摘要:

Ampullary sense organs are distributed in groups over the head of Hydrolagus colliei with their pores in clusters and innervated by the buccal, hyomandibular and superficial ophthalmic branches of the anterior lateral line nerve. The ampullae contain ciliated sense cells in an alveolate-shaped epithelium, which communicates to the surface through a jelly-filled tube. The sense cells synapse at their bases with the afferent nerve fibers that terminate in the dorsal nucleus of the anterior lateral line lobe of the medulla. The anatomy and ultrastructure support the homology with the ampullae of Lorenzini of elasmobranchs. Single units recorded from the buccal branch of the anterior lateral line nerve are either lateral line or ampullary in character, the former being sensitive only to mechanical stimuli, the latter to both mechanical and to weak electric stimuli. They are also distinguished by the positions of their receptive fields. The electroreceptive units are spontaneously active and are excited by a cathode placed near the opening of their pore and inhibited by an anode. Compound evoked potentials are recorded from beneath the lateral aspect of the tectum in response to weak electric fields in the bath. Each recording locus has a best position and orientation of the electric field. The electric fields are effective if their duration is longer than ca. 2 ms; longer than 10 ms makes no difference until an OFF effect becomes distinct at ca. 50 ms. The reception is tuned to low frequencies but is not sensitive to maintained current (DC). Evoked potentials summating moderate numbers of responses are clear at <1μV/cm. Ratfish were conditioned in a ring-shaped tank to reverse the direction of swimming when an electric field was switched ON. The stimulus was a 5 Hz square wave or the onset of a DC of 1-10 μA between a pair of electrodes on the floor of the tank. The fish responded to fields as weak as 0.2 μV/cm. A specialized sense modality for electroreception, similar to that in elasmobranchs and most other groups of nonteleost fishes, except for Myxini and Neopterygii (holosteans), is present in the subclass Holocephali. The notion is supported that this modality and its central as well as peripheral apparatus arose early in the evolution of vertebrates. Only two losses of the whole system need be hypothesized, on this idea, once in the ancestors of the hagfishes and once in the ancestors of the neopterygians, which include the teleosts. Some orders of teleosts then evolved a new system of electroreception independently. The ciliary receptor cells are probably primitive; microvillar sense cells evolved independently.

ISSN:0006-8977    

DOI:10.1159/000113849

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Ampullary sense organs are distributed in groups over the head of Hydrolagus colliei with their pores in clusters and innervated by the buccal, hyomandibular and superficial ophthalmic branches of the anterior lateral line nerve. The ampullae contain ciliated sense cells in an alveolate-shaped epithelium, which communicates to the surface through a jelly-filled tube. The sense cells synapse at their bases with the afferent nerve fibers that terminate in the dorsal nucleus of the anterior lateral line lobe of the medulla. The anatomy and ultrastructure support the homology with the ampullae of Lorenzini of elasmobranchs. Single units recorded from the buccal branch of the anterior lateral line nerve are either lateral line or ampullary in character, the former being sensitive only to mechanical stimuli, the latter to both mechanical and to weak electric stimuli. They are also distinguished by the positions of their receptive fields. The electroreceptive units are spontaneously active and are excited by a cathode placed near the opening of their pore and inhibited by an anode. Compound evoked potentials are recorded from beneath the lateral aspect of the tectum in response to weak electric fields in the bath. Each recording locus has a best position and orientation of the electric field. The electric fields are effective if their duration is longer than ca. 2 ms; longer than 10 ms makes no difference until an OFF effect becomes distinct at ca. 50 ms. The reception is tuned to low frequencies but is not sensitive to maintained current (DC). Evoked potentials summating moderate numbers of responses are clear at <1μV/cm. Ratfish were conditioned in a ring-shaped tank to reverse the direction of swimming when an electric field was switched ON. The stimulus was a 5 Hz square wave or the onset of a DC of 1-10 μA between a pair of electrodes on the floor of the tank. The fish responded to fields as weak as 0.2 μV/cm. A specialized sense modality for electroreception, similar to that in elasmobranchs and most other groups of nonteleost fishes, except for Myxini and Neopterygii (holosteans), is present in the subclass Holocephali. The notion is supported that this modality and its central as well as peripheral apparatus arose early in the evolution of vertebrates. Only two losses of the whole system need be hypothesized, on this idea, once in the ancestors of the hagfishes and once in the ancestors of the neopterygians, which include the teleosts. Some orders of teleosts then evolved a new system of electroreception independently. The ciliary receptor cells are probably primitive; microvillar sense cells evolved independently.

ISSN:0006-8977    

DOI:10.1159/000316114

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

We examined the organization of catecholaminergic neurons in the hypothalamus of the painted ray, Raja undulata, and the small-spotted dogfish, Scyliorhinus canicula, with the use of formaldehyde-induced fluorescence (FIF) methods and tyrosine hydroxylase (TH) immunohistochemistry. In both species we identified distinct populations of catecholamine-containing neurons differing in a) their immunoreactivity to antibodies against the enzyme tyrosine hydroxylase (TH), b) their fluorescence in response to FIF methods for the detection of catecholamines, and c) their relationship with the third ventricle. One population is made up of FIF-positive and TH-negative neurons (most of which are CSF [cerebrospinal fluid]-contacting) and located in two circumventricular organs, the preoptic recess organ and the organon vasculosum hypothalami. Another population comprises TH-immunoreactive (TH-IR), FIF negative neurons that are located in the suprachiasmatic nucleus and the posterior tuberculum and are not related to the third ventricle recesses. A third population of TH-IR, CSF-contacting neurons is also present in the organon vasculosum hypothalami The existence of three catecholaminergic populations suggests differences in the metabolism of catecholamines and/or different functions. The circumventricular neurons are not associated with the hypophysis and appear to accumulate catecholamine (dopamine) obtained from exogenous sources. In both Raja and Scyliorhinus the neurointermediate lobe is innervated by TH-IR fibres originating from dopamine-synthesizing neurons of the second catecholaminergic population.

ISSN:0006-8977    

DOI:10.1159/000113850

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Total brain size and the volume of several brain parts were compared in male and female ranch mink of varying age and body size in an attempt to quantify postnatal maturation and growth processes in this altricial species. Volumes of fresh whole brains and of different brain parts were calculated from prepared histological sections from juvenile (2- to 3-month-oId), subadult (5-month-old), and adult (older than 7 months) individuals. Allometrical calculations were performed on the basis of body weight. Changes in size of different parts of the brain obtained to different degrees were found to be dependent on age but independent of body size. From the juvenile stage to the subadult stage, total brain size remains unchanged, although most major brain parts increase in size, while the grey matter of the isocortex decreases. During subsequent development from subadult to adult, total brain size evidently decreases. Within the brain all major structures also decrease in size, except for the medulla oblongata and the mesencephalon, which remains relatively stable in size. The grey matter of the isocortex shows the greatest decrease, followed by the allocortex and corpus striatum, the cerebellum, the white matter of the isocortex, and the diencepha-Ion. Thus, an unusual but evident 'overshoot' in size of the total brain and certain parts apparently occurs in this species before adulthood is reached. This phenomenon is discussed in connection with size changes concomitant with domestication as well as with cageing of individuals and with postnatal and seasonal size changes known from some soricid species as the so-called Dehnel phenomenon.

ISSN:0006-8977    

DOI:10.1159/000113851

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

Microinjection of L-glutamic acid into the basal midbrain of the toad Bufo paracnemis induced a series of responses linked to antipredator behavior such as flight, backward locomotion and defensive postures. Furthermore, alerting/ orientation occurred in 20% of the animals, a behavior which is probably important for the animal to achieve the above responses. Locomotion occurred in 18% of the toads. The existence of a mesencephalic premotor control for locomotion in these animals is discussed comparatively. All responses were accompanied by changes in arterial pressure, heart rate and intrabuccal pressure. In some animals which exhibited backward locomotion responses, defensive postures and alerting/orientation, bradycardia or cardiac arrest occurred, with no appreciable changes in arterial pressure. This fact is discussed on the basis of studies which have shown the occurrence of similar alterations in situations of fear in other vertebrates. Autonomic changes without other responses occurred in 16% of the animals. Flight behavior was usually observed as a consequence of stimulation of sites located in the anterodorsal tegmental nucleus and lateral portions of the midbrain tegmentum. In contrast, locomotion was obtained by stimulating basal sites of the tegmentum located in the anteroventral nucleus and in the reticular formation lateral to it. Sites related to the remaining behaviors were located more diffusely in the basal midbrain.

ISSN:0006-8977    

DOI:10.1159/000113852

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The distribution of cholinergic neurons was studied in painted and red-eared turtles using antisera against choline acetyltransferase (ChAT). The results showed that the organization of cholinergic systems in the central nervous system of turtles was remarkably similar to that previously described in diverse other species. For example, the present studies revealed the presence of cholinergic neurons in the striatum, the basal telencephalon, the isthmo-tectal system, and a region of cells near the cerebellar peduncle. The motoneurons of the III, IV, V, VI, VII, X and XII cranial nerves and the spinal ventral horn were also shown to be cholinergic. Additional cholinergic neurons were observed in the hypothalamus and rhombencephalic reticular formation. These results help to clarify the precise extent and location of the major cholinergic cell groups of the turtle brain, thereby adding to our understanding of the organization of the turtle nervous system. The results also reveal that the cholinergic systems of the striatum, basal forebrain, isthmic region, and cerebellar peduncular region are ancestral features of the amniote brain and are common to all living amniotes that have been studied. Thus, the organization and, presumably, the function of the cholinergic systems appear to be conservative.

ISSN:0006-8977    

DOI:10.1159/000113853

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113854

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113855

出版商:S. Karger AG    

年代:1993

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113866

出版商:S. Karger AG    

年代:1993

数据来源: Karger