Increased resting and exercise-induced oxidative stress in young IDDM men

The effects of local application of the 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide (CPBG), and i.p. administration of ethanol on the extracellular levels of dopamine (DA) in the ventral tegmental area (VTA) were studied using in vivo microdialysis. Adult female Wistar rats were implanted with microdialysis probes in the VTA at least 24 h before each experiment. Stable extracellular levels of DA (101 +/- 9 fmol/20 min) were established before initiating the experiments. Application of 10-250 microM CPBG through the microdialysis probe dose-dependently enhanced the extracellular concentrations of DA but did not alter the levels of either 3,4-dihydroxyphenylacetic acid or homovanillic acid in the dialysate. The effects of CPBG were reversible and dependent upon Ca2+. Co-perfusion with the 5-HT3 receptor antagonist, 3-tropanyl-indole-3-carboxylate (ICS 205-930), inhibited the effects of CPBG on enhancing extracellular DA levels. The i.p. administration of 2 g/kg ethanol significantly (p < 0.005) enhanced the levels of DA to 150% of baseline values; this ethanol-induced increase was prevented by local perfusion with 100 microM ICS 205-930. These results suggest that 5-HT3 receptors in the VTA are involved in regulating the somatodendritic release of DA and in mediating the stimulatory effects of ethanol on this neuronal system.     

Profiles of the fatty acids in the plasma membrane of human brain tumors

The ionic channels and signal transduction pathways underlying the 5-hydroxytryptamine (5-HT)-induced hyperpolarization in neurons of the rat dorsolateral septal nucleus (DLSN) were examined by using intracellular and voltage-clamp recording techniques. Application of 5-HT (1-50 microM) caused a hyperpolarizing response associated with a decreased membrane resistance in DLSN neurons. The hyperpolarization induced by 5-HT was blocked by Ba2+ (1 mM) but not by tetraethylammonium (TEA, 3 mM), glibenclamide (100 microM) and extracellular Cs+ (2 mM). 8-Hydroxy-di-n-propylamino tetralin (8-OH-DPAT; 3 microM), a selective agonist for the 5-HT1A receptor, mimicked 5-HT in producing the hyperpolarization. The 5-HT hyperpolarization was blocked by NAN-190 (5 microM), a 5-HT1A receptor antagonist. CP93129 (100 microM), a 5-HT1B receptor agonist, and L-694-247 (100 microM), a 5-HT1B/1D receptor agonist, also produced hyperpolarizing responses. The order of agonist potency was 8-OH-DPAT > CP93129 > or = L-694-247. (+/-)-2,5-Dimethoxy-4-iodoamphetamine hydrochloride (DOI, 100 microM), a 5-HT2 receptor agonist, and RS67333 (100 microM), a 5-HT4 receptor agonist, caused no hyperpolarizing response. The voltage-clamp study showed that 5-HT caused an outward current (I5-HT) in a concentration-dependent manner. I5-HT was associated with an increased membrane conductance. I5-HT reversed the polarity at the equilibrium potential for K+ calculated by the Nernst equation. I5-HT showed inward rectification at membrane potentials more negative than-70 mV. Ba2+ (100 microM) blocked the inward rectifier K+ current induced by 5-HT. I5-HT was irreversibly depressed by intracellular application of guanosine 5'-O-(3-thiotriphosphate)(GTP-gamma S) but not by guanosine 5'-O-(2-thiodiphosphate) (GDP beta S). These results suggest that in rat DLSN neurons activation of 5-HT1A receptors causes a hyperpolarizing response by activating mainly the inward rectifier K+ channels through a GTP-binding protein.     

Serotonin efflux in the rat ventral lateral geniculate nucleus assessed by fast cyclic voltammetry is modulated by 5-HT1B and 5-HT1D autoreceptors

Fast cyclic voltammetry (FCV) was used to measure electrically stimulated monoamine efflux in the rat ventral lateral geniculate nucleus (vLGN). The electrochemical characteristics of the released species resembled 5-HT but not dopamine or noradrenaline. Amine efflux was abolished by the sodium channel blocker tetrodotoxin (0.1 microM), Ro 4-1284 (1.0 microM), the fast-acting reserpine analogue, and removal of Ca2+ from the superfusate. Amine efflux was unaffected by the monoamine oxidase inhibitor clorgyline (0.1 microM). Of paroxetine (0.1 microM), desipramine (50 nM) and vanoxerine (0.5 microM), selective blockers of 5-HT, noradrenaline and dopamine uptake respectively, only paroxetine increased monoamine efflux (to 194 +/- 25%, mean +/- SEM) and prolonged the removal half-life (to 638 +/- 105%). The non-specific 5-HT1 antagonist methiothepin (0.2 microM) increased 5-HT efflux on long (20 pulses at 20 Hz) but not short trains (20 pulses at 100 Hz). When tested on pseudo-one-pulse stimulations (5 pulses, 100 Hz), the selective 5-HT1A agonist 8-OHDPAT (1.0 microM) had no effect. CP 93129 (0.3 microM), the selective 5-HT1B agonist, decreased 5-HT efflux to 37 +/- 4% of control and was antagonised by the 5-HT1B blocker isamoltane (0.5 microM) and by the 5-HT1D/B antagonist GR 127935 (50 nM). The preferential 5-HT1D agonist sumatriptan (0.5 microM) also decreased 5-HT efflux, to 55 +/- 6% and was antagonised by GR 127935 (50 nM) but not isamoltane (0.5 microM). These results suggest that 5-HT released in the vLGN can be measured by FCV. Furthermore, released 5-HT is taken up by the 5-HT transporter and may be under the influence of 5-HT1B and 5-HT1D autoreceptors.     

5-HT1A receptor-mediated inhibition of long-term potentiation in rat visual cortex

We investigated the effect of 8-hydroxy-2-(N,N-dipropylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, on the induction of long-term potentiation in rat visual cortex slices. Perfusion of 8-OH-DPAT (0.1-10 microM) did not affect layer II/III field potentials evoked by test stimulation of layer IV, but significantly reduced long-term potentiation induced by tetanic stimulation. The inhibitory effect of 8-OH-DPAT was blocked by the 5-HT1A receptor antagonist, pindolol (10 microM), but not by the 5-HT2,7 receptor antagonist, ritanserin (100 microM), nor by the 5-HT3,4 receptor antagonist, MDL72222 (100 microM). These results suggest that the rat visual cortex long-term potentiation is inhibited by 5-HT1A receptor stimulation.     

5-HT autoreceptors in the regulation of 5-HT release from guinea pig raphe nucleus and hypothalamus

5-HT autoreceptors involved in the regulation of 5-HT release in the guinea pig dorsal raphe nucleus have been studied in comparison with those in the hypothalamus. In vitro release was measured in slices of raphe and hypothalamus prelabelled with [3H]5-HT, superfused with Krebs solution and depolarized electrically. The non-selective 5-HT receptor agonist, 5-carboxamidotryptamine (5-CT) (0.1-10 nM for raphe: 1-100 nM for hypothalamus) and antagonist, methiothepin (10-1000nM), decreased and increased, respectively, the release of [3H]5-HT evoked by electrical stimulation in either of these regions when given alone. The selective 5-HT1B/D receptor antagonist, GR127935 (100-1000 nM), and the 5-HT1D receptor antagonist, ketanserin (300-1000 nM), had no significant effect on this release in either of these regions. Methiothepin and GR127935 (100-1000 nM) shifted to the right the concentration-effect curve of 5-CT in both the raphe and the hypothalamus. At 300 nM, ketanserin shifted to the right the concentration-effect curve of 5-CT in the raphe but did not modify the 5-CT curve in the hypothalamus. In microdialysis experiments ketanserin, applied locally at 10 microM, increased the extracellular levels of 5-HT in the dorsal raphe nucleus of the freely moving guinea pig, whereas 5-HT levels were unchanged in the hypothalamus. Ketanserin at 1 microM did not affect the decrease in 5-HT output induced by the selective 5-HT1B/D receptor agonist, naratriptan (used at 10 microM in raphe and 0.1 microM in hypothalamus), in the raphe or the hypothalamus. In the raphe, WAY100635, a 5-HT1A receptor antagonist, at 1 microM, did not prevent naratriptan (10 microM) from reducing the extracellular levels of 5-HT. These results suggest that, in the conditions used in this study, the release of 5-HT in the dorsal raphe nucleus is possibly modulated in part by 5-HT1B receptors but essentially the control is through 5-HT receptors whose subtype is still to be determined. In the hypothalamus, however, it is clear that only 5-HT1B receptors are involved in the modulation of 5-HT neurotransmission.     

Retinoic acid and N-(4-hydroxy-phenyl) retinamide suppress growth of esophageal squamous carcinoma cell lines

The roles of endogenous serotonin (5-HT) and 5-HT receptor subtypes in regulation of acetylcholine (ACh) release in frontal cortex of conscious rats were examined using a microdialysis technique. Systemic administration (1 and 3 mg/kg, i.p.) of the 5-HT-releasing agent p-chloroamphetamine (PCA) elevated ACh output in a dose-dependent manner. Depletion of endogenous 5-HT by p-chlorophenylalanine significantly attenuated the facilitatory effect of PCA on ACh release. The PCA (3 mg/kg)-induced increase in ACh release was significantly inhibited by local application of the 5-HT4 receptor antagonists RS23597 (50 microM) and GR113803 (1 microM), while the 5-HT1A antagonist WAY-100135 (10 mg/kg, i.p.; 100 microM), 5-HT(1A/1B)/beta-adrenoceptor antagonists (-)-pindolol (8 mg/kg, i.p.) and (-)-propranolol (150 microM), 5-HT(2A/2C) antagonist ritanserin (1 mg/kg, i.p.; 10 microM) and 5-HT3 antagonist ondansetron (1 mg/kg, i.p.; 10 microM) failed to significantly modify the effect of PCA. These results suggest that PCA-induced enhancement of 5-HT transmission facilitates ACh release from rat frontal cortex at least in part through 5-HT4 receptors.     

Facilitation of acetylcholine release in rat frontal cortex by indeloxazine hydrochloride: involvement of endogenous serotonin and 5-HT4 receptors

Effects of indeloxazine hydrochloride, an inhibitor of serotonin (5-HT) and norepinephrine (NE) reuptake with a facilitatory effect on 5-HT release, on acetylcholine (ACh) output in frontal cortex of conscious rats were characterized using an in vivo microdialysis technique. Systemic administration of indeloxazine (3 and 10 mg/kg, i.p.) increased ACh and 5-HT output in a dose-dependent manner. Depletion of endogenous monoamines by reserpine and of 5-HT by p-chlorophenylalanine, but not that of catecholamines by alpha-methyl-p-tyrosine, significantly attenuated the facilitatory effect of indeloxazine on ACh release. When applied locally by reverse dialysis, indeloxazine (10 and 30 microM) and the selective 5-HT reuptake inhibitor citalopram (10 microM), but not the NE reuptake inhibitor maprotiline (30 microM), increased cortical ACh output. Indeloxazine (10 mg/kg)-induced increase in ACh release was significantly inhibited by local application of the 5-HT4 receptor antagonists RS23597 (50 microM) and GR113803 (1 microM), while the 5-HT1A antagonist WAY-100135 (100 microM), 5-HT1A/1B/beta-adrenoceptor antagonist (-)propranolol (150 microM), 5-HT2A/2C antagonist ritanserin (10 microM) and 5-HT3 antagonist ondansetron (10 microM) failed to significantly modify this effect. Neither depletion of monoamines nor treatment with serotonergic antagonists significantly changed the basal ACh level, indicating that endogenous monoamines do not tonically activate ACh release. These results suggest that indeloxazine-induced facilitation of ACh release in rat frontal cortex is mediated by endogenous 5-HT and involves at least in part cortical 5-HT4 receptors.     

Poor periodontal health of the pregnant woman as a risk factor for low birth weight

1. It has been hypothesized that 5-HT1A autoreceptor antagonists may enhance the therapeutic efficacy of SSRIs and other antidepressants. Although early clinical trials with the beta-adrenoceptor/5-HT1 ligand, pindolol, were promising, the results of recent more extensive trials have been contradictory. Here we investigated the actions of pindolol at the 5-HT1A autoreceptor by measuring its effect on 5-HT neuronal activity and release in the anaesthetized rat. 2. Pindolol inhibited the electrical activity of 5-HT neurones in the dorsal raphe nucleus (DRN). This effect was observed in the majority of neurones tested (10/16), was dose-related (0.2-1.0 mg kg(-1), i.v.), and was reversed by the 5-HT1A receptor antagonist, WAY 100635 (0.1 mg kg(-1), i.v.), in 6/7 cases tested. 3. Pindolol also inhibited 5-HT neuronal activity when applied microiontophoretically into the DRN in 9/10 neurones tested. This effect of pindolol was current-dependent and blocked by co-application of WAY 100635 (3/3 neurones tested). 4. In microdialysis experiments. pindolol caused a dose-related (0.8 and 4 mg kg(-1), i.v.) fall in 5-HT levels in dialysates from the frontal cortex (under conditions where the perfusion medium contained 1 microM citalopram). In rats pretreated with WAY 100635 (0.1 mg kg(-1), i.v.), pindolol (4 mg kg(-1), i.v.) did not decrease, but rather increased 5-HT levels. 5. We conclude that, under the experimental conditions used in this study, pindolol displays agonist effects at the 5-HT1A autoreceptor. These data are relevant to previous and ongoing clinical trials of pindolol in depression which are based on the rationale that the drug is an effective 5-HT1A autoreceptor antagonist.     

"High-load" polyethylene glycol-polystyrene (PEG-PS) graft supports for solid-phase synthesis

In the rat dorsal hippocampus and dorsal raphe nucleus, the microiontophoretic application of ergotamine and 5-HT suppressed the firing activity of CA3 pyramidal neurons and 5-HT neurons, an effect antagonized by selective 5-HT1A receptor antagonists. Co-application of ergotamine prevented the inhibitory action of 5-HT on the firing activity of CA3 pyramidal neurons but not of 5-HT neurons, indicating that ergotamine acted as a partial 5-HT1A receptor agonist in the dorsal hippocampus and as a full agonist at 5-HT1A autoreceptors. Ergotamine decreased, in a concentration-dependent manner, the electrically evoked release of [3H]5-HT in preloaded rat and guinea pig hypothalamus slices; this effect was prevented by the nonselective 5-HT receptor antagonist methiothepin but not by the selective 5-HT1B/1D receptor antagonist GR 127935 or the alpha 2-adrenoceptor antagonist idazoxan. Although body temperature in humans remained unchanged following inhaled ergotamine, in the rat, subcutaneously injected ergotamine produced a hypothermia that was prevented by a pretreatment with the 5-HT1A/1B receptor/beta-adrenoceptor antagonist pindolol. Finally in humans, ergotamine did not alter prolactin or adrenocorticotropic hormone levels, but increased growth hormone level, which was prevented by pindolol. Cortisol level was increased in humans by ergotamine, but this enhancement was unaltered by pindolol. In conclusion, the present results suggest that ergotamine acted in the rat brain as a 5-HT1A receptor agonist and as an agonist of terminal 5-HT autoreceptor of a yet undefined subtype. In humans, ergotamine also displayed some 5-HT1A receptor activity but, probably because of lack of receptor selectivity, it did not present the same profile as other 5-HT1A receptor agonists.     

MDMA induced dopamine release in vivo: role of endogenous serotonin

Acting as a substrate at the serotonin (5-HT) transporter, (+)-MDMA (3,4-methylenedioxymethamphetamine), is a potent releaser of 5-HT and causes toxicity to 5-HT neurons after repeated exposure. (+)-MDMA also releases dopamine (DA), although with less potency. Since we have shown previously that the intrastriatal application of 5-HT facilities DA release, it was hypothesized that increased release of striatal 5-HT after MDMA may influence extracellular levels of DA. Using microdialysis in vivo, we found that (+)-MDMA (4.7 mumol/kg, i.v.) administration increased extracellular striatal DA levels to 501% of control (p < 0.01, n = 12). However, in the presence of fluoxetine (14.4 mumol/kg, s.c.), which prevents (+)-MDMA effects on 5-HT release, the (+)-MDMA-induced increase in DA was significantly less (to 375% of control, p < 0.05, vs. no fluoxetine, n = 8). In vitro studies with striatal slices, to test drug selectivity, showed that (+)-MDMA (0.3-3 microM) increased extracellular levels of both DA and 5-HT in a dose-dependent manner. Fluoxetine (3 microM) completely blocked the effects of (+)-MDMA on 5-HT release, but did not alter (+)-MDMA-induced DA release in vitro. The selective DA transport inhibitor GBR-12909 (1 microM), blocked (+)-MDMA's effect on DA release. It is concluded that 5-HT release after (+)-MDMA treatment partially contributes to (+)-MDMA's effect on DA release in vivo.     

Hexadecylphosphocholine and 2-modified 1,3-diacylglycerols as effectors of phospholipase D

The effects of mesulergine (100 and 200 microg/kg s.c.), SB 206553 (1 and 2.5 mg/kg i.p.), RP 62203 (2.5 and 4 mg/kg i.p.) and ritanserin (630 microg/kg i.p.) were studied on the extracellular concentration of dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens of chloral hydrate-anesthetized rats, using intracerebral microdialysis. Mesulergine, a non selective serotonin2C/2B/2A (5-HT2C/2B/2A) receptor antagonist, significantly increased DA release, which reached a peak level (+ 20%) 60 min after drug injection and slowly returned back to baseline values. Mesulergine also caused a dose-dependent increase in DOPAC outflow. Pretreatment with mesulergine (200 microg/kg) did not change the inhibition of DA release induced by apomorphine (100 microg/kg), whereas it prevented the reduction of DOPAC outflow induced by apomorphine (100 microg/kg). Administration of SB 206553, a selective blocker of 5-HT2C/2B receptors, dose-dependently increased DA outflow. The dose of 2.5 mg/kg SB 206553 caused a linear increase of DA output which reached a peak (+75%) 40 min after injection, while 1 mg/kg induced a more gradual increase of DA release which peaked (+54%) 60 min after administration of the drug. Treatment with RP 62203, a selective 5-HT2A receptor antagonist, did not produce any significant effect on DA outflow. Administration of ritanserin, a mixed 5-HT2A/2C receptor antagonist, did not cause any significant change of DA and DOPAC outflow. Taken together, these data indicate that selective blockade of 5-HT2/2B receptor subtypes increases DA release in the rat nucleus accumbens.     

Clozapine, haloperidol, and the D4 antagonist PNU-101387G: in vivo effects on mesocortical, mesolimbic, and nigrostriatal dopamine and serotonin release

With in vivo microvoltammetry, the dopamine (DA) receptor antagonists, clozapine (D4/D2), haloperidol (D2) and the selective D4 antagonist, PNU-101387G, were evaluated for their effects on DA and serotonin (5-HT) release within A10 neuronal terminal fields [mesocortical, prefrontal cortex (PFC), mesolimbic, nucleus accumbens, (NAcc)] and within A9 neuronal terminal fields [nigrostriatal, caudate putamen (CPU)], in chloral hydrate anesthetized rats. Clozapine, which also has 5-HT2 receptor antagonist properties, significantly (p < 0.001) increased DA release within A10 terminal fields, PFC and NAcc; DA release was not increased by clozapine within A9 terminals, CPU. Serotonin release was significantly (p < 0.001) increased by clozapine within A10 and A9 terminal fields. Haloperidol significantly (p < 0.001) increased DA release within PFC, dramatically and significantly (p < 0.001) increased DA release within CPU, but not within NAcc; haloperidol had a small but statistically significant (p < 0.05) increase on 5-HT release within PFC [only at the highest dose studied (2.5 mg/kg)] and within CPU [only at the lowest dose studied 1.0 mg/kg) (p < 0.05)]. The selective D4 antagonist, PNU-101387G dramatically and significantly (p < 0.001) increased DA release within PFC, modestly, but significantly (p < 0.001) increased DA release within CPU, did not alter DA release within NAcc at the lowest dose studied (1.0 mg/kg) and significantly (p < 0.05) decreased DA release within NAcc at the highest dose studied (1.0 mg/kg). The selective D4 antagonist did not affect 5-HT release within either A10 or A9 terminal fields. The present data are discussed in terms of the neurochemistry, antipsychotic activity, and side effect profiles of clozapine and haloperidol, in order to provide comparative profiles for a selective D4 antagonist, PNU-101387G.     

Effect of pindolol on hormone secretion and body temperature: partial agonist effects

Pindolol has been shown to be a partial agonist at 5-HT1A receptors in preclinical studies. It has also been reported to inhibit the effects of other 5-HT1A partial agonists such as ipsapirone and buspirone on hormone secretion and body temperature in man, indicating its antagonist action at 5-HT1A receptors in man. To determine if pindolol has 5-HT1A agonist as well as antagonist effects in man, pindolol, 30 mg, p.o. and placebo, were given single blind in random order to 23 normal men with indwelling venous catheters and its effects on hormone secretion and body temperature noted. Pindolol significantly increased basal plasma cortisol concentrations, whereas it decreased plasma prolactin (PRL) concentrations and body temperature. The increase in plasma cortisol due to pindolol suggests a 5-HT1A agonist action and is consistent with a 5-HT1A partial agonist mechanism in man whereas the PRL effects are consistent with an antagonist action at 5-HT1A receptors. The effects of pindolol on plasma cortisol concentration and body temperature were significantly negatively correlated. Furthermore, these results indicate significant differences in the 5-HT1A-dependent regulation of PRL and the hypothalamo-pituitary-adrenal (HPA) axis and body temperature, and suggest that human basal PRL secretion is tonically stimulated by 5-HT1A mechanism whereas the HPA axis and body temperature are not. Since rodent studies suggest differences in 5-HT1A receptor sensitivity between males and females, the results reported here need to be replicated in females. These differences in the effect of pindolol are discussed in terms of receptor reserve theory.     

Serotonin inhibits the induction of long-term potentiation in rat primary visual cortex

1. The effect of serotonin (5-hydroxytryptamine; 5-HT) on the induction of long-term potentiation (LTP) in rat visual cortex was investigated by using slice preparations in vitro. 2. Bath application of 5-HT (0.1-10 microM) did not affect the baseline synaptic potentials evoked by single-pulse test stimulation, but inhibited the induction of LTP in a concentration-dependent manner. 3. The effect of 5-HT was blocked by the 5-HT1 receptor antagonist pindolol or the 5-HT2,7 receptor antagonist ritanserin, but not by the 5-HT3,4 receptor antagonist MDL72222. 4. These results suggest that 5-HT plays a role in suppressing the induction of LTP in the rat visual cortex.     

Twelve-month abstinence from alcohol and long-term drinking and marital outcomes in men with severe alcohol problems

In vivo microdialysis was used to investigate the mechanism behind the increase in extracellular dopamine (DA) induced by increase in extracellular serotonin (5-HT) level and 5-HT1 and 5-HT2 receptor activation. The following serotoninergic drugs were perfused in the absence or presence of nomifensine (5 microM) or tetrodotoxin (TTX; 2 microM): clomipramine (10, 500 and 1,000 microM), a selective 5-HT reuptake inhibitor; 8-OH-DPAT (50 and 500 microM), a 5-HT1A receptor agonist; and alpha-methyl-5-HT (1, 5 and 50 microM), a 5-HT2 receptor agonist. All the serotoninergic drugs studied increased DA extracellular output in a dose-dependent manner. The presence of nomifensine attenuated the effect of perfusion of clomipramine (500 microM) and completely abolished the effect of perfusion of 8-OH-DPAT (500 microM) and alpha-methyl-5-HT (5 microM) on DA extracellular output. Clomipramine (100-1,000 microM) perfusion produced a dose dependent increase in DOPAC extracellular output, which was stronger when clomipramine (500 microM) was co-perfused with nomifensine. 8-OH-DPAT and alpha-methyl-5-HT perfusion decreased DOPAC overflow. Addition of TTX to the perfusion fluid one hour before serotoninergic drugs perfusion, did not completely abolish the effect on dopamine extracellular output produced by the serotoninergic drugs. These data seem to indicate that increase in extracellular 5-HT level and 5-HT1 and 5-HT2 receptor activation increase in vivo DA extracellular output in the striatum mainly by a nonexocytotic mechanism involving DA uptake sites and, secondarily, by activation of 5-HT receptors.     

Role of 5-HT1b receptor in the pressure-induced behavioral and neurochemical disorders in rats

When human divers and experimental animals are exposed to increasing environmental pressure, they develop the high-pressure neurologic syndrome (HPNS) that has been recently demonstrated to include an increase in striatal dopamine (DA) release. This increase has been correlated with enhanced locomotor and motor activity (LMA). In the present study, we investigated the effect of the 5-HT1b receptor antagonist (+/-)cyanopindolol, which has been shown to block at normal pressure the increase in striatal DA release induced by the administration of the 5-HT1b receptor agonist CGS 12066B. Our data clearly showed that the administration of (+/-)cyanopindolol partially blocked both the pressure-induced increase in striatal DA release and the development of LMA. These results suggest the contribution of the 5-HT neurotransmission in the DA-related neurochemical and behavioral disorders that occur in rats exposed to high pressure.     

Serotonin enhances the production of type IV collagen by human mesangial cells

BACKGROUND: The plasma concentration of 5-hydroxytryptamine (5-HT) in diabetic patients is higher than that in normal subjects. Since recent reports have demonstrated the presence of 5-HT2A receptor in glomerular mesangial cells, it is possible that 5-HT may be involved in the development of diabetic nephropathy through the 5-HT2A receptor in mesangial cells. Because expansion of the glomerular mesangial lesion is a characteristic feature of diabetic nephropathy, we examined the effect of 5-HT on the production of type IV collagen by human mesangial cells. METHODS: Human mesangial cells were incubated with 5-HT with or without 5-HT receptor antagonists, protein kinase C (PKC) inhibitor or transforming growth factor-beta (TGF-beta) antibody. Type IV collagen mRNA and protein concentration in medium were measured by Northern blot analysis and enzyme-linked immunosorbent assay (ELISA), respectively. TGF-beta mRNA and bioactivity in the medium were measured by Northern blot analysis and bioassay using mink lung epithelial cells, respectively. RESULTS: 5-HT stimulated the production of type IV collagen by human mesangial cells, which was inhibited by ketanserin and sarpogrelate hydrochloride, 5-HT2A receptor antagonists, but not by ondansetron, a 5-HT3 receptor antagonist. 5-HT increased the bioactivities of both active and total TGF-beta. However, the 5-HT-enhanced production of type IV collagen was completely inhibited by an anti-TGF-beta antibody. Furthermore, a PKC inhibitor, calphostin C, inhibited the 5-HT-induced increase in type IV collagen secretion, and the activity of membrane PKC was increased by 5-HT. Phorbol ester activated type IV collagen production as well as active and total TGF-beta. Calphostin C completely inhibited the 5-HT-enhanced activity of active TGF-beta, but did not inhibit exogenous TGF-beta-induced increase in type IV collagen secretion. CONCLUSIONS: Our results suggest that 5-HT-enhanced production of type IV collagen by human mesangial cells is mediated by activation of PKC and subsequent increase in active TGF-beta activity.     

Repression of Drosophila photoreceptor cell fate through cooperative action of two transcriptional repressors Yan and Tramtrack

Using the endogenous cannabinoid receptor agonist anandamide, the synthetic agonist CP 55940 [[1alpha,2beta(R)5alpha]-(-)-5-(1,1-dimethylheptyl+ ++)-2-[5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]phenol], and the specific antagonist SR 141716 [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-me thyl-1H-pyrazole-3-carboxamide hydrochloride], second messenger activation of the central cannabinoid receptor (CB1) was examined in rat striatal and cortical slices. The effects of these cannabinoid ligands on electrically evoked dopamine (DA) release from [3H] dopamine-prelabelled striatal slices were also investigated. CP 55940 (1 microM) and anandamide (10 microM) caused significant reductions in forskolin-stimulated cyclic AMP accumulation in rat striatal slices, which were reversed in the presence of SR 141716 (1 microM). CP 55940 (1 microM) had no effect on either KCl- or neurotransmitter-stimulated 3H-inositol phosphate accumulation in rat cortical slices. CP 55940 and anandamide caused significant reductions in the release of dopamine after electrical stimulation of [3H]dopamine-prelabelied striatal slices, which were antagonised by SR 141716. SR 141716 alone had no effect on electrically evoked dopamine release from rat striatal slices. These data indicate that the CB1 receptors in rat striatum are negatively linked to adenylyl cyclase and dopamine release. That the CB1 receptor may influence dopamine release in the striatum suggests that cannabinoids play a modulatory role in dopaminergic neuronal pathways.     

Light-regulated localization of the beta-subunit of Gq-type G-protein in the crayfish photoreceptors

The role of metabotropic (mGluRs) and N-methyl-D-aspartate (NMDA) glutamate receptors on 5-hydroxytryptamine (5-HT) release has been studied in rat periaqueductal gray (PAG) matter by using in vivo microdialysis. (1S,3R)-aminocyclopentane- 1,3-dicarboxylic acid [(IS,3R)-ACPD; 0.5 or 1 mM], a group I/group II mGluRs agonist, increased the dialysate 5-HT concentration. (2S)-alpha-ethylglutamic acid (EGlu; 1 mM), an antagonist of group II mGluRs, but not (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA; 1 mM), an antagonist of group I mGluRs, antagonized the 1S,3R-ACPD-induced effect. (S)-3,5-dihydroxyphenylglycine (DHPG; 0.5 and 1 mM), an agonist of group I mGluRs, did not modify dialysate 5-HT. (2S, 3S, 4S)-alpha-(carboxycyclopropyl)-glycine (L-CCG-I; 0.5 and I mM), an agonist of group II mGluRs, increased extracellular 5-HT. This effect was antagonized by EGlu. Similarly, L-serine-O-phosphate (L-SOP; 1 and 10 mM), an agonist of group III mGluRs, increased extracellular 5-HT and this effect was antagonized by (RS)-(alpha-methylserine O-phosphate (M-SOP; 1 mM), an antagonist of group III mGluRs. Out of the several N-methylD-aspartate concentrations used (NMDA; 10, 50, 100, 500 and 1000 microM) only the 50 microM infusion significantly decreased dialysate 5-HT. The GABA(A) receptor agonist, bicuculline (30 microM), increased 5-HT release on its own and antagonized the decrease caused by the opiate antagonist, naloxone (2 mM), as well as the increases caused by CCG-I or L-SOP. These data show that stimulation of PAG's group II/group II mGluRs increases 5-HT release, while stimulation of NMDA glutamate receptors may decrease it. We speculate that glutamate does not modulate 5-HT release in the PAG directly, but via activation of tonically active GABAergic interneurons.     

Systemic morphine-induced Fos protein in the rat striatum and nucleus accumbens is regulated by mu opioid receptors in the substantia nigra and ventral tegmental area

To characterize how systemic morphine induces Fos protein in dorsomedial striatum and nucleus accumbens (NAc), we examined the role of receptors in striatum, substantia nigra (SN), and ventral tegmental area (VTA). Morphine injected into medial SN or into VTA of awake rats induced Fos in neurons in ipsilateral dorsomedial striatum and NAc. Morphine injected into lateral SN induced Fos in dorsolateral striatum and globus pallidus. The morphine infusions produced contralateral turning that was most prominent after lateral SN injections. Intranigral injections of [D-Ala2, N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO), a mu opioid receptor agonist, and of bicuculline, a GABAA receptor antagonist, induced Fos in ipsilateral striatum. Fos induction in dorsomedial striatum produced by systemic administration of morphine was blocked by (1) SN and VTA injections of the mu1 opioid antagonist naloxonazine and (2) striatal injections of either MK 801, an NMDA glutamate receptor antagonist, or SCH 23390, a D1 dopamine receptor antagonist. Fos induction in dorsomedial striatum and NAc after systemic administration of morphine seems to be mediated by dopamine neurons in medial SN and VTA that project to medial striatum and NAc, respectively. Systemic morphine is proposed to act on mu opioid receptors located on GABAergic interneurons in medial SN and VTA. Inhibition of these GABA interneurons disinhibits medial SN and VTA dopamine neurons, producing dopamine release in medial striatum and NAc. This activates D1 dopamine receptors and coupled with the coactivation of NMDA receptors possibly from cortical glutamate input induces Fos in striatal and NAc neurons. The modulation of target gene expression by Fos could influence addictive behavioral responses to opiates.