Parietal Nerve Research Articles

Douleur pelvi-périnéales et prolapsus génital : revue de la littérature

Pelvic and perineal pain after genital prolapse surgery is a serious and frequent post-operative complication which diagnosis and therapeutic management can be complex. A literature review was carried out on the Pubmed database using the following words and MeSH: genital prolapse, pain, dyspareunia, genital prolapse and pain, genital prolapse and dyspareunia, genital prolapse and surgery, pain and surgery. Among the 133 articles found, 74 were selected. Post-operative chronic pelvic pain persisting more than 3 months after surgery according to the International Association for the Study of Pain. It can be nociceptive, neuropathic or dysfunctional. Its diagnosis is mainly clinical. Its incidence is estimated between 1% and 50% and the risk factors are young age, the presence of comorbidities, history of prolapse surgery, severe prolapse, preoperative pain, invasive surgical approach, simultaneous placement of several meshes, less operator experience, increased operative time and early post-operative pain. The vaginal approach can cause a change in compliance and vaginal length as well as injury to the pudendal, sciatic and obturator nerves and in some cases lead to myofascial pelvic pain syndrome, whereas the laparoscopic approach can lead to parietal nerve damage. Therapeutic management is multidisciplinary and complex. Pelvic pain after genital prolapse surgery is still obscure to this day.

First study on the peptidergic innervation of the brain superior sagittal sinus in humans

The superior sagittal sinus (SSS) of the mammalian brain is a pain-sensitive intracranial vessel thought to play a role in the pathogenesis of migraine headaches. Here, we aimed to investigate the presence and the potential co-localization of some neurotransmitters in the human SSS. Immunohistochemical and double-labeling immunofluorescence analyses were applied to paraformaldehyde-fixed, paraffin-embedded, coronal sections of the SSS. Protein extraction and Western blotting technique were performed on the same material to confirm the morphological data. Our results showed nerve fibers clustered mainly in large bundles tracking parallel to the longitudinal axis of the sinus, close in proximity to the vascular endothelium. Smaller fascicles of fibers encircled the vascular lumen in a spiral fashion, extending through the subendothelial connective tissue. Isolated nerve fibers were observed around the openings of bridging veins in the sinus or around small vessels extending into the perisinusal dura. The neurotransmitters calcitonin gene related peptide (CGRP), substance P (SP), neuronal nitric oxide synthase (nNOS), vasoactive intestinal polypeptide (VIP), tyrosine hydroxylase (TH), and neuropeptide Y (NPY) were found in parietal nerve structures, distributed all along the length of the SSS. Overall, CGRP- and TH-containing nerve fibers were the most abundant. Neurotransmitters co-localized in the same fibers in the following pairs: CGRP/SP, CGRP/NOS, CGRP/VIP, and TH/NPY. Western blotting analysis confirmed the presence of such neurosubstances in the SSS wall. Overall our data provide the first evidence of the presence and co-localization of critical neurotransmitters in the SSS of the human brain, thus contributing to a better understanding of the sinus functional role.

Morphological and physiological characteristics of dermal photoreceptors in <i>Lymnaea stagnalis </i>

Dermal photoreceptors located in the mantle of Lymnaea stagnalis were histologically and physiologically characterized. Our previous study demonstrated that the shadow response from dermal photoreceptors induces the whole-body withdrawal response. Through the interneuron, RPeD11, we detected that the light-off response indirectly originated from a dermal photoreceptor. Previous observations, based on behavioral pharmacology, revealed that cyclic guanosine monophosphate acts as a second messenger in the dermal photoreceptor. Furthermore, gastropods possess dermal photoreceptors containing rhodopsin, as a photopigment, and another photo-sensitive protein, arrestin, responsible for terminating the light response. Thus, we chose three antibodies, anti-cGMP, anti-rhodopsin, and anti-β-arrestin, to identify the dermal photoreceptor molecules in Lymnaea mantle. Extracellular recording, using a suction electrode on the mantle, revealed a light off-response from the right parietal nerve. Overlapping structures, positive against each of the antibodies, were also observed. Numerous round, granular particles of 3–47 μm in diameter with one nucleus were distributed around pneumostome and/or inside the mantle. The cells surrounding the pneumostome area, located 10 μm beneath the surface, tended to have smaller cell soma ranging from 3 to 25 μm in diameter, while cells located in other areas were distributed uniformly inside the mantle, with a larger diameter ranging from 12 to 47 μm. The histological examination using back-filing Lucifer Yellow staining of the right parietal nerve with the three dermal photoreceptor antibodies confirmed that these overlapping-stained structures were dermal photoreceptors in Lymnaea.

Input from a chemosensory organ, the osphradium, does not mediate aerial respiration in Lymnaea stagnalis

Breathing behaviour is driven by chemosensory information sensed by oxygen or car- bon dioxide receptors that detect the level of these substances either internally or in the external environment. In terrestrial species, oxygen chemosensation is primarily through internal sensors, whereas in aquatic animals, such as the pond snail Lymnaea stagnalis, external oxygen chemo - receptors are thought to be more important, due to the low partial pressure of oxygen in water. It has been hypothesized that an external chemosensory organ, the osphradium, modulates aerial respiratory behaviour in hypoxic conditions in Lymnaea, but recent data indicate that this may not be the case. In the present study, we removed the input from this organ to the central nervous system and measured aerial respiratory behaviour. We assessed breathing behaviour prior to surgery and then operated on the snails, severing either (1) the osphradial nerve proximal to the osphradium or (2) the right internal parietal (RIP) nerve into which the osphradial nerve, in addition to other axons from the lung/pneumostome area, projects. We also used a sham-operated control group. Severing either the osphradial or RIP nerve did not alter breathing behaviour in eumoxic or hypoxic conditions relative to the behaviour prior to surgery or that of sham-operated animals. Therefore, we conclude that input from the osphradium does not drive aerial respiratory behaviour.

Central and peripheral neuronal pathways revealed by backfilling with neurobiotin in the optic, tentacular and small labial nerves ofLymnaea stagnalis

AbstractTuchina, O.P., Zhukov, V.V. and Meyer‐Rochow, V.B. 2012. Central and peripheral neuronal pathways revealed by backfilling with neurobiotin in the optic, tentacular and small labial nerves ofLymnaea stagnalis. —Acta Zoologica(Stockholm)93: 28–47.The TOLm complex inLymnaea stagnaliscontains nervesn. tentacularis, n. opticusandn. labialis minor. Ligatures close to where the complex enters the central nervous system (CNS) did not prevent penetration of retrograde‐transported neurobiotin into fibres of an adjacent nerve. Axonal bifurcation within the common nerve trunk or tight junctions may be involved, providing a basis for peripheral axon reflexes. Peripheral terminations ofn. tentacularis,n. labialis minorandn. opticusrevealed numerous cell bodies in the tentacular epithelium, some in the tentacle and lip region, and some in the retina. These cell bodies’ central projections were mapped by neurobiotin and verified by dissections of the cerebro‐cerebral commissure and cerebro‐pleural connective. Afferent fibres of the nerves form dense sensory neuropils in the ipsilateral cerebral ganglia. Direct connections betweenn. tentacularisand some visceral as well as parietal nerves were demonstrated by backfillings throughn. pallialis dexter internus et externus,n. pallialis sinisterandn. intestinalis. Labelling ofn. tentacularisrevealed neuronal bodies in every ganglion and stained fibres in most of the peripheral nerves. Fewer neurons were identified throughn. labialis minorandn. opticus. We discuss our results in relation to different behavioural forms like defence and feeding reactions inL. stagnalis.

The shadow-induced withdrawal response, dermal photoreceptors, and their input to the higher-order interneuron RPeD11 in the pond snailLymnaea stagnalis

The shadow-induced withdrawal response in Lymnaea stagnalis is mediated by dermal photoreceptors located on the foot, mantle cavity, and skin around the pneumostome area. Here, we determined whether we could obtain a neural correlate of the withdrawal response elicited by a shadow in a higher-order central neuron that mediates withdrawal behavior. We measured the electrophysiological properties of the higher-order interneuron Right Pedal Dorsal 11 (RPeD11), which has a major role in Lymnaea withdrawal behavior. In semi-intact preparations comprising the circumesophageal ganglia, the mantle cavity and the pneumostome, but not the foot and eyes, a light-on stimulus elicited a small short-lasting hyperpolarization and a light-off stimulus elicited a depolarization of RPeD11. We also determined that dermal photoreceptors make a monosynaptic contact with RPeD11. The dermal photoreceptor afferents course to the circumesophageal ganglia via the anal and genital nerves to the visceral ganglion, and/or via the right internal and external parietal nerves to the parietal ganglion. Finally, in addition to responding to photic stimuli, RPeD11 responds to both mechanical and chemical stimuli delivered to the pneumostome.

Surgical Anatomy of the Retroperitoneal Spaces, Part IV: Retroperitoneal Nerves

We present surgicoanatomical topographic relations of nerves and plexuses in the retroperitoneal space: 1) six named parietal nerves, branches of the lumbar plexus: iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, obturator, femoral. 2) The sacral plexus is formed by the lumbosacral trunk, ventral rami of S1-S3, and part of S4; the remainder of S4 joining the coccygeal plexus. From this plexus originate the superior gluteal nerve, which passes backward through the greater sciatic foramen above the piriformis muscle; the inferior gluteal nerve also courses through the greater sciatic foramen, but below the piriformis; 3) sympathetic trunks: right and left lumbar sympathetic trunks, which comprise four interconnected ganglia, and the pelvic chains; 4) greater, lesser, and least thoracic splanchnic nerves (sympathetic), which pass the diaphragm and join celiac ganglia; 5) four lumbar splanchnic nerves (sympathetic), which arise from lumbar sympathetic ganglia; 6) pelvic splanchnic nerves (nervi erigentes), providing parasympathetic innervation to the descending colon and pelvic splanchna; and 7) autonomic (prevertebral) plexuses, formed by the vagus nerves, splanchnic nerves, and ganglia (celiac, superior mesenteric, aorticorenal). They include sympathetic, parasympathetic, and sensory (mainly pain) fibers. The autonomic plexuses comprise named parts: aortic, superior mesenteric, inferior mesenteric, superior hypogastric, and inferior hypogastric (hypogastric nerves).

In Vitro Odor-Aversion Conditioning in a Terrestrial Mollusk

We developed an in vitro odor-aversion conditioning system in the terrestrial mollusk, Limax, and found a behavioral correlate of network oscillation in the olfactory CNS. We first examined the odor-induced behavior of Limax, after odor-aversion conditioning in vivo. Shortening of mantle muscles was specifically observed in response to aversively conditioned odors. We previously identified that parietal nerves, which project to the mantle muscle in Limax, regulate shortening of the mantle muscle. We therefore isolated whole brains containing noses (sensory organs) and parietal nerves (motor output), and applied an odor-aversion conditioning paradigm to these in vitro preparations. Before the in vitro conditioning, application of attractive odors to the noses did not elicit any discharge in the parietal nerves. However, after odor-aversion conditioning, discharges in the parietal nerves were observed in response to the natively attractive but aversively conditioned odors. We also found that network oscillation frequency in the procerebrum (PC), the olfactory CNS of Limax, increased specifically in response to the aversively conditioned odors that elicited avoidance behavior. In naive (nonconditioned) preparations, increases in the PC oscillation frequency were observed specifically in response to innately aversive odors. These results indicate that the isolated brains have an ability of odor learning. They also suggest that changes in PC network oscillation are associated with aversively conditioned and innately aversive odors, both of which elicit avoidance behavior. This in vitro conditioning system would be an effective approach for exploring the neural mechanism to determine the aversion to odors.

Influence of HgCl2 on the osphradial multisensory system of Lymnaea stagnalis L.

The osphradial multisensory system of Lymnaea stagnalis L. (Pulmonata, Basommatophora) was used to demonstrate the modulation of chemosensory information both at periphery and central nervous system (CNS) following heavy metal treatments. A semi-intact preparation including osphradium, CNS and the right inner parietal nerve (r.i.p.n.) connecting them was used to record both extracellular activity of nerve and intracellular activity of central neurons receiving information from osphradium. The ion currents of osphradium were recorded using patch-clamp method. The changes in nerve and neuronal activity were expressed by averaging of firing frequency and interspike intervals. The chemosensory function of osphradium was shown by application of L-aspartate, urea, saccharose and stagnant water to its surface. The central neurons reacting to the stimulation ofosphradium were located to visceral, right parietal, pedal and cerebral ganglia of Lymnaea. Both the acute and chronic treatments with HgCl2 damaged the sensory function of osphradium traced on the flow of information from periphery to central neurons. At the same time, mercury chloride modified the synaptic connections of respiratory pattern generators as well as the Ca- and K-dependent ion currents of osphradial neurons. The results proved the multisensory role of osphradium sensing the alterations in the environment and its usefulness in monitoring the effects of pollutants at various level of regulation from chemosensory epithelium to CNS.

Distinct responses of osphradial neurons to chemical stimuli and neurotransmitters in Lymnaea stagnalis L.

1. In Lymnaea stagnalis L. (Pulmonata, Basommatophora) the neurons in the osphradium were visualized by staining through the inner right parietal nerve by 5,6-carboxyfluorescein (5,6-CF). Three types of neurons were identified: three large ganglionic cells (GC1-3; 80-100 microns), the small putative sensory neurons (SC; 20 microns) and very small sensory cells (3-5 microns). 2. The ganglionic and putative sensory neurons were investigated by whole cell patch-clamp method in current-clamp condition. The three giant ganglionic neurons (GC1-3) located closely to the root of osphradial nerve, had a membrane potential (MP) between -30 and -70 mV and showed tonic or bursting activities. The small putative sensory cells (SCs) scattered throughout the osphradial ganglion, possessed a MP between -25 and -55 mV and showed an irregular firing pattern with membrane oscillations. At resting MP the GC1-3 cells were depolarized and increased the frequency of their firing, while the SCs were hyperpolarized and inhibited by NaCl (10(-2) M) and L-aspartate (10(-5) M) applied to the osphradium. 3. 5-Hydroxytryptamine (5HT, 10(-6) M), gamma-aminobutyric acid (GABA; 10(-6) M) and the GABAB agonist baclofen (10(-6) M) depolarized the neurons GC1-3 and increased their firing frequency. In contrast, on the GC1-3 neurons, acetylcholine (Ach; 10(-6) M) and FMRFamide (10(-6) M) caused hyperpolarization and cessation of the firing activity. The 5HT effect was blocked by mianserin (10(-6) M) but picrotoxin (10(-5) M) failed to block the GABA-induced effect on the GC1-3 cells. 4. The small putative sensory neurons (SCs) were excited by Ach (10(-6) M) and 5HT (10(-6) M) but were inhibited by GABA (10(-6) M). FMRFamide (10(-6) M) had a biphasic response. The Ach effect was blocked by hexamethonium (10(-6) M) and tetraethylammonium (10(-6) M), indicating the involvement of nicotinic cholinergic receptors. 5. The distinct responses of the two populations of osphradial neurons to chemical stimuli and neurotransmitters suggest that they can differently perceive signals from environment and hemolymph.

Dissociate behaviour of frontal and parietal median nerve SEPs components following implant of thalamic stimulators in Parkinsonian patients

Dissociate behaviour of frontal and parietal median nerve SEPs components following implant of thalamic stimulators in Parkinsonian patients

Immunoreactive excitatory amino acids in the parietal eye of lizards, a comparison with the pineal organ and retina.

The fine structure of the organ and the localization of the excitatory amino acids glutamate and aspartate were studied in the parietal eye of lizards by postembedding immunoelectron microscopy. The parietal eye contains cone photoreceptor cells, secondary neurons, and ependymal and lens cells. The photoreceptors form long inner and outer segments, some of them being paired as "twin-photoreceptors" by zonulae adherentes. Perikarya of neurons bear sensory cilia (containing 9x2+0 pairs of tubules) extending into the intercellular space. No neurohormonal terminals are present in the parietal eye. A higher immunoreactivity to glutamate than to aspartate is found in the photoreceptors and in the secondary neurons of the parietal eye. Glutamate immunogold labeling is more intense in the axonal processes of photoreceptors and neurons and in most of the nerve fibers of the parietal nerve running to the brain stem. Weak aspartate and glutamate immunoreactivity can be detected in the ependymal and lens cells. A similar distribution of immunoreactive amino acids is found in the photoreceptors, secondary neurons, and ependymal glial elements of the pineal organ, and retina of the lateral eye of the same animals. Immunoreactive glutamate accumulates in the axons of photoreceptors and secondary neurons of the parietal eye suggesting that this excitatory amino acid acts as a synaptic mediator in the neural efferentation of the organ. Thus, the efferent light-conducting pathway of the parietal organ is similar to that of the pineal organ and lateral eye retina. As the Mullerian cells of the retina, the ependymal and lens cells of the parietal eye and the ependymal-glial cells of the pineal organ may play a role in the metabolism and/or elimination of excitatory amino acids released by photoreceptors.

Genomic organization of the FMRFamide gene in Lymnaea: multiple exons encoding novel neuropeptides

Based on the sequencing of genomic and cDNA clones, we were able to determine that the FMRFamide gene consists of five exons covering at least 20 kb and predict the presence of further novel peptides. The exons are alternatively spliced: exon I (hydrophobic leader sequence) to exon II (tetrapeptides) and exon I to exons III (heptapeptides), IV, and V. A cDNA clone encoding the heptapeptides is described and has also been shown to encode further novel peptides SKPYMRFamide, HDYMRFamide, and SSFPRYamide. Analysis of the right internal parietal nerve using mass spectrometry showed that the novel peptide SKPYMRFamide was cleaved from the precursor. This peptide excites neurons, suggesting a physiological function in the CNS.

Axonal mapping of the giant peptidergic neurons VD 1 and RPD 2 located in the CNS of the pond snail Lymnaea stagnalis, with particular reference to the innervation of the auricle of the heart

VD 1 and RPD 2 are two giant neuropeptidergic neurons located respectively in the visceral and right parietal ganglion of the central nervous system (CNS) of the pond snail Lymnaea stagnalis. They are the most prominent representatives of a system of neurons expressing a gene that is similar to the gene expressed in R 15 of Aplysia californica. Both neuronal systems are involved in the regulation of cardiorespiratory phenomena. In the present study the axonal branches of VD 1 and RPD 2 were mapped using immunocytochemical and tracer studies. To this end the α1-antiserum (directed to one of the VD 1/RPD 2 neuropeptides) was used in combination with Lucifer yellow (LY) and Ni-lys tracers. In whole mount preparations of the CNS, immunostained axons of VD 1 and RPD 2 were observed to run to the pleural, cerebral and pedal ganglia and in several nerves. Upon LY injection of VD 1 thin axon branches were observed in the internal right parietal nerve. These run to the skin in the mantle area near the pneumostome and osphradium. The skin of the lips appeared to receive a similar innervation via the lip nerves. Thick LY filled axons of VD 1 and RPD 2 were observed in the intestinal nerve. They could be traced to the heart region. The pericardial branch of the intestinal nerve innervates the pericardium and heart (Ni-lys tracing). Immunocytochemically, using the α1-antiserum, it was demonstrated that this nerve branch carries the axons of VD 1 and RPD 2 to the venous side of the auricle, where they enter the pericardial cavity and ramify in the auricle (but not in the ventricle). Many immunopositive varicosities were observed on the auricular muscle fibers. Comparison of the stainings in the auricle with those obtained with antisera to the cardioactive neuropeptides FMRFamide and SCP showed no colocalization. The functional significance of the axonal distribution patterns of VD 1 and RPD 2 and the morphological and functional homology of the neurons to R 15 of Aplysia are discussed.

The Whole-Body Withdrawal Response Of Lymnaea Stagnalis I. IdentificatIon Of Central Motoneurones And Muscles

Two muscle systems mediated the whole-body withdrawal response of Lymnaea stagnalis: the columellar muscle (CM) and the dorsal longitudinal muscle (DLM). The CM was innervated by the columellar nerves and contracted longitudinally to shorten the ventral head-foot complex and to pull the shell forward and down over the body. The DLM was innervated by the superior and inferior cervical nerves and the left and right parietal nerves. During whole-body withdrawal, the DLM contracted synchronously with the CM and shortened the dorsal head-foot longitudinally. The CM and the DLM were innervated by a network of motoneurones. The somata of these cells were located in seven ganglia of the central nervous system (CNS), but were especially concentrated in the bilaterally symmetrical A clusters of the cerebral ganglia. The CM was innervated by cells in the cerebral and pedal ganglia and the DLM by cells in the cerebral, pedal, pleural and left parietal ganglia. Individual motoneurones innervated large, but discrete, areas of muscle, which often overlapped with those innervated by other motoneurones. Motoneuronal action potentials evoked one-for-one non-facilitating excitatory junction potentials within muscle fibres. No all-or-nothing action potentials were recorded in the CM or DLM, and they did not appear to be innervated by inhibitory motoneurones. The whole network of motoneurones was electrotonically coupled, with most cells on one side of the CNS strongly coupled to each other but weakly coupled to cells on the contralateral side of the CNS. This electrotonic coupling between motoneurones is probably important in producing synchronous contraction of the CM and DLM when the animal retracts its head-foot complex during whole-body withdrawal.

Experimental investigation of the propagation mechanism and the nerve regulatory mechanism of the interdigestive migrating electric complex in intestinal movement.

Segments and Thirty-Vella type loops of the small intestine of dogs were prepared, and the excitation propagation pattern of the interdigestive migrating electric complex (IMEC) was observed by electromyography. The nerve regulatory mechanism in intestinal movement was investigated. The results indicated that first, the frequency of the basic electric rhythm (BER) is controlled so that a downward gradient is formed from the upper to the lower intestine, but this gradient continues to be controlled by a two-dimensional control mechanism involving parietal factors and extrinsic nerves due to transection of the intestines and damage to the extrinsic nerves in the dominant region. However, propagation of the IMEC in the small intestine appeared to be regulated by a combination of the two-dimensional control mechanism involving extrinsic and parietal nerves corresponding to the BER control mechanism. It was clear that the propagation mechanism of IMEC is related to the BER frequency, and propagation of the IMEC is downward in accordance with the frequency gradient of BER.

Substance P-like immunoreactivity in the parietal eye visual system of the lizard Uta stansburiana.

We examined the parietal eye visual system of the iguanid lizard Uta stansburiana for the presence of substance P-like immunoreactivity by use of both immunofluorescence and peroxidase-antiperoxidase techniques. In the parietal eye no substance P-containing somata were found; however, its plexiform layer contained small (ca. 1 micron diam) immunoreactive fibers. These fibers apparently originate outside the parietal eye. Immunoreactive fibers also were found in the parietal nerve, the dorsal sac, and the leptomeninx of the pineal gland. No labeled somata were observed in any of these regions in either normal or colchicine treated animals. Previously we demonstrated that a system of centrifugal fibers to the parietal eye originates from neurons in the dorsal sac (Engbretson et al. 1981). The apparent absence of substance P-containing neurons in the dorsal sac suggests that the substance P-containing fibers in the parietal eye are not the previously observed centrifugal fibers. The source of the substance P-containing fibers in the parietal eye is unknown. The pars dorsolateralis of the left medial habenular nucleus receives a dense substance P-positive projection. No such projection was seen in the right habenula. Simultaneous visualization of the terminals of ganglion cells of the parietal eye (labeled with orthograde intraaxonally transported horseradish peroxidase) and substance P-like immunofluorescence showed that the locus of habenular immunoreactivity is distinct from the projection field of the parietal eye. Thus the substance P-positive terminals in the habenula do not originate in the parietal eye. Transection of the parietal nerve confirmed this conclusion.

Nervous connections of the parietal eye in adult Lacerta s. sicula Rafinesque as demonstrated by anterograde and retrograde transport of horseradish peroxidase.

Subsequent to the injection of horseradish peroxidase into the parietal eye of adult Lacerta sicula, the course of the parietal nerve and its projections were determined. The parietal nerve enters the left habenular ganglion where it branches into a medial and a lateral route. Some nerve fibers decussate within the habenular commissure. Whereas this pathway exhibits a striking asymmetry at the level of the habenular ganglia, its projections to the dorsolateral nucleus of the thalamus, the periventricular hypothalamic area, the preoptic hypothalamic and telencephalic regions, and the pretectal area are arranged in a strictly symmetric manner. A possible innervation of tegmental areas could not be proven due to the presence of endogenous peroxidase within these regions. No parietal nerve fibers were observed in the optic tectum. In a few animals investigated, scattering labeled perikarya were located in the periventricular hypothalamic gray indicating a parietopetal innervation in Lacerta sicula. The injection of horseradish peroxidase into one of the lateral eye revealed terminal areas of the optic nerve within the preoptic region, and the thalamic and pretectal nuclei, displaying partial overlapping with the projection of the parietal nerve to these areas. From the present investigation further evidence is obtained that the pineal complex of lower vertebrates is a component of the photoneuroendocrine system. Particular emphasis is placed upon the nervous connections between the parietal eye and the hypothalamus, described for the first time in the present study.

The morphology of neurosecretory neurones in the pond snail, Lymnaea stagnalis, by the injection of Procion Yellow and horseradish peroxidase.

The morphology of neurosecretory neurones, the Dark Green Cells, Yellow Cells, Yellow-green Cells, Light Green Cells, Caudodorsal Cells and Canopy Cells, in the central nervous system of the snail,Lymnaea stagnalis, was investigated by the intracellular injection of Procion Yellow and, for the Yellow Cells only, of horseradish peroxidase. The cerebral ganglia neurosecretory cells (Light Green Cells, Caudodorsal Cells and Canopy Cells) had discrete neurohaemal organs and their axons projected exclusively to nerves and connectives close to the central nervous system. The Light Green Cells had single, undividing axons, which projected exclusively to the ipsilateral median lip nerve. Hormone release is thought to take place principally from the lateral edges of axons, at various points along their lengths, within the median lip nerve. The Caudodorsal Cells projected to the cerebral commissure, where their axons often branched before terminating at the edge of the neuropil. The degree of axonal branching and the location of the Caudodorsal Cell terminals varied widely in different cells. Axon terminals penetrated the perineurium and travelled for several hundred micrometres within the connective tissue sheath of the cerebral commissure. Again, release of neurosecretory material at various points along their lengths seems likely. The Canopy Cells (a pair of individually identifiable giant cells) had a single axon, which projected to the contralateral cerebral ganglion via the cerebral commissure. Axons of left and right Canopy Cells were closely apposed in the cerebral commissure and this is the likely site of the electrotonic junction known to connect them. Neurohaemal organs for the Caudodorsal Cells are the ipsilateral lateral lobe, cerebral commissure and contralateral median lip nerve. Neurosecretory neurones whose cell bodies were located in the pleural, parietal and visceral ganglia (Yellow Cells, Yellow-green Cells and Dark Green Cells) had extensive non-localized neurohaemal areas in the connective tissue sheath surrounding the central ganglia as well as peripheral nerve projections. The Yellow Cells had one or two axons, which, in neurones located in the visceral and right parietal ganglia, projected extraganglionically to the central sheath or to the intestinal and internal right parietal nerves. These nerve projections are appropriate for the innervation of the kidney, the peripheral target organ of the Yellow Cells. Yellow Cells, located in the pleural ganglia, only had axonal projections to the central sheath. Yellow Cells and Yellow-green Cells had well developed dendritic branching terminating in the central neuropil. Yellow-green Cells project mainly to the anal and external right parietal nerves. Pleural ganglia Dark Green Cells had a few terminals located beneath the perineurium of the pleural ganglia but most of their axonal projections were to peripheral nerves. All Dark Green Cells projected to the ipsilateral pedal ganglion and then to pedal nerves. In addition, some pleural Dark Green Cells had further projections to the internal and external right parietal nerves and median lip nerve of the cerebral ganglion. The widespread distribution of Dark Green Cell axons was consistent with their supposed role in regulating ion and water transport across the skin of the foot and mantle. The electrotonic junctions known to connect Dark Green Cells whose cell bodies are close together on the pleural ganglion surface are located in the pleural ganglion, pleuro-pedal connective and pedal ganglion.

Independent effects of the pineal and a bacterial pyrogen in behavioural thermoregulation in lizards.

The pineal complex of lizards is comprised of an extracranial photoreceptive structure known as the parietal eye, and an intracranial pineal organ which is homologous to the pineal gland of birds and mammals. Studies have shown that removing the parietal eye or severing the parietal nerve causes lizards to select higher temperatures when allowed to thermoregulate behaviourally in thermal or photothermal laboratory gradients. Although comparable studies involving removal of the lizard pineal organ have not previously been attempted, field data indicate that pinealectomy may have an antagonistic effect to parietalectomy. We present evidence here which shows that (1) following pinealectomy, collared lizards (Crotaphytus collaris) behaviourally select or prefer lower temperatures than their controls in thermal laboratory gradients, and (2) the effect of surgical treatment is independent of the effects of a behavioural fever-inducing substance which elevates by a fixed amount the environmental temperatures selected.