal and occipitomesencephalic tracts. A separate dorsally situated bundle derived from LoC neurons reaches many dorsal thalamic nuclei. The telencephalic projections of the LoC and subcoeruleus nuclei are bilateral and symmetrical, although projections to the contralateral hemisphere are sparse. Crossing fibers project to contralateral targets primarily via the dorsal supraoptic decussation and along the dorsal and ventral margins of the anterior commissure. Within the telencephalon, the following neural structures receive input from neurons in the LoC and subcoeruleus cell groups: the paleostriatal complex including the paleostriatum augmentatum and lobus parolfactorius, septal nuclei, nucleus accumbens, olfactory tubercle, hippocampus and parahippocampal area, nucleus taeniae, dorsal archistriatum, lateral neostriatum, hyperstriatum dorsale, hyperstriatum ventrale, and preoptic area. Large portions of the cerebral hemispheres including the hyperstriatum accessorium, much of the neostriatum and hyperstriatum ventrale, and all but the dorsal portion of the archistriatum receive little or no input from either the locus coeruleus or subcoeruleus cell groups. This is apparently different from the condition in mammals in which virtually all cortical fields receive input from neurons within the LoC. Moreover, the pattern of projections of the subcoeruleus nuclei upon telencephalic fields described here as well as recent histochemical data suggest that these cell groups are comparable to the lateral tegmental (A8) cell group of mammals rather than to the mammalian subcoeruleus nuclei.

Animals↗

PubMed1986

Telencephalic projections from midbrain and isthmal cell groups in the pigeon. II. The nigral complex.

The trajectories and telencephalic terminal fields of neurons within the area ventralis of Tsai (AVT) and nucleus tegmenti pedunculopontinus pars compacta (TPc) were determined in the pigeon by using amino acid autoradiography and horseradish peroxidase histochemistry. Previous histochemical studies have considered these cell groups comparable to the A10 and A9 components of the mammalian nigral complex. The results show the efferents derived from these cell groups ascend to the telencephalon via the medial and lateral forebrain bundles, ansa lenticularis, and quintofrontal and occipitomesencephalic tracts. All projections are bilateral and symmetrical, although projections to the contralateral hemisphere are extremely sparse. Within the telencephalon many cell fields receive projections from the AVT and TPc nuclei; however, the most substantial projections reach structures within the basal telencephalon, especially the paleostriatal complex. Within the paleostriatal complex the paleostriatum augmentatum (PA) receives a very heavy projection from the TPc. AVT projections reach primarily rostromedial portions of PA as well as the lobus parolfactorius. The large-celled portions of the paleostriatum including the paleostriatum primitivum and nucleus intrapeduncularis do not appear to receive projections from either AVT or TPc neurons. Projections from AVT and TPc neurons terminate within other structures of the basal telencephalon including the lateral and medial septal nuclei, the olfactory tubercle, the ventral paleostriatum and the preoptic area. Pallial derivatives including the hyperstriatum dorsale, hyperstriatum ventrale, dorsal archistriatum, and hippocampus also receive projections from AVT and TPc neurons, although these projections are much sparser than those reaching subpallial structures. Large portions of the telencephalon including the hyperstriatum accessorium, most of the hyperstriatum ventrale, much of the archistriatum, and much of the neostriatum do not receive projections from AVT or TPc neurons. Furthermore, there is substantial overlap between the telencephalic projections of TPc and AVT neurons, as well as considerable overlap between the projections of both these nigral cell groups and the projections of the locus coeruleus complex in the pigeon. This high degree of overlap between locus coeruleus and nigral telencephalic terminal fields is quite different from the condition in mammals and suggests possible functional divergence for some of these pathways in contemporary amniote forms.

Amino Acids↗

PubMed1978

Prosencephalic pathways related to the paleostriatum of the pigeon (Columba livia).

Afferent connections of the avian paleostriatal complex were traced by means of anterograde and retrograde transport of horseradish peroxidase (HRP). The paleostriatum augmentatum (PA), a cell field comparable to mammalian caudate nucleus and putamen, was found to receive projections from a distinct population of elencephalic neurons in the temporal-parietal-occipital (TPO) and lateral cortical (CDL) areas of the neostriatum. TPO neurons, in turn, were found to receive projections from the contralateral ventral archistriatum (Av) and from neurons in the ipsilateral frontal neostriatum adjacent to the rostral portion of the ectostriatum (e). the paleostriatum primitivum (PP), comparable to globus pallidus, receives projections from the small cells of PA, and from neutrons in the anterior nucleus of the ansa lenticularis (ALa). ALa appears similar to the mammalian subthalamic nucleus on the basis of its afferent and efferent connections. In addition, PA was also found to receive extensive projections from the nucleus tegmenti pedunculopontinus of the midbrain, a dopamine-containing cell group. Evidence of projections from the nucleus dorointermedius posterior (DIP), a cell group receiving both cerebellar and paleostriatal afferents, to the rostral telencephalon was also found.

Animals↗

PubMed1978

Distribution of neurons projecting to the retina of Caiman crocodilus.

Horseradish peroxidase (HRP) was injected into the vitreous of the eye, the orbital cavity, or the optic tectum of Caiman crocodilus. Following intravitreal injections, retrograde transport of the enzyme was observed bilaterally, but predominantly contralaterally, in a large oblong field of cells at the isthmic level of the midbrain, bounded medially by the trochlear nucleus and laterally by the nucleus isthmi. Control injections of HRP into the orbital cavity and eye muscles labelled motoneurons of the extraocular muscles but not cells of this isthmic field. The field is therefore the source of a projection efferent to the retina in Caiman. Injections of HRP into the dorsal optic tectum produced a fine pattern of anterograde labelling in fibers projecting to the region in which retinopetal cells were identified, but no retrograde labelling of cells in this area. In contrast, the nucleus isthmi showed dense anterograde labelling of fibers and terminals as well as retrograde labelling of cells following tectal injections. These results extend recent evidence for a close evolutionary relationship between the order Crocodilia and modern birds, since birds also possess a well-developed retinopetal system derived from a cell group in the isthmic midbrain.

Alligators and Crocodiles↗

PubMed1977

Midbrain unit activity during classical conditioning.

In behaving rats, unit activity recorded from the ventral tegmentum and from the reticular formation was monitored during classical conditioning. Rewarding electric stimulation of the medial forebrain bundle was used as the unconditioned stimulus (UCS). Only those cells possessing prior responses to the conditioned stimulus (CS) changed their responses as a result of conditioning. Responses recorded from cells which were driven by both the auditory CS and the brain shock UCS were significantly more often changed than those driven by the CS alohe. These data show that the auditory and brain shock fields of influence interact in at least some brain regions prior to conditioning and that pairing the two kinds of stimuli is more likely to influence auditory responses recorded from these regions than those recorded elsewhere. It is possible to imagine that the intersection of the two fields is a sine qua non of conditioning and that the two prior actions caused the change by interacting at or near the recording point.

Action Potentials↗

PubMed1977

Direct accessory optic projections to the vestibulo-cerebellum: a possible channel for oculomotor control systems.

The nucleus of the basal optic root (nBOR) receives direct retinal projections in all classes of vertebrates. This nucleus is also known as the medial terminal nucleus of the accessory optic tract, or as the nucleus extomamillaris. Following a series of HRP injections into the uvula and flocculonodular lobe of pigeons, both large and small cells of the nBOR were labelled bilaterally with the marker. No significant transport of HRP to nBOR was observed following injections of more rostral folia of the posterior or anterior lobes of the cerebellum. In view of the prominence of the tract from retina to nBOR and the presence of a monosynaptic pathway from nBOR directly to the vestibulo-cerebellum, we suggest this bisynaptic, "lemniscal", retino-cerebellar channel may be the substrate by which visual stimuli directly trigger oculomotor responses mediated by the vestibulo-cerebellum.

Afferent Pathways↗

PubMed1975

Correlation of overt escape behavior, multiunit thalamic activity, and midbrain lemniscal stimulation in rats.

An acute and a chronic experiment were conducted in order to assess the extent to which ventral thalamic multiunit activity could account for the specific form of bar-pressing escape behavior in rats stimulated by trains of midbrain medial lemniscal pulse pairs. A paradigm used by Kestenbaum, Deutsch, and Coons was utilized in which the intra-pair interval of the train was varied. Results in anesthetized and freely moving animals indicated that midbrain lemniscal stimulation produces both an excitatory short-latency thalamic response showing the property of temporal facilitation and a long-lasting inhibitory process consistent with results of studies using anesthetized cats. The overall electrophysiological response, however, correlated significantly with the behavioral response function.

Anesthesia, Intravenous↗