Cholinergic Neurons In Culture Research Articles

Stimulation of choline acetyltransferase by C3d, a neural cell adhesion molecule ligand

Septal cholinergic neurons project to the hippocampus and release acetylcholine, a neurotransmitter involved in learning and memory. The enzyme choline acetyltransferase (ChAT) is responsible for synthesizing acetylcholine. Promoting ChAT activity and acetylcholine release can lead to new treatments for neurodegenerative diseases with cholinergic deficits, such as Alzheimer's disease. We present evidence that the synthetic molecule C3d, which is a peptide mimetic of the neural cell adhesion molecule (NCAM), promotes ChAT activity in cultures of rat embryonic septal neurons. Our data demonstrate that ChAT activity triggered by C3d is dependent on the fibroblast growth factor receptor (FGFR) and the mitogen-activated protein kinase (MAPK) pathway. C3d did not affect the number of cholinergic neurons in culture, indicating that NCAM homophilic binding enhances ChAT activity, without affecting cholinergic cell survival. In conclusion, the NCAM mimetic peptide C3d promotes ChAT activity in septal neurons through FGFR and MAPK. These findings are relevant to the design of new strategies aimed at stimulating cholinergic function and improving cognition in disorders such as Alzheimer's disease.

The Neurotransmitter Noradrenaline Rescues Septal Cholinergic Neurons in Culture from Degeneration Caused by Low-Level Oxidative Stress

We have developed a model system in which rat basal forebrain cholinergic neurons degenerate progressively when maintained in culture conditions that make them susceptible to low-level oxidative stress. In this study, we showed that cholinergic neurons identified by acetylcholinesterase cytochemistry or choline acetyl transferase immunocytochemistry are rescued efficiently by the neurotransmitter noradrenaline (NA). The effect of NA required neither adrenoceptor activation nor intracellular accumulation. NA operated via a mechanism that precluded activation of a cell death pathway in which reactive oxygen species (ROS) and proapoptotic caspases were crucially involved. It is noteworthy that NA remained protective even when applied late in the degenerative process but before intracellular ROS began to increase. The high efficacy of iron chelators and catalase in preventing the death of cholinergic neurons in this model suggested that NA neutralized the effects of hydroxyl radicals produced through a Fenton-type reaction. Pyrocatechol [the diphenolic moiety of NA] was sufficient in itself to prevent ROS production and cholinergic cell demise, indicating that the catechol structure was instrumental for the neuroprotective function of NA. Therefore, the noncatecholic neurotransmitter GABA failed to prevent neurodegeneration. Nerve growth factor and brain derived neurotrophic factor, two trophic peptides for septal cholinergic neurons, did not afford protection by themselves and did not improve neuroprotection provided by NA. However, in the presence of NA, they both retained their efficacy to stimulate cholinergic parameters. These data indicate that NA-based therapeutic strategies may be of interest in such neurodegenerative conditions as Alzheimer's disease, where progressive cholinergic deficits occur.

Neurturin and persephin promote the survival of embryonic basal forebrain cholinergic neurons in vitro

The GDNF family ligands (GFLs) are a group of neurotrophic factors that influence the development, survival, and maintenance of specific populations of neurons in the central and peripheral nervous systems. The cholinergic neurons of the basal forebrain provide cholinergic innervation to cortical structures and their integrity is vital to normal cognitive function. GDNF, the original member of the GFL family promotes the survival of developing basal forebrain cholinergic neurons in vitro. We have now found that neurturin (NRTN) and persephin (PSPN) also promote the survival of basal forebrain neurons including both cholinergic neurons and a population of non-cholinergic neurons with an efficacy comparable to NGF. We also demonstrate that developing and mature basal forebrain cholinergic neurons (BFCN) express GFL receptors. Ret, the signaling component of the GFL-receptor complex, is expressed in most adult rat BFCN. In addition, Ret and the GFL co-receptors GFRα1 and GFRα2 are expressed in developing cholinergic neurons in cultures of embryonic basal forebrain. Our results suggest that the GFLs may be effective as neuroprotective agents for BFCNs in vivo.

PACAP has a neurotrophic effect on cultured basal forebrain cholinergic neurons from adult rats

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the vasoactive intestinal polypeptide gene family (VIP) that was originally isolated from rat hypothalamus. The high affinity PACAP receptor, PAC1, is expressed in the basal forebrain area of adult, as well as developing rat brain. Hippocampus, a targeting area of basal forebrain cholinergic neurons, contains PACAP. Thus, hippocampal-derived PACAP may have an effect on basal forebrain cholinergic neurons. Indeed, we have reported that PACAP showed neurotrophic effects on these neurons in embryonic and early postnatal culture. Here we report that PACAP has a neurotrophic effect on adult cholinergic neurons in culture. PACAP increases the number of choline acetyltransferase immunoreactive neurons about 2-fold. A similar effect was observed on treatment with cAMP analogue but not nerve growth factor. PACAP also improved the survival and neurite outgrowth of total neurons. These results indicate that PACAP acts as a neurotophic factor even on adult neurons in vitro.

Action of lanthanoide ion on amino-acid receptor-channel-Is this ion species specifically recognized?

Lanthanoides are known to affect a variety of membrane phenomena; for example, an inhibition of voltage-dependent Ca2+ channels. Recent studies have revealed that each of aminoacid receptor-channels is affected in its activation by La3+ in a different manner. La3+ inhibits kainate and NMDA receptor-channel responses while potentiating AMPA, GABAA, GABAC and glycine receptor-channel responses. A positive modulation by La3+ of GABAA receptorchannels on rat septal cholinergic neurons in culture is shared by other lanthanoide ions and Y3+ but not by Sc3+, all of which belong to the same group (III a) in the periodic table. It is suggested that there may be a specific site for binding of lanthanoides on GABAA receptorchannels.

Action of furosemide on GABA and glycine currents in rat septal cholinergic neurons in culture

The action of furosemide on GABA- and glycine-induced currents in rat septal cholinergic neurons in culture was examined by use of the whole-cell voltage-clamp technique. Furosemide inhibited the peak amplitude of either GABA or glycine current in a dose-dependent manner; its half-maximal concentration for them was some 2 and 1 mM, respectively. Furosemide at a concentration of 1 mM depressed the maximal peak amplitude of the dose–response curve for either GABA or glycine to about 70% of control. These results indicate that furosemide inhibits in a noncompetitive fashion GABA and glycine receptor-channels in septal neurons.

Comparative effects of FK-506, rapamycin and cyclosporin A, on the in vitro differentiation of dorsal root ganglia explants and septal cholinergic neurons

There is increasing evidence that immunophilins play a role in neural development and differentiation. We have studied the neurotrophic effects of FK-506, rapamycin and cyclosporin A (CsA) on dorsal root ganglia (DRG) taken from different segmental levels (cervical, thoracic and lumbar/sacral), and on rat embryonic septal cholinergic neurons in culture. At a low concentration (1 nM), FK-506 significantly increased (+ 83%) the number of neurites of thoracic DRG expiants. At a higher concentration (100 nM), it also enhanced the neuritogenesis of thoracic (+ 100%) and lumbar/sacral (+ 57%) DRG, but not cervical DRG explants. Rapamycin displayed a converse effect, reducing the development of DRG explants from cervical and thoracic segments. CsA (from 1 to 100 nM) was without effect on DRG neuritogenesis. In contrast to nerve growth factor (NGF), which increased neurite length (+ 116% at 3 ng/ml), neither FK-506 nor rapamycin affected this parameter.

217 Inhibition by furosemide of GABA- and glycine-induced currents in rat septal cholinergic neurons in culture

217 Inhibition by furosemide of GABA- and glycine-induced currents in rat septal cholinergic neurons in culture

Inhibition by furosemide of GABA- and glycine-induced currents in rat septal cholinergic neurons in culture

Inhibition by furosemide of GABA- and glycine-induced currents in rat septal cholinergic neurons in culture

Glycine current in rat septal cholinergic neuron in culture: monophasic positive modulation by Zn2+

1. Membrane currents induced by glycine (Iglys) were investigated in cholinergic neurons in primary culture, isolated from the septal region of fetal rat brains, by use of the whole cell voltage-clamp recording configuration. A glycine response was observed in 131 of 150 neurons examined. 2. Igly was accompanied by an increase in conductance and reversed the direction at the Cl- equilibrium potential. The Igly-voltage relation was a little outwardly rectifying in a range of -40 to +30 mV in a nearly symmetrical Cl- solution system. 3. Glycine applied by local perfusion produced an Igly, which increased in amplitude sigmoidally with increasing concentrations (EC50 = 110 microM; nH = 1.75) and desensitized at higher concentrations. There was no nondesensitizing component in Igly (100 microM). Strychnine inhibited Igly in a dose-dependent and competitive manner; it took at most 1 min for this action to be attained to a steady level. Schild analysis yielded the dissociation constant for strychnine to be 0.062 microM. Igly was depressed noncompetitively by a gamma-aminobutyric acid-A (GABAA) receptor-channel blocker, picrotoxin, in a dose-dependent manner (IC50 = 45 microM for peak Igly at 100 microM). On the contrary, another GABAA inhibitor, bicuculline (10 microM), did not affect Igly. 4. Igly was unaffected by spermine (1 mM), ethanol (1-100 mM), and diazepam (1 microM) and was depressed by 14% by pentobarbital (100 microM). On the other hand, Zn2+ potentiated Igly in a dose-dependent (EC50 = 9.1 microM; nH = 1.3; 38% increase for Igly at 50 microM by 100 microM Zn2+) and reversible manner. The facilitatory action was due to an increase in the apparent affinity for glycine (by 139% by 100 microM Zn2+), and did not depend on holding potentials. Pb2+ (100 microM) and La3+ (100 microM) also enhanced Igly (50 microM) by 23 and 14%, respectively; these actions were abolished in the presence of Zn2+ (100 microM). Igly was not affected by Ba2+, Sr2+, Co2+, Mn2+, Cd2+, and Al3+ (100 microM each). 5. Rat septal cholinergic neurons in culture were endowed with a Cl(-)-selective glycine receptor channel whose activation was sensitive to strychnine and picrotoxin. Zn2+ induced a positive modulation of the glycine response, possibly through an allosteric interaction with the glycine-binding site; this action was shared by Pb2+ and La3+ with a potency sequence of Zn2+ > Pb2+ > La3+. This metal-ion binding site could serve to enhance a glycine action.

Enhancement by lanthanide of general anesthetic-induced GABAA-receptor current in rat septal cholinergic neurons in culture.

1. Actions of lanthanide ions were examined on general anesthetic-induced currents mediated by the activation of gamma-aminobutyric acid-A receptors (GABAARs) in rat septal cholinergic neurons in primary culture, by means of a whole cell voltage-clamp technique. 2. La3+ enhanced a pentobarbital sodium (500 microM)-induced GABAAR current in a reversible and dose-dependent manner (median effective concentration = 15.7 microM; Hill coefficient = 1.58; 89% increase by 100 microM La3+). This action was independent of holding potentials (-34-26 mV), and was due to an increase in the apparent affinity for pentobarbital (295% increase with 100 microM La3+). 3. The action of La3+ on pentobarbital current was mimicked particularly by other lanthanide ions (Ce3+, Nd3+, Gd3+, Tb3+, Er3+, and Yb3+) and by Y3+ among a number of multivalent cations. There was no correlation between the potentiated proportions by lanthanide ions and their crystal ionic radii. 4. La3+ (100 microM) also augmented a GABAAR response evoked by either alpha-chloralose (500 microM), 2,6-diisopropylphenol (50 microM), or 3-alpha-hydroxy-5-alpha-pregnane-11,20-dione (20 microM) (144, 80, and 153% increase, respectively). 5. We suggest that the GABAAR channels on septal neurons are endowed with a novel "lanthanide site" whose activation results in a positive allosteric interaction with a binding site of the general anesthetics that is involved in a direct activation of GABAAR channels without any added exogenous GABA.

Lack of correlation between the molecular size and the efficacy of lanthanides for potentiating GABA Acurrents in rat septal cholinergic neurons in culture

Actions of lanthanides were examined on GABAA receptor-activated responses in rat septal neurons in culture by using the whole-cell voltage-clamp technique. GABA (10 μM) currents were enhanced by these ions at 100 μM with an efficacy sequence of Pr 3+ (1.11) ≥ Lu 3+ (1.07) ≥ Gd 3+ (1.02) ≥ Er 3+ (1.01) ≥ La 3+ (1: 40% increase) ≥ Ce 3+ (0.980) ≥ Nd 3+ (0.932) ≥ Yb 3+ (0.913) ≥ Tb 3+ (0.912), indicating the lack of correlation between the potentiating efficacy and ionic size of lanthanides.

The survival of striatal cholinergic neurons cultured from postnatal 2-week-old rats is promoted by neurotrophins

Although the expression of nerve growth factor (NGF) in the rat striatum is the highest at 2 postnatal weeks (P2w), the action of NGF at that age has not been studied in detail. We examined the effects of several neurotrophic factors, including NGF, on striatal cholinergic neurons cultured from P2w rats. We also examined the effects of a cyclic AMP (CAMP) analog and high K +-evoked depolarization. NGF specifically promoted the survival of choline acetyltransferase (ChAT)-positive neurons, and consequently increased the ChAT activity per well, whereas it did not induce the ChAT activity per cholinergic neuron. NGF-responsiveness was the highest in striatal cultures from P2w rats, but it was almost lost in cultures from P4w rats. Brain-derived neurotrophic factor (BDNF), neurotrophin- 4 5 ( NT- 4 5 ), and a CAMP analog had survival-promoting effects on striatal total neurons including cholinergic neurons. On the other hand, high K + hardly promoted the survival of striatal cholinergic neurons in cultures from P2w rats, although it increased the viable number of total striatal neurons. High K + did not increase the ChAT activity in any tested cultures from postnatal 3- to 28-day-old rats. These results demonstrated that NGF prevented the death of striatal cholinergic neurons in cultures from P2w rats, but not from P4w rats, and that high K + could not rescue these deaths. We propose that cholinergic neurons in the striatum are programmed to die at P2w, and that this programmed cell death can be restored by neurotrophins, but not by depolarization.

Differential effects of nerve growth factor on expression of choline acetyltransferase and sodium-coupled choline transport in basal forebrain cholinergic neurons in culture.

Nerve growth factor (NGF) treatment of primary cultures of embryonic day 17 rat basal forebrain differentially altered activity of choline acetyltransferase (ChAT) and high-affinity choline transport; ChAT specific activity was increased by threefold in neurons grown in the presence of NGF for between 4 and 8 days, whereas high-affinity choline transport activity was not changed relative to control. Dose-response studies revealed that enhancement of neuronal ChAT activity occurred at low concentrations of NGF with an EC50 of 7 ng/ml, with no enhancement of high-affinity choline transport observed at NGF concentrations up to 100 ng/ml. In addition, synthesis of acetylcholine (ACh) and ACh content in neurons grown in the presence of NGF for up to 6 days was increased significantly compared with controls. These results suggest that regulation of ACh synthesis in primary cultures of basal forebrain neurons is not limited by provision of choline by the high-affinity choline transport system and that increased ChAT activity in the presence of NGF without a concomitant increase in high-affinity choline transport is sufficient to increase ACh synthesis. This further suggests that intracellular pools of choline, which do not normally serve as substrate for ACh synthesis, may be made available for ACh synthesis in the presence of NGF.

105 Positive modulation by lanthanides of GABA a-receptor channels on rat septal cholinergic neurons in culture

105 Positive modulation by lanthanides of GABA a-receptor channels on rat septal cholinergic neurons in culture

Synthesis, storage and release of acetylcholine at and from growth cones of rat central cholinergic neurons in culture

Neurons from the nucleus diagonal band of Broca (DBB) from new born rats protrude neuronal processes and growth cones in culture. Cytochemical observations with the light and electron microscope indicate that growth cones of these neurons take up choline, synthesize acetylcholine (ACh) and store ACh in the vesicles. Electrical stimuli at the soma of DBB neurons evoked inward currents in ACh-sensitive neurons attached to DBB growth cones. These currents were suppressed by TTX, a Ca 2+ channel blocker (Cd 2+), and an ACh nicotinic antagonist (C 6). These results suggest that ACh is synthesized, stored and released from the growth cones of DBB neurons prior to synapse formation.

Characterization of GABA current in rat septal cholinergic neurons in culture and its modulation by metal cations

1. With the aim of characterizing the functional and pharmacological properties of gamma-aminobutyric acid-receptor (type A; GABAAR) channels expressed in a given type of brain neurons, we obtained whole cell voltage-clamp recordings from rat septal cholinergic neurons in primary culture. 2. GABA-induced currents (IGABAS) were accompanied by an increase in conductance and reversed the direction at the Cl- equilibrium potential. The permeability sequence of GABA-activated Cl- channel for various anions (ratio to Cl- permeability) was found to be SCN- (1.72) > or = I- (1.60) > or = Br- (1.55) > Cl- (1) > HCO2- (0.42) >> F- (0). 3. GABA applied by local perfusion produced an IGABA that enhanced in amplitude with increasing concentrations (EC50 = 21.4 microM; nH = 1.70) and desensitized at higher concentrations. Bicuculline inhibited IGABA (20 microM) competitively (IC50 = 0.963 microM) with a dissociation constant of approximately 0.5 microM. Picrotoxin depressed IGABA (20 microM) noncompetitively in a dose- and use-dependent manner (IC50: approximately 100 microM for peak IGABA). 4. IGABA was potentiated by diazepam at 1 and 10 microM (by 20% at 1 microM for IGABA evoked at 10 microM) but not at 0.1 and 100 microM. IGABA was facilitated by pentobarbital sodium (5-200 microM) in a dose-dependent fashion with an increase in an apparent affinity for GABA (by 251% at 50 microM). 5. Zn2+ (2-100 microM) inhibited IGABA (limited to approximately 20% decrease) in a noncompetitive manner. IGABA was also depressed by Cu2+ and Cd2+ (by 50 and 15%, respectively, at 100 microM); its recovery process from their depressions was slow and fast, respectively. The Cu2+ but not Cd2+ action persisted in the presence of Zn2+. La3+ (50-500 microM) potentiated IGABA by enhancing an apparent affinity for GABA (by 158% by 100 microM La3+); this action disappeared in the presence of pentobarbital but not Zn2+. La3+ applied alone induced an inward current at negative holding potentials, but this was not due to the activation of GABAAR channels. 6. Septal cholinergic neurons were endowed with GABAAR channels that were similar to those on other types of neurons in the affinities for GABA, bicuculline, picrotoxin, and pentobarbital, and in an anion-permeability sequence, but were greatly different in the actions of metal cations. The septal GABAA response was depressed strikingly by Cu2+ and to a little extent by Zn2+, whose action was shared by Cd2+ but not by Cu2+, while being potentiated by La3+, possibly through the action on a pentobarbital site. It is suggested that a distinction in properties among native GABAAR channels may be largely reflected in the actions of not only Zn2+ but also Cu2+ and La3+.

Excitatory amino acid-induced currents in rat septal cholinergic neurons in culture.

Whole-cell voltage-clamp recordings were used to study excitatory amino acid-induced currents in neurons isolated from the septum of fetal rat brains. The neurons were cultured for more than four weeks on a feeder layer composed of glial cells obtained from the septal region. Septal neurons were either fusiform, triangular or multipolar and 83% of cells showed acetylcholinesterase activity. L-Glutamate, kainate, quisqualate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) applied by local perfusion produced inward currents (Iglu, Ikai, Iquis and IAMPA, respectively) at -44mV which increased in amplitude with increasing concentration of agonist; they desensitized when induced at higher concentrations except for the Ikai. The EC50s for the peak Ikai and sustained Iglu, Iquis and IAMPA were 55, 13, 0.39 and 3.5 microM, respectively. 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX) depressed Ikai and IAMPA evoked at a concentration of 10 microM (IC50s: 0.58 and 0.84 microM, respectively). Schild analysis for the CNQX action on Ikai gave a dissociation constant of 0.27 microM for CNQX. n-Methyl-D-aspartate (NMDA) (with glycine, 3 microM) produced an inward current (INMDA) at -44 mV whose peak amplitude enhanced with increased concentrations (EC50 = 32 microM). INMDA was potentiated by glycine (EC50 = 0.15 microM) and inhibited by D-2-amino-5-phosphovalerate (IC50 = 9.9 microM for INMDA evoked at a concentration of 50 microM). MK-801 (0.1-10 microM) inhibited INMDA in a dose- and use-dependent manner. INMDA was (0.1-10 microM) inhibited INMDA in a dose- and use-dependent manner. INMDA was potentiated by spermine (EC50 = 247 microM; 91% increase at 1mM) in a manner independent of holding potential (VH). INMDA was inhibited by Mg2+ and Zn2+ (IC50 = 673 and 39 microM, respectively, at -44 mV) in a manner dependent on VH; the magnitudes of a depolarization required for an e-fold increase in their IC50s in a range of -64 to -24 mV were 16 and 22 mV, respectively. The action of Zn2+ was independent of VH > -24 mV. Current-voltage relations for Ikai, Iquis and IAMPA exhibited outward rectification, while that of INMDA showed a region of negative conductance at VH < -30 mV, which disappeared in a Mg(2+)-free solution. Reversal potentials for Ikai, Iquis, IAMPA and INMDA were close to 0 mV, indicating the involvement of non-specific cation channels. Increasing extracellular Ca2+ concentration from 2.4 to 30 mM did not affect the Ikai and Iquis, reversal potential showing negligible Ca2+ component, but shifted INMDA reversal potential to a more positive potential, yielding a ratio of Ca2+ permeability to that of monovalent cation to be 13. Cholinergic septal neurons in culture express non-NMDA-(AMPA/kainate-) and NMDA-type of glutamate receptor channels. Their properties were quantitatively similar to those of glutamate receptor channels on other types of neurons in the brain except for the actions of endogenous neuromodulators (Mg2+, Zn2+ and spermine) on NMDA receptor channels. It is suggested that NMDA receptor channels on different types of neurons may play a distinct role depending on a difference in the actions of these neuromodulators.

Overlapping and Additive Effects of Neurotrophins and CNTF on Cultured Human Spinal Cord Neurons

Ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) have been shown both in vitro and in vivo to support the survival and differentiation of developing chick or rat motoneurons. To explore the potential use of these and other neurotrophic factors as therapeutic agents in human motoneuron diseases, we have examined the effects of the neurotrophins NGF, BDNF, neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5) and the cytokines CNTF and cholinergic differentiation factor/leukemia inhibitory factor (CDF/LIF) and combinations of these factors on fetal human spinal cord neurons grown for 7-10 days in monolayer cultures. The level of choline acetyltransferase (ChAT) was determined in cultures grown in the presence of NGF, BDNF, NT-3, NT-4/5, CNTF, or CDF/LIF or with combinations of these factors. With the exception of NGF, each of these factors alone increased ChAT activity by two- to threefold above control levels; combinations of NT-3 and CNTF were greater than either alone. As a single factor NT-4/5 produced the greatest increase in ChAT activity, but was not additive with any other neurotrophin or CNTF. A combination of the three factors CNTF, BDNF, and NT-3 or the four factors CNTF, BDNF, NT-3, and NT-4 increased ChAT levels by four-fold, an effect greater than any individual factor. The finding that combinations of these factors show some additive effects toward human spinal cord cholinergic neurons in culture has prompted the testing of such combinations in animal models of motoneuron disease.

Neurotrophic effects of ipsapirone and other 5-HT 1A receptor agonists on septal cholinergic neurons in culture

Repeated treatment of primary cultures of fetal rat septal neurons with 5-HT 1A receptor agonists (8-OH-DPAT, ipsapirone, gepirone and buspirone) increased choline acetyltransferase activity after 6–7 days in culture. This effect was optimal with ipsapirone (+50–80% at 1 μM of the agonist), and could be prevented by potent 5-HT 1A receptor antagonists such as (−)-tertatolol and (+)-WAY 100135. Under conditions where they completely suppressed the stimulatory effect of NGF on choline acetyltransferase in these cultures, specific anti-NGF antibodies did not alter the stimulatory effect of ipsapirone, suggesting that a possible release of NGF from some septal cells did not account for the effect of 5-HT 1A receptor stimulation. Autoradiographic investigations with [ 3H8-OH-DPAT as radioligand and immunocytochemistry with specific anti-choline acetyltransferase antibodies and anti-rat 5-HT 1A receptor antibodies showed that 5-HT 1A receptors were expressed on septal neurons in culture, notably on the cholinergic neurons identified by their positive staining with anti-choline acetyltransferase antibodies. Detailed morphometrical analysis by computer-assisted imaging revealed that repeated exposure to ipsapirone (1 μM for 7 days) did not influence the survival of cholinergic as well as non-cholinergic neurons, but specifically altered the neuritic tree (i.e. the total length of neurites and the number of branching points) of cholinergic neurons only. These data suggest that under in vitro conditions ipsapirone and other 5-HT 1A receptor agonists may exert a direct trophic action on septal cholinergic neurons.