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Abstract Background The impact of an aging population on the psychiatric emergency service (PES) has not been fully ascertained. Cognitive dysfunctions aside, many DSM-IV disorders may have a lower prevalence in the elderly, who appear to be underrepresented in the PES. We therefore attempted to more precisely assess their patterns of PES use and their clinical and demographic characteristics. Methods Close to 30,000 visits to a general hospital PES (Montreal, Quebec, Canada) were acquired between 1990 and 2004 and pooled with over 17,000 visits acquired using the same methodology at three other services in Quebec between 2002 and 2004. Results The median age of PES patients increased over time. However, the proportion of yearly visits attributable to the elderly (compared to those under 65) showed no consistent increase during the observation period. The pattern of return visits (two to three, four to ten, eleven or more) did not differ from that of patients under 65, although the latter made a greater number of total return visits per patient. The elderly were more often women (62%), widowed (28%), came to the PES accompanied (42%) and reported « illness » as an important stressor (29%). About 39% were referred for depression or anxiety. They were less violent (10%) upon their arrival. Affective disorders predominated in the diagnostic profile, they were less co-morbid and more likely admitted than patients under 65. Conclusion Although no proportional increase in PES use over time was found the elderly do possess distinct characteristics potentially useful in PES resource planning so as to better serve this increasingly important segment of the general population.

Abstract Background Several recent studies have reported a significant increase in medical emergency department (ED) use for reasons of mental health. The diagnostic profile of these patients however differs from that usually described for patients visiting the psychiatric emergency service (PES). Few studies have specifically focused upon long-term PES utilization rates. Those that do typically present data from the early 80s, suggesting that deinstitutionalization may be an important contributing factor to the increases found. The aim of this study was to assess PES use using a more recent time frame and, the effects of non-specific factors, such as population growth, on this use. Methods Visits per year at several different types of PESs were obtained; (a) for an 11-year period at a general hospital PES while the surrounding population remained stable, (b) at that same PES while the catchment area population doubled over a period of a few years, (c) for an 11-year period at two PESs without catchment areas while the surrounding population increased and (d-) for a 12-year period at a PES in a mental health facility while the surrounding population increased. Moderately conservative criteria were used to define either a trend or, a significant increase in utilization rates. Results Each site had an inherent, 7 to 15% yearly variability in the number of PES visits. Over time however, only those where the surrounding population increased (either by an increase in the catchment area size or a regional increase in the population census) showed a trend or, a significant increase in utilization rates. These increases however were modest and of the order of 12 to 19%. Conclusion Long observation periods are required in order to detect stable changes in PES utilization rates over time. As such, population growth may be but one of several factors underlying these increases. Organizational changes in mental health care delivery in the vicinity of the services that showed an increase could also have contributed. These latter would simply have redistributed (to the PES) the pre existing pool of mental health care patients, resulting in an increase that is more apparent than real.

Abstract Background Patients with major depression refractory to repeated pharmacological trials (TRD) may remain symptomatic for many years after their index episode. Augmentation strategies (with lithium or an atypical antipsychotic) or combining an antidepressant with short-term psychotherapy have been used with relative success in these patients. The aim of this study was to assess the effectiveness of the concomitant administration of quetiapine, an atypical antipsychotic, or placebo, to cognitive-behavior therapy (CBT) in TRD. Methods Thirty-one patients who met entrance criteria for unipolar major depression (TRD stage II or greater) underwent 3 weeks of lithium augmentation after which non-responders (N = 22) were randomized to receive either quetiapine or placebo as an adjunct to their 12 weekly CBT sessions (quetiapine/CBT or placebo/CBT groups). Primary efficacy measures were the Hamilton and the Montgomery-Asberg rating scales for depression. Results Overall, there was a significant reduction in both primary efficacy measure scores at LOCF for the 11 patients in the quetiapine/CBT group but not in the placebo/CBT treated patients. Patients in the quetiapine/CBT group, compared to those receiving placebo/CBT, showed a significantly greater degree of improvement on one primary and one secondary efficacy measure, were more likely to complete the trial and, completed a greater number of CBT sessions. Conclusion Although preliminary, our results suggest that the adjunctive administration of quetiapine to CBT may prove useful in the treatment of stage II TRD. Trial Registration Current Controlled Trials ISRCTN12638696.

Abstract Background The psychiatric emergency service (PES) is a major hub in the mental health care delivery system. The aim of this study was to more precisely define what psychiatrists consider to be a psychiatric emergency and to examine the underlying basis of this assessment. Methods Over twenty-two thousand PES visits were assessed prospectively for pertinence and urgency by psychiatrists in four functionally and structurally different services in the province of Quebec, Canada. This study took place between July 15 1996 and August 31, 2004. Results Overall, 57% of visits were judged pertinent and urgent (P/U), 30% pertinent but not urgent (P/NU) and 13% neither pertinent nor urgent (NP/NU). Between 50 and 60% of P/U tagged visits were diagnosed with an affective or a psychotic disorder, often with a suicidal content. They also more frequently resulted in a short-term observation in the PES or a hospitalization. Variables suggesting the presence of a behaviorally disturbed state (aggressive behaviors, involuntary or police referrals) were equally likely to be found in P/U or NP/NU visits. Legal confinement following the consultation was almost exclusively seen in visits judged P/U. The percent of visits tagged P/U at the four individual sites varied substantially above and below the 57% value for the combined data. Interestingly, no major inter-site differences in diagnostic profiles for the three pertinence and urgency anchor points were found that might account for this variability. Finally, visits from high frequency users were less likely to be judged P/U than visits from patients attending less frequently. Conclusion Primary consideration for a P/U tag was a visit characterized by a behaviorally disturbed state and/or, suicidal ideation (or attempts) within the context of either an underlying psychotic or affective disorder, especially if poor judgment was an issue. Some specific diagnoses appeared to qualify the above core clinical considerations, increasing or decreasing the probability of a P/U tag. Finally, non-clinical site-specific factors related to the individual services themselves, such as the number of readily available specialized resources, also appeared to qualify this assessment. These data may prove useful for the future development of this service.

Abstract Background: Frequent users of the psychiatric emergency service (PES) place a heavy burden upon the mental health care delivery system. The aim of this study was to identify distinct temporal or geographical patterns of PES use by these patients as potential markers for their early detection. Methods: Diagnostic profiles were obtained for patients making an intermediate (4 to 10) or a high (11 or more) number of visits to a general hospital PES in Montreal (Canada) between 1985 and 2004. Between-group comparisons were made with regards to several parameters. These included the time intervals between consecutive visits, visit clustering (single, repeating, and the time interval to the first cluster) and visits made to three other services where data was similarly acquired from 2002 to 2004. Results: The two multiple visit groups differed with regards to diagnostic profiles and actual time between consecutive visits (significantly shorter in patients with 11 or more visits). Patients with 11 or more visits were more likely to have a single cluster (3 or more visits/3 months) or repeating clusters (4 visits/3 months) in their patterns of use. Personality disorders were more prevalent in patients with single clusters as they were, along with schizophrenia, in those with repeating clusters. In addition, clusters were found to occur sufficiently early so as to be potentially useful as markers for early detection. Ten percent of those with 11 or more visits and 16% of those with an intermediate number of visits frequented at least one other PES. A small number of patients, primarily those with substance abuse, made over 50% of their visits to other services. Conclusion: Temporal and geographical patterns of use differed significantly between the multiple visit groups. These patterns, combined with distinct diagnostic profiles, could potentially lead to the more rapid identification and treatment of specific sub-groups of multiple visit patients.

Substance misuse is frequently encountered in the psychiatric emergency service (PES) and may take many forms, ranging from formal DSM-IV diagnoses to less obvious entities such as hazardous consumption. Detecting such patients using traditional screening instruments has proved problematic. We therefore undertook this study to more fully characterize substance misuse in the PES and to determine whether certain variables might help better screen these patients. We used a prospectively acquired database of over 18,000 visits made to four PESs during a 2-year period in the province of Quebec, Canada. One of the variables acquired was a subjective rating by the nursing staff as to whether substance misuse was a contributing factor to the visit (graded as direct, indirect, or not at all). Substance misuse accounted for 21% of all diagnoses and alcohol was the most frequent substance used. Patients were divided into those with primary (PSM), comorbid (CSM) or no substance misuse (NSM). Depressive disorders were the most frequent primary diagnoses in CSM, whereas personality and substance misuse disorders were frequent secondary diagnoses in PSM. Although many variables significantly differentiated the three groups, few were sufficiently detailed to be used as potential screening tools. Those situations that did have sufficient details included those with a previous history of substance misuse, substance misuse within 48 hours of the visit, and visits graded by the nursing staff as being directly and/or indirectly related to substance misuse. Variables related to substance misuse itself were the primary predictors of PSM and, less significantly, CSM. The nursing staff rating, although promising, was obtained in less than 30% of all visits, rendering its practical use difficult to assess.

Background: The impact of an aging population on the psychiatric emergency service (PES) has not been fully ascertained. Cognitive dysfunctions aside, many DSM-IV disorders may have a lower prevalence in the elderly, who appear to be underrepresented in the PES. We therefore attempted to more precisely assess their patterns of PES use and their clinical and demographic characteristics., Methods: Close to 30,000 visits to a general hospital PES (Montreal, Quebec, Canada) were acquired between 1990 and 2004 and pooled with over 17,000 visits acquired using the same methodology at three other services in Quebec between 2002 and 2004., Results: The median age of PES patients increased over time. However, the proportion of yearly visits attributable to the elderly (compared to those under 65) showed no consistent increase during the observation period. The pattern of return visits (two to three, four to ten, eleven or more) did not differ from that of patients under 65, although the latter made a greater number of total return visits per patient. The elderly were more often women (62%), widowed (28%), came to the PES accompanied (42%) and reported « illness » as an important stressor (29%). About 39% were referred for depression or anxiety. They were less violent (10%) upon their arrival. Affective disorders predominated in the diagnostic profile, they were less co-morbid and more likely admitted than patients under 65., Conclusion: Although no proportional increase in PES use over time was found the elderly do possess distinct characteristics potentially useful in PES resource planning so as to better serve this increasingly important segment of the general population.

Introduction: Studies of aggressive behaviors in a nonforensic mental health setting have focused primarily on the inpatient ward and, on event prediction, using behavior-based clinical rating scales. Few studies have specifically targeted aggressive behaviors in the psychiatric emergency service or determined whether assessing the demographic and clinical characteristics of such patients might prove useful for their more rapid identification., Methods: We used a prospectively acquired database of over 20,900 visits to four services in the province of Quebec, Canada, over a two-year period from September 2002 onwards. A maximum of 72 variables could be acquired per visit. Visits with aggression (any verbally or physically intimidating behavior), both present and past, were tagged. Binary logistic regressions and cross-tabulations were used to determine whether the profile of a variable differed in visits with aggression from those without aggression., Results: About 7% of visits were marked by current aggression (verbal 49%, physical 12%, verbal and physical 39%). Including visits with a "past only" history of aggression increased this number to 20%. Variables associated with aggression were gender (male), marital status (single/separated), education (high school or less), employment (none), judicial history (any type), substance abuse (prior or active), medication compliance (poor), type of arrival to psychiatric emergency services (involuntary, police, judiciary, landlord), reason for referral (behavioral dyscontrol), diagnosis (less frequent in anxiety disorders), and outcome (more frequently placed under observation or admitted)., Conclusion: Our results suggest that many state-independent variables are associated with aggressive behaviors in the psychiatric emergency service. Although their sum may not add up to a specific patient profile, they can nevertheless be useful in service planning, being easily integrated alongside state-dependent rating scales in a triage and/or observation instrument for daily use in the psychiatric emergency service.

Background: Several recent studies have reported a significant increase in medical emergency department (ED) use for reasons of mental health. The diagnostic profile of these patients however differs from that usually described for patients visiting the psychiatric emergency service (PES). Few studies have specifically focused upon long-term PES utilization rates. Those that do typically present data from the early 80s, suggesting that deinstitutionalization may be an important contributing factor to the increases found. The aim of this study was to assess PES use using a more recent time frame and, the effects of non-specific factors, such as population growth, on this use., Methods: Visits per year at several different types of PESs were obtained; (a) for an 11-year period at a general hospital PES while the surrounding population remained stable, (b) at that same PES while the catchment area population doubled over a period of a few years, (c) for an 11-year period at two PESs without catchment areas while the surrounding population increased and (d-) for a 12-year period at a PES in a mental health facility while the surrounding population increased. Moderately conservative criteria were used to define either a trend or, a significant increase in utilization rates., Results: Each site had an inherent, 7 to 15% yearly variability in the number of PES visits. Over time however, only those where the surrounding population increased (either by an increase in the catchment area size or a regional increase in the population census) showed a trend or, a significant increase in utilization rates. These increases however were modest and of the order of 12 to 19%., Conclusion: Long observation periods are required in order to detect stable changes in PES utilization rates over time. As such, population growth may be but one of several factors underlying these increases. Organizational changes in mental health care delivery in the vicinity of the services that showed an increase could also have contributed. These latter would simply have redistributed (to the PES) the pre existing pool of mental health care patients, resulting in an increase that is more apparent than real.

Background: The psychiatric emergency service (PES) is a major hub in the mental health care delivery system. The aim of this study was to more precisely define what psychiatrists consider to be a psychiatric emergency and to examine the underlying basis of this assessment., Methods: Over twenty-two thousand PES visits were assessed prospectively for pertinence and urgency by psychiatrists in four functionally and structurally different services in the province of Quebec, Canada. This study took place between July 15 1996 and August 31, 2004., Results: Overall, 57% of visits were judged pertinent and urgent (P/U), 30% pertinent but not urgent (P/NU) and 13% neither pertinent nor urgent (NP/NU). Between 50 and 60% of P/U tagged visits were diagnosed with an affective or a psychotic disorder, often with a suicidal content. They also more frequently resulted in a short-term observation in the PES or a hospitalization. Variables suggesting the presence of a behaviorally disturbed state (aggressive behaviors, involuntary or police referrals) were equally likely to be found in P/U or NP/NU visits. Legal confinement following the consultation was almost exclusively seen in visits judged P/U. The percent of visits tagged P/U at the four individual sites varied substantially above and below the 57% value for the combined data. Interestingly, no major inter-site differences in diagnostic profiles for the three pertinence and urgency anchor points were found that might account for this variability. Finally, visits from high frequency users were less likely to be judged P/U than visits from patients attending less frequently., Conclusion: Primary consideration for a P/U tag was a visit characterized by a behaviorally disturbed state and/or, suicidal ideation (or attempts) within the context of either an underlying psychotic or affective disorder, especially if poor judgment was an issue. Some specific diagnoses appeared to qualify the above core clinical considerations, increasing or decreasing the probability of a P/U tag. Finally, non-clinical site-specific factors related to the individual services themselves, such as the number of readily available specialized resources, also appeared to qualify this assessment. These data may prove useful for the future development of this service.

Objective: Pathological gambling (PG) has been associated with several negative mental health outcomes. We attempted to assess the impact of PG at the level of the psychiatric emergency service (PES)., Methods: In a first trial, clinical and demographic data were acquired from patients visiting the PES of a major university teaching hospital in downtown Montreal from July 1, 1996, to December 31, 2000. In a second trial, data were simultaneously acquired for a 2-year period in the above PES and in 3 others, beginning in September 2002., Results: In the first trial, from 2000 onward, the number of visits by PG patients to the PES increased by over 50%. In the second trial, the high level of PES use observed from 2000 onward in the first trial was similarly observed at all 4 PESs. The clinical and demographic characteristics of these patients were typical of help-seeking PG patients. They were, however, significantly less likely to be frequent users of the PES or to be hospitalized., Conclusion: Although still manageable, the clinical impact of PG on the PES increased significantly during the course of this study.

The purpose of this study was to evaluate the comparative efficacy and tolerability of sertraline and fluoxetine in the treatment of obsessive-compulsive disorder (OCD). Outpatients meeting DSM-IV criteria for OCD, with a Yale-Brown Obsessive-Compulsive (Y-BOCS) total score >or= 17, an NIMH Global Obsessive-Compulsive (NIMH-OC) scale score >or= 7, and a CGI-Severity score >or= 4 were randomized to 24 weeks of double-blind treatment with sertraline (N = 77) or fluoxetine (N = 73). Primary efficacy measures consisted of the Y-BOCS, the NIMH-OC scale, and the CGI-Severity (CGI-S) and Improvement (CGI-I) scales. Equivalent and significant (p < 0.001) improvement was found at week 24 in Y-BOCS and NIMH-OC scale scores for sertraline and fluoxetine. After 12 weeks, 49.2% of patients on sertraline were rated on the CGI-S scale as being mildly ill or not ill compared to 24.6% on fluoxetine (p < 0.01). A Cox analysis found patients on sertraline to have a statistically nonsignificant 42% greater likelihood of achieving a response by week 12 (CGI-I, much or very much improved; 95% CI, 0.85, 2.38; p = 0.18). Sertraline treatment also resulted in a higher proportion of remissions than fluoxetine (defined as a CGI-I

1. The authors conducted a retrospective exploratory computerized EEG study on the effect of clozapine in treatment-refractory schizophrenics, 10 high-responders (HRs) and 10 low-responders (LRs), in an attempt to correlate amplitude but especially coherence changes with a positive clinical response to clozapine. 2. EEGs with eyes closed were obtained before and during a clozapine treatment. Both groups had a similar drug profile with regards to non-clozapine medication. Probability maps were computed to illustrate changes of amplitude and coherence (for all combinations of paired electrodes) for 4 frequency bands (theta, alpha, beta 1 and 2). 3. The effect on AMPLITUDE was a generalized increase in lower bands and a decrease in anterior regions in higher bands of both HRs and LRs. Considerable changes of COHERENCE were observed on a wide set of paired electrodes in most frequency bands with some electrodes involved in HRs but uninvolved or differently involved in LRs suggesting differences in selected brain regions. 4. Changes of coherence but not amplitude were correlated with changes on the BPRS, thus to clinical improvement, and concerned mostly the right anterior-medial temporal (T4) and central (C4) electrodes paired with prefrontal electrodes, left central (C3), temporal (T3) and parietal (P3) electrodes in the theta band. 5. Clozapine has both generalized and regional effects as can be suspected considering its effect on many subtypes of brain receptors. A brain dysfunction centralized on the right anterior-medial temporal region may characterize treatment-refractory schizophrenics.

The maze test is a complex cognitive task involving visuoperceptual, planning and foresight abilities. EEGs were recorded from 20 healthy subjects according to the 10/20 system. Coherence is analogous to a correlation coefficient between the signals recorded by two electrodes and is computed between each electrode paired to all other electrodes. The maze test provoked changes of coherence mainly within the prefrontal regions, between parietal and central electrodes paired with frontal electrodes, especially the right frontopolar and the left prefrontal electrodes, and in the posterior temporal, parietal and occipital regions. EEG coherence analysis detects changes in regions known to be involved in visual processing and executive functions.

The neurobiologic mechanisms whereby the long-term administration of different antidepressant treatments enhance the efficacy of 5-HT synaptic transmission was investigated using an electrophysiologic paradigm in chloral hydrate anesthetized rats. Repeated electroconvulsive shocks (ECS; administered every other day for 14 days) as well as the sustained 21-day administration of the tricyclic antidepressant imipramine (10 mg/kg/day) and of the selective 5-hydroxytryptamine (5-HT) reuptake blocker paroxetine (5 mg/kg/day), increased the suppressant effect of the electrical stimulation of the afferent 5-HT pathway on the firing activity of CA3 hippocampus pyramidal neurons. The long-term treatments with imipramine and ECS, but not with paroxetine, increased the responsiveness of postsynaptic CA3 hippocampus pyramidal neurons to the microiontophoretic application of 5-HT and to that of the selective 5-HT1A receptor ligand 8-OH-DPAT. In contrast, the long-term treatment with paroxetine, but not with imipramine or ECS, attenuated the negative feedback exerted by terminal 5-HT autoreceptors on 5-HT release. This was indicated by two series of experiments. First, the capacity of the acute intravenous injection of the terminal 5-HT autoreceptor antagonist methiothepin to increase the efficacy of the stimulation was abolished in paroxetine-treated rats. Second, the decreased suppressant effect on pyramidal neuron firing activity usually obtained by increasing the frequency of the stimulation from 1 to 5 Hz (shown to be due to an increase in terminal 5-HT autoreceptor activation at the higher frequency) was also reduced in paroxetine-treated rats. The present data confirm and extend those of previous electrophysiologic studies showing that an enhanced 5-HT synaptic transmission is a common end result of long-term administration of various types of antidepressant treatments. Furthermore, they suggest that the mechanisms underlying this enhanced synaptic transmission differ according to the type of treatment administered. Tricyclic antidepressants and ECS enhance 5-HT synaptic transmission by increasing the sensitivity of postsynaptic 5-HT1A receptors, whereas selective 5-HT reuptake blockers produce this effect by reducing the function of terminal 5-HT autoreceptors, thereby increasing the amount of 5-HT released per stimulation-triggered action potential.

The authors investigated the mechanism of action of the antidepressant serotonin (5-HT) reuptake blocker citalopram in the rat by means of an in vivo electrophysiologic paradigm. In control animals, the acute intravenous administration of citalopram reduced the firing rate of dorsal raphe nucleus serotonergic neurons with an ED50 of 230 micrograms/kg. Rats were treated with citalopram (20 mg/kg/day i.p.) for 2, 7, and 14 days. Two-day treatment was accompanied by a marked reduction of the firing activity of serotonergic neurons; there was a partial recovery after 7 days of treatment, and a complete one following 14-day citalopram administration. The response of serotonergic neurons to intravenously administered lysergic acid diethylamide (LSD), a somatodendritic 5-HT autoreceptor agonist, was reduced in rats treated with citalopram for 14 days, suggesting that such a treatment reduces the sensitivity of the somatodendritic autoreceptor. Fourteen-day citalopram treatment also markedly enhanced the efficacy of the stimulation of the afferent serotonergic pathway in suppressing the firing activity of postsynaptic CA3 dorsal hippocampus pyramidal neurons. This enhanced efficacy of serotonergic synaptic transmission was not the result of an increased sensitivity of postsynaptic neurons to serotonin, as the effect of the direct microiontophoretic application of serotonin onto these same neurons was not modified. That serotonin reuptake blockade per se was responsible for this enhancement could also be ruled out, as the acute intravenous administration of citalopram (1 mg/kg) in control rats failed to enhance the efficacy of the stimulation. To determine an involvement of the 5-HT terminal autoreceptor, methiothepin (1 mg/kg), a terminal autoreceptor antagonist, was injected intravenously in control and citalopram-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration of serotonin (5-hydroxytryptamine, 5-HT) to pyramidal cells of the CA1 region of the hippocampus results in a hyperpolarizing response which is followed by a rebound depolarization and a decrease in the calcium-activated afterhyperpolarization (AHP). While the hyperpolarizing response has been previously shown to be mediated by receptors of the 5-HT1A subtype, the identity of the receptor(s) involved in the depolarizing response and decrease of the AHP have not been identified. In the present study the effectiveness of a series of 5-HT receptor antagonists in blocking the membrane depolarization and reduction of the AHP was assessed. While a variety of 5-HT1 and 5-HT2 antagonists were found to be ineffective, the substituted benzamide BRL 24924 was found to be a potent and selective antagonist of the 5-HT-induced depolarization and decrease in the AHP in this region. This effect however appeared unrelated to the ability of this compound to block 5-HT3 receptors, as ICS 205-930 and MDL 72222 were markedly less efficacious in blocking these effects of 5-HT. Upon blockade of 5-HT1A receptors, 5-HT elicits a depolarization which is accompanied by a marked increase in excitability. These effects were also dose-dependently antagonized by BRL 24924. The present results thus suggest the presence in the CA1 region of the hippocampus of a novel 5-HT receptor at which BRL 24924 functions as a selective antagonist and which is capable of mediating slow excitatory responses in central neurons.

The electrophysiologic assessment of the action of different types of antidepressant treatments on the serotonin (5-hydroxytryptamine [5-HT]) system revealed as a common effect an enhancement of 5-HT neurotransmission, albeit each treatment achieved this result via a different mechanism. Tricyclic antidepressant drugs and electroconvulsive shock treatment sensitize postsynaptic neurons to 5-HT. Monoamine oxidase inhibitors enhance the availability of releasable 5-HT. Serotonin reuptake blockers increase the efficacy of 5-HT neurons by desensitizing 5-HT autoreceptors located on 5-HT nerve terminals. Serotonin1A receptor agonists would enhance the tonic activation of postsynaptic 5-HT1A receptors. Such results suggest that this effect of antidepressant treatments on the 5-HT system might be intimately related to their therapeutic effect in major depression.

The effects of short-term serotonin (5-HT) depletion by p-chlorophenylalanine (PCPA) on the firing activity of dorsal raphe nucleus 5-HT neurons, on the responsiveness of dorsal hippocampus pyramidal neurons to microiontophoretically applied 5-HT and on the efficacy of the electrical stimulation of the ascending 5-HT pathway in suppressing the firing activity of CA3 dorsal hippocampus pyramidal neurons were assessed in chloral hydrate-anesthetized rats. PCPA (250 mg/kg/day i.p. for 2 days) reduced the 5-HT content of the dorsal hippocampus by 90%. However, the number of spontaneously active 5-HT neurons per microelectrode trajectory through the dorsal raphe or their average rate of firing was unaltered. The effect of afferent 5-HT pathway stimulation was reduced in only 40% of treated rats, whereas the sensitivity of CA3 pyramidal neurons to microiontophoretic 5-HT was not modified. The function of the terminal 5-HT autoreceptor was assessed using methiothepin, an autoreceptor antagonist. Methiothepin (1 mg/kg, i.v.) significantly enhanced the efficacy of the stimulation in PCPA-treated rats, although the degree of enhancement was much less than in controls. A greater reduction of the effectiveness of the stimulation was obtained by increasing the dose of PCPA (350 mg/kg/day i.p. for 2 days). This regimen reduced the 5-HT content of the dorsal hippocampus by 95%. In these rats, the sensitivity of the terminal 5-HT autoreceptor was assessed by increasing the frequency of the stimulation from 1 to 5 Hz. This procedure reduced to a similar extent the efficacy of the stimulation in treated and control rats, suggesting that the reduced effectiveness of methiothepin in enhancing 5-HT synaptic transmission in PCPA-treated rats is due to a lower degree of activation of the terminal 5-HT autoreceptor. The present results showing that the 350 mg/kg/day regimen of PCPA, but not the 250 mg/kg/day regimen, reduced the efficacy of the stimulation of the ascending 5-HT pathway suggest that a greater than 90% depletion is required to affect 5-HT neurotransmission significantly. The reduced level of activation of terminal 5-HT autoreceptors in rats treated with the lower dose of PCPA may facilitate the release of the remaining 5-HT per stimulation-triggered action potential, ensuring a virtually unaltered synaptic efficacy.

Citalopram (CIT), is a selective serotonin (5-HT) reuptake blocker and a clinically effective antidepressant. The present electrophysiological studies were undertaken to investigate in vivo the acute and long-term effects of CIT administration on 5-HT neurotransmission. In a first series of experiments, a single dose of CIT (0.05-0.5 mg/kg) was administered intravenously to naive rats while recording the activity of a 5-HT-containing neuron in the nucleus raphe dorsalis. A dose-response relationship of the inhibitory effect of CIT on the firing activity of 5-HT neurons was obtained with an ED50 of 0.23 +/- 0.03 mg/kg. In a second series of experiments, rats were treated with CIT (20 mg/kg/day, i.p.) for 2, 7 and 14 days. In rats treated for 2 days, there was a marked reduction in the firing activity of 5-HT neurons in the nucleus raphe dorsalis; there was a partial recovery after 7 days and a complete recovery after 14 days of treatment. The response of 5-HT neurons to intravenously administered LSD was decreased in rats treated for 14 days with CIT, indicating a desensitization of the somatodendritic 5-HT autoreceptor. In a third series of experiments, carried out in rats treated with CIT (20 mg/kg/day, i.p.) for 14 days, the suppression of firing activity of CA3 hippocampal pyramidal neurons produced by microiontophoretically-applied 5-HT and by the electrical activation of the ascending 5-HT pathway was measured. Long-term treatment with CIT did not modify the responsiveness of these neurons to microiontophoretically-applied 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)

The intravenous administration of low doses of lysergic acid diethylamide (LSD) or of the selective 5-hydroxytryptamine1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) depresses the firing activity of dorsal raphe 5-HT-containing neurons, presumably via the activation of 5-HT1A receptors. The present studies were undertaken to determine the effect of different types of 5-HT receptor antagonists on this effect of LSD and 8-OH-DPAT. (-)-Propranolol (2 mg/kg i.v.), methiothepin (2 mg/kg i.p., twice daily for 4 days followed by an additional dose of 2 mg/kg i.p., prior to the experiment), pelanserine (0.5 mg/kg i.v.), and indorenate (125 micrograms/kg i.v.) failed to block the effects of either LSD or 8-OH-DPAT on the firing activity of 5-HT neurons of the dorsal raphe nucleus. However, spiperone (1 mg/kg i.v.) significantly reduced the effect of both LSD and 8-OH-DPAT. These results indicate that, among the five putative 5-HT receptor antagonists tested, only spiperone can antagonize the suppressant effect of 5-HT receptor agonists on the firing of dorsal raphe 5-HT neurons.

5-HT-containing terminals possess autoreceptors which modulate the release of 5-HT into the synaptic cleft. Tritiated imipramine ([3H]IMI), and more specifically [3H]citalopram and [3H]paroxetine, bind to a site associated with the 5-HT reuptake carrier on the 5-HT terminals. The function of terminal 5-HT autoreceptors is decreased following long-term treatment with the 5-HT reuptake blocker citalopram. The present study was undertaken to determine whether an increased synaptic availability of 5-HT or, the occupation of the [3H]IMI site, were responsible for this modification. Unitary extracellular recordings were obtained from CA3 dorsal hippocampus pyramidal neurons under chloral hydrate anesthesia in rats treated daily with fluoxetine (10 mg/kg/day X 14 days), a selective 5-HT reuptake blocker, or clorgyline (1 mg/kg/day X 21 days), an inhibitor of type A monoamine oxidase. The function of the terminal 5-HT autoreceptors was assessed by comparing the effectiveness of the electrical stimulation of the ascending 5-HT pathway on the firing activity of hippocampus pyramidal neurons prior to, and following, the administration of methiothepin, an antagonist of the terminal 5-HT autoreceptor, and, by determining the ratio of effectiveness of 0.8 Hz (S1) and 5 Hz (S2) stimulations. Long-term administration of fluoxetine or clorgyline both increased the efficacy of the stimulation of the 5-HT pathway. However, the enhancing effect of methiothepin on the efficacy of the stimulation was attenuated by the fluoxetine, but not by the clorgyline, treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

The efficacy of serotoninergic (5-HT) neurotransmission was assessed in the rat brain following different types of antidepressant treatments. First, the firing rate of 5-HT neurons was assessed. Second, the responsiveness of postsynaptic neurons to 5-HT was evaluated by applying directly onto these neurons the neurotransmitter by microiontophoresis. Finally, the effect of the electrical stimulation of the 5-HT pathway on the firing activity of the same postsynaptic neurons was studied in order to determine the efficacy of synaptic transmission. Long-term administration of tricyclic antidepressant drugs induces a sensitization of rat forebrain neurons to 5-HT without altering 5-HT neuron properties. This sensitization results in an enhancement of the effect of the stimulation of the 5-HT pathway on the firing activity of postsynaptic neurons. Long-term administration of antidepressant monoamine oxidase inhibitors also results in an enhancement of the effectiveness of the stimulation of the 5-HT pathway. This is not due to a modification of postsynaptic neuron properties, since there is no enhancement of their responsiveness to 5-HT. Furthermore, the function of the terminal 5-HT autoreceptor is not altered by long-term treatment with a monoamine oxidase inhibitor. Therefore, the enhancement of 5-HT neurotransmission produced by this type of drugs is due to an increased availability of releasable 5-HT. The acute administration of 5-HT reuptake blockers does not enhance the efficacy of the stimulation of the 5-HT pathway. However, their long-term administration produces such an enhancement without altering the responsiveness of postsynaptic neurons to 5-HT. This modification of 5-HT transmission is attributable to a desensitization of the terminal 5-HT autoreceptor, thereby allowing a greater amount of 5-HT to be released per impulse in the synaptic cleft. The electrophysiological assessment of the effects of these different types of antidepressant treatments on the 5-HT system therefore revealed as a common effect an enhancement of 5-HT neurotransmission, albeit each one achieving this via a different mechanism.

Results of electrophysiological single-cell recording studies suggest that most, if not all, types of antidepressant treatments increase 5-hydroxytryptamine (5-HT) neurotransmission. Tricyclic antidepressants, electroconvulsive shock treatment, mianserin, adinazolam, and possibly sleep deprivation may exert their therapeutic effect through sensitization of postsynaptic neurons to 5-HT. Serotonin reuptake blockers may relieve depression through an increased efficacy of the presynaptic element resulting from a desensitization of somatodendritic and terminal 5-HT autoreceptors. Similarly, monoamine oxidase inhibitors may act by increasing the efficacy of 5-HT neurons. Intensification of 5-HT function appears to be a common denominator to antidepressant treatments; however, evidence suggests that this modification may only be a link in a chain of events leading to an antidepressant response.