Rapid Evolution of a Squamous Cell Carcinoma In Situ to Locally Invasive With Perineural Involvement

We present a case of rapidly progressing squamous cell carcinoma in situ (SCCis) with progression to aggressive SCC. An elderly gentleman with multiple medical comorbidities presented with a left zygomatic tumor initially diagnosed as SCCis with adnexal extension on histology. After a period of approximately 10 weeks, the patient underwent Mohs micrographic surgery (MMS) with evidence that the tumor was now consistent with a well-differentiated SCC, with perineural involvement. MMS was stopped after two stages and the patient was sent to head and neck surgical oncology for further evaluation and management. It has been reported in the literature that 3–5% of SCCis will progress to invasive SCC; although the inciting event to cause such progression is unknown, it is thought that mutations in key oncogenes or tumor suppressor genes such as TP53 may play a role. In addition, as many as 31% of SCCis may have a component of invasive SCC that is missed on initial histology due to sampling bias. This case reminds us that sampling bias can occur during biopsy, SCCis can rarely progress to invasive SCC, and highly aggressive SCCs may prove to be therapeutically challenging requiring a multidisciplinary approach. J Drugs Dermatol. 2020;19(11):1110-1111. doi:10.36849/JDD.2020.5184.

[Juxtaoral organ of Chievitz]

This review presents the analysis of the systematized data on human juxtaoral organ (JOO) development, structure and function based on the results of classical and recent morphological studies. JOO morphogenesis is traced, including the appearance of its anlage at the bottom of the primitive mouth, epithelial invagination into the mesenchyme, JOO detachment from the oral epithelium, its innervation, connective tissue capsule formation, and final maturation. The analysis of the results of macroscopical, histological, electron microscopical, histochemical and immunohistochemical studies is presented, suggesting high metabolic and synthetic activity of its epithelium, which expresses several neural markers, and emphasizing a rich innervation of both its epithelial and stromal components. The findings supporting the concepts of JOO secretory and mechanosensory functions, are examined. The data on the differential diagnosis between JOO and tumoral processes are discussed, as well as the pathological changes of JOO itself and their significance for the diagnosis of the diseases.

Humoral serotonin and dopamine modulate the feeding in the snail, Helix pomatia

We investigated the effect of elevated levels of humoral 5HT and DA on the feeding latency of Helix pomatia, 1 day, 3 days and 10 days following satiation, by injecting monoamines into the haemocoel. HPLC assay of monoamines showed that both 5HT and DA are present in pmol/ml concentrations in the haemolymph of both starved and non-starved animals. Elevated levels of 5HT and DA were most effective at decreasing the feeding latency 10 days following satiation when DA decreased the feeding latency in a concentration dependent manner between 10(-7) and 10(-5) M whereas 5HT levels decreased the feeding latency only at 10(-6) M but increased it at 10(-5) M. Immunocytochemistry revealed that both 5HT3 and D1 receptor-like immuno-reactivity are present in cell bodies located in the same areas of the buccal ganglia. Our observations suggest that both humoral DA and 5HT mutually modulate the activity of the feeding CPG through neurons which have these receptors.

Functional neuroanatomy of the 5-HTergic system in the developing and adult buccal complex of the pond snail, Lymnaea stagnalis

Organization of the innervation of the buccal region by 5-HT-immunoreactive (IR) elements was investigated in the pond snail, Lymnaea stagnalis, with special attention to developmental aspects. A gradual maturation is characteristic for the 5-HT-IR muscle innervation, appearing first by late (E80-90%) embryogenesis. It runs parallel with the muscle development and the maturation of the 5-HTergic innervation in the buccal ganglia, peaking by the mid-postembryogenesis (P3) with the presence of a 5-HT-IR network in the buccal mass and rich innervation in the buccal ganglia, including axo-somatic contacts. The whole process seems to match with the appearance of the adult-like feeding (radula protrusion).

Cutaneous Distribution of Zygomaticofacial Nerve

The aim of this study is to elucidate the cutaneous distribution of the zygomaticofacial nerve (ZFN). Twenty hemifaces of 10 adult Korean cadavers were dissected. ZFN-innervated limits were rectangular and each side was 18.8 +/- 4 mm and 15.8 +/- 3.4 mm. The center of the rectangle was located laterally at 17.3 +/- 5.5 mm from the lateral canthus and then inferiorly at 18.1 +/- 3.1 mm. The cutaneous area innervated by the ZFN was rectangular shaped having a horizontal side that was 9.3 +/- 4% to 27.3 +/- 7.5%of the line from the lateral canthus to the root of helix and a vertical side that was 13.9 +/- 5.8% to 35.7 +/- 5.4% of the line from the lateral canthus to the oral commissure level. Knowledge of ZFN innervation is available with an intraoral approach in maloplasty or midface lift.

[Reestablishment of sensory function after greater auricular nerve implanted into flap for reconstruction of buccal defect in rabbits]

OBJECTIVE

To assess the sensory restoration after the greater auricular nerve is implanted into the flap to repair the buccal defect in rabbits.

METHODS

Fifteen Japanese white rabbits, weighing 2.0-2.5 kg, were randomly divided into the experimental group (nerve implanted), the control group (nerve unimplanted), and the normal group (without any treatment). In the experimental and the control group, circular defects (2.0 cm x 2.0 cm) were constructed in the left cheek of the rabbits. Then, the cervical flaps (4.5 cm x 2.5 cm) were transferred and the great auricular nerve was implanted into the defects in the experimental group, and the flaps without any nerve were implanted into the defects in the control group. The subjects in the normal group were given no treatment. After 6 months, the nerve discharge, the HE staining, and the immunohistochemical method were used to assess the regeneration of the nerve fibers.

RESULTS

The nerve discharge and the percentage of the different kinds of the nerve fibers in the experimental group (124.2 +/- 33.8 roots) were not statistically different from those in the normal group (138.4+/-20.4 roots, P>0.05), but significantly different from those in the control group (18.8+/-5.6 roots, P<0.05). In the center of the flap in the experimental group, the receptive field of the nerve fibers was identical to the implanting approach of the greater auricular nerve. The HE staining and the immunohistochemical staining showed that the density of the regenerated fibers in the center of the flap in the experimental group reached the normal level. There was no regenerated fibers in the control group.

CONCLUSION

The great auricular nerve implanted into the cervical flaps has a good effect on reconstruction of the buccal defect in rabbits.

Endogenous motor neuron properties contribute to a program-specific phase of activity in the multifunctional feeding central pattern generator of Aplysia

Multifunctional central pattern generators (CPGs) are circuits of neurons that can generate manifold actions from a single effector system. This study examined a bilateral pair of pharyngeal motor neurons, designated B67, that participate in the multifunctional feeding network of Aplysia californica. Fictive buccal motor programs (BMPs) were elicited with four distinct stimulus paradigms to assess the activity of B67 during ingestive versus egestive patterns. In both classes of programs, B67 fired during the phase of radula protraction and received a potent inhibitory postsynaptic potential (IPSP) during fictive radula retraction. When programs were ingestive, the retraction phase IPSP exhibited a depolarizing sag and was followed by a postinhibitory rebound (PIR) that could generate a postretraction phase of impulse activity. When programs were egestive, the depolarizing sag potential and PIR were both diminished or were not present. Examination of the membrane properties of B67 disclosed a cesium-sensitive depolarizing sag, a corresponding I(h)-like current, and PIR in its responses to hyperpolarizing pulses. Direct IPSPs originating from the influential CPG retraction phase interneuron B64 were also found to activate the sag potential and PIR of B67. Dopamine, a modulator that can promote ingestive behavior in this system, enhanced the sag potential, I(h)-like current, and PIR of B67. Finally, a pharyngeal muscle contraction followed the radula retraction phase of ingestive, but not egestive motor patterns. It is proposed that regulation of the intrinsic properties of this motor neuron can contribute to generating a program-specific phase of motor activity.

Evaluation of mandibular block using a standardized method

The purpose of this prospective randomized study was to investigate the manifestations and efficiency of mandibular block (MB) using a standardized method. In this study, 123 patients requiring MB were randomly assigned to receive MB using a repeated measures design. Mandibular block was administered in each patient by using 2.1 mL of 2% lidocaine with 1:100 000 epinephrine for the inferior alveolar nerve, lingual nerve, and/or buccal nerve. Clinical parameters including the electric pulp test and test for soft tissue sensation using a sharp dental explorer were assessed on both the operated side and contralateral side before and 5, 10, and 15 minutes after injection, and at the end of surgical procedure. Results of the test of the contralateral tooth served as the control group. No response to the electric pulp test at a maximum output (80 readings) was used as the criterion for pulpal anesthesia. Results obtained with electric pulp test and sharp explorer test were not significantly different during various intervals on the contralateral side, indicating the reliability of this standardized method for assessing MB. The MB technique achieved a high rate of subjective numbness (100%) according to the perception of the patients of overall numbness and lip numbness. Overall anesthetic success rates of pulpal anesthesia were 5.7% for the central incisor, 38.2% for the canine, 55.3% for the first premolar, and 90.2% for the first molar. No significant difference was found in the efficiency of anesthesia related to sex or age of the patients. A slower onset of pulpal anesthesia after MB was found for the anterior teeth than for the posterior teeth. This study suggests that the use of a standardized method might produce a clearer and more comprehensive evaluation of the efficiency and manifestations of MB.

A CPG component LE generates depolarization of buccal neurons by producing constant plateau potentials during feeding responses of Aplysia kurodai

In the buccal ganglia of Aplysia kurodai we have identified neurons (here termed LE neurons, or LE) producing plateau potentials lasting several seconds by application of short depolarizing currents. Results obtained from experiments using various bath solutions suggest that generation of these plateau potentials may be an endogenous property of LE. Application of various intensities or lengths of depolarizing currents induced in LE almost constant plateau potentials with fixed duration and depolarizing size. LE spikes produced monosynaptic EPSPs in the ipsilateral multi-action neuron (MA) and the jaw-closing motor neuron (JC) in the buccal ganglia. Conversely, MA spikes produced monosynaptic IPSPs in LE. There was electrical coupling between LE and both MA and JC. During the feeding-like response elicited by electrical stimulation of the nerve, LE showed rhythmic depolarization almost simultaneously with MA and JC, and firing on the plateau potentials occurred during the period of JC firing, the later phase of radula retraction. Hyperpolarization of LE during the feeding-like response suppressed generation of plateau potentials, though rhythmic small depolarization was still induced. During LE hyperpolarization, the duration of the depolarization of MA and JC was shortened. These results suggest that LE may be an element of the feeding CPG circuit and may contribute to part of the depolarization of MA and JC by generating constant plateau potentials during the feeding response, though LE may not have rhythm-generating ability.

Anatomic landmarks of the buccal branches of the facial nerve

The aim of this study was to classify the buccal branches of the facial nerve in relation to the parotid duct and its relevance to surgical procedures such as rhytidectomy and parotid gland surgery. In this study, 30 cadaver heads (60 specimens) were dissected. The vertical and horizontal relationships between the buccal branches of the facial nerve and tragus, and parotid duct were recorded and analyzed. The buccal branches of the facial nerve were classified into four types: Type I: a single buccal branch of the facial nerve at the point of emergence from the parotid gland and inferior to the parotid duct. Type II: a single buccal branch of the facial nerve at the point of emergence from the parotid gland and superior to the parotid duct. Type III: buccal and other branches of the facial nerve formed a plexus. Type IV: two branches of buccal branch; one superior and one inferior to the duct at the point of emergence from the parotid gland. The buccal branches of the facial nerve are very vulnerable to surgical injury because of its location in the midface. For this reason, the surgeons who are willing to operate on this area should have a true knowledge about the anatomy of these branches.

Octopamine increases the excitability of neurons in the snail feeding system by modulation of inward sodium current but not outward potassium currents

BACKGROUND

Although octopamine has long been known to have major roles as both transmitter and modulator in arthropods, it has only recently been shown to be functionally important in molluscs, playing a role as a neurotransmitter in the feeding network of the snail Lymnaea stagnalis. The synaptic potentials cannot explain all the effects of octopamine-containing neurons on the feeding network, and here we test the hypothesis that octopamine is also a neuromodulator.

RESULTS

The excitability of the B1 and B4 motoneurons in the buccal ganglia to depolarising current clamp pulses is significantly (P < < 0.05) increased by (10 microM) octopamine, whereas the B2 motoneuron becomes significantly less excitable. The ionic currents evoked by voltage steps were recorded using 2-electrode voltage clamp. The outward current of B1, B2 and B4 motoneurons had two components, a transient IA current and a sustained IK delayed-rectifier current, but neither was modulated by octopamine in any of these three buccal neurons. The fast inward current was eliminated in sodium-free saline and so is likely to be carried by sodium ions. 10 microM octopamine enhanced this current by 33 and 45% in the B1 and B4 motoneurons respectively (P < < 0.05), but a small reduction was seen in the B2 neuron. A Hodgkin-Huxley style simulation of the B1 motoneuron confirms that a 33% increase in the fast inward current by octopamine increases the excitability markedly.

CONCLUSION

We conclude that octopamine is also a neuromodulator in snails, changing the excitability of the buccal neurons. This is supported by the close relationship from the voltage clamp data, through the quantitative simulation, to the action potential threshold, changing the properties of neurons in a rhythmic network. The increase in inward sodium current provides an explanation for the polycyclic modulation of the feeding system by the octopamine-containing interneurons, making feeding easier to initiate and making the feeding bursts more intense.

Neurological complications following extrusion of sodium hypochlorite solution during root canal treatment

AIM

To report the presentation and management of two cases with neurological complications secondary to the extrusion of sodium hypochlorite solution into the facial soft tissues during root canal treatment.

SUMMARY

The clinical features, with particular emphasis on nerve deficit following inadvertent extrusion of sodium hypochlorite, are discussed and its management highlighted. Early and aggressive treatment is advocated following such incidents in order to reduce potentially serious complications.

KEY LEARNING POINTS

*Neurological sequelae can follow inadvertent hypochlorite extrusion. *Early recognition may avert a potentially more serious outcome. *Active hospital treatment including intravenous steroids and antibiotics is recommended.

Predictive factors in infraorbital sensitivity disturbances following zygomaticomaxillary fractures

The aim of this study was to define if the alterations in sensory modalities could be a predictive factor in the prognostic recovery of the ION. Ten patients that had suffered facial trauma, associated with sensitivity alterations of the ION were evaluated prospectively. Touch detection thresholds (TD) were measured using Von Frey's filaments aesthesiometer. A warm/cold discrimination (W/C) was also done to the patients, on the same areas. The patients were examined in both sides of the face, using the non-traumatized side as control. The tests were done before surgery and several times postoperatively. For statistical analysis of the results, the two-sample t test was used. A significant difference (P < 0.0001) in the mean tactile recovery time between the areas without thermal sensitivity before surgery and those with normal thermal sensitivity before surgery was observed. Therefore, we propose that during the preoperative examination, the surgeon examines the thermal discrimination in order to establish prognosis and approximate recovery times.

Interrelated Buccal Fat Pad With Facial Buccal Branches and Parotid Duct

The facial nerve branches are vulnerable during manipulation of the buccal fat pad. The aim of this study is to describe the precise anatomical interrelation among the buccal fat pad, buccal branches of the facial nerve, and parotid duct. Nineteen hemifaces of Korean cadavers (11 male and 8 female) fixed in 10% formaldehyde solution were dissected. An average 3.6 buccal branches of the facial nerve were found. The facial buccal branches and parotid duct crossed each other within a semicircle with a 30-mm radius. The base (diameter) is parallel to a horizontal line passing the corner of the mouth and 12 mm above. Its center is located 53 mm lateral to it. The buccal branches of the facial nerve have two locations at the buccal fat pad: Type I, branches crossing superficial to the buccal fat pad in 14 of 19 (73.7%) specimens; and Type II, two twigs passing through buccal extension of the buccal fat pad in 5 of 19 (26.3%). An interrelation of parotid duct and buccal fat pad is as follows: parotid duct crossing superficial to the buccal extension of buccal fat pad in 8 of 19 (42.1%) specimens, crossing deep to the buccal extension of buccal fat pad in 5 of 19 (26.3%) specimens and crossing along the superior border of the buccal extension of buccal fat pad in 6 of 19 (31.6%) specimens. There is a 26.3% chance of injury to the buccal branch during total removal of buccal fat pad. The parotid duct runs deep to the buccal extension of buccal fat pad in 26.3% of cases.

Face representation in the human secondary somatosensory cortex

OBJECTIVE

To investigate the somatotopic organization of the facial skin area in the secondary somatosensory cortex (SII) in humans.

METHODS

Somatosensory evoked magnetic fields following air-puff stimulation of 5 body sites, the foot, the lip and 3 points of the facial skin (forehead, cheek and mandibular angle point), were recorded. We focused on activities in SII following stimulation of these 5 sites and compared dipole locations among them.

RESULTS

There was a clear somatotopic organization in SII with lip in the most lateral area, foot in the most medial area and face in an intermediate area close to the lip area. However, there was no significant difference of dipole localization in SII among the 3 areas of facial skin, similar to the overlapped somatotopic organization of facial skin areas in the primary somatosensory cortex in our previous study.

CONCLUSIONS

The facial skin areas are considered to occupy a small area in SII with insufficient spatial separation to differentiate each area of facial skin even using magnetoencephalography which has a high spatial resolution.

SIGNIFICANCE

This is the first systematic study of the activated regions in SII following stimulation of the facial skin.

Tactile and pain thresholds in the intra- and extra-oral regions of symptom-free subjects

The aim of the present study was to evaluate the tactile detection threshold (TDT), the filament-prick pain detection threshold (FPT), the pressure pain threshold (PPT), and the pressure pain tolerance detection threshold (PTOL) at multiple measuring points in the orofacial region of normal subjects. Sixteen males and 16 females (age range from 20 to 41 years) participated. The TDT and the FPT were measured on the cheek skin overlying the central part of the masseter muscles (MM), on the maxillary gingiva, and at the tip of the tongue, using Semmes-Weinstein monofilaments. The PPT and PTOL were measured at the central part of the MM, using a pressure algometer. The pain intensity during the FPT, PPT and the PTOL measurements was assessed on a numeric rating scale (NRS). The tongue tip had the lowest value in TDT and FPT compared to the other sites. Females showed a significantly lower TDT and FPT at the cheek skin than males. Further, measurements of PPT and PTOL confirmed the previously reported higher thresholds in males. In contrast, while the intra-oral threshold measurements revealed no gender differences, a significantly higher pain perception as evaluated using NRS, was seen in the males. A strong correlation was found between the pain responses at the same measuring site (FPT, PPT, and PTOL over the MM). In addition, the TDT and the pain responses were also correlated positively.

The zygomaticotemporal branch of the trigeminal nerve: an anatomical study

This study was conducted to determine the site of emergence of the zygomaticotemporal branch of the trigeminal nerve from the temporalis muscle and to identify the number of its accessory branches and their locations. A pilot study, conducted on the same number of patients, concluded that the main zygomaticotemporal branch emerges from the deep temporal fascia at a point on average 17 mm lateral and 6 mm cephalad to the lateral palpebral commissure, commonly referred to as the lateral canthus. These measurements, however, were obtained after dissection of the temporal area, rendering the findings less reliable. The current study included 20 consecutive patients, 19 women and one man, between the ages of 26 and 85 years, with an average age of 47.6 years. Those who had a history of previous trauma or surgery in the temple area were excluded. Before the start of the endoscopic forehead procedure, the likely topographic site of the zygomaticotemporal branch was marked 17 mm lateral and 6 mm cephalad to the lateral orbital commissure on the basis of the information extrapolated from the pilot study. The surface mark was then transferred to the deeper layers using a 25-gauge needle stained with brilliant green. After endoscopic exposure of the marked site, the distance between the main branch of the trigeminal nerve or its accessory branches and the tattoo mark was measured in posterolateral and cephalocaudal directions. In addition, the number and locations of the accessory branches of the trigeminal nerve were recorded. On the left side, the average distance of the emergence site of the main zygomaticotemporal branch of the trigeminal nerve from the palpebral fissure was 16.8 mm (range, 12 to 31 mm) in the posterolateral direction and an average of 6.4 mm (range, 4 to 11 mm) in the cephalad direction. On the right side, the average measurements for the main branch were 17.1 mm (range, 15 to 21 mm) in the lateral direction and 6.65 mm (range, 5 to 11 mm) in the cephalic direction. Three types of accessory branches were found in relation to the main branch: (1) accessory branch cephalad, (2) accessory branch lateral, and (3) accessory branches in the immediate vicinity of the main branch. This anatomical information has proven colossally helpful in injection of botulinum toxin A in the temporalis muscle to eliminate the trigger sites in the parietotemporal region and surgical management of migraine headaches triggered from this zone.

Pacemaker potentials are the physiologic basis of epileptiform activity in the buccal ganglia of Helix pomatia

Mechanisms of epileptic activity in nervous systems were studied using the identified neurons B1 through B4 in the buccal ganglia of the snail Helix pomatia as a model system. Activities were recorded with intracellular microelectrodes. Epileptiform activity was induced by bath application of an epileptogenic drug (pentylenetetrazol: 1 mM to 40 mM, or etomidate: 0.1 mM to 1.0 mM). Epileptiform potentials recorded from the somata of neurons consisted of paroxysmal depolarization shifts (PDSs). With increasing concentration of an epileptogenic drug, pacemaker potentials in neuron B3 developed into PDS. Simultaneously several types of chemical post-synaptic potentials were suppressed in amplitude. Since on the one hand epileptic seizures only appear when PDS are synchronized in many neurons and since on the other hand synaptic potentials were found to be suppressed during epileptic conditions, mechanisms underlying neuronal synchronization were studied. Evidence was found that, under epileptogenic conditions only, neurons were synchronized by an non-synaptic release of substances. Strong depolarizations accompanied by an increase in intracellular calcium concentration are known to induce an unspecific exocytosis. Thus, an unspecific exocytosis from the dendrites of PDS-generating neurons probably appears under epileptic conditions and synchronizes neighbouring neurons.

Extending in vitro conditioning in Aplysia to analyze operant and classical processes in the same preparation

Operant and classical conditioning are major processes shaping behavioral responses in all animals. Although the understanding of the mechanisms of classical conditioning has expanded significantly, the understanding of the mechanisms of operant conditioning is more limited. Recent developments in Aplysia are helping to narrow the gap in the level of understanding between operant and classical conditioning, and have raised the possibility of studying the neuronal processes underlying the interaction of operant and classical components in a relatively complex learning task. In the present study, we describe a first step toward realizing this goal, by developing a single in vitro preparation in which both operant and classical conditioning can be studied concurrently. The new paradigm reproduced previously published results, even under more conservative and homogenous selection criteria and tonic stimulation regime. Moreover, the observed learning was resistant to delay, shortening, and signaling of reinforcement.

Continuous increase of epileptogenic effects following application of proteolytic enzymes (buccal ganglia of Helix pomatia)

Epileptic activity of neurons consists of paroxysmal depolarization shifts (PDS) which can be induced presumably in any nervous system by application of an epileptogenic drug. The spontaneous appearance of epileptic activity, however, is based on a largely unknown process which increases susceptibility to epileptic activity (seizure susceptibility in man). It is presently shown that the treatment of ganglia with proteolytic enzymes (Pronase) decreases the effective concentration of epileptogenic drugs, i.e. increases seizure susceptibility. Since proteolytic enzymes are known to primarily affect glial cells a contribution of glia to seizure susceptibility is discussed.

Successful treatment of hemifacial spasm with selective facial nerve block using doxorubicin (adriamycin) under local anesthesia

OBJECTIVE

To describe our experience with selective chemical rhizotomy of facial nerves using adriamycin (ADM) in a patient with hemifacial spasm (HFS). This unique technique is less invasive than intracranial neurosurgery and enables one to perform a permanent nerve block under local anesthesia.

PATIENT

The patient, a 73-year-old female, had difficulty opening her left eye. Following unsuccessful treatment with anti-epileptic medicine, she received selective intraneural injections of ADM under local anesthesia. One week after the surgery the spasms had disappeared completely. No major complications were caused by this procedure and there had been no recurrence of spasms 3 years after the surgery.

RESULTS

It is thought that recurrence of HFS should be observed after simple neurotomy due to regrowth of nerve fibers. However, this did not occur after chemical rhizotomy with ADM. This method clearly differs from previously used varieties of simple neurotomy because the latter technique does not cause severe destructive changes in the facial motor nucleus.

CONCLUSION

Selective facial nerve chemical rhizotomy with ADM under local anesthesia may be effective in treating a subgroup of patients with HFS, especially elderly patients and those in the high-risk group for general anesthesia and intracranial neurosurgery.

Cutaneous distribution of infraorbital nerve

The aim of this study is to elucidate precisely the cutaneous distribution of the infraorbital nerve. Ten hemifaces of five Korean adult cadavers (2 males and 3 females) were subjected to the dissection. The cutaneous branches of the infraorbital nerve were distributed over the infraorbital area, which bounds on superiorly the lower eyelid margin, inferiorly the horizontal line crossing the mouth corners, medially 0.5 cm to midline, and laterally 2 cm lateral to the temporal canthus of the eyes. The infraorbital nerve had 19.5 branches (range, 15-24 branches). The mean area supplied by the infraorbital nerve was 25.8 cm2 (range, 24.0-28.2 cm2). The mean area of the superior labial branch was 13.1 cm2 (range, 11.2-14.3 cm2) and broader than either the 7.5 cm2 (range, 6.6-8.8 cm2) of the lower palpebral branch or the 7.6 cm2 (range, 6.7-9.3 cm2) of the external nasal branch. The external nasal branch was overlapped with the lower palpebral and superior labial branch, but the last two branches do not overlap each other. The nonoverlapped branch of the infraorbital nerve exhibits a restricted anesthesia, but the overlapped branch sustains sensory perception to some extent when being damaged.

Communication of Infraorbital Nerve and Facial Nerve: Anatomic and Histologic Study

The maxillary nerve, second division of the trigeminal nerve, is entirely sensory. It has been reported that drooling may occur later in the event of fracture of the zygoma in which hypesthesia prevails. The aim of the study is to elucidate additional detailed anatomy of the infraorbital plexus, consisting of the superior labial branch of the infraorbital nerve and facial nerve in the cheek. The authors dissected infraorbital nerves and facial nerves in 16 cadavers. Most terminals of the zygomatic branch of the facial nerve emerged from under the levator labii superiors and zygomatic muscle and infraorbital nerve. A hazardous zone of infraorbital plexus is found in a circle 36 mm in diameter. Its center is located 22 mm below the inferior orbital foramen. This hazardous zone of infraorbital plexus should be kept in mind when performing any procedures related to zygoma, maxilla, or deep cheek injuries.

Schwannoma of the mental nerve: usefulness of preoperative imaging: a case report

Schwannoma of the head and neck region is relatively uncommon. We report a case of schwannoma arising from the left mental nerve. A 21-year-old male presented at our hospital with a painless swelling of the left cheek. Because the lesion had rapidly increased in size, a malignant tumor was suspected. Magnetic resonance imaging (MRI), computed tomography, and ultrasonography were performed. MRI and ultrasonography revealed that the tumor was connected to the mental nerve. Both MRI and ultrasonography were found to be useful in making a preoperative diagnosis. It was possible to determine prior to surgery that this was a peripheral nerve sheath tumor. The lesion was completely resected. The pathological diagnosis was Antoni type A schwannoma. There has been no sign of recurrence 1 year after surgery.

Helospectin I and II evoke vasodilation in the intact peripheral microcirculation

Helospectin I and II, two closely related mammalian neuropeptides of the secretin/glucagons/vasoactive intestinal peptide (VIP) superfamily of peptides, are co-localized with VIP in nerve fibers surrounding vascular smooth muscle. However, the role if any, VIP receptors play in transducing the vasorelaxant effects of helospectin I and II in the intact peripheral microcirculation is uncertain. The purpose of this study was to determine whether helospectin I and II elicit vasodilation in the intact peripheral microcirculation and, if so, whether this response is mediated, in part, by VIP or pituitary adenylate cyclase activating peptide (PACAP) receptor engagement, and through local elaboration of cyclooxygenase products of arachidonic acid metabolism. Using intravital microscopy, we found that suffusion of helospectin I and II (each, 1.0 nmol) evoked potent vasodilation and of similar magnitude in the intact hamster cheek pouch microcirculation (P < 0.05). Suffusion of 0.1 nmol helospectin I and II had no significant effects on arteriolar diameter. Pretreatment with VIP(10-28), a VPAC1/VPAC2 receptor antagonist, or PACAP(6-38), a PAC1/VPAC2 receptor antagonist, had no significant effects on helospectin I- and II-induced responses. In addition, pretreatment with indomethacin had no significant effects on helospectin I- and II-induced vasodilation. Collectively, these data indicate that helospectin I and II evoke potent vasodilation in the intact peripheral microcirculation that is not transduced by VIP or PACAP receptors nor through cyclooxygenase products of arachidonic acid metabolism.

Frequency-Dependent Regulation of Afferent Transmission in the Feeding Circuitry of Aplysia

During rhythmic behaviors, sensori-motor transmission is often regulated so that there are phasic changes in afferent input to follower neurons. We study this type of regulation in the feeding circuit of Aplysia. We characterize effects of the B4/5 interneurons on transmission from the mechanoafferent B21 to the radula closer motor neuron B8. In quiescent preparations, B4/5-induced postsynaptic potentials (PSPs) can block spike propagation in the lateral process of B21 and inhibit afferent transmission. B4/5 are, however, active during the retraction phase of motor programs, i.e., when mechanoafferent transmission to B8 presumably occurs. To determine whether mechanoafferent transmission is necessarily inhibited when B4/5 are active, we characterize the B4/5 firing frequency during retraction and show that, for the most part, it is low (below 15 Hz). There is, therefore, a low probability that spike propagation will be inhibited. The relative ineffectiveness of low frequency activity is not simply a consequence of insufficient PSP magnitude, because a single PSP can block spike propagation. Instead, it is related to the fact that PSPs have a short duration. When B4/5 fire at a low frequency, there is therefore a low probability that afferent transmission in the lateral process of B21 can be inhibited. In conclusion, we demonstrate that afferent transmission will not always be affected when a neuron that exerts inhibitory effects is active. Although a cell may be ineffective when it fires at a low frequency, ineffectiveness is not necessarily a consequence of spike frequency per se. Instead it may be due to spike timing.

Intra- and interactive touch on the face

Experiments were performed in which the subjective size of steel balls was judged by the method of absolute magnitude estimation (AME). The balls were rolled actively ("scripting") by the right index finger pad of the subject over the passively receiving areas of the face, namely the forehead, cheek and the vermilion border of the lower lip. These areas were stimulated on the subject's own person (intra-active touch), on another person's face (interactive touch) and by another person upon the face of the subject (interactive touch). Results indicate that size perception appears to be governed primarily by the mechanical characteristics of the stimuli, including the balls and the sites on the face. When the subject's finger was used to script upon another's face, there were significant differences among or between the sites. When another person scripted upon the subject's face there were no significant differences among any of the sites. The results are discussed considering mode of stimulation and tissue mechanics.

A population of pedal-buccal projection neurons associated with appetitive components of Aplysia feeding behavior

Backfills of the cerebral-buccal connective (CBC) of Aplysia californica revealed a cluster of five to seven pedal-buccal projection neurons in the anterolateral quadrant of the ventral surface of each pedal ganglion. Intra- and extracellular recordings showed that the pedal-buccal projection neurons shared common electrophysiological properties and synaptic inputs. However, they exhibited considerable heterogeneity with respect to their projection patterns. All pedal-buccal projection neurons that were tested received a slow excitatory postsynaptic potential from the ipsi- and contralateral cerebral-pedal regulator (C-PR) neuron, a cell that is thought to play a key role in the generation of a food-induced arousal state. Tests were conducted to identify potential synaptic follower neurons of the pedal-buccal projection neurons in the cerebral and buccal ganglia, but none were detected. Finally, nerve recordings revealed projections from the pedal-buccal projection neurons in the nerves associated with the buccal ganglion. In tests designed to determine the functional properties of these peripheral projections, no evidence was obtained supporting a mechanosensory or proprioceptive role and no movements were observed when they were fired. It is proposed that peripheral elements utilized in consummatory phases of Aplysia feeding may be directly influenced by a neuronal pathway that is activated during the food-induced arousal state.

Ingestion motor programs of Aplysia are modulated by short-term synaptic enhancement in cerebral-buccal interneuron pathways

In the sea slug Aplysia, buccal synapses of cerebral-buccal interneurons (CBIs) CBI-2 and CBI-12 exhibit short-term synaptic enhancement (STE), including frequency-dependent facilitation and augmentation/post-tetanic potentiation (AUG/PTP). The STE that results from driving CBI-2 or CBI-12 is associated with significantly decreased latency to burst onset in buccal premotor neurons and motor neurons, increased cycle frequency of ingestion buccal motor programs (iBMPs) and increased intraburst firing frequency of buccal neurons during iBMPs. Tests of paired-pulse facilitation during AUG/PTP suggest that the locus for this plasticity is presynaptic. The AUG/PTP is not elicited by heterosynaptic pathways, indicating that its origin is homosynaptic. At low CBI-2 and CBI-12 firing frequencies, STE is likely to contribute to iBMP initiation, while at higher firing frequencies, STE is correlated with increased cycle frequency of iBMPs. Thus, STE is an important component of the mechanisms whereby cerebral neurons regulate cyclic feeding programs and likely contributes to observed variations in behavioral responses, including feeding arousal.

Colocalization of gamma-aminobutyric acid-like immunoreactivity and catecholamines in the feeding network of Aplysia californica

Functional consequences of neurotransmitter coexistence and cotransmission can be readily studied in certain experimentally favorable invertebrate motor systems. In this study, whole-mount histochemical methods were used to identify neurons in which gamma-aminobutyric acid (GABA)-like immunoreactivity (GABAli) was colocalized with catecholamine histofluorescence (CAh; FaGlu method) and tyrosine hydroxylase (TH)-like immunoreactivity (THli) in the feeding motor circuitry (buccal and cerebral ganglia) of the marine mollusc Aplysia californica. In agreement with previous reports, five neurons in the buccal ganglia were found to exhibit CAh. These included the paired B20 buccal-cerebral interneurons (BCIs), the paired B65 buccal interneurons, and an unpaired cell with projections to both cerebral-buccal connectives (CBCs). Experiments in which the FaGlu method was combined with the immunohistochemical detection of GABA revealed double labeling of all five of these neurons. An antibody generated against TH, the rate-limiting enzyme in the biosynthesis of catecholamines, was used to obtain an independent determination of GABA-CA colocalization. Biocytin backfills of the CBC performed in conjunction with TH immunohistochemistry revealed labeling of the rostral B20 cell pair and the unpaired CBI near the caudal surface of the right hemiganglion. THli was also present in a prominent bilateral pair of caudal neurons that were not stained with CBC backfills. On the basis of their position, size, shape, and lack of CBC projections, the lateral THli neurons were identified as B65. Double-labeling immunohistochemical experiments revealed GABAli in all five buccal THli neurons. Finally, GABAli was observed in individual B20 and B65 neurons that were identified using electrophysiological criteria and injected with a marker (neurobiotin). Similar methods were used to demonstrate that a previously identified catecholaminergic cerebral-buccal interneuron (CBI) designated CBI-1 contained THli but did not contain GABAli. Although numerous THli and GABAli neurons and fibers were present in the cerebral and buccal ganglia, additional instances of their colocalization were not observed. These findings indicate that GABA and a catecholamine (probably dopamine) are colocalized in a limited number of interneurons within the central pattern generator circuits that control feeding-related behaviors in Aplysia.

Participation of GABA in establishing behavioral hierarchies in the terrestrial snail

GABA-immunoreactive fibers were observed in the neuropile of each ganglion of Helix lucorum, while GABA-immunoreactive neural somata were found only in the buccal, cerebral, and pedal ganglia. Bath application of 10(-5) M GABA to the preparation "buccal mass-buccal ganglia" elicited a sequence of radula movements characteristic of feeding behavior. Corresponding bursts of activity were recorded in the buccal nerves under GABA application and in the buccal neurons recorded optically. In preparations of isolated central nervous system, the bath applications of GABA (10(-5) to 10(-4) M) elicited no changes in synaptic input of the premotor interneurons involved in the withdrawal behavior. However, a significant decrease in amplitude of the synaptic input and in the number of spikes in responses elicited by the test nerve stimulation was observed in metacerebral serotonergic neurons involved in modulating the feeding behavior. GABA application inhibited the spontaneous spike activity in some pedal serotonergic neurons involved in the network underlying withdrawal responses and evoked bursting activity in the other neurons of this functional group. The effects of GABA application on mechanically isolated serotonergic neurons suggest that the primary effect of GABA is inhibition. Thus, our results give evidence of the putative role of GABA in activating the feeding behavior and in the synergistic suppression of serotonergic modulation of the withdrawal behavior and serotonergic modulation of feeding, which has corresponded to the observed behavioral suppression of withdrawal reactions during feeding.

Ryanodine-, IP3- and NAADP-dependent calcium stores control acetylcholine release

Injections of inositol trisphosphate (IP3) or nicotinamide adenine dinucleotide phosphate (NAADP) into the presynaptic neurone of an identified cholinergic synapse in the buccal ganglion of Aplysia californica increased the amplitude of the inhibitory postsynaptic current evoked by a presynaptic action potential. This suggests that Ca2+ release from various Ca2+ stores can modulate acetylcholine (ACh) release. Specific blockade of the calcium-induced calcium release (CICR) mechanism with ryanodine, or of IP3-induced calcium release with heparin, abolished the effects of IP3, but not the effects of NAADP, suggesting the presence of an intracellular Ca2+ pool independent of those containing ryanodine receptors (RyR) or IP3 receptors. To reinforce electrophysiological observations, intracellular [Ca2+]i changes were measured using the fluorescent dye rhod-2. Injections of cyclic ADP-ribose (an activator of RyR), IP3 or NAADP into the presynaptic neurone induced transient increases in the free intracellular Ca2+ concentration. RyR- and IP3-induced increases were prevented by application of respective selective antagonists but not NAADP-induced increases. Our results show that RyR-dependent, IP3-dependent, and NAADP-dependent Ca2+ stores are present in the same presynaptic terminal but are differently involved in the regulation of the presynaptic Ca2+ concentration that triggers transmitter release.

Blocking the buccal nerve using two methods of inferior alveolar block injection

The anatomic relations of the buccal nerve branch of the mandibular division of the trigeminal nerve were studied to explain the rationale for the discrepancy in blocking the buccal nerve using two methods of blocking the inferior alveolar nerve, the conventional method and the Gow-Gates method. The conventional method rarely blocks the buccal nerve, while the Gow-Gates method is reported to consistently block the buccal nerve. Eight head and mandibular specimens were dissected to observe the path of buccal nerve and its relationship to the path of needles in the conventional and Gow-Gates techniques. The buccal nerve descends on the medial and then anterior aspect of the deep head of the temporalis muscle (Tdh). At the latter position the buccal nerve enters the retromolar fossa and is encased in a fascial sleeve created by a dense fascial band that spans between the temporalis muscle tendons and the buccinator muscle. At the level of the conventional block injection the buccal nerve was shielded from the path of the needle by the Tdh and the fascial band. In the Gow-Gates block injection, the buccal nerve was exposed on the medial surface of the Tdh, immediately lateral to the path of the needle and proximal to the fascial sleeve. Consequently, the anatomical relations of the buccal nerve in the conventional block method essentially shield the nerve from being bathed by anesthetic solution while in the Gow-Gates method the relations are such that the buccal nerve can be exposed to anesthetic solution and thus blocked, explaining the findings in clinical dentistry.

Syndrome auriculotemporal

Two cases of auriculotemporal syndrome are presented in two male children that began in the first years of life to present reactions of linear erythema itinerary on the cheeks after eating several foods. The allergologic study with these foods was negative, reproducing the clinical picture after their ingestion.

Buccal hemineglect

OBJECTIVES

To determine whether the peripersonal and intrapersonal buccal space can be affected by a hemispheric stroke and to evaluate the clinical signs resulting from buccal neglect.

METHODS

A prospective study comparing 2 groups of patients with hemiplegia, 1 with a right hemispheric lesion and the other with a left hemispheric lesion. Patients were selected consecutively on the basis of specific criteria at least 1 month after stroke.

RESULTS

Buccal hemineglect was usually concomitant with other hemineglect phenomena resulting from lesions of the right hemisphere (10 of 12 in right lesions and 1 of 12 in left lesions). Clinical signs associated with this condition consisted of impaired swallowing (retention, defective insalivation, presence of food debris in the left hemibuccal space, loss of saliva from the left side of the mouth, and choking); loss of the ability to perceive salty, sweet, or acid tastes; and impaired buccal representation. These problems were usually incorrectly diagnosed initially. Outcome was usually favorable, but functional disorders persisted in some patients for more than 18 months. The underlying attention and representation mechanisms are discussed with reference to experimental lesions of the postarcuate (area 6) cortex in rhesus monkeys. The area around the mouth may be considered to be, as in monkeys, a peripersonal space, ie, probably of little functional importance. The lesion may involve area 6 or its projections to the thalamus or posterior parietal cortex.

CONCLUSIONS

Buccal hemineglect, which is likely to cause social embarrassment, should be considered whenever the oral phase of swallowing is impaired in a context of neglect syndromes. Prophylactic measures and rehabilitation can reduce the impact and complications of the condition (food bolus).

Accessory innervation of the mandible: identification and anesthesia options

The nerves commonly associated with accessory innervation of the mandible are identified and alternative techniques to gain their anesthesia are recommended, based on sound anesthetic principles and the current understanding of nerve anatomy.

Changes in tactile spatial discrimination and cutaneous coding properties by skin hydration in the elderly

Neurosensory tactile functions were investigated in human subjects by two different and complementary experimental approaches. First, a conventional psychophysical method (two-point gap discrimination) was used to determine the tactile discrimination threshold by analyzing the subjects' ability to detect a gap of variable width between two contact points when a series of stimuli was applied to the skin. Using this method we confirmed the marked degradation of tactile spatial acuity with age and showed that skin discriminative function was partially restored after hydration of the skin with a moisturizer. The second approach consisted of a microneurographic recording of tactile afferent fibers in response to two types of mechanical stimuli applied reproducibly to the corresponding receptive fields. With this method, we found that the afferent messages were depressed following hydration of the skin surface. Thus, partial restoration of tactile spatial acuity after hydration appears to be due to both a softening of the stratum corneum permitting better localization of the stimulus and a weaker transfer of the stimulus toward the sensory receptors.

An axon pacemaker: diversity in the mechanism of generation and conduction of action potentials in snail neurons

One of the main principles in neuroscience is that in vertebrate motoneurons and certain interneurons the decision to initiate an action potential is made at the initial segment of the axon, the axon hillock [Kandel E. R. and Schwartz J. H. (1991) In Principles of Neural Science (eds Kandel E. R., Schwartz J. H. and Jessell T. M. ), pp. 166-167. Elsevier, New York]. The situation in invertebrate motoneurons is different. The axon has many arborizations near its soma, in the nearby neuropil, and many branches in the target region. The action potentials are generated in the region of the axon in the neuropil and in some cases the trigger zone can be found more than 1mm apart from the soma [Tauc C. (1962) Aplysia. J. gen. Physiol. 45, 1077-1097]. Thus, it is obvious that, in a neuron, the removal of the trigger zone would cease the spiking activity in the axon. The purpose of this work is to demonstrate that, in snails, there are axons of certain neurons, like neuron B2, which are able to maintain their firing activity after the removal of their cell body and the so-called trigger zone.

Rabbit facial nerve regeneration in autologous nerve grafts after antecedent injury

OBJECTIVE

The effect of incomplete antecedent injuries on subsequent facial nerve regeneration within cable graft repairs is not known. The purpose of this study is to compare facial nerve regeneration after an immediate and delayed neural cable graft repair.

METHOD

Rabbit facial nerve regeneration after complete transectional injuries of the buccal division was compared in two experimental models. In one, a 10-mm segment of the nerve was transected, rotated 180 degrees, and immediately repaired as a cable graft (N=8). In the second, a preliminary nerve crush was allowed to recover over a 4-week period and a 10-mm segment of nerve centered on the crush site was then transected, rotated 180 degrees, and delay repaired as a cable graft (N = 7). Data are presented as total numbers of regenerating myelinated axons that traverse the surgical repair to innervate the cable graft and distal nerve stumps, as well as the percentage of regenerating neurites compared with preoperative pooled and individual controls. Subpopulations of regenerating neurons are delineated to quantify the pattern of neural innervation.

RESULTS

Five weeks after cable graft repair both groups had similar myelinated outgrowth from the proximal nerve stump across the proximal anastomosis to innervate the cable graft (3995 +/- 1209 vs. 3284 +/- 651; P = .89). However, the delayed repair group had more intrafascicular regeneration within cable grafts (2261 +/- 931 vs. 1660 +/- 1169; P = .02) and distal nerve stump (1532 +/- 281 vs. 445 +/- 120; P = .004) than the immediate repair group. The immediate repair group had greater extrafascicular nerve regeneration in the cable graft (2335 +/- 1954 vs. 437 +/- 236; P = .001) and more myelin and axonal debris in pre-existing neural fascicles of the cable graft (P = .02) and distal nerve stump (463 +/- 187 vs. 103 +/- 87; P = .02).

CONCLUSIONS

Antecedent priming lesions do not enhance axonal survival as determined by regenerating myelinated axonal counts. However, antecedent injuries enhance the efficiency of neural innervation of the affected mimetic musculature by increasing the number of myelinated intrafascicular neural regenerants in the cable graft and distal nerve stump. This is accomplished by two factors: increased perineural fibrosis and decreased intrafascicular myelin and axonal debris.

A proprioceptive role for an exteroceptive mechanoafferent neuron in Aplysia

Afferent regulation of centrally generated activity is likely to be more complex than has been established. We show that a neuron that is an exteroceptor can also function as a proprioceptor. We study the Aplysia neuron B21. Previous data suggest that B21 functions as an exteroceptor during the radula closing/retraction phase of ingestive feeding. We show that the tissue innervated by B21, the subradula tissue (SRT), is innervated by a motor neuron (B66) and that B66-induced SRT contractions trigger centripetal spikes in B21. Thus, B21 is also a proprioceptor. To determine whether exteroceptive and proprioceptive activities occur during the same phase of ingestive feeding, we further characterize B66. We show that B66 stimulation does not close or retract the radula. Instead it opens it. Moreover, B66 is electrically coupled to other opening/protraction neurons. Finally, we elicit motor programs in semi-intact preparations and show that during radula opening/protraction we observe B66 activity, SRT contractions, and spikes in B21 that can be eliminated if B66 is indirectly hyperpolarized. B21 is, therefore, likely to act as an exteroceptor during one phase of ingestive feeding and as a proprioceptor during the antagonistic phase. Previous experiments have shown that centripetal spikes in B21 are only transmitted to one follower if they are "gated in" by depolarization. During ingestive programs B21 is centrally depolarized during closing/retraction, but it is not depolarized during opening/protraction. We sought to determine whether there are other followers that receive B21 input when it is not centrally depolarized. We found one such cell. Moreover, we found that stimulation of B21 during radula opening/protraction significantly decreases the duration of this phase of behavior. Thus, proprioceptive activity in B21 is likely to have an impact on motor programs.

[The effect of gabapentin in bucco-facial allodynia. Experimental correlation of the trigeminal nerve]

INTRODUCTION

Trigeminal neuralgia is an unilateral alteration of the trigeminal nerve, characterized by recurrent paroxysms of pain in one or more of the nerve's branches. Trigger areas are described in points of the facial skin (allodynia).

OBJECTIVE

To evaluate the effects of gabapentin (monotherapy) and associated with carbamazepine in allodynia of trigeminal neuralgia.

PATIENTS AND METHODS

The effects of these drugs were studied in 14 patients with trigeminal allodynia and with 12 experimental cats, with microelectrodes of multiple connections in the central nervous system and in dental pulp to precipitate pain in injured zones, area of primary hyperalgesia, secondary hyperalgesia and allodynia zone. Unitary registrations and evoked potentials were evaluated in neuronal trigeminal organizations, encephalon, limic system and neocortex.

RESULTS

The pairing of innocuous stimulus (allodynia) plus painful stimulus precipitate classic conditioned reflex. Unitary alteration and evoked potentials correlated with learning and memory were evaluated, involving the hippocampus in the results. The allodynia treatment obtains better results with the combined treatment than with the monotherapy.

CONCLUSIONS

Allodynia can be the result of a neuronal sensitization due to the increment on intracellular calcium facilitating the exocytosis. Changes in the mechano-receptors of low threshold establish communication with nociceptive neurons by a presynaptic mechanism, considering new synaptic and morphologic contacts associated with learning and memory. The major effectiveness in the combined treatment is the base of an association of the gabaergic mechanism of gabapentin and the blockade of sodium and potassium ionic channels by the carbamazepine.

Pattern generation in the buccal system of freely behaving Lymnaea stagnalis

Central pattern generators (CPGs) are neuronal circuits that drive active repeated movements such as walking or swimming. Although CPGs are, by definition, active in isolated central nervous systems, sensory input is thought play an important role in adjusting the output of the CPGs to meet specific behavioral requirements of intact animals. We investigated, in freely behaving snails (Lymnaea stagnalis), how the buccal CPG is used during two different behaviors, feeding and egg laying. Analysis of the relationship between unit activity recorded from buccal nerves and the movements of the buccal mass showed that electrical activity in laterobuccal/ventrobuccal (LB/VB) nerves was as predicted from in vitro data, but electrical activity in the posterior jugalis nerve was not. Autodensity and interval histograms showed that during feeding the CPG produces a much stronger rhythm than during egg laying. The phase relationship between electrical activity and buccal movement changed little between the two behaviors. Fitting the spike trains recorded during the two behaviors with a simple model revealed differences in the patterns of electrical activity produced by the buccal system during the two behaviors investigated. During egg laying the bursts contained less spikes, and the number of spikes per burst was significantly more variable than during feeding. The time between two bursts of in a spike train was longer during egg laying than during feeding. The data show what the qualitative and quantitative differences are between two motor patterns produced by the buccal system of freely behaving Lymnaea stagnalis.

Glutamate is a fast excitatory transmitter at some buccal neuromuscular synapses in Aplysia

Studies of the modulation of synaptic transmission in buccal muscle of Aplysia were limited because the conventional fast transmitter used by a number of large buccal motor neurons was unknown. Most of the identified buccal motor neurons are cholinergic because they synthesize acetylcholine (ACh) and their excitatory junction potentials (EJPs) are blocked by the cholinergic antagonist hexamethonium. However, three large identified motor neurons (B3, B6, and B38) do not synthesize ACh and their EJPs are not inhibited by hexamethonium. To identify the fast excitatory transmitter used by these noncholinergic motor neurons, we surveyed putative transmitters for their ability to evoke contractions. Of the noncholinergic transmitters tested, glutamate was the most effective at evoking contractions. The pharmacology of the putative glutamate receptor is different from previously characterized glutamate receptors in that glutamate agonists and antagonists previously used to classify glutamate receptors had little effect in this system. In addition, glutamate itself was the most effective agent tested at reducing EJPs evoked by the noncholinergic motor neurons presumably by desensitizing glutamate receptors. Finally, immunocytology using an antiserum raised to conjugated glutamate in parallel with intracellular fills indicated that the varicose axons of these motor neurons were glutamate-immunoreactive. Taken together, these results indicate that the fast transmitter used by the noncholinergic neurons is almost certainly glutamate itself. This information should help us understand the role of transmitters and cotransmitters in the generation of feeding behaviors in Aplysia.

Heptanol exerts epileptiform effects in identified neurons of the buccal ganglia of Helix pomatia

1-Heptanol (0.2-5.0 mM) known to block electrical contacts was tested under epileptic and non-epileptic conditions in the buccal ganglia of Helix pomatia. Synchronicity of epileptiform activity was not affected. In concentrations below 1 mM, heptanol accelerated epileptiform activity induced by pentylenetetrazol. In concentrations above 1 mM, it evoked epileptiform activity without admixture of an epileptogenic drug. Coupling coefficient was increased and decreased in low and high concentration ranges of heptanol, respectively. The measured decrease of coupling is interpreted as a result of the activation of 'epileptiform' membrane conductances accompanied by decreased length constants of neuronal fibers.

Spread of vasodilatation and vasoconstriction along feed arteries and arterioles of hamster skeletal muscle

1. In arterioles of the hamster cheek pouch, vasodilatation and vasoconstriction can spread via the conduction of electrical signals through gap junctions between cells that comprise the vessel wall. However, conduction in resistance networks supplying other tissues has received relatively little attention. In anaesthetized hamsters, we have investigated the spread of dilatation and constriction along feed arteries and arterioles of the retractor muscle, which is contiguous with the cheek pouch. 2. When released from a micropipette, acetylcholine (ACh) triggered vasodilatation that spread rapidly along feed arteries external to the muscle and arterioles within the muscle. Responses were independent of changes in wall shear rate, perivascular nerve activity, or release of nitric oxide, indicating cell-to-cell conduction. 3. Vasodilatation conducted without decrement along unbranched feed arteries, yet decayed markedly in arteriolar networks. Thus, branching of the conduction pathway dissipated the vasodilatation. 4. Noradrenaline (NA) or a depolarizing KCl stimulus evoked constriction of arterioles and feed arteries of the retractor muscle that was constrained to the vicinity of the micropipette. This behaviour contrasts sharply with the conduction of vasodilatation in these microvessels and with the conduction of vasoconstriction elicited by NA and KCl in cheek pouch arterioles. 5. Focal electrical stimulation produced constriction that spread rapidly along feed arteries and arterioles. These responses were inhibited by tetrodotoxin or prazosin, confirming the release of NA along perivascular sympathetic nerves, which are absent from arterioles studied in the cheek pouch. Thus, sympathetic nerve activity co-ordinated the contraction of smooth muscle cells as effectively as the conduction of vasodilatation co-ordinated their relaxation. 6. In the light of previous findings in the cheek pouch, the properties of vasoconstriction and vasodilatation in feed arteries and arterioles of the retractor muscle indicate that substantive differences can exist in the nature of signal transmission along microvessels of tissues that differ in structure and function.

Immediate complications of local anesthetic administered to 1,007 consecutive patients

BACKGROUND

Probably the most common procedure in dentistry is the administration of local anesthetic, or LA. Immediate complications of LA administration include positive blood aspiration, blanching of the tissue and burning sensation on impingement of the nerve. Because studies about the immediate complications of LA administration were conducted before 1980, more recent data regarding this procedure are needed.

MATERIALS AND METHODS

In this prospective study, an experienced dentist administered, 2,528 LA injections to 1,007 consecutive patients with 1-inch 27-gauge needles, using a solution of 2 percent lidocaine and 1:100,000 nordefrine hydrochloride.

RESULTS

The authors observed positive blood aspiration in 73 injections (2.9 percent) without any further complications. The most severe immediate complication-syncope-occurred only in one case. In 63 injections (2.5 percent), the dentist touched the nerve, and the patient reported feeling an electric current sensation (40 times with inferior alveolar nerve blocks, 18 times with lingual nerve blocks, four times with mental nerve blocks and one time with a second injection to the same site) without any further complications.

CONCLUSIONS

The results confirm that LA injections that are properly carried out appear to be safer today than they were in the past.

CLINICAL IMPLICATIONS

LA is a safe procedure when the appropriate technique is used. It is even safer when an inferior alveolar nerve block is administered.

In vitro analog of operant conditioning in aplysia. I. Contingent reinforcement modifies the functional dynamics of an identified neuron

Previously, an analog of operant conditioning in Aplysia was developed using the rhythmic motor activity in the isolated buccal ganglia. This analog expressed a key feature of operant conditioning, namely a selective enhancement in the occurrence of a designated motor pattern by contingent reinforcement. Different motor patterns generated by the buccal central pattern generator were induced by monotonic stimulation of a peripheral nerve (i.e., n.2,3). Phasic stimulation of the esophageal nerve (E n.) was used as an analog of reinforcement. The present study investigated the neuronal mechanisms associated with the genesis of different motor patterns and their modifications by contingent reinforcement. The genesis of different motor patterns was related to changes in the functional states of the pre-motor neuron B51. During rhythmic activity, B51 dynamically switched between inactive and active states. Bursting activity in B51 was associated with, and predicted, characteristic features of a specific motor pattern (i.e., pattern I). Contingent reinforcement of pattern I modified the dynamical properties of B51 by decreasing its resting conductance and threshold for eliciting plateau potentials and thus increased the occurrences of pattern I-related activity in B51. These modifications were not observed in preparations that received either noncontingent reinforcement (i.e., yoke control) or no reinforcement (i.e., control). These results suggest that a contingent reinforcement paradigm can regulate the dynamics of neuronal activity that is centrally programmed by the intrinsic cellular properties of neurons.