Identification of penile inputs to the rat gracile nucleus

Neurons in the medullary reticular formation (MRF) of the rat receive a vast array of urogenital inputs. Using select acute and chronic spinal cord lesions to identify the location of the ascending neural circuitries providing either direct or indirect inputs to MRF from the penis, our previous studies demonstrated that the dorsal columns and dorsal half of the lateral funiculus convey low- and high-threshold inputs, respectively. In the present study, the gracile nucleus was targeted as one of the likely sources of low-threshold information from the penis to MRF. Both electrophysiological recordings and neuroanatomical tracing [injection of cholera toxin B subunit (CTB) into a dorsal nerve of the penis] were used. After discrimination of a single neuron responding to penile stimulation, testing for somatovisceral convergence was done (mechanical stimulation of the distal colon and the skin over the entire hindquarters). In 12 rats, a limited number of neurons (43 in total) responded to penile stimulation. Many of these neurons also responded to scrotal stimulation (53.5%, dorsal and/or ventral scrotum) and/or prepuce stimulation (46.5%). Histological reconstruction of the electrode tracks showed that the majority of neurons responding to penile stimulation were located ventrally within the medial one-third of the gracile nucleus surrounding obex. This location corresponded to sparse innervation by CTB-immunoreactive primary afferent terminals. These results indicate that neurons in the gracile nucleus are likely part of the pathway that provides low-threshold penile inputs to MRF, a region known to play an important role in mating processes.     

Efferent connections of the striatum in Tupinambis nigropunctatus

The striatum of the lizard Tupinambis nigropunctatus lies in the lateral wall of the telencephalon and consists of two major subdivisions: the dorsal striatum and the ventral striatum. Electrolytic lesions were placed in all parts of the striatal complex and in adjacent areas and the subsequent anterograde degeneration was studied using the Nauta-Gygax and Fink-Heimer techniques. Lesions in the dorsal striatum cause terminal degeneration in the ventral striatum both ipsi- and contralaterally. In addition, projections have been found to the lateral amygdaloid nucleus and to parts of the dorsal striatum not affected by the lesion. Following lesions in the ventral striatum fiber degeneration could always be observed in the ventral peduncle of the lateral forebrain bundle. Corresponding terminal degeneration was found in the anterior and posterior entopeduncular nuclei, the tegmentum mesencephali, the substantia nigra, the prerubral area, the mesencephalic central grey and the lateral cerebellar nucleus. When the large celled part of the ventral striatum was involved in the lesion additional degeneration could be traced to the nucleus rotundus via the dorsal peduncle of the lateral forebrain bundle.     

Rat dorsal prostate is necessary for vaginal adhesion of the seminal plug and sperm motility in the uterine horns

The rat prostate comprises dorsal, ventral and lateral lobes that are morphologically and biochemically distinct. Lesions to these structures are expected to affect the quality of the ejaculate and male fertility. In experiment 1, we analyzed ejaculate parameters of males that had chemical lesions of the dorsal or ventral lobes. At pre-lesion and at 5 and 20 days post-lesion males were mated, and after ejaculation, seminal fluid and seminal plug were obtained from the mated females. In experiment 2, the ventral lobes were ablated, and the ejaculate was analyzed. In experiment 3, the fertility of males with chemically-lesioned dorsal lobes or ablation of the ventral lobes was evaluated. Chemical lesion of the dorsal lobe prevented the adhesion of the seminal plug to vaginal walls. When these males were tested at 5-days postlesion, no sperm were found in uterus, and at 20-days post-lesion, the few sperm encountered showed slow progressive motility. None of the females that mated with dorsal lobe-lesioned males became pregnant. However, chemical lesion or ablation of the ventral lobes did not affect ejaculate or fertility. Our results indicate that the dorsal prostatic lobes are indispensable for reproductive success in males, and define parameters of ejaculate with which fertility can be estimated.     

Somite subdomains, muscle cell origins, and the four muscle regulatory factor proteins

We show by immunohistology that distinct expression patterns of the four muscle regulatory factor (MRF) proteins identify subdomains of mouse somites. Myf-5 and MyoD are, at specific stages, each expressed in both myotome and dermatome cells. Myf-5 expression is initially restricted to dorsal cells in all somites, as is MyoD expression in neck somites. In trunk somites, however, MyoD is initially expressed in ventral cells. Myogenin and MRF4 are restricted to myotome cells, though the MRF4-expressing cells are initially less widely distributed than the myogenin-expressing cells, which are at all stages found throughout the myotome. All somitic myocytes express one or more MRFs. The transiently distinct expression patterns of the four MRF proteins identify dorsal and ventral subdomains of somites, and suggest that skeletal muscle cells in somites originate at multiple sites and via multiple molecular pathways.     

Some regional anatomical relationships of TRH to 5-HT in rat limbic forebrain

It is now a recognized principle that various neuropeptides are neuronally co-localized with biogenic amine or aminoacid neurotransmitters. In the rat CNS it has previously been shown that TRH is co-localized with 5-HT (and also with substance P) in cell bodies of the posterior raphe that project to the spinal cord. Although TRH cell bodies are known to be widely distributed throughout the forebrain there is no other known co-localization with 5-HT. In this study we further specify the anatomical relationship of TRH with 5-HT by use of surgical and neurotoxic lesioning with reference to limbic forebrain regions wherein TRH is greatly increased following seizures. In groups of rats, the fimbria-fornix was lesioned alone, or combined with a lesion of the dorsal perforant path or the ventral perforant path. There was a sham lesioned control group. Additional groups were lesioned with 5, 7 dihydroxytryptamine, 100 g i.v.t., 45 min. after i.p. desipramine, 25 mg/kg. All rats were sacrificed three weeks after lesions. Indoleamines were determined by HPLC in left anterior cortex, left pyriform/olfactory cortex, left dorsal hippocampus and left ventral hippocampus. TRH was determined by specific RIA in the corresponding right brain regions. The modal n was 7 rats. The surgical lesions reduced 5-HT to below the detection limit in dorsal hippocampus in all three groups, and to 31–52% of control in all the ventral hippocampus groups. 5-HIAA was reduced to 19–37% of control in dorsal and to 30–51% of control in ventral hippocampus. TRH was reduced to 44–61% of control in dorsal hippocampus and to 48–53% of control in ventral hippocampus. As was repeatedly observed in our previous reports all TRH levels in ventral hippocampus were higher than in dorsal hippocampus. The 5, 7 dihydroxytryptamine treatment nearly eliminated the indoleamines from all the forebrain regions examined while TRH levels were unchanged. These results can be explained by our previous data showing that immunoreactive TRH is intrinsic and localized to the vicinity of both CA and dentate granule cells of the hippocampus, but about half of hippocampal TRH enters via fibers of the fimbria-fornix. The perforant path appears to contribute no TRH to hippocampus, but, results with the combined lesion groups showed some reduction of 5-HIAA in ventral hippocampus as is expected from the known perforant path contribution of 5-HT. Since the neurotoxic lesion had no effect on TRH, the 5-HT pathway through the fimbria-fornix is probably anatomically separate from a parallel TRH pathway there. This study shows that co-localization of TRH with 5-HT is very unlikely in four specific limbic forebrain regions.Special issue dedicated to Dr. Morris H. Aprison.     

Histopathology of idiopathic lesions in the eyes of Homarus americanus from Long Island Sound

In 1999, American lobsters, Homarus americanus, from western Long Island Sound (WLIS) experienced a significant mortality. In 2001 and 2004, the eyes and eyestalks of lobsters from WLIS and central LIS were examined for histopathological changes. Idiopathic lesions were identified in the ommatidia and optic nerve fibers proximal to the ommatidia in 29 (56%) of the lobsters from LIS. Lesions were categorized as either moderate or severe. Moderate lesions had altered rhabdoms, clumped pigment, and altered optic nerve fibers. Severe lesions were marked by absent rhabdoms, clumped pigment in both the ommatidial region and in the optic nerve region; and optic nerve fibers that had been completely destroyed and were replaced by vascular tissue. Idiopathic lesions occurred primarily in the central and ventral regions of the eye, and with much less frequency in the dorsal region. In addition, damage to the dorsal area tended to occur only when the severity of lesions was high, indicating a spatially progressive pattern to the lesion development. The lesions occurred in both western and central Long Island Sound, with no significant differences in severity between locations. The prevalence of lesions did not vary between years, but in 2004, several eyes had less severe pathology than those from 2001. These data indicate that the etiological agent is present throughout a large portion of the Sound, and that lobsters are probably continually exposed to it.     

Control of visuotemporal attention by inferior parietal and superior temporal cortex

The human cortical visual system is organized into major pathways: a dorsal stream projecting to the superior parietal lobe (SPL), considered to be critical for visuospatial perception or on-line control of visually guided movements, and a ventral stream leading to the inferotemporal cortex, mediating object perception. Between these structures lies a large region, consisting of the inferior parietal lobe (IPL) and superior temporal gyrus (STG), the function of which is controversial. Lesions here can lead to spatial neglect, a condition associated with abnormal visuospatial perception as well as impaired visually guided movements, suggesting that the IPL+STG may have largely a "dorsal" role. Here, we use a nonspatial task to examine the deployment of visuotemporal attention in focal lesion patients, with or without spatial neglect. We show that, regardless of the presence of neglect, damage to the IPL+STG leads to a more prolonged deployment of visuotemporal attention compared to lesions of the SPL. Our findings suggest that the human IPL+STG makes an important contribution to nonspatial perception, and this is consistent with a role that is neither strictly "dorsal" nor "ventral". We propose instead that the IPL+STG has a top-down control role, contributing to the functions of both dorsal and ventral visual systems.     

Regeneration of dorsal column fibers into and beyond the lesion site following adult spinal cord injury.

Regeneration is abortive following adult mammalian CNS injury. We have investigated whether increasing the intrinsic growth state of primary sensory neurons by a conditioning peripheral nerve lesion increases regrowth of their central axons. After dorsal column lesions, all fibers stop at the injury site. Animals with a peripheral axotomy concomitant with the central lesion show axonal growth into the lesion but not into the spinal cord above the lesion. A preconditioning lesion 1 or 2 weeks prior to the dorsal column injury results in growth into the spinal cord above the lesion. In vitro, the growth capacity of DRG neurite is also increased following preconditioning lesions. The intrinsic growth state of injured neurons is, therefore, a key determinant for central regeneration.     

Ascending and descending efferent pathways of the midbrain reticular formation of the cat (radioautographic study)

By means of the anterograde axoplasmic transport technique for a mixture of labelled aminoacids (3H-leucine and 3H-proline), ascending and descending systems of the reticular formation fibers in the cat mesencephalon have been studied. Projections from the mesencephalon reticular formation (MRF) ascend to the subthalamus, lateral, dorsal and periventricular hypothalamus, to the periventricular nuclei of the midline and to the intralaminar nuclei of the thalamus. The descending pathways project to the grey substance surrounding the aqueduct of cerebrum, locus coeruleus, parabrachial region and reticular formation of the pons and medulla oblongata. The projections to the reticular nucleus of the thalamus, ventral nucleus of the external geniculate body and superior colliculi arise from the dorsal half of the MRF, and projections to the striatum, lateral reticular nucleus of the medulla oblongata--from its ventral half. Most of the structures are reciprocally connected with the MRF.     

Histopathologic features of the vagus nerve after electrical stimulation in swine

This paper describes the histological features of the vagus nerve after its stimulation with an electrostimulation system that is being developed for morbid obesity treatment. An electrostimulation system was implanted laparoscopically around the ventral vagal trunk of five Large White female pigs (49.63+/-1.94 kg.). Vagal nerve stimulation was performed by continuous constant voltage current pulses. Thoracic samples of both ventral and dorsal vagal trunks were obtained thoracoscopically one month after implantation. Animals were sacrificed one month after thoracoscopic vaguectomy. Tissue samples were then harvested from the vagal nerve at the implantation site, 1cm cranial to it, thoracic portion of ventral and dorsal vagal trunks, sub-diaphragmatic dorsal vagal trunk, left and right vagus nerves. Specimens were analysed with light microscope. The severity of the lesions was graded from 0 to 4 (0: no lesion, 1: mild, 2: moderate, 3: severe and 4: extremely severe), taking into account fibrosis, vascularization, necrosis, fiber degeneration and inflammation. Electrode implantation resulted in thickened epineurium and endoneural connective tissue. The greatest lesion score was evidenced at the leads implantation site in the ventral vagal trunk, followed by, in order of decreasing lesion severity, left vagus nerve, thoracic portion of ventral vagal trunk, subdiaphragmatic dorsal vagal trunk, thoracic portion of dorsal vagal trunk and right vagus nerve. The stimulation device used in this study caused connective tissue growth, greatest in the samples located closer to the implantation site. However, there was no sign of altered vascularization in any studied specimen.     

Histology and lectin-binding patterns in the skin of the terrestrial horned frog Ceratophrys ornata

The terrestrial horned frog, Ceratophrys ornata, lives on a wet substratum and absorbs water through the ventral epidermis; water is lost by evaporation from the dorsal skin. Thus, this species may be useful as a model for determining whether or not skin histology and lectin-binding patterns, indicative of glycoconjugates, are related to skin functions such as osmoregulation and water balance. With this in mind, a histological and lectin-histochemical study was carried out on dorsal and ventral skin of aquatic tadpoles and of a young terrestrial frog of C. ornata. Sections of skin were stained with various dyes to demonstrate general histological features and with two horseradish peroxidase (HRP)-conjugated lectins, Ulex europaeus agglutinin (UEA 1) and soybean agglutinin (SBA) which bind to specific terminal sugar residues of glycoconjugates, namely L-fucose and N-acetyl-D-galactosamine or D-galactose, respectively. In early stage tadpoles both lectin-binding patterns were similar in the bilaminar epidermis of dorsal and ventral skin (i.e., each lectin stained the apical cell layer). However, metamorphic changes resulted in a young frog with typical adult-type skin composed of a stratified squamous epidermis and three distinct types of glands containing glycoconjugates in their secretions. Strikingly different lectin-binding patterns were evident in the epidermis from dorsal and ventral regions of the body. The epidermis from the dorsal region was stained by both lectins; in contrast, that from the ventral region although stained strongly by HRP-SBA, did not react with HRP-UEA 1 indicating that few, if any, fucose residues were present in the ventral epidermis. These findings, as suggested in the discussion, indicate that different glycoconjugate patterns in dorsal and ventral skin may be associated with the regulation of water balance in the frog.     

A GABAergic mechanism is necessary for coupling dissociable ventral and dorsal regional oscillators within the circadian clock

BACKGROUND: Circadian rhythms in mammalian behavior, physiology, and biochemistry are controlled by the central clock of the suprachiasmatic nucleus (SCN). The clock is synchronized to environmental light-dark cycles via the retino-hypothalamic tract, which terminates predominantly in the ventral SCN of the rat. In order to understand synchronization of the clock to the external light-dark cycle, we performed ex vivo recordings of spontaneous impulse activity in SCN slices of the rat. RESULTS: We observed bimodal patterns of spontaneous impulse activity in the dorsal and ventral SCN after a 6 hr delay of the light schedule. Bisection of the SCN slice revealed a separate fast-resetting oscillator in the ventral SCN and a distinct slow-resetting oscillator in the dorsal SCN. Continuous application of the GABA(A) antagonist bicuculline yielded similar results as cut slices. Short application of bicuculline at different phases of the circadian cycle increased the electrical discharge rate in the ventral SCN but, unexpectedly, decreased activity in the dorsal SCN. CONCLUSIONS: GABA transmits phase information between the ventral and dorsal SCN oscillators. GABA can act excitatory in the dorsal SCN and inhibits neurons in the ventral SCN. We hypothesize that this difference results in asymmetrical interregional coupling within the SCN, with a stronger phase-shifting effect of the ventral on the dorsal SCN than vice versa. A model is proposed that focuses on this asymmetry and on the role of GABA in phase regulation.     

Unveiling functions of the visual cortex using task-specific deep neural networks

The human visual cortex enables visual perception through a cascade of hierarchical computations in cortical regions with distinct functionalities. Here, we introduce an AI-driven approach to discover the functional mapping of the visual cortex. We related human brain responses to scene images measured with functional MRI (fMRI) systematically to a diverse set of deep neural networks (DNNs) optimized to perform different scene perception tasks. We found a structured mapping between DNN tasks and brain regions along the ventral and dorsal visual streams. Low-level visual tasks mapped onto early brain regions, 3-dimensional scene perception tasks mapped onto the dorsal stream, and semantic tasks mapped onto the ventral stream. This mapping was of high fidelity, with more than 60% of the explainable variance in nine key regions being explained. Together, our results provide a novel functional mapping of the human visual cortex and demonstrate the power of the computational approach.     

Absence of Intraspinal Sprouting in Dorsal Root Axons Caudal to a Partial Spinal Hemisection: A Horseradish Peroxidase Transport Study

Primary afferent sprouting in the spinal cord was evaluated by comparing the central projection of horseradish peroxidase (HRP)-labeled sciatic nerve afferent axons in nonlesioned control rats, and in rats subjected to acute or chronic partial spinal hemisections as adults. The lesions were performed at various levels from T₁₀ to L₃, and removed supraspinal and varying amounts of descending propriospinal afferents to lumbar segments receiving the maximal sciatic projection. The hemisections typically involved all but the dorsal column, although in some cases a portion of the dorsal column, including the corticospinal tract, was also transected.

The distribution pattern and density of spinal HRP reaction product was not significantly different in experimental and control preparations in any segment below the lesion, regardless of the quantity of denervation, or the density of the normal sciatic projection in a given terminal region. These results, together with our previous finding concerning an absence of primary afferent sprouting following long-term dorsal root ganglionectomies, suggest that current concepts concerning collateral sprouting as a factor in functional plasticity in the mature mammalian spinal cord warrant re-evaluation.     

强啡肽对纹状体内D_1多巴胺受体反应的调节

用6-羟多巴胺破坏黑质纹状体通路,使大鼠多巴胺耗竭后,应用原位杂交组织化学方法测量D1多巴胺受体对即早基因c－fos和zif268诱导反应,分析强啡肽对突触前、后调节作用。先用D1多巴胺受体激动剂SKF－38393反复处理动物,促进纹状体内强啡肽表达,在伏隔核强啡肽表达增加,同时伴随着即早基因c-fos和zif268的减少．在纹状体的背部和两侧,强啡肽表达虽大量增加,而D1多巴胺受体反应仍然维持原水平．在中央纹状体区,即早基因的表达处于中间水平。结果提示,纹状体内强啡肽起着调节多巴胺输入到纹状体黑质神经元的作用,包括突触前、后位置;并且调节作用在纹状体的腹、背侧区是不同的     

Functional structure of the intermediate and ventral hippocampo–prefrontal pathway in the prefrontal convergent system

The hippocampo–prefrontal pathway is a unique projection that connects distant ends of the cerebral cortex. The direct hippocampo–prefrontal projection arises from the ventral to intermediate third of the hippocampus, but not from the dorsal third. It forms a funnel-shaped structure that collects information from the large hippocampal area and projects it to the prefrontal cortex. The anatomical regional differentiation of the projection has not been described. The hippocampal region is differentiated into structural and behavioural roles. For example, it has been shown that the ventral, but not the dorsal, hippocampus reciprocally connects with the amygdala and influences emotional behaviours. These data imply that hippocampal variation along the dorso–ventral axis is contained within the hippocampo–prefrontal pathway. Here, we present electrophysiological studies that demonstrate regional differences in short- but not long-term plasticity in the intermediate/posterior-dorsal and ventral routes of the hippocampo–prefrontal pathway. Furthermore, behavioural studies revealed that each route appears to play a different role in working memory. These results suggest that hippocampal regional information is processed through different routes, with the integration of individual regulatory functions in the prefrontal convergent system.     

Functional role of the dorsal and ventral hippocampus in defensive behavior in the rat

Bilateral electrolytic lesions of the dorsal hippocampus of white rats were shown to facilitate elaboration of a conditioned response of active avoidance of pain shock in a shuttle-box. The lesions of the ventral hippocampus had no effect on conditioning. The ventral hippocampal lesions led to a complete failure to form differential inhibition. In rats with the dorsal hippocampal lesions an acquisition of partial (up to 60 per cent) discrimination of stimuli was possible. The differences in avoidance conditioning and elaboration of differential inhibition in rats with the dorsal and ventral hippocampal lesions are supposed to be caused by the changes of general excitability and emotional state of animals as well as by a specific role of the ventral hippocampus in memory consolidation.     

Different role of various regions of the caudate nucleus in phenamine-induced stereotyped behavior in cats

Electrolytic ablation of the ventral parts of the cat caudate nucleus head results in an increase of frequency and disorganization of the pattern of the stereotype head turnings, induced by large doses of amphetamine. Lesion of the dorsal parts, on the other hand, is attended with a decreased number and limited manifestation of stereotype movements. A similar effect appears following a low frequency electrical stimulation of the nucleus ventral part. The disrupting action of neuroleptic haloperidol on the amphetamine-induced stereotype is weakened in animals with ventral lesions and enhanced in those with dorsal lesions. Due to dopaminergic activity, the amphetamine, apparently, produces a functional unbalance between different zones of the caudate nucleus, which underlies stereotype behaviour.