Depolarization and muscarinic excitation induced in a sympathetic ganglion by vasoactive intestinal polypeptide.

The effects of vasoactive intestinal polypeptide (VIP) in the superior cervical ganglion of the cat were studied in vitro and in vivo with sucrose gap and multiunit recording, respectively. At a dose of 0.03 to 0.12 nanomole, VIP produced a dose-dependent, prolonged (3 to 15 minutes) depolarization of the ganglion and enhanced the ganglionic depolarization elicited by the muscarinic agonist acetyl-beta-methylcholine. At a dose of 1.8 to 10 nanomoles, the peptide enhanced and prolonged the postganglionic discharge elicited by acetyl-beta-methylcholine, enhanced muscarinic transmission in ganglia treated with an anticholinesterase agent, and enhanced the late muscarinic discharge elicited by acetylcholine. VIP did not affect the early nicotinic discharge elicited by acetylcholine or by electrical stimulation of the preganglionic nerve. It is concluded that VIP has a selective facilitatory action on muscarinic excitatory mechanisms in the superior cervical ganglion of the cat.

Widening spectrum of a reversible splenial lesion with transiently reduced diffusion.

Four patients with encephalitis/encephalopathy and parenchymal lesions accompanying reversible splenial lesions were retrospectively evaluated. In 3 patients, reversible lesions with transiently reduced diffusion were seen in the splenium and symmetrically in the peripheral frontoparietal white matter, clinical signs and symptoms were mild, and recovery was complete. These and previous observations suggest a less severe course and outcome for patients with reversible lesions isolated to the splenium or to the splenium and peripheral frontoparietal white matter.

Identification of neuropeptides in pelvic and pudendal nerve afferent pathways to the sacral spinal cord of the cat.

The distribution of several neuropeptides, including vasoactive intestinal polypeptide (VIP), substance P, somatostatin, leucine enkephalin, methionine enkephalin, and cholecystokinin, in sacral afferent pathways of the cat was examined by immunohistochemical techniques. Certain peptides (substance P, somatostatin, and leucine enkephalin) could be demonstrated in normal dorsal root ganglion cells; however, topical administration or injections of colchicine solution into ganglia 36-56 hours prior to removal markedly increased the number of cells labeled and the intensity of staining. Other peptides (VIP, cholecystokinin, and methionine enkephalin) were only detected in significant numbers of cells following intraganglionic injections of colchicine. The distribution of peptides in dorsal root ganglion cells projecting to the pelvic nerve (visceral) and the pudendal nerve (somatic) was examined by retrograde dye labeling combined with immunohistochemistry. Fluorescent dyes were applied to the cut ends of the nerves 2 weeks prior to removal. A considerably higher percentage of pelvic nerve afferent neurons than pudendal nerve afferent neurons exhibited peptide immunoreactivity; e.g., VIP (42% vs. 10%), cholecystokinin (29% vs. 12%), substance P (24% vs. 21%), leucine enkephalin (30% vs. 24%), and methionine enkephalin (10% vs. 3%). Somatostatin was present in only a small percentage of either type of afferent neuron (0.3-2%). The total percentage of peptide-containing pelvic afferent neurons exceeded 100% (137%), suggesting that more than one peptide is present in some visceral afferent neurons. This has been confirmed in preliminary experiments. The peptide-containing cells were in general less than 40 micron in average diameter; however, a significant percentage of substance P and cholecystokinin neurons ranged from 40 to 60 micron in average diameter. VIP cells had the smallest average diameter (30 micron) whereas somatostatin cells had the largest average diameter (36 micron). Statistical analysis of cell sizes revealed that substance P cells projecting to the pelvic nerve were smaller than substance P cells sending axons into the pudendal nerve. On the other hand, VIP cells in the two afferent pathways were not significantly different in size. Sacral visceral and somatic afferent neurons contain a wide spectrum of neuropeptides, some of which (e.g., VIP and cholecystokinin) seem to be preferentially distributed in the visceral afferent systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Central distribution of afferent pathways from the uterus of the cat.

Afferent pathways from the uterus of the cat were labeled by injections of horseradish peroxidase (HRP), wheat germ agglutinin-HRP, or fluorescent dyes into the uterine cervix and uterine horns. Afferent input to the uterus arises from small to medium size neurons (average size 31 x 28 microns) in dorsal root ganglia at many levels of the spinal cord (T12-S3). The segmental origin correlates with the location of the afferent terminal field in the uterus. Eighty-seven percent of the dorsal root ganglion cells (average, 822 on one side) innervating the cervix are located in sacral ganglia, whereas 97% of the cells innervating the uterine horn (average 479 on one side) are located in lumbar ganglia. Double dye labeling experiments indicate that a small percentage (average 15%) of lumbar neurons innervating the uterine cervix also innervate the uterine horn. The majority (70-80%) of afferent input to the uterine cervix passes through the pelvic nerve and the remainder through the pudendal nerve, whereas afferent input to the uterine horn must travel in sympathetic nerves. Ovariectomy (10-14 days) did not change significantly the number, sizes, or segmental distribution of uterine afferent neurons. In some cats (25%) injections of WGA-HRP into the uterine cervix labeled neurons (90-125 per animal) in lamina VII in the S2 spinal segment in the region of the sacral parasympathetic nucleus. Central projections of uterine horn afferent neurons were not labeled; however, afferent projections from the cervix were detected in the sacral spinal cord. The most prominent labeling was present in Lissauer's tract and in lamina I and outer lamina II on the lateral edge of the dorsal horn. From this region some labeled axons extended through lamina V into the dorsal gray commissure. Very few afferents were labeled on the medial side of the dorsal horn. These results are discussed in regard to the physiological function of uterine afferents and the possible transmitter role of vasoactive intestinal polypeptide, which is present in a large percentage (70%) of cervical afferent neurons.

Vasoactive intestinal polypeptide and substance P in primary afferent pathways to the sacral spinal cord of the cat.

An analysis of vasoactive intestinal polypeptide immunoreactivity (VIP-IR) and substance P-IR in the cat spinal cord has revealed marked differences in the distribution of the two peptides. While substance P-IR was located at all levels of the cord, VIP-IR was most prominent in the sacral segments in Lissauer's tract and lamina I on the lateral edge of the dorsal horn. VIP-IR was also present in the sacral cord in (1) laminae V, VII, and X, (2) a thin band on the medial side of the dorsal horn, (3) the dorsal commissure, (4) the lateral band of the sacral parasympathetic nucleus, and (5) in a few animals in Onuf's nucleus. In other segments of the spinal cord VIP-IR was much less prominent but was present in Lissauer's tract and laminae I, II, and X. Substance P-IR was more uniformly distributed at all segmental levels in laminae I-III, V, VII, and X and in the dorsal commissure. In ventrolateral lamina I of the sacral spinal cord both VIP-IR and substance P-IR exhibited a distinctive periodic pattern in the rostrocaudal axis. The peptides were associated with bundles of dorsoventrally oriented axons and varicosities spaced at approximately 210-micron intervals center to center along the length of the spinal cord. The bundles in lamina I continued into lamina V where they further divided into smaller bundles that extended medially through laminae V and VII. The most prominent bundles of VIP axons passed ventrally from lateral laminae V and VII to enter lamina X and the ventral part of the dorsal gray commissure. On the other hand the majority of substance P axons in lamina V turned dorsally to join with axons on the medial side of the dorsal horn and to pass into the dorsal part of the dorsal gray commissure. Rostrocaudal VIP axons were present not only in Lissauer's tract but also in dorsolateral lamina I, in the lateral funiculus and in the ependymal cell layer of the central canal. Following unilateral transection of the sacral dorsal roots (2 weeks-22 months) the density of VIP axons and terminals was markedly reduced in ipsilateral Lissauer's tract and lateral laminae I and V; however, no change was detected in lamina X. Sacral deafferentation reduced substance P-IR in the dorsal gray commissure and in lateral laminae I and V.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultrastructural analysis of enkephalinergic terminals in parasympathetic ganglia innervating the urinary bladder of the cat.

Leucine enkephalin immunoreactivity was identified in axons and varicosities in parasympathetic ganglia located in the pelvic plexus and on the surface of the urinary bladder of the cat. Electron microscopic immunohistochemical studies revealed that varicosities containing leucine enkephalin exhibited large dense core vesicles and small, clear, spherical vesicles, which were similar to those found in cholinergic terminals. Leucine enkephalin immunoreactivity was primarily associated with large dense core vesicles. The varicosities formed axodendritic and axosomatic synapses with principal ganglion cells. Axoaxonic synapses were not detected. Some axosomatic enkephalinergic synapses were detected embedded within or invaginating the principal ganglion cells. Varicosities containing flattened and/or small dense core vesicles did not exhibit enkephalin immunoreactivity. Bladder ganglion cells identified by retrograde HRP tracing from the urinary bladder exhibited similar leucine enkephalinergic synapses. These observations, coupled with previous reports that leucine enkephalin is present in sacral preganglionic neurons and released by preganglionic nerve stimulation, suggest that leucine enkephalin and acetylcholine are cotransmitters stored and released from the same nerve terminals in bladder parasympathetic ganglia.

Plasticity in spinal opioid control of lower urinary tract function in paraplegic cats.

Spinal cord injury disrupts micturition reflexes, which produces morbidity. The contribution of endogenous opioid systems to urinary retention were assessed in chronic spinal cats by administering the opioid receptor antagonist, naloxone (5-500 micrograms kg-1, i.p.), to unanesthetized paraplegic cats while monitoring lower urinary tract function and observing hind limb reflexes. While naloxone had no overt effect in acute spinal cats, in chronic spinal cats naloxone induced the release of large volumes of urine and produced marked hind limb hyper-reflexia. Prominent tachyphylaxis and tolerance to the effects of naloxone were evident. Immunohistochemical studies indicated a marked increase in leucine enkephalin and dynorphin in sacral spinal neurons. Together, these data indicate hyperactivity of the endogenous spinal opioid system following recovery from spinal cord injury and, furthermore, suggest that the spinal neural circuitry may become 'dependent' upon elevated levels of endogenous opioid peptides.

Dibutyryl cGMP raises cytosolic concentrations of Ca2+ in cultured nodose ganglion neurons of the rabbit.

The effect of dibutyryl cGMP (dbcGMP), a membrane permeant cGMP analogue, on cytosolic concentrations of Ca2+ ([Ca2+]i) was studied in cultured nodose ganglion neurons of the rabbit using fura-2AM and microfluorometry. Application of dbcGMP (10-1000 microM) increased [Ca2+]i in 42% of neurons (n=67). The effect was observed in a dose-dependent fashion. The threshold dose was 100 microM and the increase at 500 microM averaged 117+/-8%. Removal of extracellular Ca2+ abolished the dbcGMP effect. Application of Ni2+ (1 mM) or neomycin (50 microM), a non-L-type voltage-gated Ca2+ channel (VGCC) antagonist, eliminated the dbcGMP effect. omega-conotoxin GVIA (2 microM), the N-type Ca2+ channel antagonist, or L-type Ca2+ channel antagonists (D600, 50 microM, or nifedipine, 10 microM) did not alter the dbcGMP effect. Ryanodine (10 microM) did not alter the effect of dbcGMP. Therefore, cGMP could play a part of role of an intracellular messenger in primary sensory neurons of the autonomic nervous system.

Selective facilitatory effect of vasoactive intestinal polypeptide (VIP) on muscarinic firing in vesical ganglia of the cat.

VIP immunoreactivity was identified in nerve fibers and in 10-13% of the neurons in pelvic and bladder ganglia of the cat. Ninety percent of the VIP positive neurons contained acetylcholinesterase. VIP immunoreactivity was not altered in decentralized ganglia 1 week to 8 months after transection of the pelvic and hypogastric nerves indicating that VIP fibers arose from neurons within the peripheral nervous system. The intra-arterial administration of VIP (1-50 micrograms/kg) enhanced the postganglionic discharge elicited by the muscarinic agonist, acetyl-beta-methylcholine, but did not alter the postganglionic firing elicited by the nicotinic agonist, tetramethylammonium or by electrical stimulation of preganglionic axons in the pelvic nerve. VIP did not elicit a postganglionic discharge in untreated ganglia, but did evoke a prolonged discharge in ganglia treated with an irreversible anticholinesterase agent, 217AO. This discharge was not affected by hexamethonium but was blocked by atropine. VIP suppressed the muscarinic inhibition of ganglionic transmission produced by acetyl-beta-methylcholine without altering the response to other inhibitory agents (norepinephrine, leucine-enkephalin and gamma-aminobutyric acid (GABA). VIP (0.1-0.3 micrograms/kg) also had a direct inhibitory effect on bladder smooth muscle. These findings raise the possibility that intraganglionic pathways containing VIP may exert a selective modulatory influence on muscarinic transmission in vesical parasympathetic ganglia.

Cutaneous hyperalgesia induced by peripheral injection of interleukin-1 beta in the rat.

The contribution of the activity of afferent fiber filaments to pain and hyperalgesia after administration of a plantar injection of interleukin-1 beta (IL-1 beta) to the hind-paw skin was investigated by recording action potentials of the rat dorsal root in response to mechanical and thermal stimuli. Touch stimuli were delivered by stroking with a cotton-tipped applicator and thermal stimulation was applied by cooling or heating of the skin. After the administration of IL-1 beta (100 pg-1 microgram), responses to touch, cold, and heat stimulation increased to 143%, 200%, and 392%, respectively, of control values on average. IL-1 beta induced transient spontaneous discharge in 50% of experiments. The effects of IL-1 beta were apparent within 1 min. To examine responses to pressure stimulation, an area of 1 mm2 of the hind-paw skin was pressed by a mechanical stimulator. IL-1 beta (0.1 pg-200 ng) decreased the threshold value to 58% of the control pressure required for firing. IL-1 beta also increased responses to various levels of pressure (range: 1-20 g/mm2). These data suggest that IL-1 beta may play an important role in cutaneous hyperalgesia by activating polymodal receptors to mechanical and thermal stimulation.

Effects of pituitary adenylate cyclase activating polypeptide on lumbosacral preganglionic neurons in the neonatal rat spinal cord.

The effects of PACAP-38 on phasic and tonic preganglionic neurons (PGN) in L6 and S1 spinal cord slices from neonatal rats (5--11 days old) were studied using the whole-cell patch clamp technique. PGN were identified by retrograde axonal transport of a fluorescent dye (Fast Blue, 5 microl of 4% solution) injected into the intraperitoneal space 3--7 days prior to the study. Bath application of pituitary adenylate cyclase activating polypeptide (PACAP) (20 nM) increased the frequency of spontaneous excitatory postsynaptic potentials (EPSPs) and spontaneous firing in both types of PGN. PACAP markedly increased the number (200--800%) and frequency of action potentials elicited by depolarizing current pulses in phasic PGN, but had a smaller effect on tonic PGN. PACAP decreased the threshold for action potential generation by approximately 25% in both types of neurons (e.g. -34.0+/-1.5 to -38.4+/-1.7 mV from a holding potential of -50 mV in phasic PGN, P<0.005). PACAP did not affect the duration of the action potential. The amplitude of the spike after hyperpolarization was not changed but the duration was significantly reduced by PACAP from 204.4+/-12.2 to 106.2+/-8.1 ms in tonic but not in phasic PGN. PACAP suppressed a transient outward current that was also suppressed by 4-aminopyridine (0.5 mM). These results coupled with the immunohistochemical identification of a dense collection of PACAP fibers in the region of the PGN, raises the possibility that PACAP may function as an excitatory transmitter in lumbosacral parasympathetic reflex pathways in the neonatal rat.

Morphological and electrophysiological analysis of the peripheral and central afferent pathways from the clitoris of the cat.

Afferent neurons projecting to the clitoris of the cat were identified by WGA-HRP tracing in the S1 and S2 dorsal root ganglia. An average of 433 cells were identified on each side of the animal. 85% and 15% of the labeled cells were located in the S1 and S2 dorsal root ganglia, respectively. The average cross sectional area of clitoral afferent neuron profiles was 1,479 +/- 627 micron2. Unilateral transection of the pudendal nerve reduced the number of labeled cells to 1% of that on the control side. Central projections of clitoral afferents were identified in the lumbo-sacral segments (L7-S3) of the spinal cord. HRP labeled fibers were located in the marginal zone on the medial side of dorsal horn and extended into the dorsal half of the dorsal gray commissure. Electrophysiological recordings detected axonal volleys in the pudendal nerve and S1 dorsal root in response to electrical stimulation (threshold, 1-4 V) of the clitoral surface. Estimated axonal conduction velocities at the two sites ranged from 7-27 m/s and 0.6-30 m/s, respectively. Multi-unit recordings from dorsal roots in the lumbo-sacral segments revealed that non-noxious pressure stimulation of the clitoris evoked discharges in the S1 dorsal root. Small increases were also detected in the S2 and L7 roots. Single unit discharges recorded from S1 dorsal roots were activated by electrical stimulation of the clitoral surface at thresholds of 0.6-1.2 V and latencies of 1.5-1.8 ms (estimated conduction velocities of 24-30 m/s.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological properties of lumbosacral preganglionic neurons in the neonatal rat spinal cord.

The electrophysiological properties of parasympathetic preganglionic neurons (PGN) in L6 and S1 spinal cord slices from neonatal rats were studied using the patch clamp techniques. PGN were identified by retrograde axonal transport of a fluorescent dye (Fast Blue) injected intraperitoneally before the experiment. PGN in the intermediolateral region of the spinal cord were divided into two classes (tonic PGN and phasic PGN) on the basis of firing properties during prolonged (300 ms) depolarizing current pulses. Tonic neurons exhibited a prolonged discharge (average maximum: 5.6); whereas phasic PGN fired on average only 1.4 spikes during depolarizing pulses. PGN were usually oval in shape. The mean long axis of tonic PGN (20.7+/-0.5 microm) was significantly (P<0.05) larger than that of phasic PGN (16.7+/-0.3 microm). Tonic and phasic PGN had similar resting membrane potentials, thresholds for spike activation, input resistances and action potential durations. The duration of the after-hyperpolarization (AHP) in tonic PGN (200.5+/-11.9 ms) was longer than in phasic PGN (137.6+/-9.8 ms). 4-aminopyridine (4-AP, 0. 5 mM) reduced the threshold for spike activation in tonic and phasic PGN. 4-AP also unmasked tonic firing in phasic PGN (average maximum: 5.5 spikes during 300 ms depolarizing current pulses) and increased firing frequency by 19% in tonic PGN. These data indicate that the different discharge patterns of parasympathetic PGN are dependent in part on differences in the expression of 4-AP-sensitive K(+) channels. The two types of PGN may provide an innervation to different targets in the pelvic viscera.

Vasoactive intestinal polypeptide identified in the thoracic dorsal root ganglia of the cat.

Neurons which exhibited vasoactive intestinal polypeptide (VIP) immunoreactivity were identified with immunohistochemical techniques in the cat thoracic dorsal root ganglia (DRG, T8-T11) injected with colchicine 2 days prior to sacrifice. VIP-positive cells (5-40 cells per section) were small to medium size ranging from 14-41 micron in diameter. VIP-immunoreactivity was weaker in the thoracic DRG exposed to colchicine by topical administration. The neuropeptide could not be detected in the thoracic DRG (T1-T13) in the absence of colchicine. VIP-immunoreactivity was also identified in the superficial laminae (I and II) of the thoracic spinal cord. The findings indicate that VIP in afferent pathways in the cat is distributed more extensively than previously reported and is not restricted only to the lower lumbar and sacral levels of the spinal cord.

Vasoactive intestinal polypeptide elicits a discharge in chronically decentralized sympathetic ganglia.

Vasoactive intestinal polypeptide (VIP, 5-50 micrograms) injected intraarterially to the chronically decentralized cat superior cervical ganglion elicited a prolonged (2-5 min) postganglionic discharge which was resistant to cholinergic blocking agents but was blocked by [Leu5]enkephalin and GABA (10-200 micrograms i.a.). VIP did not elicit a discharge in acutely decentralized ganglia. These findings indicate that VIP has direct excitatory effects on ganglion cells and that these excitatory effects are enhanced following degeneration of the preganglionic nerve terminals.

Postnatal development of opioid regulation of micturition in the kitten.

Endogenous opioids tonically regulate micturition in adult mammals. The present study sought to determine if opioids regulate micturition in neonatal kittens. Naloxone (up to 2 mg/kg given i.p. or i.v. to unanesthetized/ketamine-anesthetized or chloralose-anesthetized kittens, respectively), an opioid receptor antagonist, produced no effects in unanesthetized, ketamine-anesthetized, or chloralose-anesthetized kittens that had been prepared for bladder pressure recording, until 3 weeks of age. This indicates that endogenous opioids are not tonically regulating micturition in neonatal kittens. From 3 weeks up to at least 6 weeks of age, naloxone (100 micrograms/kg i.p. or i.v.) weakly facilitated bladder activity by transiently increasing the amplitude and/or duration of bladder contractions, but no effects on frequency of contractions was recorded. Morphine (up to 2 mg/kg given i.p. or i.v. to unanesthetized/ketamine-anesthetized or chloralose-anesthetized kittens, respectively), an opioid agonist, did not inhibit bladder contractions in unanesthetized or ketamine-anesthetized neonatal kittens, but it did inhibit (at a threshold dose of 100 micrograms/kg) and completely abolished (at a dose of 300 micrograms/kg) bladder activity in chloralose-anesthetized kittens in a dose-dependent, naloxone-reversible manner. Surprisingly, following morphine administration to unanesthetized or ketamine-anesthetized neonatal kittens, naloxone now produced an adult-like enhancement of bladder activity. These latter results indicate that opioid receptors, whose inhibitory effects are anesthetic-dependent, are present along the micturition reflex pathway in neonates. Immunohistochemical studies of the sacral spinal cord revealed that opioid peptides are distributed similarly in neonatal and adult cats.

Nitric oxide raises cytosolic concentrations of Ca2+ in cultured nodose ganglion neurons from rabbits.

The effects of donors of nitric oxide (NO), namely, S-nitroso-N-acetylpenicillamine-(SNAP) and E-methyl-2-E-hydroxyimino-5-nitro-6-methoxy-3-hexeneamide (NOR1), on cytosolic concentrations of Ca2+ ([Ca2+]i) were studied in cultured nodose ganglion neurons from newborn and young rabbits by loading with fura-2AM and microfluorometry. Application of SNAP (5 microM-1 mM) increased [Ca2+]i in 46% of neurons tested. The threshold dose of the response was 10 microM and the response increased in a dose-dependent fashion. The increase in [Ca2+]i at 50 microM averaged 74 +/- 8% above the control value. [Ca2+]i rose immediately after injection of SNAP and the plateau level was maintained in the presence of SNAP.NOR1, another donor of NO, increased [Ca2+]i with an average increase of 82 +/- 7% at 50 microM. Quantitation of NO gas in the solution of NOR1 by a redox chemiluminescence method revealed the constant release of 0.06 ppm NO from 5 ml of a 20 microM solution of NOR1. These data suggest that NO released from donors of NO induced an increase in [Ca2+]i in nodose ganglion neurons and, therefore, that NO might play a role as a transmitter or a modulator in autonomic primary sensory systems.

Inhibitory effect of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) on the micturition reflex in rat.

The effect of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an alpha-amino-hydroxy-5-methyl-4-isoxazole propionate (AMPA) glutamate receptor antagonist, on bladder contractions was examined under isometric conditions in urethane anesthetized rats. Intravenous administration of CNQX (33 ng-50 micrograms/kg) inhibited or abolished bladder contraction. Before complete inhibition, the frequency of bladder contractions was reduced without altering the amplitude or duration. Intrathecal administration of CNQX (2 ng/kg-11 micrograms/kg) similarly inhibited bladder contractions. In contrast, CNQX did not affect bladder contractions in chronically spinalized animals (6.7 ng/kg-400 micrograms/kg i.v.), or contractions evoked by stimulation of the decentralized pelvic nerve (1-100 micrograms/kg i.v.).

Optical imaging of the spontaneous neuronal activities in the male rat major pelvic ganglion following denervation of the pelvic nerve.

Measurement of groups of neuronal activities following pelvic nerve transection to the major pelvic ganglion (MPG) of the rat was performed using voltage-sensitive dye (RH795) and an optical recording system. In control MPG, averaged neuron diameters were 32.0 +/- 0.6 x 22.6 +/- 0.4 microm. Application of KCl (10-50 mM) to the ganglia exhibited excitation which increased in a dose-dependent fashion. Fluctuating membrane potentials were not observed in control ganglion neurons. After the denervation of pelvic nerve chronically (2-6 weeks), the spontaneous neuronal activities were recorded in 91% of the experiments (n = 32). The activity was occurring somewhat periodically (2-15 s). Averaged neuron diameters were 41.3 +/- 1.3 x 24.7 +/- 0.9 microm in denervated MPG which is significantly larger than control. Since average neuron size increased 4 weeks after the denervation, the new excitatory activities could have influenced the change of the neuron size. The new activities might produce contraction of target organs in the pelvic viscera.

Diode laser irradiation selectively diminishes slow component of axonal volleys to dorsal roots from the saphenous nerve in the rat.

Ga-Al-As laser irradiation (830 nm wavelength) inhibits the action potentials in the dorsal roots elicited from the saphenous nerve of the rat. Following laser irradiation to the saphenous nerve, the amplitude of slower conduction parts of action potentials (conduction velocity < 12 m/s) were suppressed. This suppression was irradiation time dependent. After 3 min irradiation, slowest conduction velocity group (< 1.3 m/s) were totally diminished and 1.3-12 m/s group were reduced to 12-67%. In contrast, faster component (> 12 m/s) was unaffected by laser irradiation. These findings suggest that laser irradiation may selectively target fibers conducting at slow velocities which include afferent axons from nociceptors.