Margin of safety of pentylene glycol derived using measurements of cutaneous absorption and volatility.

The safety assessment of pentylene glycol (PG) has been based on a bioavailability extrapolated from those of other 1,2-glycols or an assumed 100% absorption. To make a better safety assessment and an accurate calculation of the margin of safety (MoS), the skin penetration of PG present in a commercially available sunscreen was measured in pig skin at different exposure durations. The mass balance of PG decreased with increasing exposure durations, from 98% (1 h) to 29% (24 h) and the amount of PG detected in the skin wash decreased over time from 93% to 3%. The decrease in mass balance was attributed to an unexpected volatility of PG, which was confirmed in additional experiments. The maximum bioavailable amount of PG was 123 µg/cm2 after 24 h and was considered to be worst case scenario (10 mg/cm2 i.e. 5-fold the recommended application standard dose, 2 mg/cm2). MoS values for the application of a standard dose of sunscreen after 1-24 h exposure were 140-671 in adults and, if calculated for children ratios, 87-217 Based on the available toxicological data for PG in comparison to the amounts determined to be potentially bioavailable, PG in the test sun protection product SPF 50 + does not show any safety concerns for daily usage at the recommended dosage of 2 mg/cm2 or lower.

Detailed immunohistology of Pax6 protein and tyrosine hydroxylase in the early zebrafish brain suggests role of Pax6 gene in development of dopaminergic diencephalic neurons.

Spatiotemporal developmental dynamics of Pax6 protein containing (i.e., Pax6) cells were investigated immunohistochemically in embryonic and postembryonic zebrafish brain sections (especially at 2 and 5 day), allowing for a neuroanatomically detailed resolution previously only reported for the mouse. Besides strikingly close correspondences of early Pax6 domains - including many spatiotemporal changes - in mouse and zebrafish brains, some critical differences were noted. There is no pallial (i.e., cortical) Pax6 expression domain in the ventricular proliferative layer in the zebrafish as in the mouse. The main pallial Pax6 domain in the zebrafish is comparable to the migrating stream of Pax6 cells at the pallial-subpallial boundary. This indicates that some developmental functions of Pax6 (i.e., inhibition of subpallial cell migration into pallium by Pax6 migrating stream) might be shared with the mouse and maybe all vertebrates, while others (i.e., control of intrapallial neuronal radial migration via Pax6 expressing radial glia cells) may be special for mammals. Another prominent feature in the early zebrafish forebrain is that the alar plate ventral thalamic Pax6 domain extends far caudolaterally into the periphery of the basal plate posterior tuberculum and hypothalamic inferior lobe. This indicates that the alar plate ventral thalamus invades the forebrain basal plate and contributes to the development of basal forebrain structures. The close spatiotemporal association of Pax6 cells and TH cells of the ventral thalamus indicates a local role of Pax6 in the development of ventral thalamic (as recently demonstrated in the mouse) and, maybe, posterior tubercular TH cells. However, our confocal microscopical analysis of zebrafish brain sections double-immunostained for Pax6 and TH did not reveal cells double-labeled for these two proteins in this location, but rather indicates an inductive interaction of Pax6 cells onto TH cells.

The teleostean (zebrafish) dopaminergic system ascending to the subpallium (striatum) is located in the basal diencephalon (posterior tuberculum).

Tyrosine hydroxylase immunohistochemistry is used to demonstrate catecholaminergic neuronal populations in the fore- and midbrain of adult zebrafish (Danio rerio). While no catecholaminergic neurons are found in the midbrain, various immunoreactive populations were found in the diencephalon (hypothalamus, posterior tuberculum, ventral thalamus, pretectum) and telencephalon (preoptic region, subpallium, olfactory bulb). The posterior tubercular catecholaminergic cells include three cytological types (small round, large pear-shaped, and bipolar liquor-contacting cells). Furthermore, the retrograde neuronal tracers DiI or biocytin were applied to demonstrate ascending projections to the basal telencephalon (incl. the striatum). A double-label approach was used - together with tyrosine hydroxylase immunohistochemistry - in order to visualize neurons positive for tyrosine hydroxylase and a retrograde tracer. Double-labeled cells were identified in two locations in the posterior tuberculum (i.e, small round neurons in the periventricular nucleus of the posterior tuberculum and large pear-shaped cells adjacent to it). They are interpreted as the teleostean dopaminergic system ascending to the striatum, since previous work [16] established that no noradrenergic neurons exist in the forebrain of the adult zebrafish.

Proliferation pattern changes in the zebrafish brain from embryonic through early postembryonic stages.

Proliferating cell nuclear antigen (PCNA)-immunohistochemistry was used for demonstrating the spatiotemporal course of proliferation in the brains of embryonic (24 h) through postembryonic (5 days) zebrafish (Danio rerio). Parallel series of the same stages prepared according to the combined Bodian fiber silver-stain/cresyl Nissl-stain were used for improved morphogenetic analysis (i.e., in detecting critical neuroanatomical landmarks). Starting from an essentially ubiquituous proliferation throughout the neural tube before 24 h, PCNA-immunoreactive cells become successively more restricted to a subset of gray matter cells around 48 h and even more distinct proliferation zones become apparent around 72 h. Both hindbrain and forebrain reveal a segmental organization with regard to the distribution of proliferation zones, but the rhombomeric pattern of PCNA-immunoreactive cells emerging between 48 h and 72 h precedes a similar prosomeric pattern by about 48 h. Two divisions of the midbrain-hindbrain boundary are described here morphologically and both are demonstrated to show sustained proliferation throughout the investigated time frame. In contrast, proliferation in the adjacent mesencephalic and cerebellar domains is rapidly down-regulated during the first 5 days of development.

Early postembryonic neural development in the zebrafish: a 3-D reconstruction of forebrain proliferation zones shows their relation to prosomeres.

Based on a section-by-section analysis of the morphology (combined silver/Nissl stain) and of the distribution of proliferation zones (immunohistochemical detection of the proliferating cell nuclear antigen) in the zebrafish (Danio rerio) forebrain at 5 days postfertilization, we created a three-dimensional reconstruction of proliferation zones of that developmental stage. The resulting model visualizes the size, number, location and morphology of forebrain proliferation zones. The latter foreshadow closely adult neuroanatomical forebrain entities. Furthermore, the detailed distribution of proliferation zones in the posterior forebrain - but not in the more anterior secondary prosencephalon - supports a segmental prosomeric organization.

Postembryonic neural proliferation in the zebrafish forebrain and its relationship to prosomeric domains.

Large gaps of knowledge exist regarding postembryonic brain morphogenesis of the zebrafish Danio rerio (Cyprinidae, Teleostei). The zebrafish represents together with the frog (Xenopus), chick and mouse--one of four major models for the genetic study of early brain development. Here, we used normal silver-stained Bodian material and immunohistochemical material stained with a monoclonal antibody against the proliferating cell nuclear antigen (PCNA, cyclin) to study the morphogenetic appearance and location of proliferation zones of the zebrafish brain between day 1 and day 10, focussing on the forebrain at day 5 postfertilization. Our results directly demonstrate that the dorsal telencephalic proliferation zone (i.e. the pallium) extends--consistent with the process of eversion--some distance laterally on top of the telencephalon. The subpallial telencephalic proliferation consists of dorsal and ventral zones. The preoptic region also includes dorsal and ventral proliferation zones. In the diencephalon proper, separate proliferation zones are present in the habenula, and in the periventricular cell masses of the dorsal thalamus, the ventral thalamus, and the pretectum. More ventrocaudally, the latter three massive proliferation zones appear to be replaced each by thinner, but distinct proliferation zones. Two of them represent ventrocaudal continuations of the dorsal and ventral thalamus and lie in the region referred to as the posterior tubercular area in adult teleostean neuroanatomy. The third lies in the region of the nucleus of the medial longitudinal fascicle. In addition, several hypothalamic proliferation zones are present. The data for the diencephalon are largely in agreement with the neuromeric model of brain organization of Puelles and Rubenstein (1993), which is mostly based on amniote data. Generally, the understanding of the prosomeric origin of teleostean prosencephalic cell masses may be regarded as pivotal for their comparative interpretation.

Readiness of zebrafish brain neurons to regenerate a spinal axon correlates with differential expression of specific cell recognition molecules.

We analyzed changes in the expression of mRNAs for the axonal growth-promoting cell recognition molecules L1.1, L1.2, and neural cell adhesion molecule (NCAM) after a rostral (proximal) or caudal (distal) spinal cord transection in adult zebrafish. One class of cerebrospinal projection nuclei (represented by the nucleus of the medial longitudinal fascicle, the intermediate reticular formation, and the magnocellular octaval nucleus) showed a robust regenerative response after both types of lesions as determined by retrograde tracing and/or in situ hybridization for GAP-43. A second class (represented by the nucleus ruber, the nucleus of the lateral lemniscus, and the tangential nucleus) showed a regenerative response only after proximal lesion. After distal lesion, upregulation of L1.1 and L1.2 mRNAs, but not NCAM mRNA expression, was observed in the first class of nuclei. The second class of nuclei did not show any changes in their mRNA expression after distal lesion. After proximal lesion, both classes of brain nuclei upregulated L1.1 mRNA expression (L1.2 and NCAM were not tested after proximal lesion). In the glial environment distal to the spinal lesion, labeling for L1.2 mRNA but not L1.1 or NCAM mRNAs was increased. These results, combined with findings in the lesioned retinotectal system of zebrafish (Bernharnhardt et al., 1996), indicate that the neuron-intrinsic regulation of cell recognition molecules after axotomy depends on the cell type as well as on the proximity of the lesion to the neuronal soma. Glial reactions differ for different regions of the CNS.

Some forebrain connections of the gustatory system in the goldfish Carassius auratus visualized by separate DiI application to the hypothalamic inferior lobe and the torus lateralis.

The neuroanatomical connections of the diencephalic torus lateralis and inferior lobe of the goldfish (Carassius auratus) were studied by retrograde and anterograde labeling with the carbocyanine dye DiI. Both structures have afferents originating in the central zone of the dorsal telencephalic area as well as in the supracommissural nucleus of the ventral telencephalic area, and in the secondary gustatory, tertiary gustatory, and posterior thalamic nuclei. Both structures investigated have efferents to the tertiary gustatory and posterior thalamic nuclei, as well as to the dorsal hypothalamus (dorsal hypothalamic neuropil) and superior reticular formation. The torus lateralis receives additional afferents from the secondary general visceral nucleus and, sparsely, from the dorsal tegmental nucleus. The inferior lobe receives additional afferents from the medial zone of the dorsal telencephalic area, as well as from the suprachiasmatic, posterior pretectal, central posterior thalamic, caudal preglomerular, two tegmental nuclei (T1 and T2), corpus mamillare, and, sparsely, from the cerebellar valvula. The inferior lobe has additional efferents to the dorsal and ventral thalamus and subglomerular nucleus. The lateral torus and inferior lobe are also mutually interconnected. The lateral torus and inferior lobe map topographically onto the vagal-related (intraoral) or onto the facial-related (extraoral) portions, respectively, of both the secondary and tertiary gustatory nuclei. Because the posterior thalamic nucleus is reciprocally connected with the lateral torus and inferior lobe and is further known to project in turn to the area doralis telencephali, it likely represents a quaternary gustatory projection nucleus to the telencephalon in cyprinids. Whereas the lateral torus seems to be exclusively involved with gustatory and general visceral systems, the inferior lobe has inputs from additional sensory (e.g., octavolateralis, visual) systems, and, thus, likely represents a multisensory integration center.

Axonal regrowth after spinal cord transection in adult zebrafish.

Using axonal tracers, we characterized the neurons projecting from the brain to the spinal cord as well as the terminal fields of ascending spinal projections in the brain of adult zebrafish with unlesioned or transected spinal cords. Twenty distinct brain nuclei were found to project to the spinal cord. These nuclei were similar to those found in the closely related goldfish, except that additionally the parvocellular preoptic nucleus, the medial octavolateralis nucleus, and the nucleus tangentialis, but not the facial lobe, projected to the spinal cord in zebrafish. Terminal fields of axons, visualized by anterograde tracing, were seen in the telencephalon, the diencephalon, the torus semicircularis, the optic tectum, the eminentia granularis, and throughout the ventral brainstem in unlesioned animals. Following spinal cord transection at a level approximately 3.5 mm caudal to the brainstem/spinal cord transition zone, neurons in most brain nuclei grew axons beyond the transection site into the distal spinal cord to the level of retrograde tracer application within 6 weeks. However, the individually identifiable Mauthner cells were never seen to do so up to 15 weeks after spinal cord transection. Nearly all neurons survived axotomy, and the vast majority of axons that had grown beyond the transection site belonged to previously axotomized neurons as shown by double tracing. Terminal fields were not re-established in the torus semicircularis and the eminentia granularis following spinal cord transection.

The zebrafish brain: a neuroanatomical comparison with the goldfish.

The zebrafish Danio rerio is an important model system for genetic and developmental studies of the vertebrate central nervous system. Considerable knowledge concerning the embryonic development of the central nervous system of the zebrafish has accumulated in recent years. However, there is an apparent lack of information on the organization of the adult zebrafish brain. We have therefore recently studied in detail the neuroanatomy of the adult zebrafish. Here we compare the brains of the zebrafish and of the closely related and neurobiologically well-investigated goldfish, Carassius auratus. Two sensory systems, the visual and the gustatory systems, were identified as differing on the gross morphological and histological levels in the two species. The goldfish shows the simple (evolutionarily reduced) pattern of pretectal organization, and its gustatory system is massively enlarged. The pretectum of the zebrafish conforms to this simplified visual pretectal pattern, although the retention of some ancestral pretectal characters indicates a lesser degree of reduction of the visual system compared to the goldfish. The gustatory system shows many similarities with the evolutionarily derived and functionally specialized gustatory system of the goldfish. However, some peripheral and central gustatory characters are missing in the zebrafish, indicating a less specialized gustatory system.

The teleostean torus longitudinalis: a short review on its structure, histochemistry, connectivity, possible function and phylogeny.

The older idea that the torus longitudinalis (TL) is part of the ascending cerebellotectal circuitry involved in control of eye movements is at odds with facts on the histological, hodological and physiological level. Instead of an input from the valvula cerebelli, the TL and the cerebellum both receive a collateral mossy fiber input from the same source (nucleus lateralis valvulae, dorsal tegmental nucleus). The new hodological information is more consistent with fine histological and physiological data and suggests that the TL is a link in premotor circuitry descending from telencephalon to brain stem.

Descending telencephalic information reaches longitudinal torus and cerebellum via the dorsal preglomerular nucleus in the teleost fish, Pantodon buchholzi: a case of neural preaptation?

The weakly electric mormyrids are known to have an ascending neuronal pathway that reaches the diencephalon and carries information concerned with electrolocation. The recipient diencephalic center, the dorsal preglomerular nucleus, receives a massive telencephalic input and projects to the corpus and valvula cerebelli. This circuitry has been interpreted as a uniquely derived (autapomorphic) feature for mormyrids. In the present study, we demonstrate with the fluorescent neuronal tracer DiI that the closely related, but non-electroreceptive, teleost Pantodon buchholzi possesses a dorsal preglomerular nucleus with similar telencephalo-cerebellar circuitry. The projection to the cerebellum only reaches the corpus, however, not the valvula cerebelli. Further, the dorsal preglomerular nucleus of Pantodon displays a descending pathway via the torus longitudinalis. Two phylogenetic interpretations for the presence of telencephalo-cerebellar pathways in both mormyrids and Pantodon are possible: if such a pathway existed as a preaptation in the common ancestor of mormyrids and Pantodon, it must be an exaptation for electroreception in mormyrids, since this sensory modality evolved anew in this teleost group; alternatively, the pathway evolved in parallel homoplasy, once in Pantodon, as part of a descending premotor pathway, and independently in mormyrids, where the system gains access to ascending electrosensory information.

Is the nucleus corticalis of teleosts a new cholinergic central nervous system for vertebrates?

Acetylcholinesterase histochemistry suggests that the pretectal nucleus corticalis of teleost fish may be cholinergic. Because immunohistochemical analysis with antibodies against choline acetyltransferase provides a more reliable means of recognizing cholinergic central nervous structures, we investigated transverse brain sections of the African cichlid fish, Hemichromis lifalili and Hemichromis guttatus, with standard immunohistochemical techniques and found the nucleus corticalis to contain choline acetyltransferase. This supports the hypothesis that teleosts (unlike all other known vertebrates) have a cholinergic second-order sensory (i.e. visual) circuit.

The visually related posterior pretectal nucleus in the non-percomorph teleost Osteoglossum bicirrhosum projects to the hypothalamus: a DiI study.

This study was done to elucidate the ancestral (plesiomorphic) condition for visual pathways to the hypothalamus in teleost fishes. Three patterns of pretectal organization can be discerned morphologically and histochemically in teleosts. Their taxonomic distribution suggests that the intermediately complex pattern (seen in most teleost groups) is ancestral to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). The pretectal nuclei involved can be demonstrated with acetylcholinesterase histochemistry selectively and reliably in different species of teleosts, suggesting that the same-named nuclei are homologous in representatives of the three different patterns. Whereas there are visual pathways to the hypothalamus in both the elaborate (percomorph) and the simple (cyprinid) patterns, different pretectal and hypothalamic nuclei are involved. Thus visual hypothalamic pathways in these two patterns would not appear to be homologous. In this study, circuitry within the third, i.e., the intermediately complex, pattern is investigated. It is demonstrated that visual pathways project via the pretectum to the hypothalamus in Osteoglossum bicirrhosum and that they are very similar to the visual pathways in the elaborate pattern. This suggests that the circuitry in the intermediately complex pattern, as represented by Osteoglossum, is plesiomorphic (evolutionarily primitive) and the circuitry in both the simple pattern (seen in cyprinids) and the elaborate pattern (seen in percomorphs) is apomorphic (evolutionarily derived) for teleosts.

Histochemical, connectional and cytoarchitectonic evidence for a secondary reduction of the pretectum in the European eel, Anguilla anguilla: a case of parallel evolution.

There are at least three different patterns of pretectal organization in teleost fishes: a simple pattern observed in cyprinids, an elaborate pattern present in percomorphs, and an intermediately complex pattern seen in many other teleost groups. The taxonomic distribution of the pretectal patterns indicates that the simple and the elaborate patterns are both evolutionarily derived (apomorphic) from the primitive (plesiomorphic) intermediately complex one. In anguillids, the pretectal pattern observed cytoarchitectonically has an anatomical configuration similar to that of the simple pattern in cyprinids. The distribution of acetylcholinesterase positivity in the pretectum (namely acetylcholinesterase positivity in the parvo- and magnocellular superficial and posterior pretectal nuclei, and acetylcholinesterase negativity in the pretectal cell plate and the ovoid preglomerular cell aggregate), as well as the retinal projections (namely retinal terminals in the parvocellular superficial and central pretectal nuclei, and absence of such terminals in the magnocellular superficial and posterior pretectal nuclei and the pretectal cell plate), strongly supports the interpretation suggested by the cytoarchitectonic analysis. As anguillids (elopomorpha) and cyprinids (ostariophysi) are related only distantly, this secondary simplification in the pretectum likely occurred independently, i.e. this simplification represents a case of parallel reduction.

Comparative cytoarchitectonic analysis of some visual pretectal nuclei in teleosts.

The posterior pretectal nucleus, which in Osteoglossum receives second order visual input and projects to the inferior lobe of the hypothalamus, was identified and characterized in species from all major groups of non-neoteleost teleosts. The hypothesis that the posterior pretectal nucleus in these species is homologous to both the pars intermedius of the superficial pretectal nucleus and nucleus glomerulosus in acanthopterygians is supported by multiple similarities in relative position and cytoarchitecture. Nucleus corticalis, which receives retinal input and projects to the posterior pretectal nucleus (or to nucleus glomerulosus), was identified in species belonging to three of the four major teleost radiations. Both the posterior pretectal nucleus and nucleus corticalis are plesiomorphic for teleosts. The presence of glomeruli in the posterior pretectal nucleus and nucleus glomerulosus in esocids and acanthopterygians, respectively, and the presence of two nuclei, the pars intermedius and nucleus glomerulosus, in acanthopterygians, as opposed to one nucleus, the posterior pretectal nucleus, are apomorphies.

Visual and electrosensory circuits of the diencephalon in mormyrids: an evolutionary perspective.

Mormyrids are one of two groups of teleost fishes known to have evolved electroreception, and the concomitant neuroanatomical changes have confounded the interpretation of many of their brain areas in a comparative context, e.g., the diencephalon, where different sensory systems are processed and relayed. Recently, cerebellar and retinal connections of the diencephalon in mormyrids were reported. The present study reports on the telencephalic and tectal connections, specifically in Gnathonemus petersii, as these data are critical for an accurate interpretation of diencephalic nuclei in teleosts. Injections of horseradish peroxidase into the telencephalon retrogradely labeled neurons ipsilaterally in various thalamic, preglomerular, and tuberal nuclei, the nucleus of the locus coeruleus (also contralaterally), the superior raphe, and portions of the nucleus lateralis valvulae. Telencephalic injections anterogradely labeled the dorsal preglomerular and the dorsal tegmental nuclei bilaterally. Injections into the optic tectum retrogradely labeled neurons bilaterally in the central zone of area dorsalis telencephali and ipsilaterally in the torus longitudinalis, various thalamic, pretectal, and tegmental nuclei, some nuclei in the torus semicircularis, the nucleus of the locus coeruleus, the nucleus isthmi and the superior reticular formation, basal cells in the ipsilateral valvula cerebelli, and eurydendroid cells in the contralateral lobe C4 of the corpus cerebelli. Weaker contralateral projections were also observed to arise from the ventromedial thalamus and various pretectal and tegmental nuclei, and from the locus coeruleus and superior reticular formation. Tectal injections anterogradely labeled various pretectal nuclei bilaterally, as well as ipsilaterally the dorsal preglomerular and dorsal posterior thalamic nuclei, some nuclei in the torus semicircularis, the dorsal tegmental nucleus, nucleus isthmi, and, again bilaterally, the superior reticular formation. A comparison of retinal, cerebellar, tectal, and telencephalic connections in Gnathonemus with those in nonelectrosensory teleosts reveals several points: (1) the visual area of the diencephalon is highly reduced in Gnathonemus, (2) the interconnections between the preglomerular area and telencephalon in Gnathonemus are unusually well developed compared to those in other teleosts, and (3) two of the three corpopetal diencephalic nuclei are homologues of the central and dorsal periventricular pretectum in other teleosts. The third is a subdivision of the preglomerular area, rather than an accessory optic or pretectal nucleus, and is related to electroreception. The preglomerulo-cerebellar connections in Gnathonemus are therefore interpreted as uniquely derived characters for mormyrids.

A direct cerebello-telencephalic projection in an electrosensory mormyrid fish.

After injections of the posterior part of the lateral zone of the area dorsalis telencephalic (Dlp) with either horseradish peroxidase or the newly available carbocyanine dye DiI, efferent cells were labeled in the valvula cerebelli of the mormyrid fish, Gnathonemus petersii. This may be a unique connection for this group of electrosensory teleosts, since no other vertebrate has ever been reported before to have a direct cerebello-telencephalic projection.

Phylogeny of putative cholinergic visual pathways through the pretectum to the hypothalamus in teleost fish.

Three patterns of pretectal organization can be discerned morphologically in teleosts. The taxonomic distribution of these pretectal patterns suggests that the intermediately complex pattern (seen in most teleost groups) has given rise to both the elaborate pattern (seen in percomorphs) and the simple pattern (seen in cyprinids). Two pretectal patterns (intermediately complex and elaborate) form part of similar, homologous visual pathways to the hypothalamus; the third pattern is involved in a nonhomologous pathway to the hypothalamus. Acetylcholinesterase (AChE) histochemistry was used in the present study in order to characterize these pretectal patterns further. It is demonstrated that AChE is a highly selective and reliable interspecific marker for all divisions of the superficial pretectum, the nucleus corticalis, the posterior pretectal nucleus (or nucleus glomerulosus) and portions of the inferior lobe. Therefore, the histochemical data support the hypothesis of a homology between the three patterns of pretectal organization in teleosts. Furthermore, the present data provide a basis for more specific investigations regarding the involvement of acetylcholine as a neurotransmitter within the visual pathways to the hypothalamus in teleosts.

Afferent connections of the valvula cerebelli in two teleosts, the common goldfish and the green sunfish.

The afferent connections of the valvula cerebelli were examined in one cypriniform teleost (Carassius auratus) and one perciform teleost (Lepomis cyanellus) with the use of horseradish peroxidase as a retrograde tracer. Both species have ipsilateral input to the valvula from the central pretectal and dorsal accessory optic nuclei, the dorsal and ventral tegmental nuclei, the lateral nucleus of the valvula, the perilemniscal nucleus, and nucleus isthmi and contralateral input from the inferior olivary nucleus. In addition, Carassius has ipsilateral valvulopetal projections from the eminentia granularis, the prae-eminential nucleus, and the isthmic primary sensory trigeminal nucleus, whereas Lepomis has bilateral (stronger ipsilaterally) valvulopetal projections from the nucleus of the locus coeruleus and the rostral corpus cerebelli. The topographical order of the cerebellopetal projections of the lateral nucleus of the valvula and inferior olive is also described, as are differential inputs to various subdivisions of the cerebellum in the two species. Information on valvulopetal projections in teleosts has thus far been limited to electroreceptive mormyrids. The present study shows that many valvular inputs related to electroreception in mormyrids have no homologue in Carassius and Lepomis. Finally, the present study indicates that the rostral part of the corpus cerebelli, but not the valvula cerebelli, in teleosts is the homologue of the anterior lobe of the corpus cerebelli in cartilaginous fishes. Thus, the valvula cerebelli is a shared derived feature (synapomorphy) of all ray-finned fishes.