Phylogenetic conservatism in the presence of a neurotensin-related hexapeptide in neurons of globus pallidus

The vast majority of the pallidal neurons of the hamster, pigeon, caiman and turtle basal telencephalon were positively labeled by an antiserum against LANT-6, a neurotensin-like hexapeptide. In sharks also, LANT-6-positive neurons were observed in the apparent equivalent of the globus pallidus. These results, which imply the coexistence of a LANT-6-like peptide with gamma-aminobutyric acid (GABA) in pallidal neurons, suggest that a LANT-6-like peptide may be an important and evolutionarily conserved neurotransmitter/neuromodulator in pallidal neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25594/1/0000138.pd

Evolution of the amniote basal ganglia

Recent findings indicate that the basal ganglia of amniotes, i.e. modern birds, reptiles and mammals, contain similar neuronal subpopulations, as defined by the transmitters these neurons use and their connections. These data suggest that the evolution of the basal ganglia has been much more conservative than once believed and that this region of the forebrain performs a similar motor role in birds, reptiles and mammals. The basal ganglia of birds and reptiles, however, differ from those of mammals in that they appear to have their major influence over motor functions by an output to the tectum via the pretectum. In contrast, the mammalian basal ganglia are thought to have their major influence over motor functions by an output to the motor cortex via the thalamus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24712/1/0000133.pd

The distribution of proenkephalin-derived peptides in the central nervous system of turtles

The present study was carried out to examine if peptides similar to the various opioid peptide products of mammalian proenkephalin are present in the turtle central nervous system and to determine their distribution. Antisera against several enkephalin peptides were used: (1) leucine-enkephalin (LENK), (2) methionine-enkephalin (MENK), (3) methionine-enkephalin-arg 6 -phe 7 (MERF), (4) methionine-enkephalin-arg 6 -gly 7 -leu 8 (MERGL), (5) Peptide E (PEPE), and (6) BAM22P. Their specificity and cross-reactivity were carefully examined. The results indicated that LENK, MENK, and MERF (or highly similar peptides) are present in the turtle central nervous system, and that a peptide showing immunological similarity to BAM22P and PEPE also appeared to be present. In contrast, MERGL did not appear to be present. The distributions of the immunoreactive labeling for LENK, MENK, MERF, BAM22P, and PEPE were indistinguishable, and double-label studies showed that LENK, MERF, and BAM22P were colocalized within individual neurons and fibers. Although all of the above substances were observed in the same cell groups, there was some regional variation, in terms of which enkephalin peptide appeared to be most abundant. The distributions of these enkephalin peptides were very similar to those previously described in mammals and birds. Enkephalin was more abundant in the basal ganglia than in overlying telencephalic regions. Within the basal ganglia, enkephalin was present in striatal neurons and fibers and in pallidal fibers, thereby suggesting the existence of an enkephalinergic striatopallidal projection. Sensory relay nuclei of the thalamus were generally poor in enkephalinergic fibers, whereas the hypothalamus was rich in enkephalinergic neurons and fibers. Enkephalinergic neurons and fibers were present in the midbrain central gray. As is true of neurons of the nucleus spiriformis lateralis of the avian pretectum, the neurons of the homologous cell group in turtles, the dorsal nucleus of the posterior commissure of the pretectum, were found to contain enkephalin and have an enkephalinergic projection to the deep layers of the ipsilateral tectum. Enkephalinergic neurons and fibers were also abundant in the entry zones of the trigeminal nerve and dorsal root fibers of the spinal cord. The present results indicate that: (1) consistent with previously published biochemical studies (Lindberg and White, '86), proenkephalin in reptiles is similar in structure to that of mammals and, with the exception of MERGL, gives rise to similar or identical enkephalin peptides, and (2) the enkephalin peptides are found in many of the same systems of reptilian brain as mammalian and avian brain, and, therefore, may play a role in similar functions (e.g., basal ganglia motor functions) as in mammals and birds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50034/1/902590106_ftp.pd

The distribution of enkephalinlike immunoreactivity in the telencephalon of the adult and developing domestic chicken

Immunohistochemical techniques were used to determine the distribution of enkephalinlike immunoreactivity in the telencephalon of chicken. The densest accumulation of enkephalinergic neurons and fibers was observed within the paleostriatal complex, the avian equivalent of the mammalian basal ganglia. Numerous small enkephalinergic neurons were observed in both lobus parolfactorius (LPO) and the paleostriatum augmentatum (PA), the two components of the small-celled portion of the paleostriatal complex. The enkephalinergic neurons of LPO-PA appeared to give rise to a dense plexus of enkephalinergic fibers within the large-celled zone of the paleostriatal complex, the paleostriatum primitivum (PP). The distribution of enkephalin within the avian paleostriatial complex, when compared to the distribution of enkephalin within the mammalian basal ganglia, supports previous proposals that PP is comparable to the mammalian globus pallidus and that PA-LPO are comparable to the caudate-putamen (Karten and Dubbeldam, '73; Kitt and Brauth, '81; Parent and Olivier, '70; Reiner et al., '83). Observations on the development of enkephalinlike immunoreactivity within the chicken paleostriatal complex also support the suggestion that the major component nuclei of the avian paleostriatal complex have correspondents within the mammalian basal ganglia. Enkephalinlike immunoreactivity was also observed within cell bodies and fibers in other portions of the avian telencephalon. Within the ventrolateral telencephalon, the nucleus accumbens, nucleus of the diagonal band, and tuberculum olfactorium contained enkephalinergic cell bodies and fibers while only enkephalinergic fibers were observed in the portion of the avian telencephalon that has been termed the ventral paleostriatum (Kitt and Brauth, '81; Reiner et al., '83). Within the medial wall of the telencephalon, enkephalinergic fibers were observed in the lateral septal nucleus, while enkephalinergic cell bodies and fibers were observed in the parahippocampal area. Little enkephalinlike immunoreactivity was observed dorsal to the paleostriatal complex except in the hyperstriatum dorsale. Within the hyperstriatum dorsale, a band of enkephalinergic neurons appeared to give rise to an overlying parallel band of dense enkephalinergic fibers. The distribution of enkephalinlike immunoreactivity within the avian telencephalon thus shows remarkable similarity to that seen in the mammalian telencephalon. The largest accumulation of enkephalinlike immunoreactivity within the telencephalon of both vertebrate classes appears to be found within the ventrolateral wall of the telencephalon, including the basal ganglia. In comparison, much less enkephalinlike immunoreactivity is observed in either the mammalian neocortex or in the avian correspondent of mammalian neocortex.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50024/1/902280210_ftp.pd

Reduced Performance of Prey Targeting in Pit Vipers with Contralaterally Occluded Infrared and Visual Senses

Both visual and infrared (IR) senses are utilized in prey targeting by pit vipers. Visual and IR inputs project to the contralateral optic tectum where they activate both multimodal and bimodal neurons. A series of ocular and pit organ occlusion experiments using the short-tailed pit viper (Gloydius brevicaudus) were conducted to investigate the role of visual and IR information during prey targeting. Compared with unoccluded controls, snakes with either both eyes or pit organs occluded performed more poorly in hunting prey although such subjects still captured prey on 75% of trials. Subjects with one eye and one pit occluded on the same side of the face performed as well as those with bilateral occlusion although these subjects showed a significant targeting angle bias toward the unoccluded side. Performance was significantly poorer when only a single eye or pit was available. Interestingly, when one eye and one pit organ were occluded on opposite sides of the face, performance was poorest, the snakes striking prey on no more than half the trials. These results indicate that, visual and infrared information are both effective in prey targeting in this species, although interference between the two modalities occurs if visual and IR information is restricted to opposite sides of the brain

A LANT6-like substance that is distinct from neuromedin N is present in pallidal and striatal neurons in monkeys

The basal ganglia of rhesus and squirrel monkeys were examined using immunohistochemical techniques with antibodies against the neurotensin-related hexapeptides Lys8-Asn9-Neurotensin(8-13) (LANT6) and Neuromedin N. A high percentage of neurons in both segments of globus pallidus and many large neurons of the striatum were found to label for LANT6, but not Neuromedin N. Previous studies have shown that LANT6 or a LANT6-like substance is present in many pallidal neurons in a wide range of vertebrate species. The current results indicate that a LANT6-like substance that is distinct from Neuromedin N is also present in many pallidal neurons in primates. This raises the possibility that this substance may be involved in neurotransmission between the pallidum and its projection targets.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26572/1/0000111.pd

Confirmation of functional zones within the human subthalamic nucleus: Patterns of connectivity and sub-parcellation using diffusion weighted imaging

The subthalamic nucleus (STN) is a small, glutamatergic nucleus situated in the diencephalon. A critical component of normal motor function, it has become a key target for deep brain stimulation in the treatment of Parkinson's disease. Animal studies have demonstrated the existence of three functional sub-zones but these have never been shown conclusively in humans. In this work, a data driven method with diffusion weighted imaging demonstrated that three distinct clusters exist within the human STN based on brain connectivity profiles. The STN was successfully sub-parcellated into these regions, demonstrating good correspondence with that described in the animal literature. The local connectivity of each sub-region supported the hypothesis of bilateral limbic, associative and motor regions occupying the anterior, mid and posterior portions of the nucleus respectively. This study is the first to achieve in-vivo, non-invasive anatomical parcellation of the human STN into three anatomical zones within normal diagnostic scan times, which has important future implications for deep brain stimulation surgery

Anatomical Specializations for Nocturnality in a Critically Endangered Parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds

The distribution of cholecystokinin-8 in the central nervous system of turtles: An immunohistochemical and biochemical study

Immunohistochemical techniques, radioimmunoassay (RIA) and high performance liquid chromatography (HPLC) were used to: (1) determine the regional distribution and amounts of cholecystokinin-8 (CCKS)-like immunoreactivity in the turtle central nervous system, and (2) chemically characterize the CCK8-like material present in the turtle central nervous system. High levels of CCK8-like immunoreactivity were found in the turtle central nervous system, with the highest levels being present in the hypothalamus and neurohypophysis. Moderate levels of the CCK8-like material were found in all other regions of the turtle nervous system except the cerebellum, the olfactory bulbs and the dorsal ventricular ridge of the telencephalon, which contained low levels. The bulk (87%) of the CCK8-like material in turtle central nervous system co-eluted with CCK8-sulfate in gradient elution HPLC. The distribution of CCK8-like immunoreactivity (CCK8LI) observed using immunohistochemistry was consistent with the results of the RIA studies. Numerous CCK8LI-containing neurons and fibers were observed in the hypothalamus and neurohypophysis. Neurons and fibers containing CCK8 were, however, more sparsely distributed outside the hypothalamus. The immunohistochemical data provided evidence for the existence of two major CCK8-containing pathways in turtles that have been previously described in mammals: a pathway from the supraoptic and paraventricular magnocellular nuclei to the external zone of the median eminence and neurohypophysis and a pathway from dorsal root ganglia to the dorsal horn of the spinal cord. Overall, the present results, in conjunction with several previous studies, indicate that CCK8 has had a relatively stable evolutionary history as a CNS neuropeptide among land vertebrates. The molecular structure of CCK8 appears to have been largely (if not entirely) conserved, as has its concentration in many brain regions. A noteworthy exception to such conservatism in the localization of CCK8 is that the concentration of CCK8 in the telencephalon, particularly in the telencephalic cortex, is much lower in turtles than in mammals. The present results therefore suggest that CCK8 may not have become a prominent peptide in the telencephalic cortex (or its anatomical equivalents) until the evolution of neocortex in the mammalian lineage.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25605/1/0000152.pd