Adult Rat Superior Cervical Ganglion Research Articles

Double-pulse calcium channel current facilitation in adult rat sympathetic neurones.

1. Double-pulse facilitation of Ca2+ channel currents in enzymatically dispersed adult rat superior cervical ganglion neurones was investigated using the whole-cell variant of the patch-clamp technique. Voltage-clamp recordings were performed at room temperature (21-24 degrees C) in solutions designed to isolate Ca2+ channel currents. 2. Ba2+ currents, elicited by a 0 mV test pulse, were increased in amplitude when preceded by a 40 ms pulse to voltages greater than 0 mV. The magnitude of facilitation was dependent on pre-pulse voltage and reached a maximum of 50% (i.e. 1.5 x the current amplitude elicited without a pre-pulse) at a pre-pulse voltage of +80 mV. Half-maximal facilitation occurred at about +25 mV. A small decrease (-6%) in test pulse amplitude was present at pre-pulse voltages between -40 and 0 mV. The magnitude of facilitation was also dependent on test pulse voltage. Facilitation was greatest between test pulse voltages of -10 and 0 mV. 3. Facilitation slowly decreased during prolonged (1 h) dialysis of the neurone even though the Ba2+ current amplitude was well maintained. 4. Increasing the pre-pulse duration over the range 0-120 ms produced an exponential increase in facilitation with a time constant of 17.3 ms. Conversely, lengthening the interpulse duration over the range 5-915 ms, while maintaining a constant pre-pulse amplitude and duration, resulted in an exponential decrease in facilitation with a time constant of 197 ms. 5. At a test potential of 0 mV, the decay of the facilitated Ba2+ current component was fitted to a double exponential function with time constants of about 25 and 150 ms. The time constants had little pre-pulse voltage dependence between +30 to +80 mV. 6. The initial rising phase of both the control and facilitated Ba2+ current were reasonably well described by a single exponential (tau rise) after a delay of 300 microseconds. The tau rise versus test pulse potential relationship was 'bell shaped' over the test pulse voltage of -20 to +30 mV reaching a maximum near -5 mV. tau rise was similar for control and facilitated currents except at potentials greater than +10 mV where the rise of the facilitated current was accelerated. 7. Control and facilitated activation curves, as derived from tail current amplitudes, were described by the sum of two Boltzmann functions. A facilitating pre-pulse produced an increase in the proportion of the current contributed by the component activated at more hyperpolarized test potentials.(ABSTRACT TRUNCATED AT 400 WORDS)

A diffusible second messenger mediates one of the pathways coupling receptors to calcium channels in rat sympathetic neurons

Muscarinic and α-adrenergic suppression of current through Ca 2+ channels was studied in adult rat superior cervical ganglion neurons using whole-cell and cell-attached configurations of the patch-clamp technique. Oxotremorine methiodide suppressed I ca by both a rapid (<1 s) and a slow (>4 s) process, whereas norepinephrine suppressed I ca only by a rapid process. The slow muscarinic suppression could be prevented by adding 20 mM BAPTA, a Ca 2+ chelator, to the recording pipette, whereas the adrenergic suppression was not affected. Muscarinic, but not α-adrenergic, receptors can couple to Ca 2+ channels by a second messenger capable of diffusing into an on-cell patch. This signal seems not to be carried by intracellular Ca 2+ cGMP, cAMP, or protein kinase C.

Norepinephrine blocks a calcium current of adult rat sympathetic neurons via an α2-adrenoceptor

The effects of α-adrenoceptor agonist and antagonist drugs on the Ca 2+ current of acutely isolated adult rat superior cervical ganglion (SCG) neurons were investigated to characterize the adrenoceptor which mediates a catecholamine-induced decrease of the Ca 2+ current. Ca 2+ currents were recorded using the whole-cell variant of the patch-clamp technique from neurons isolated enzymatically from adult rat SCG. Norepinephrine (1 μM) produced a rapid, reversible, and concentration-dependent decrease in Ca 2+ current amplitude and slowed the rising phase of the Ca 2+ current. These effects could be mimicked by clonidine (1 μM), an α 2-gonist but not by the α 1-agonist phenylephrine (1 μM). The norepinephrine-induced decrease in Ca 2+ current amplitude was attenuated in the presence of idazoxan (1 μM), an α 2-antagonist, but was unaffected in the presence of the α 1-antagonist prazosin (1 μM). Neither antagonist displayed any Ca 2+ current blocking activity. These results suggest that the α-receptor which mediates the norepinephrine-induced decrease of the Ca 2+ current in adult rat SCG neurons is of the α 2-subtype.

Muscarinic suppression of the M-current in the rat sympathetic ganglion is mediated by receptors of the M1-subtype.

1. Under voltage-clamp dissociated adult and foetal rat superior cervical ganglion (s.c.g.) cells exhibited a non-inactivating voltage- and time-dependent component of K+ current termed the M-current (IM). IM was detected and measured from the current decay during hyperpolarizing voltage steps applied from potentials where IM was pre-activated. 2. Neither the resting membrane current nor the amplitude of these current decay relaxations were reduced by omitting Ca from the bathing fluid, showing that the M-current was not a 'Ca-activated' K-current dependent on a primary Ca-influx. Concentrations of (+)-tubocurarine sufficient to block the slow Ca-activated K-current IAHP did not inhibit IM or antagonize the effect of muscarinic agonists on IM, showing that IM was not contaminated by IAHP. Tetraethylammonium (1 mM), which blocks the fast Ca-activated K-current IC, produced a small inhibition of IM. This was not due to contamination of IM by IC since muscarinic agonists did not consistently block IC. 3. The muscarinic agonists muscarine, oxotremorine, McN-A-343 and methacholine reversibly suppressed IM, resulting in an inward (depolarizing) current. The rank order of potency was: oxotremorine greater than or equal to muscarine greater than McN-A-343 greater than methacholine. 4. The suppression of IM by muscarine was similar in cultured cells derived from adult and foetal tissue to that seen in the intact ganglia. 5. IM-suppression by muscarine was inhibited by pirenzepine (Pz) and AF-DX 116 with mean pKB values of 7.53 +/- 0.13 (n = 3) and 6.02 +/- 0.13 (n = 4) respectively. 6. The suppression of IM by muscarinic agonists was not affected by gallamine (10-30 microM). 4-Diphenylacetoxy-N-methylpiperidine methiodide inhibited the response at 300 nM. 7. Pirenzepine inhibited the contractions of the guinea-pig isolated ileum produced by muscarine with a mean pKB of 6.37 +/- 0.03 (n = 8). 8. These results suggest that the receptors mediating suppression of the M-current accord with those designated pharmacologically as M1 and that these receptors reach maturity at a very early stage in the development of the rat s.c.g.

Peripheral target regulation of dendritic geometry in the rat superior cervical ganglion

Dendritic arborizations of neurons in the adult rat superior cervical ganglion were measured in control ganglia and in ganglia innervating peripheral targets that were relatively larger or smaller than normal. The relative size of the target--the submandibular gland in these experiments--was manipulated during development by changing the ratio between the amount of target tissue and the number of innervating ganglion cells. Thus, ligating the submandibular salivary duct reduced the size of the gland, whereas partially denervating the gland produced a relatively larger target by making a smaller number of ganglion cells innervate a gland of normal size. Neurons innervating targets that were smaller than normal had significantly smaller dendritic arborizations and cell bodies than control cells. Conversely, neurons projecting to relatively larger than normal targets had larger dendritic arborizations and cell bodies, and more primary dendritic branches. Such cells were also innervated by a larger than normal number of preganglionic inputs. A similar change in dendritic geometry was observed when relative target size was increased after cutting the cervical sympathetic trunk, showing that target regulation of dendritic geometry is not dependent on ganglion cell activity or the presence of presynaptic innervation. Dendrites in the superior cervical ganglion normally grow in parallel with body size throughout life (Purves et al., 1986a; Voyvodic, 1987a). The present results imply that an important aspect of dendritic growth is an ongoing responsiveness of ganglion cells to feedback signals arising from the peripheral targets they innervate.

Interaction between calcium channel ligands and guanine nucleotides in cultured rat sensory and sympathetic neurones.

1. Voltage-activated Ca2+ channel currents were recorded from cultured rat dorsal root ganglion (DRG) neurones using the whole-cell clamp technique with Ba2+ as the charge carrier. 2. Inclusion of the GTP analogue guanosine 5'-O-3-thiotriphosphate (GTP-gamma-S, 500 microM) or guanylylimidodiphosphate (GMP-PNP, 500 microM) or GTP itself (1 mM) in the patch pipette solution resulted in a smaller, slowly activating Ca2+ channel current which did not inactivate during a 100 ms voltage step. This current was inhibited by CdCl2 (10-100 microM) and omega-conotoxin (1 microM). 3. Nifedipine (5 microM), (-)-(R)-201-791 (5 microM), D600 (10 microM), and diltiazem (30 microM) inhibited Ca2+ channel currents recorded from control neurones, although in some cells a biphasic response was observed, with an initial increase preceding the inhibition of the currents. In the presence of internal GTP-gamma-S, at a holding potential (VH) of -80 mV, only potentiation of the Ca2+ channel current was observed in the presence of all three Ca2+ channel ligands. Internal GMP-PNP, while less effective than GTP-gamma-S, also resulted in D600 showing an agonist response. Similarly, in the presence of internal GTP (1 mM), (-)-(R)-202-791 gave a prolonged agonist response. 4. Nifedipine, whether acting as an antagonist in control cells or as an agonist in GTP-gamma-S-containing cells, induced a shift to more hyperpolarized potentials of the steady-state inactivation curves. 5. Potentiation of Ca2+ channel currents induced by D600 in GTP-gamma-S-containing cells, was not observed when the neurones were pre-treated with pertussis toxin. The presence of internal GDP-beta-S (500 microM) did not significantly alter the maximum inhibitory action of D600 compared with controls. However, 1 mM-GDP-beta-S increased the rate of onset of inhibition by (-)-(R)-202-791. 6. Depolarizing VH to -30 mV accelerated the onset of inhibition induced by the Ca2+ channel ligands in control cells. In the presence of internal GTP-gamma-S at VH -30 mV, biphasic responses were produced by all the Ca2+ channel antagonist ligands with initial stimulation for 1-2 min being followed by inhibition of the Ca2+ channel currents. 7. The agonist actions of (+)-(S)-202-791 were potentiated by the presence of internal GTP-gamma-S. 8. The expression of an agonist response to (-)-(R)-202-791 induced by internal GTP-gamma-S was also present in sympathetic neurones cultured from adult rat superior cervical ganglion (SCG).(ABSTRACT TRUNCATED AT 400 WORDS)

On the transduction mechanism for muscarine‐induced inhibition of M‐current in cultured rat sympathetic neurones.

1. Dissociated adult or fetal rat superior cervical ganglion cells were voltage-clamped through a single patch pipette. The voltage-dependent K+ current, IM (M-current), was maintained by including MgATP in the pipette solution and by buffering the solution pH to 6.7. 2. Bath-applied muscarine (0.4 microM) produced a reversible inhibition of IM. 3. Addition of Gpp(NH)p (200 microM) or GTP-gamma-S (500 microM) to the pipette solution induced a slowly developing inhibition of IM and prevented recovery from subsequent muscarine-induced inhibition. 4. Addition of GDP-beta-S (500 microM) to the pipette solution reduced the amount of IM inhibition produced by 0.4 microM-muscarine by 42% and reduced the associated inward shift of the holding current by 56%. 5. Cells responded normally to muscarine after pre-treatment for 4-27 h with 500 ng ml-1 pertussis toxin (PTx). 6. IM was not diminished by extracellular addition of 1 mM-dibutyryl cyclic AMP, 8-bromo-cyclic AMP or dibutyryl cyclic GMP, or of 10 microM-forskolin. 7. IM was not reduced by inclusion of Li+ (2 mM) or inositol 1,4,5-trisphosphate (IP3, 100 microM) in the patch pipette, nor by ionophoretic injection of IP3 from an inserted micropipette. 8. Addition of 4-beta-phorbol 12,13-dibutyrate (PDBu, 0.5-2 microM) to the extracellular medium partly inhibited IM and reduced an additional component of resting membrane current. This effect was not replicated by 4-alpha-phorbol 12,13-didecanoate. 9. It is concluded that the inhibition of IM by muscarine is mediated through activation of a PTx-insensitive GTP-binding protein. The effect of muscarine appears not to be mediated by cyclic nucleotides or IP3 but may possibly involve the generation of diacylglycerols and activation of protein kinase C.

Potassium currents of acutely isolated adult rat superior cervical ganglion neurons

K+ currents of adult rat superior cervical ganglion neurons were studied using the voltage-clamp technique. Neuronal somata were dissociated from the ganglion using an enzymatic dispersion technique and voltage-clamped using the whole-cell patch-clamp technique. In solutions designed to isolate K+ currents, depolarization from a prepulse potential of -100 mV induced both transient and sustained outward current components. The transient current was completely eliminated by depolarization to -50 mV. The remaining sustained current component could be separated further into Ca2+-sensitive and Ca2+-insensitive components by superfusion with a Ca2+-free external solution. The transient current, which could be isolated by digital subtraction, rose rapidly and decayed over the subsequent 80 ms. Reversal potential determinations in different K+-containing solutions demonstrated that the current was carried primarily by K+. The transient current showed voltage-dependent inactivation, showing 50% inactivation near -87 mV and was completely inactivated at potentials more positive than -60 mV. The transient current recovered from inactivation with a voltage-dependent time course, the time course of inactivation decreasing with hyperpolarization. This transient outward current had characteristics of IA. The sustained Ca2+-insensitive outward current showed little decay over 800 ms and was also carried primarily by K+. This current component had characteristics similar to the delayed rectifier. A third sustained outward current eliminated by superfusion with Ca2+-free external solution had characteristics similar to the Ca2+-dependent K+ current.

Somatostatin blocks a calcium current in rat sympathetic ganglion neurones.

1. The effects of somatostatin and somatostatin analogues on a Ca2+ current from acutely isolated and short-term (24-48 h) cultured adult rat superior cervical ganglion (SCG) neurones were studied using the whole-cell variant of the patch-clamp technique. 2. [D-Trp8]Somatostatin (SOM) produced a rapid, reversible and concentration-dependent reduction of the Ca2+ current. Ca2+ current amplitude was reduced over the voltage range -15 to +40 mV with the greatest reduction occurring where the amplitude was maximal (ca +10 mV). In the presence of SOM, the Ca2+ current rising phase was slower and biphasic at potentials between 0 and +40 mV. 3. Application of 0.1 microM-SOM for greater than 10 s resulted in a desensitization of the response. During a 4 min application of 0.1 microM-SOM, Ca2+ current amplitude returned to about 90% of control. A second application of 0.1 microM-SOM produced less block than the initial application. 4. Concentration-response curves for SOM, somatostatin-14 (SOM-14) and somatostatin-28 (SOM-28) were fitted to a single-site binding isotherm. The concentrations producing half-maximal block and the maximal attainable blocks of the Ca2+ current for SOM, SOM-14 and SOM-28 were 3.3, 5.4 and 35 nM, respectively and 55, 51 and 54%, respectively. SOM-14 and SOM-28 slowed the Ca2+ current rising phase in a manner similar to that of SOM. Somatostatin-28 had no effect on the Ca2+ current at 1 microM. 5. The magnitude of the Ca2+ current block produced by 0.1 microM-SOM was not significantly altered in the presence of 1 microM-idazoxan, atropine, naloxone or the somatostatin antagonist aminoheptanoyl-Phe-D-Trp-Lys-O-benzyl-Thr. 6. Internal dialysis with solutions containing 500 microM-guanylyl-imidodiphosphate (Gpp(NH)p) or guanosine-5'-O-(3-thiotriphosphate)(GTP-gamma-S) decreased the Ca2+ current amplitude by 36 and 41%, respectively, and induced a biphasic rising phase in the Ca2+ current. Under these conditions, application of 0.1 microM-SOM produced significantly less block of Ca2+ current amplitude (7.1 and 14.7%, respectively) when compared with controls. 7. Internal dialysis with solutions containing 500 microM-guanosine-5'-O-(2-thiodiphosphate)(GDP-beta-S) had no significant effect on either the Ca2+ current amplitude or block produced by 0.1 microM-SOM. 8. Internal dialysis with solutions containing 500 microM-cyclic adenosine 3',5'-monophosphate (cyclic AMP) and 3-isobutyl-1-methylxanthine had no significant effect on either the Ca2+ current block produced by 0.1 microM-SOM or the Ca2+ current amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatostatin cyclic octapeptide analogs which preferentially bind to SOMa receptors block a calcium current in rat superior cervical ganglion neurons

To characterize further the somastatin (SOM) receptor mediating Ca 2+ current reduction in rat superior cervical ganglion (SCG) neurons, the effects of three synthetic SOM octapeptide analogs, ▪ which bind preferentially to pituitary SOM receptors (SOMa) were investigated. Ca 2+ currents were recorded using the whole-cell variant of the patch-clamp technique from neurons isolated enzymatically from adult rat SCG. Application of the SOM analogs (0.003–3 μM) produced a rapid, reversible, and concentration-dependent decrease in Ca 2+ current amplitude in addition to slowing the rising phase of the Ca 2+ current. Estimates of the concentration producing half-maximal block (EC 50) and maximum attainable block ( B max) for DC 13–116, IM 4–28, and SMS 201–995 were 196, 67, and 9.5 nM, respectively, and 52, 57, and 48%, respectively. The results suggest that the SOM receptor on SCG neurons more closely resembles the SOMa receptor of the anterior pituitary than the SOMb receptor of cerebral cortical membranes.

Changes in expression of a synaptic vesicle antigen in aging sympathetic neurons

The effects of altering synaptic activity of sympathetic neurons on the expression of a synaptic vesicle protein (p65) were studied by deafferentation of the superior cervical ganglion (SCG) in adult and aged Fischer-344 rats. Levels of p65, an integral membrane protein of synaptic vesicles, were assayed by radioimmunoassay. After deafferentation, a transient increase in p65 levels is observed in the SCG of adult rats. In aged animals, the response to deafferentation is delayed and enhanced, and levels do not drop to values observed in operated adults. After SCG deafferentation, p65 levels in the iris, an SCG target, initially are depressed below control levels; p65 levels return to control values in adult animals after 14 days, but remain depressed in aged animals. In contrast, a transient increase in p65 levels is observed in the pineal of both adult and aged animals. These results suggest that while the aged sympathetic nervous system retains the ability to respond to alterations in synaptic activity, it is unable to reregulate once a response is initiated.

Transsynaptic impulse activity regulates postsynaptic density molecules in developing and adult rat superior cervical ganglion.

Ganglionic postsynaptic density protein (PSDp) was used to monitor the influence of transsynaptic impulse activity on synaptic structure in the developing and adult rat superior cervical sympathetic ganglion (SCG). Since transsynaptic activity is known to regulate ontogeny of postsynaptic transmitter enzymes, we initially studied the developing ganglion. Denervation in neonates prevented normal development, decreasing calmodulin binding to the ganglionic PSDp by 71% after 4 weeks. During this period, denervation elicited only a 42% decrease in total protein of the synaptic membrane fraction, suggesting that innervation regulates development of various synaptic components differentially. Effects of denervation were extremely rapid, resulting in a 44% decrease in calmodulin binding within 1 day, consistent with regulation by a signaling process such as impulse activity. The effect of impulse activity was examined more directly in adults by treatment with the agents reserpine or phenoxybenzamine, which elicit reflex increases in sympathetic transmission. Administration of reserpine resulted in a progressive 90% increase in calmodulin binding to the PSDp over 4 weeks. Phenoxybenzamine also elicited an increase, mimicking the effects of reserpine. Neither agent altered total protein of the synaptic membrane fraction, suggesting that impulse activity regulates specific synaptic components. Finally, ganglionic denervation in adults decreased PSDp binding within 12 hr, consistent with acute effects of impulse reduction. Our results suggest that transsynaptic impulse activity plays an important role in regulation of specific molecular components of the synapse.

Sodium and calcium currents of acutely isolated adult rat superior cervical ganglion neurons.

Neurons enzymatically isolated from the adult rat superior cervical ganglion (SCG) were investigated using the whole-cell variant of the patch-clamp technique. Current-clamp studies revealed the following mean passive and active membrane properties: resting membrane potential, -54.9 mV; input resistance, 349 M omega; action potential (AP) threshold, -29.8 mV; AP overshoot, 53.3 mV; AP maximum rate of rise, 166.4 V/s; and AP duration, 3.2 ms. Chemosensitivity to acetylcholine remained intact following enzymatic dispersion. Voltage-clamp studies of a transient tetrodotoxin-sensitive Na+ current revealed activation and inactivation processes which could be fit to modified Boltzmann equations. Na+ current activation parameters for the half activation potential (Vh) and slope factor (K) were -23.3 mV and 5.3 mV, respectively. Inactivation parameters for Vh and K were -59.3 mV and 7.6 mV, respectively. Voltage-clamp studies also revealed a high voltage-activated sustained inward current which was eliminated upon removal of external Ca2+, greatly reduced by 500 microM Cd2+, and supported by Ba2+ or Sr2+. Tail current analysis of this Ca2+ current revealed a sigmoidal activation. A low voltage-activated transient Ca2+ current was not observed. We conclude that isolated SCG neurons retain the properties of neurons in intact ganglia and provide several advantages over conventional preparations for the study of voltage-gated membrane currents.

Deafferentation-induced increases in a synaptic vesicle protein in the adult rat superior cervical ganglion are associated with new protein synthesis.

Previous studies have shown that deafferentation of the adult rat superior cervical ganglion results in a transient increase in levels of a 65 kDa synaptic vesicle membrane protein (SV). The present study indicates that the observed increase in SV after deafferentation is the result of new protein synthesis. Treatment with cycloheximide, a protein synthesis inhibitor, for 8 h at selected times after surgery produces decreases in SV which are greater than that observed after treatment of unoperated animals. The results suggest that an increased rate of synthesis of this protein is induced by deafferentation. Transsynaptic factors may play important roles in regulation of protein synthesis in sympathetic ganglia.

Regulation of molecular components of the synapse in the developing and adult rat superior cervical ganglion.

Rat superior cervical sympathetic ganglion was used to begin studying the regulation of molecular components of the synapse. Ganglionic postsynaptic densities (PSDs)exhibited a thin, disc-shaped profile electron microscopically, comparable to that described for brain. Moreover, the presumptive ganglionic PSD protein (PSDp) was phosphorylated in the presence of Ca2+ and calmodulin, bound 125I-labeled calmodulin, and exhibited a Mr of 51,000, all characteristic of the major PSD protein of brain. These initial studies indicated that ganglionic PSDp and the major PSD protein of brain are comparable, allowing us to study synaptic regulation in the well-defined superior cervical sympathetic ganglion. To obtain enough quantities of ganglionic PSDp, we used synaptic membrane fractions. During postnatal development, calmodulin binding to the ganglionic PSDp increased 411-fold per ganglion from birth to 60 days, whereas synaptic membrane protein increased only 4.5-fold. Consequently, different synaptic components apparently develop differently. Moreover, denervation of the superior cervical sympathetic ganglion in adult rats caused an 85% decrease in ganglionic PSDp-calmodulin binding, but denervation caused no change in synaptic membrane protein 2 weeks postoperatively. Our observations suggest that presynaptic innervation selectively regulates specific molecular components of the postsynaptic membrane structure.

Somatostatin blocks a calcium current in acutely isolated adult rat superior cervical ganglion neurons

Somatostatin-like immunoreactivity has been reported to occur in the postganglionic neurons of sympathetic ganglia. We therefore investigated the effect of somatostatin (SOM) on the Ca 2+ current in sympathetic neurons. Voltage-clamp recordings, using the whole-cell patch-clamp technique, were made from acutely isolated adult rat superior cervical ganglion (SCG) neurons in solutions (external and internal) designed to isolate Ca 2+ currents. Application of 0.001–1.0 μM [ d-Trp 8]SOM resulted in a rapid, reversible and concentration-dependent decrease in the amplitude of the Ca 2+ current evoked from a holding potential of −80 mV. The concentration-response relationship for SOM could be fitted to a single-site binding model with an apparent dissociation constant of 11 nM; the maximal attainable block of Ca 2+ current by SOM was 50%. SOM also produced a pronounced slowing of the Ca 2+ current rising phase, especially at more depolarized potentials. At higher concentrations (0.03 1.0 μM), prolonged application of SOM resulted in a progressive decrease in blocking ability. The results are consistent with a neurotransmitter and/or neuromodulator role for SOM in the sympathetic nervous system.

Neurofilament-like and glial fibrillary acidic protein-like immunoreactivities in rat and guinea-pig sympathetic ganglia in situ and after perturbation.

The presence of neurofilament (NF)-like and glial fibrillary acidic protein (GFAP)-like immunoreactivities was studied in sympathetic ganglia of adult rats and guinea pigs during normal conditions and after perturbation. In the superior cervical ganglion (SCG) of normal rats, many ganglion cells and nerve fibers show NF immunoreactivity. Some of these nerve fibers disappear after preganglionic decentralization of SCG; this indicates the presence of a mixture of pre- and postganglionic NF-positive nerves in the ganglion. Cuts in both pre- and postganglionic nerves result in a marked increase in GFAP immunoreactivity in SCG, whereas NF immunoreactivity increases in nerve cell bodies after preganglionic cuts. Only a few ganglion cells show NF immunoreactivity in the normal SCG of guinea pig. All intraganglionic NF-positive nerves are of preganglionic origin; decentralization abolishes NF immunoreactivity in these nerve fibers. The inferior mesenteric ganglion, the hypogastric nerves and colonic nerves in guinea pigs contain large numbers of strongly NF-immunoreactive nerve fibers. When the SCG of adult rat is grafted to the anterior eye chamber of adult rat recipients, both ganglionic cell bodies and nerve fibers, forming on the host iris from the grafted ganglion, are NF-positive. As only the perikarya of these neurons normally exhibit NF immunoreactivity, and the terminal iris arborizations are NF-negative, it appears that the grafting procedure causes NF immunoreactivity to become more widespread in growing SCG neurons.

Membrane currents in adult rat superior cervical ganglia in dissociated tissue culture

Intracellular and whole-cell recordings were made from young adult superior cervical ganglion neurones maintained in dissociated tissue culture. The neurones possessed an M-current, A-current and calcium-activated potassium currents in addition to inward sodium and calcium currents. The properties of these currents closely resembled those observed in intact sympathetic ganglia. In contrast to neurones cultured from foetal tissue, these adult cultures exhibited consistent responses to nicotinic agonists.

Plasticity of expression of a synaptic vesicle antigen in adult rat superior cervical ganglion

The effects of deafferentation and alterations of synaptic activity on levels of a synaptic vesicle-specific membrane protein (SV) were studied in the adult rat superior cervical ganglion (SCG) in vivo, using a monoclonal antibody directed against the protein. Levels of SV were quantified by radioimmunoassay. Deafferentation of the SCG results in a transient increase in SV levels in the SCG on days 7 and 10 after surgery, with levels then dropping below control levels on days 14, 21, and 30 after surgery. Immunohistochemical labeling of deafferented ganglia indicates that the increase is confined to the perikarya of principal ganglionic neurons. Levels of SV in an SCG target tissue, the iris, do not differ from control levels on day 7 after deafferentation, but are elevated at days 10, 14, and 30 after surgery. After reinnervation of the SCG, levels of SV in the SCG are elevated above control values, but do not differ from control values in the iris. Treatment with chlorisondamine, which blocks synaptic transmission in sympathetic ganglia, produces a significant increase in SV levels in the SCG after 7 d of treatment. Long-term chlorisondamine treatment results in reductions in SV in the SCG after 14 and 28 d. Treatment with phenoxybenzamine for 6 d, which reflexly increases synaptic activity, produces a marked decrease in SV in the SCG. These results suggest that activity, mediated by transsynaptic factors, contributes to the regulation of synthesis of a synaptic vesicle protein in the SCG. The results further suggest that accumulation of synaptic vesicles in terminals of the principal ganglion neurons may help regulate the maintenance of normal synaptic vesicle pools within sympathetic neurons.

Promotion by sodium bromide of functional synapse formation from foreign nerves in the superior cervical ganglion of adult rat with intact preganglionic nerve supply

The possible effect of sodium bromide (NaBr) (a substance with known inhibitory action on synaptic transmission) was studied on synapse formation with foreign nerves, implanted into the superior cervical ganglion of adult rats. It was found that in spite of the presence of preganglionic nerve supply, both implanted nerves (n.XII and n.X, respectively) were enabled to establish functional synapses with the principal ganglion cells in NaBr-treated animals. In contrast, synapse formation was almost absent in ganglia of sodium chloride drinking (control) rats with intact preganglionic nerve supply. This effect of NaBr is considered to be analogous to that of GABA, whose promoting action on synaptogenesis in adult rat superior cervical ganglion has been previously described.