The nicotinic activation of the denervated sympathetic neuron of the rat.

Nicotinic responses to endogenous acetylcholine and to exogenously applied agonists have been studied in the intact or denervated rat sympathetic neuron in vitro, by using the two-microelectrode voltage-clamp technique. Preganglionic denervation resulted in progressive decrease of the synaptic current (excitatory postsynaptic current, EPSC) amplitude, which disappeared within 24 h. These effects were accompanied by changes in ion selectivity of the nicotinic channel (nAChR). The extrapolated EPSC null potential (equilibrium potential for acetylcholine action, E(Syn)) shifted from a mean value of -15.9+/-0.7 mV, in control, to -7.4+/-1.6 mV, in denervated neurons, indicating a decrease of the permeability ratio for the main components of the synaptic current (P(K)/P(Na)) from 1.56 to 1.07. The overall properties of AChRs were investigated by applying dimethylphenylpiperazinium or cytisine and by examining the effects of endogenous ACh, diffusing within the ganglion after preganglionic tetanization in the presence of neostigmine. The null potentials of these macrocurrents (equilibrium potential for dimethylphenylpiperazinium action, E(DMPP); and equilibrium potential for diffusing acetylcholine, E(ACh), respectively) were evaluated by applying voltage ramps and from current-voltage plots. In normal neurons, E(Syn) (-15.9+/-0.7 mV) was significantly different from E(DMPP) (-26.1+/-1.0) and E(ACh) (-31.1+/-3.3); following denervation, nerve-evoked currents displayed marked shifts in their null potentials (E(Syn)=-7.4+/-1.6 mV), whereas the amplitude and null potential of the agonist-evoked macrocurrents were unaffected by denervation and its duration (E(DMPP)=-26.6+/-1.2 mV). It is suggested that two populations of nicotinic receptors, synaptic and extrasynaptic, are present on the neuron surface, and that only the synaptic type displays sensitivity to denervation.

Biophysical properties of the silent and activated rat sympathetic neuron following denervation.

A biophysical description of the denervated rat sympathetic neuron is reported, obtained by the two-electrode voltage-clamp technique in mature intact superior cervical ganglia in vitro. At membrane potential values negative to -50 mV, the normal, quiescent neuron displays voltage-dependent K and Cl conductances; following direct or synaptic stimulation (15Hz for 10 s), the neuron moves to a new resting state characterized by increased amplitude and voltage dependence of Cl conductance. Denervation produces two main effects: 1) resting Cl conductance gradually increases while its voltage-dependence decreases; by 30 days a high-conductance resting state prevails, almost independent of membrane potential in the -50/-110 mV range; 2) the increase in amplitude and voltage-dependence of Cl conductance, produced by direct stimulation in control neurons, is less marked in denervated neurons, and is observed over an increasingly small range of membrane potentials. Thirty days after denervation, the prevailing high-conductance resting state appears virtually insensitive to changes in membrane potential and stimulation. Voltage-dependent potassium currents involved in spike electrogenesis (the delayed compound potassium current and the fast transient potassium current) exhibit an early drastic decrease in peak amplitude in the denervated neuron; the effect is largely reversed after 6 days. Remarkable changes in fast transient potassium current kinetics occur following denervation: the steady-state inactivation curve shifts by up to +15 mV toward positive potential and voltage sensitivity of inactivation removal becomes more steep. A comprehensive mathematical model of the denervated neuron is presented that fits the neuron behavior under current-clamp conditions. It confirms that neuronal excitability is tuned by the conductances (mostly chloride conductance) that control the resting membrane potential level, and by fast transient potassium current. Impairment of the latter reduces both inward threshold charge for firing and spike repolarization rate, and fast transient potassium current failure cancels the voltage dependence of both processes.

Synaptic stimulation of nicotinic receptors in rat sympathetic ganglia is followed by slow activation of postsynaptic potassium or chloride conductances.

Two slow currents have been described in rat sympathetic neurons during and after tetanization of the whole preganglionic input. Both effects are mediated by nicotinic receptors activated by native acetylcholine (ACh). A first current, indicated as IAHPsyn, is calcium dependent and voltage independent, and is consistent with an IAHP-type potassium current sustained by calcium ions accompanying the nicotinic synaptic current. The conductance activated by a standard synaptic train was approximately 3.6 nS per neuron; it was detected in isolation in 14 out of a 52-neuron sample. A novel current, IADPsyn, was described in 42/52 of the sample as a post-tetanic inward current, which increased in amplitude with increasing membrane potential negativity and exhibited a null-point close to the holding potential and the cell momentary chloride equilibrium potential. IADPsyn developed during synaptic stimulation and decayed thereafter according to a single exponential (mean tau = 148.5 ms) in 18 neurons or according to a two-exponential time course (tau = 51.8 and 364.9 ms, respectively) in 19 different neurons. The mean peak conductance activated was approximately 20 nS per neuron. IADPsyn was calcium independent, it was affected by internal and external chloride concentration, but was insensitive to specific blockers (anthracene-9-carboxylic acid, 9AC) of the chloride channels open in the resting neuron. It is suggested that gADPsyn represents a specific chloride conductance activatable by intense nicotinic stimulation; in some neurons it is even associated with single excitatory postsynaptic potentials (EPSCs). Both IAHP and IADPsyn are apparently devoted to reduce neuronal excitability during and after intense synaptic stimulation.

Nicotinic EPSCs in intact rat ganglia feature depression except if evoked during intermittent postsynaptic depolarization.

The involvement of the postsynaptic membrane potential level in controlling synaptic strength at the ganglionic synapse was studied by recording nicotinic fast synaptic currents (EPSCs) from neurons in the intact, mature rat superior cervical ganglion, using the two-electrode voltage-clamp technique. EPSCs were evoked by 0.05-Hz supramaximal stimulation of the preganglionic sympathetic trunk over long periods; their peak amplitude (or synaptic charge transfer) over time appeared to depend on the potential level of the neuronal membrane where the nicotinic receptors are embedded. EPSC amplitude remained constant (n = 6) only if ACh was released within repeated depolarizing steps of the postganglionic neuron, which constantly varied between -50 and -20 mV in consecutive 10-mV steps, whereas it decreased progressively by 45% (n = 9) within 14 min when the sympathetic neuron was held at constant membrane potential. Synaptic channel activation, channel ionic permeation and depolarization of the membrane in which the nicotinic receptor is localized must occur simultaneously to maintain constant synaptic strength at the ganglionic synapse during low-rate stimulation (0.03-1 Hz). Different posttetanic (20 Hz for 10 s) behaviors were observed depending on the mode of previous stimulation. In the neuron maintained at constant holding potential during low-rate stimulation, the depressed EPSC showed posttetanic potentiation, recovering approximately 23% of the mean pretetanic values (n = 10). The maximum effect was immediate in 40% of the neurons tested and developed over a 3- to 6-min period in the others; thereafter potentiation vanished within 40 min of 0.05-Hz stimulation. In contrast, no statistically significant synaptic potentiation was observed when EPSC amplitudes were kept constant by repeated -50/-20-mV command cycles (n = 12). It is suggested that, under these conditions, posttetanic potentiation could represent an attempt at recovering the synaptic strength lost during inappropriate functioning of the ganglionic synapse.

Participation of a chloride conductance in the subthreshold behavior of the rat sympathetic neuron.

The presence of a novel voltage-dependent chloride current, active in the subthreshold range of membrane potential, was detected in the mature and intact rat sympathetic neuron in vitro by using the two-microelectrode voltage-clamp technique. Hyperpolarizing voltage steps applied to a neuron held at -40/-50 mV elicited inward currents, whose initial magnitude displayed a linear instantaneous current-voltage (I-V) relationship; afterward, the currents decayed exponentially with a single voltage-dependent time constant (63.5 s at -40 mV; 10.8 s at -130 mV). The cell input conductance decreased during the command step with the same time course as the current. On returning to the holding potential, the ensuing outward currents were accompanied by a slow increase in input conductance toward the initial values; the inward charge movement during the transient ON response (a mean of 76 nC in 8 neurons stepped from -50 to -90 mV) was completely balanced by outward charge displacement during the OFF response. The chloride movements accompanying voltage modifications were studied by estimating the chloride equilibrium potential (E(Cl)) at different holding potentials from the reversal of GABA evoked currents. [Cl(-)](i) was strongly affected by membrane potential, and at steady state it was systematically higher than expected from passive ion distribution. The transient current was blocked by substitution of isethionate for chloride and by Cl(-) channel blockers (9AC and DIDS). It proved insensitive to K(+) channel blockers, external Cd(2+), intracellular Ca(2+) chelators [bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA)] and reduction of [Na(+)](e). It is concluded that membrane potential shifts elicit a chloride current that reflects readjustment of [Cl(-)](i). The cell input conductance was measured over the -40/-120-mV voltage range, in control medium, and under conditions in which either the chloride or the potassium current was blocked. A mix of chloride, potassium, and leakage conductances was detected at all potentials. The leakage component was voltage independent and constant at approximately 14 nS. Conversely, gCl decreased with hyperpolarization (80 nS at -40 mV, undetectable below -110 mV), whereas gK displayed a maximum at -80 mV (55.3 nS). Thus the ratio gCl/gK continuously varied with membrane polarization (2.72 at -50 mV; 0.33 at -110 mV). These data were forced in a model of the three current components here described, which accurately simulates the behavior observed in the "resting" neuron during membrane migrations in the subthreshold potential range, thereby confirming that active K and Cl conductances contribute to the genesis of membrane potential and possibly to the control of neuronal excitability.

A model of signal processing at a mammalian sympathetic neurone.

A computational model has been developed for the action potential and, more generally, the electrical behaviour of the rat sympathetic neurone. The neurone is simulated as a complex system in which five voltage-dependent conductances (gNa, gCa, gKV, gA, gKCa), one Ca2+-dependent voltage-independent conductance (gAHP) and the activating synaptic conductance coexist. The individual currents are mathematically described, based on a systematic analysis obtained for the first time in a mature and intact mammalian neurone using two-electrode voltage-clamp experiments. The simulation initiates by setting the starting values of each variable and by evaluating the holding current required to maintain the imposed membrane potential level. It is then possible to simulate current injection to reproduce either the experimental direct stimulation of the neurone or the physiological activation by the synaptic current flow. The subthreshold behaviour and the spiking activity, even during long-lasting current application, can be analysed. At every time step, the program calculates the amplitude of the individual currents and the ensuing changes; it also takes into account the accompanying K+ accumulation process in the perineuronal space and changes in Ca2+ load. It is shown that the computed time course of membrane potential must be filtered, in order to reproduce the limited bandwidth of the recording instruments, if it is to be compared with experimental measurements under current-clamp conditions. The membrane potential trajectory and single current data are written in files readable by graphic software. Finally, a screen image is obtained which displays in separate graphs the membrane potential time course, the synaptic current and the six ionic current flows. The simulated action potentials are comparable to the experimental ones as concerns overshoot amplitude and rising and falling rates. Therefore, this program is potentially helpful in investigating many aspects of neurone behaviour.

Synaptic current at the rat ganglionic synapse and its interactions with the neuronal voltage-dependent currents.

The membrane current activated by fast nicotinic excitation of intact and mature rat sympathetic neurons was studied at 37 degrees C, by using the two-microelectrode voltage-clamp technique. The excitatory postsynaptic current (EPSC) was modeled as the difference between two exponentials. A fast time constant (tau2; mean value 0.57 ms), which proves to be virtually voltage-independent, governs the current rise phase and a longer time constant (tau1; range 5.2-6.8 ms in 2 mM Ca2+) describes the current decay and shows a small negative voltage dependence. A mean peak synaptic conductance of 0.58 muS per neuron is measured after activation of the whole presynaptic input in 5 mM Ca2+ external solution (0.40 muS in 2 mM Ca2+). The miniature EPSCs also rise and decay with exponential time constants very similar to those of the compound EPSC recorded at the same voltage. A mean peak conductance of 4.04 nS is estimated for the unitary event. Deconvolution procedures were employed to decompose evoked macrocurrents. It is shown that under appropriate conditions the duration of the driving function describing quantal secretion can be reduced to <1 ms. The shape of the EPSC is accurately mimicked by a complete mathematical model of the sympathetic neuron incorporating the kinetic properties of five different voltage-dependent current types, which were characterized in a previous work. We show that IA channels are opened by depolarizing voltage steps or by synaptic potentials in the subthreshold voltage range, provided that the starting holding voltage is sufficiently negative to remove IA steady-state inactivation (less than -50 mV) and the voltage trajectories are sufficiently large to enter the IA activation range (greater than -65 mV). Under current-clamp conditions, this gives rise to an additional fast component in the early phase of membrane repolarization-in response to voltage pulses-and to a consistent distortion of the excitatory postsynaptic potential (EPSP) time course around its peak-in response to the synaptic signal. When the stimulation initiates an action potential, IA is shown to significantly increase the synaptic threshold conductance (up to a factor of 2 when IA is fully deinactivated), compared with that required when IA is omitted. The voltage dependence of this effect is consistent with the IA steady-state inactivation curve. It is concluded that IA, in addition to speeding up the spike repolarization process, also shunts the excitatory drive and delays or prevents the firing of the neuron action potential.

N-(2-hydroxyethyl)hexadecanamide is orally active in reducing edema formation and inflammatory hyperalgesia by down-modulating mast cell activation.

Mast cells play a key role in inflammatory reactions triggered by tissue injury or immune perturbations. Little is known about endogenous molecules and mechanisms capable of modulating inappropriate mast cell activity. N-(2-Hydroxyethyl)hexadecanamide (palmitoylethanolamide), found in peripheral tissues, has been proposed to act as a local autacoid capable of negatively regulating mast cell activation and inflammation-hence the acronym Autacoid Local Inflammation Antagonism (ALIA). Recently, N-(2-hydroxyethyl)hexadecanamide (LG 2110/1) has been reported to down-modulate mast cell activation in vitro by behaving as an agonist at the peripheral cannabinoid CB2 receptor. Here, we have characterized and functionally correlated the anti-inflammatory actions of LG 2110/1 with its ability to control mast cell activation, when given orally in a battery of rodent models of inflammation. LG 2110/1 diminished, in a dose-dependent and correllated manner, the number of degranulated mast cells and plasma extravasation induced by substance P injection in the mouse ear pinna. In addition, LG 2110/1 reduced dose dependently plasma extravasation induced by passive cutaneous anaphylaxis reaction. In adult rats LG 2110/1 decreased, in a dose-dependent manner, carrageenan-induced hindpaw edema and hyperalgesia, but not phospholipase A2-induced hindpaw edema. Further, anti-edema effects were observed when utilizing dextran and formalin, known to also cause mast cell activation. Locally administered LG 2110/1 was likewise effective in minimizing dextran-induced hind paw edema. In contrast, equivalent amounts of palmitic acid plus ethanolamine were ineffective against plasma extravasation provoked by substance P. LG 2110/1 did not decrease plasma extravasation induced by the substance P fragment, substance P-(6-11), known to be inactive on mast cells. These results indicate that orally administered N-(2-hydroxyethyl)hexadecanamide is effective in: (a) directly down-modulating mast cell activation in vivo; (b) suppressing pathological consequences initiated by mast cell activation independently of the activating stimuli; (c) exerting an anti-inflammatory action distinguishable from that of classical steroidal and non-steroidal anti-inflammatory agents. These findings raise the possibility that N-(2-hydroxyethyl)hexadecanamide and related saturated N-acylamides ('ALIAmides') represent novel therapeutic agents useful in the management of inflammatory disease conditions.

The slow Ca(2+)-activated K+ current, IAHP, in the rat sympathetic neurone.

1. Adult and intact sympathetic neurones of the rat superior cervical ganglion maintained in vitro at 37 degrees C were analysed using the two-electrode voltage-clamp technique in order to investigate the slow component of the Ca(2+)-dependent K+ current, IAHP. 2. The relationship between the after-hyperpolarization (AHP) conductance, gAHP, and estimated Ca2+ influx resulting from short-duration calcium currents evoked at various voltages proved to be linear over a wide range of injected Ca2+ charge. An inflow of about 1.7 x 10(7) Ca2+ ions was required before significant activation of gAHP occurred. After priming, the gAHP sensitivity was about 0.3 nS pC-1 of Ca2+ inward charge. 3. IAHP was repeatedly measured at different membrane potentials; its amplitude decreased linearly with membrane hyperpolarization and was mostly abolished close to the K+ reversal potential, EK (-93 mV). The monoexponential decay rate of IAHP was a linear function of total Ca2+ entry and was not significantly altered by membrane potential in the -40 to -80 mV range. 4. Voltage-clamp tracings of IAHP could be modelled as a difference between two exponentials with tau on approximately 5 ms and tau off = 50-250 ms. 5. Sympathetic neurones discharged only once at the onset of a long-lasting depolarizing step. If IAHP was selectively blocked by apamin or D-tubocurarine treatments, accommodation was abolished and an unusual repetitive firing appeared. 6. Summation of IAHP was demonstrated under voltage-clamp conditions when the depolarizing steps were repeated sufficiently close to one another. Under current-clamp conditions the threshold depolarizing charge for action potential discharge significantly increased with progressive pulse numbers in the train, suggesting that an opposing conductance was accumulating with repetitive firing. This frequency-dependent spike firing ability was eliminated by pharmacological inhibition of the slow IAHP. 7. The IAHP was significantly activated by a single action potential; it was turned on cumulatively by Ca2+ load during successive action potential discharge and acted to further limit cell excitability.

Orally administered glycolipid derivative LIGA20 reduces infarct volume and behavioral impairment after focal cerebral ischemia.

The efficacy of p.o. semisynthetic glycolipid LIGA20 (II3Neu5-AcGgOse4-2-d-erythro-1,3-dihydroxy-2-dichloro-aceta mide-4-trans- octadecene) treatment in stroke was studied in a permanent left middle cerebral artery occlusion model in the rat. A dose-dependent increase of plasma LIGA20 and its presence in the brain were documented after p.o. drug application. Oral administration of 50 to 200 mg/kg of LIGA20, initiated 24 hr before middle cerebral artery occlusion and continued for 7 days, reduced the motor and cognitive impairment after the stroke, measured by the rotarod and the passive avoidance test, respectively. The 10-mg/kg dose was effective when given i.v. but not p.o. Oral treatment with 100 mg/kg of LIGA20 reduced the infarct size in the cortex but not in the ischemic core (the striatum). No biochemical or behavioral adverse effects of LIGA20 treatment were observed. Further studies are needed to evaluate the full therapeutic potential of this compound.

Nerve growth factor promotes functional recovery of retinal ganglion cells after ischemia.

PURPOSE: To investigate the effect of a transient complete ischemia on the function of cat retina and to determine whether nerve growth factor (NGF), which was previously shown to enhance retinal ganglion cell (RGC) survival after optic nerve section in the adult rat, can promote recovery of retinal neurons after the ischemic insult. METHODS: Function of distal and proximal retina was assessed by recording the electroretinogram in response to both homogeneous flickering light (FERG) and contrast reversing gratings (PERG), respectively, 30 days after the induction of a 60-minute episode of ischemia. Visual evoked potentials in response to contrast reversing gratings were also recorded to evaluate visual acuity and contrast thresholds. Cell survival after ischemia was assessed in retinal whole-mounts stained with cresyl violet. Cats were intraocularly treated with NGF every other day, 3 times a week, for 30 days. Controls were treated with either phosphate buffered saline or cytochrome c. RESULTS: After ischemia, the FERG was not significantly affected. On the contrary, the PERG, visual acuity, and contrast thresholds were severely impaired. After NGF treatment, PERG response amplitudes were much less reduced compared to controls, and visual acuity and contrast thresholds were virtually normal. In addition, a larger number of presumed RGCs was present in the NGF-treated retinas compared to the cyt c-treated ones. CONCLUSIONS: The more proximally located retinal neurons, in particular RGCs, are highly vulnerable to ischemia. Intraocular NGF treatment was effective in enhancing the survival and functional recovery of these neurons. This suggests that NGF may represent a novel therapeutic agent for the treatment of ischemic ocular pathologies.

Time course, localization and pharmacological modulation of immediate early inducible genes, brain-derived neurotrophic factor and trkB messenger RNAs in the rat brain following photochemical stroke.

A focal, unilateral thrombotic stroke was produced in the rat sensorimotor cortex. The time course of expression and localization of the immediate early inducible genes: c-fos, c-jun, zif268; nerve growth factor, brain-derived neurotrophic factor and the related tyrosine kinase high-affinity receptor (trkB) messenger RNAs were studied by in situ hybridization. The levels of messenger RNAs for c-fos, zif268, brain-derived neurotrophic factor (but not nerve growth factor) and trkB were consistently increased in cortex ipsilaterally to the lesion, while c-jun messenger RNA content was only slightly increased. The brain-derived neurotrophic factor messenger RNA was increased from 2 to 18 h following the stroke, mainly in cells having a normal morphological appearance. The trkB messenger RNA displayed temporal and spatial increases similar to brain-derived neurotrophic factor messenger RNA. The time course and pattern of expression of immediate early inducible gene and trophic factor messenger RNAs did not clearly support a causal relationship between these two families of factors. The observed messenger RNA increases were greatly attenuated by the non-competitive N-methyl-D-aspartate-sensitive glutamate receptor antagonist (+)-5-methyl-10,11-dihydroxy-5H-dibenzo(a,d)cyclohepten-5,10-imine , but substantially unaffected by the non-N-methyl-D-aspartate receptor antagonist 2,3-dihydroxy-6-nitrosulphanoylbenzoquinoxaline. The results suggest a major contribution of N-methyl-D-aspartate-sensitive glutamate receptor activation to the transcriptionally directed events subsequent to stroke. Future studies should clarify the contribution of these processes to either the progression of neuronal degeneration or the establishment of protective compensatory responses.

Effects of nerve growth factor on neuronal plasticity of the kitten visual cortex.

1. The effect of intraventricular administration of nerve growth factor (NGF) by means of a cannula-minipump system was studied in kittens monocularly deprived during the critical period. The ocular dominance of area 17 neurones of NGF-treated and control kittens was determined by conventional extracellular recordings. The soma size of cells in A and A1 laminae of the lateral geniculate nucleus (LGN) was also evaluated in Cresyl Violet preparations. 2. Binocularly responsive neurons were found to be significantly more numerous in NGF-treated than in control kittens. The shrinkage of cells from the deprived LGN laminae normally observed in control kittens was prevented by NGF administration. 3. Following an initial period of monocular deprivation (MD) kittens subsequently treated with NGF showed a substantial recovery of functional binocular connections. 4. These findings indicate that the administration of NGF during the period of deprivation reduces the amblyopic effects of MD, while its administration to kittens with both eyes open following the initial deprivation promotes recovery of the deprived eye. 5. Neurotrophic factors may contribute to the regulation of experience-dependent modifications of synaptic connectivity in the visual cortex.

Photochemical stroke and brain-derived neurotrophic factor (BDNF) mRNA expression.

In situ hybridization and Northern blotting were used to study the expression of brain-derived neurotrophic factor (BDNF) mRNA in the rat brain following photochemical stroke. A focal thrombotic lesion of the sensorimotor cortex was produced by intravenously injecting the light-sensitive dye rose bengal and exposing the skull to a controlled beam of light. Four hours after the light exposure the level of BDNF mRNA was increased in the hippocampus and cortex ipsilateral and perifocal to the lesion. The stroke-induced BDNF mRNA increase was prevented by the non-competitive glutamate receptor blocker dizocilpine (MK-801). The results indicate that the activation of N-methyl-D-aspartate (NMDA)-sensitive glutamate receptors is involved in the stroke-triggered stimulation of BDNF mRNA increase.

N-methyl-D-aspartate-induced neurotoxicity in the adult rat retina.

The present study provides evidence that the adult mammalian retina is highly sensitive to the excitotoxic action of NMDA. In particular, we have investigated the effects of a single intravitreal injection of different doses of N-methyl-D-aspartate (NMDA) (2-200 nmoles) on the adult rat retina. Morphological evaluation of transverse sections of retinae demonstrated a dose-dependent loss of cells in the ganglion cell layer (GCL) and a reduction in the thickness of the inner plexiform layer. No obvious alterations were noted in the more distal retinal layers. Quantitative analyses of Nissl-stained whole-mounted retinae revealed that administration of 20 nmoles of NMDA resulted in a 70% loss of cells with a soma diameter greater than 8 microns (presumed retinal ganglion cells); a 20% loss of cells with a soma diameter smaller than 8 microns (presumed displaced amacrine cells) was also observed. In addition, NMDA produced a dose-dependent decrease of retinal choline acetyltransferase (ChAT) activity, suggesting that NMDA affects cholinergic amacrine cells as well. MK-801, a non-competitive NMDA antagonist, completely prevented the NMDA-induced loss of cells in the GCL and blocked, in a dose-dependent manner, the NMDA-induced decrease of ChAT activity. The excitotoxic action of NMDA observed in these experiments is thus likely mediated through the NMDA receptor subtype. This "in vivo" model may be utilized to identify potential drugs that antagonize or limit the deleterious effects consequent to NMDA receptor overstimulation in the central nervous system.

Genetic structures in the Po Delta: principal components, systemic functions and the relative age of the beta-thalassemia polymorphism.

The principal component representations of the genetic structure of the human population of the Po Delta, obtained from 7 polymorphic loci, are compared with the representations obtained from the systemic function of gene frequencies devised by Womble 1951. It is noted that, when tridimensional representations are used, some consistency is visible in the results of the two methods for the description of the genetic population structure in the area under study. Both methods indicate that the present structure of the balanced polymorphism for beta-thalassemia in the area appears to be more recent than the structure of the neutral polymorphisms studied.

Isonymy in records of births and deaths in Ferrara.

Surname distributions were studied in records of male and female births in Ferrara in the period 1982-89, and in records of male and female deaths in the same period. Average year of birth and standard deviation was 1985 +/- 2.3 for the birth series, and 1912 +/- 14.4 for the death series. Then the surname distributions, in two independent samples at an average distance of 73 years, were compared. It was observed that random isonymy within series, which depends on the shape of the distribution, stays fairly constant at three generations of distance, indicating near-equilibrium of surname turnover. The migrational contribution is indicated by the significant decrease of random isonymy between series, measured with the method of Lasker. It was also observed that immigrants to Ferrara have a life-span significantly longer than people born in the town.

PIP: In the study of surname distribution in population structure, there are 2 lines of inquiry: surnames as alleles at a haploid locus with models of neutral evolution, and surnames in a diploid state with estimation of marital and random isonymy in males and females. Both approaches are used in the analysis of surname distribution among births and deaths in Ferrara, Italy, in the period 1982-89. The purposes were to determine whether surname distribution had changed perceptibly in the population in the course of an average human life span and to report on the variation of isonymy in deaths and births. A comparison was made of the shape of the surname distributions and of isonomy within and between samples. The assumption was that a random sample of people born at an average of 73 years ago are representative of surname distributions existing at the time of their birth in Ferrara. The data were classified by sex and place of birth for death and sex only for births. There were 7509 deaths of those born in Ferrara with 1894 surnames among the deaths and 14,572 deaths total with 3896 surnames among the total deaths. There were 6066 births with 2561 surnames among births. Surnames were studied fitting a regression to the log-log transformation to the number of surnames which were represented "k" times. Entropy and the equivalent surname number were also calculated. Random isonymy was calculated within series and between series using the method of Lasker, and standardized isonymy between 2 series was calculated according to Chen and Cavalli-Sforza. Estimates of abundance of surnames and migration rates were calculated according to the method of Fisher, and Karlin and McGregor. The results revealed that the distribution of surnames in Ferrara in 19185 maintain a shape very similar to the shape in 1912. The slopes of the log-log regressions for migration show a significant affect, but migration affects the shape only slightly. Isonymy remains almost the same during the 73 years. The reason random isonymy did not change significantly over the years may be due to only recent growth of birth rates and the immigration of entire family groups. It would appear that the genetic structure of the population stayed almost constant, as described by isonymy. An interesting characteristic was that immigrants were the most long-lived, even after infant deaths are excluded.

Reproductive behaviour of families segregating for Cooley's anaemia before and after the availability of prenatal diagnosis.

The reproductive behaviour of couples with heterozygous beta thalassaemia, with at least one affected child, was investigated for the period 1955 to 1984 and was compared to the behaviour of control couples matched for age, age at marriage, and presence of at least one child. The comparisons were made as a function of knowledge of the risk and availability of prenatal diagnosis and abortion. It was found that the couples segregating for Cooley's anaemia, before knowledge of the risk, had a higher reproductive rate than that of control couples. Knowledge of the genetic risk had a different effect on reproductive behaviour in the 1950s from that in later years. The difference was attributed both to the influence of cultural factors and to technical, therapeutic, and diagnostic advances.

Kinship structures and migration in the Po Delta.

The kinship analysis of seven genetic systems in the province of Ferrara permits some considerations on the possible chronology of emergence of their polymorphisms in the area. It is proposed that, assuming neutrality of these systems, and under several restrictions, the emergence by migration of the polymorphisms in the seven systems ACP, ESD, GLO, GPT, PGD, PGM1, PGP might have had the following sequence: PGP and GLO and possibly PGD; PGM1 and GPT; ACP and ESD. All polymorphisms must be older than the beta-thalassemia polymorphism in the area.

Reproductive behavior of thalassemic couples segregating for Cooley anemia.

The reproductive behavior in 1984 of families segregating for Cooley anemia in Ferrara was compared with that of a control group of families, matched for some biological variables which affect fertility. At the resolution power of the sample, it was found that there is no significant difference in these variables due to segregation for Cooley anemia, and it appears that there is no longer significant reproductive compensation in thalassemic couples, although a tendency to compensate does still exist. The increased life span of children affected by Cooley anemia, due to improvements in treatment in the past decade, is probably the main reason why the compensatory reproductive behaviour of the past has almost disappeared.