Increased number of offspring in first degree relatives of psychotic individuals: a partial explanation for the persistence of psychotic illnesses.

OBJECTIVE: As patients with psychotic illness have fewer offspring than controls, the persistence of psychotic illness is puzzling. We hypothesized that unaffected first-degree relatives of patients have more offspring than controls. METHOD: Probands were 4904, individuals with non-affective psychotic disorders identified from a hospitalization registry. Unaffected first degree relatives and matched controls were identified from the Israeli Population Registry. The number of offspring of unaffected parents, biological siblings and controls was ascertained. RESULTS: Unaffected parents of psychotic patients had more offspring/person than controls; 4.5 +/- 2.7 vs. 3.4 +/- 2.2, P = 0.000. Unaffected parents from familial psychosis families (more than one affected family member) had 1.83 more offspring than controls; unaffected parents from non-familial psychosis families had 0.97 more offspring than controls (both P < 0.001). CONCLUSION: These findings might imply that genes which increase susceptibility for schizophrenia may be associated with increased number of offspring, perhaps supplying a partial explanation for the persistence of psychosis.

Self-report of family functioning and risk for psychotic disorders in male adolescents with behavioural disturbances.

OBJECTIVE: Previous studies indicate that a poor family environment might affect vulnerability for the later manifestation of psychotic illness. The current study aims to examine family functioning prior to the onset of psychosis. METHOD: Subjects were 42,948, 17-year old males with behavioural disturbances who were asked about the functioning of their family by the Israeli Draft Board. Data on later psychiatric hospitalizations were obtained from a National Psychiatric Hospitalization Registry. RESULTS: Poorer self-reported family functioning was associated with greater risk for later hospitalization for psychosis [adjusted hazard ratio (HR) = 1.16, 95% CI = 1.05-1.27], with a trend in the same direction for schizophrenia (adjusted HR = 1.1, 95% CI = 0.98-1.24). CONCLUSION: In male adolescents with behavioural disturbances, perceived poorer family functioning is associated with increased risk for non-affective psychotic disorders and schizophrenia. These data do not enable us to determine if perceived familial dysfunction increases vulnerability for psychosis, if premorbid behavioural abnormalities disrupt family life, or neither.

Agonistic behavior in naïve juvenile lobsters depleted of serotonin 5,7-dihydroxytryptamine.

We have been exploring the role of serotonin in fighting behavior in lobsters using a specific model of agonistic behavior, the establishment of hierarchical relationships between pairs of socially naive juvenile lobsters. We selected this model because the behavior is easily evoked, readily quantifiable, and the effects of experience are eleminated by using socially naive animals. In these studies we injected a specific neurotoxin, 5,7-dihydroxytryptamine, into juvenile lobsters over a 4-week period and then measured the effects on fighting behavior. This treatment reduces the levels of serotonin in the nervous system and immunocytochemical studies show a dramatic reduction in neuropil staining for the amine. Control animals received vehicle injection alone. All injected animals were paired against larger or smaller non-injected opponents, and three successive 30-min fights were carried out and statistically analyzed. The results were surprising: As with elevations of serotonin, reduced levels of serotonin increased the amount of time animals engaged in fighting behavior. No significant effects were seen on who initiated encounters, who retreated first, or who the eventual winner would be. Thus, in this model, elevation or reduction of serotonergic function increases the tendency of animals to engage in agonistic encounters.

Aminergic neuron systems of lobsters: morphology and electrophysiology of octopamine-containing neurosecretory cells.

In the American lobster (Homarus americanus) the biogenic amines serotonin and octopamine appear to play important and opposite roles in the regulation of aggressive behavior, in the establishment and/or maintenance of dominant and subordinate behavioral states and in the modulation of the associated postural stances and escape responses. The octopamine-containing neurosecretory neurons in the thoracic regions of the lobster ventral nerve cord fall into two morphological subgroups, the root octopamine cells, a classical neurohemal group with release regions along second thoracic roots, and the claw octopamine cells, a group that selectively innervates the claws. Cells of both subgroups have additional sets of endings within neuropil regions of ganglia of the ventral nerve cord. Octopamine neurosecretory neurons generally are silent, but when spontaneously active or when activated, they show large overshooting action potentials with prominent after-hyperpolarizations. Autoinhibition after high-frequency firing, which is also seen in other crustacean neurosecretory cells, is readily apparent in these cells. The cells show no spontaneous synaptic activity, but appear to be excited by a unitary source. Stimulation of lateral or medial giant axons, which excite serotonergic cells yielded no response in octopaminergic neurosecretory cells and no evidence for direct interactions between pairs of octopamine neurons, or between the octopaminergic and the serotonergic sets of neurosecretory neurons was found.

Patterns of shaker family gene expression in single identified neurons of the American lobster, Homarus americanus.

The patterns of expression of voltage gated potassium channel genes of the Shaker family have been mapped in identified neurons of the lobster (Homarus americanus) ventral nerve cord using a single cell reverse transcriptase polymerase chain reaction procedure. Using specific oligonucleotides derived from the sequences of the shaker, shab, and shaw genes of the spiny lobster, Panulirus interruptus, we detected the corresponding potassium channel DNA fragments from Homarus americanus. The Homarus DNA fragments are 87-98% identical at the nucleotide level to the Panulirus DNA fragments. We used the Panulirus primers to measure the complement of RNAs for shaker, shab, and shaw in single identified cells that use GABA, glutamate, octopamine or serotonin as chemical messengers. Shaker and shaw RNAs were found in all four identified neuron types but shab RNA was not detected in serotonin cells under the present experimental conditions. All cells expressed alpha-tubulin RNA, which serves as an internal control suggesting that cells are intact after dissection. In glial cells that surround the neuronal cell bodies, the potassium channel genes are expressed at low to non-detectable levels.

Serotonin and aggression: insights gained from a lobster model system and speculations on the role of amine neurons in a complex behavior.

The amine serotonin has been suggested to play a key role in aggression in many species of animals, including man. Precisely how the amine functions, however, has remained a mystery. As with other important physiological questions, with their large uniquely identifiable neurons, invertebrate systems offer special advantages for the study of behavior. In this article we illustrate that principal with a description of our studies of the role of serotonin in aggression in a lobster model system. Aggression is a quantifiable behavior in crustaceans, the amine neuron systems believed to be important in that behavior have been completely mapped, and key physiological properties of an important subset of these netirons have been defined. These results are summarized here, including descriptions of the "gain-setter" role and "autoinhibition" shown by these neurons. Results of other investigations showing socially modulated changes in amine responsiveness at particular synaptic sites also are described. In addition, speculations are offered about how important developmental roles served by amines like serotonin, which have been well described by other investigators, may be related to the behaviors we are examining. These speculations draw heavily from the organizational/activational roles proposed for steroid hormones by Phoenix et al. (1959).

Crustacean hyperglycemic hormone in the lobster nervous system: localization and release from cells in the subesophageal ganglion and thoracic second roots.

Crustacean hyperglycemic hormones (CHHs) are neuropeptides involved in the regulation of hemolymph glucose. The primary source of CHHs has been identified as the neurosecretory neurons of the eyestalk X-organ and its associated neurohemal organ, the sinus gland. We have identified another source of CHH-like peptides in the nervous system. With the use of immunocytochemistry, cells in the second roots of the thoracic ganglia have been observed to stain positively for CHH-reactive material. We also identified a pair of cells in the subesophageal ganglion that contain large amounts of CHH-reactive material. Depolarization of these cells with elevated potassium mediates a calcium-dependent release of CHH-like material from the ganglion as quantified with an enzyme-linked immunosorbent assay (ELISA).

Autoinhibition of serotonin cells: an intrinsic regulatory mechanism sensitive to the pattern of usage of the cells.

After periods of high-frequency firing, the normal rhythmically active serotonin (5HT)-containing neurosecretory neurons of the lobster ventral nerve cord display a period of suppressed spike generation and reduced synaptic input that we refer to as "autoinhibition." The duration of this autoinhibition is directly related to the magnitude and duration of the current injection triggering the high-frequency firing. More interesting, however, is that the autoinhibition is inversely related to the initial firing frequency of these cells within their normal range of firing (0.5-3 Hz). This allows more active 5HT neurons to resume firing after shorter durations of inhibition than cells that initially fired at slower rates. Although superfused 5HT inhibits the spontaneous firing of these cells, the persistence of autoinhibition in saline with no added calcium, in cadmium-containing saline, and in lobsters depleted of serotonin suggests that intrinsic membrane properties account for the autoinhibition. A similar autoinhibition is seen in spontaneously active octopamine neurons but is absent from spontaneously active gamma-aminobutyric acid cells. Thus, this might be a characteristic feature of amine-containing neurosecretory neurons. The 5HT cells of vertebrate brain nuclei share similarities in firing frequencies, spike shapes, and inhibition by 5HT with the lobster cells that were the focus of this study. However, the mechanism suggested to underlie autoinhibition in vertebrate neurons is that 5HT released from activated or neighboring cells acts back on inhibitory autoreceptors that are found on the dendrites and cell bodies of these neurons.

Long-Term Culture of Lobster Central Ganglia: Expression of Foreign Genes in Identified Neurons.

The ventral nerve cords of lobsters (Homarus americanus) can be cultured in vitro for at least 7 weeks. Over this period, neurons maintain their normal electrophysiological features and continue, among other measures of neuronal health, to synthesize RNA and proteins. One application of this culture system is demonstrated: the manipulation of gene expression in identified neurons. After intracellular injection of complementary RNA (cRNA) encoding green fluorescent protein (GFP), the amount of protein product measured by fluorescent confocal microscopy increases for 4 days and then decreases to background by day 10. Thus, translation of the injected message must have increased for 4 days before declining. Moreover, after injection of cRNA encoding {beta}-galactosidase, the levels of enzyme activity were measured using a fluorogenic substrate, revealing a peak of {beta}-galactosidase activity at 6 to 9 days; this activity was still detectable for at least 10 days after injection. Therefore, either GFP or {beta}-galactosidase can be used as an injectable marker, allowing in vivo quantitation of expression in individual cells over time. We measured long-lasting expression of these proteins after a single injection, suggesting that it may be possible to manipulate the levels of expression of any gene of interest.

Central nervous system abnormalities in complex regional pain syndrome (CRPS): clinical and quantitative evidence of medullary dysfunction.

OBJECTIVE: Sensory and motor abnormalities are common among patients with complex regional pain syndrome (CRPS). The purpose of the present study was to define and characterize these abnormalities and to develop a hypothesis regarding the area of the central nervous system from which they derive. DESIGN: Data were acquired from study subjects using clinical examination and quantitative assessment of neurological function. Subjects were divided into four groups. CRPS patients were differentiated into two groups based on the presence or absence of sensory deficit on the face to clinical examination. The other two groups were composed of patients with other chronic pain syndromes and normal individuals without chronic pain or disability. Clinical and quantitative data were compared between groups. PATIENTS: One hundred forty-five CRPS patients, 69 patients with other pain conditions, and 26 normal individuals were studied. RESULTS: A high incidence of trigeminal hypoesthesia was observed in CRPS patients. CRPS patients with trigeminal hypoesthesia manifested bilateral deficits of sensory function, with a predominant hemilateral pattern. These patients also manifested bilateral motor weakness with a more prominent hemiparetic pattern. Both sensory and motor deficits were greatest ipsilateral to the painful side of the body. These features differed significantly from those of CRPS patients lacking clinical trigeminal deficit, other pain patients, and normals. A lower cranial nerve abnormality (sternocleidomastoid weakness) and a myelopathic feature (Hoffman's reflex) were more common in CRPS patients with trigeminal hypoesthesia. CONCLUSIONS: Nearly half of CRPS patients had abnormalities of spinothalamic, trigeminothalamic, and corticospinal function that may represent dysfunction of the medulla. One-third of the remaining CRPS patients had neuroimaging evidence of spinal cord or brain pathology. The majority of CRPS patients in this study have measurable abnormalities of the sensory and motor systems or neuroimaging evidence of spinal cord or brain dysfunction.

Diagnosis and treatment of gastroesophageal reflux in children and adolescents with severe asthma.

BACKGROUND: The ability of gastroesophageal reflux disease to provoke asthma is controversial. Recent reports have suggested that reflux to the proximal esophagus may be especially likely to aggravate asthma, but the prevalence of proximal reflux in children and adolescents is poorly documented. It is also unclear how sensitive and specific the commonly used tests of reflux, barium swallow, and scintiscan are compared with pH probe studies in young patients. There is limited information on the effectiveness of the combination of H2 blockers and prokinetic agents in controlling reflux in children. OBJECTIVE: There were three objectives in this study: (1) to determine the prevalence of both proximal and distal gastroesophageal reflux in asthmatic children and adolescents; (2) to determine the sensitivity, specificity, positive and negative predictive values of barium swallow and scintiscan studies; and (3) to determine the effectiveness of standard antireflux pharmacotherapy. METHODS: A 24-hour, 2-channel pH probe study was carried out in 79 asthmatic children aged 2 to 17 years. The prevalence of abnormal proximal and distal gastroesophageal reflux was calculated from the findings. In 63 of these patients, barium swallow and Technetium99 scintiscan were carried out and the findings used to calculate the sensitivity, specificity, positive and negative predictive value of these studies relative to pH probe. In 11 subjects a follow-up, 24-hour pH probe was carried out after at least 3 weeks of therapy with an H2 blocker and prokinetic agent to determine the efficacy of therapy. RESULTS: There was abnormal proximal esophageal reflux in 64.5% of subjects and abnormal distal reflux in 73.4%. The sensitivity, specificity, positive and negative predictive values of barium swallow were 46.1%, 83.3%, 82% and 51%, respectively. Those of scintiscan were 15%, 72.7%, 50% and 32%, respectively. Of 11 subjects studied by repeat pH probe, 10 had persistent abnormal reflux. CONCLUSION: Abnormal reflux into the proximal esophagus occurs in the majority of asthmatic children with difficult-to-control disease. The barium swallow and scintiscan compare poorly with pH probe in diagnosing reflux. Treatment of reflux with recommended does of H2 blockers and prokinetic agents has a high failure rate, and follow-up studies are essential.

Presynaptic action of the neurosteroid pregnenolone sulfate on inhibitory transmitter release in cultured hippocampal neurons.

The effects of the neurosteroid pregnenolone sulfate (PS) were studied in 3- to 9-week-old hippocampal cultures from neonatal rats. Cells were voltage clamped using CsCl filled electrodes, while action potentials and excitatory glutamatergic currents were abolished by superfusing with a combination of tetrodotoxin, 6-cyano-7-nitroquinoxaline (CNQX) and 2-amino-5-phosphonopentanoic acid (AP-5). Under these conditions spontaneous GABAergic inhibitory postsynaptic currents (sIPSCs) were seen as inward currents at a holding potential of -70 mV. Their amplitude distributions were skewed without clearly detectable peaks. PS at 1-50 microM concentrations decreased the frequency of sIPSCs, with 1 microM being the most effective concentration. The effect appeared after 10-15 min of steroid application and the magnitude of the reduction increased during the early wash period. No recovery of sIPSC frequency was found after 30 min of washing with steroid-free medium. sIPSC amplitudes were not significantly changed at the time the effect of PS on sIPSC frequency was observed. The slow onset of this effect and its duration suggest a novel presynaptic action of the neurosteroid PS on GABAergic inhibition in the mammalian brain.

Excitation of identified serotonergic neurons by escape command neurons in lobsters.

Serotonin-containing neurosecretory neurons in the first abdominal ganglion (A1 5-HT cells) of the lobster (Homarus americanus) ventral nerve cord have been shown previously to function as 'gain setters' in postural, slow muscle, command neuron circuitries. Here we show that these same amine neurons receive excitatory input from lateral (LG) and medial (MG) giant axons, which are major interneurons in phasic, fast muscle systems. Activation of either LG or MG axons elicits short-latency, non-fatiguing, long-lasting excitatory postsynaptic potentials (EPSPs) in A1 5-HT cells which follow stimulus frequencies of up to 100 Hz in a 1:1 fashion. Single spikes triggered in either giant axon can produce EPSPs in the A1 5-HT cells of sufficient magnitude to cause the cells to spike and to fire additional action potentials after variable latencies; action potentials elicited in this way reset the endogenous spontaneous spiking rhythm of the A1 5-HT neurons. The giant-axon-evoked EPSP amplitudes show substantial variation from animal to animal. In individual preparations, the variation of EPSP size from stimulus to stimulus was small over the first 25 ms of the response, but increased considerably in the later, plateau phase of each response. When tested in the same preparation, EPSPs in A1 5-HT cells evoked by firing the LG axons were larger, longer-lasting and more variable than those triggered by firing the MGs. Firing A1 5-HT cells through an intracellular electrode, prior to activation of the giant fiber pathway, significantly reduced the size of LG-evoked EPSPs in A1 5-HT cells. Finally, morphological and physiological results suggest that similarities exist between giant fiber pathways in lobsters and crayfish. The possible functional significance of an involvement of these large amine-containing neurosecretory neurons in both tonic and phasic muscle circuitries will be discussed.

Serotonin and aggressive motivation in crustaceans: altering the decision to retreat.

In crustaceans, as in most animal species, the amine serotonin has been suggested to serve important roles in aggression. Here we show that injection of serotonin into the hemolymph of subordinate, freely moving animals results in a renewed willingness of these animals to engage the dominants in further agonistic encounters. By multivariate statistical analysis, we demonstrate that this reversal results principally from a reduction in the likelihood of retreat and an increase in the duration of fighting. Serotonin infusion does not alter other aspects of fighting behavior, including which animal initiates an encounter, how quickly fighting escalates, or which animal eventually retreats. Preliminary studies suggest that serotonin uptake plays an important role in this behavioral reversal.

Biogenic amines and aggression: experimental approaches in crustaceans.

This review summarizes our experimental approaches attempting to link amines and their metabolites to aggression in crustaceans. The results demonstrate (i) that agonistic behavior in crustaceans can be quantified, (ii) that the amines themselves have telling and subtle effects on the fighting behavior of animals, (iii) that pharmacological interventions are possible that might allow a biochemical dissection of the underlying mechanisms involved in processes like decision making in these animals, and (iv) that selective metabolites of amines are excreted in the urine of lobsters where they may serve behavioral roles. Many of the studies presented here are preliminary. Nonetheless, we believe the results are provocative and nicely complement previous detailed physiological, morphological and biochemical studies exploring the roles of amines in aggression in crustaceans. We expect that the continued use of this invertebrate model system will allow us to gain considerable insight into, and understanding of, the role served by biogenic amines in a complex behavioral process like aggression.

Serotonin, social status and aggression.

Serotonin, social status and aggression appear to be linked in many animal species, including humans. The linkages are complex, and, for the most part, details relating the amine to the behavior remain obscure. During the past year, important advances have been made in a crustacean model system relating serotonin and aggression. The findings include the demonstration that serotonin injections will cause transient reversals in the unwillingness of subordinate animals to engage in agonistic encounters, and that at specific synaptic sites involved in activation of escape behavior, the direction of the modulation by serotonin depends on the social status of the animal.

Developmental expression of the octopamine phenotype in lobsters, Homarus americanus.

We have used immunocytochemical methods to examine the sequence of appearance of octopamine-immunoreactive neurons during development, and to try to correlate that appearance with the emergence of behavioral or physiological capabilities. The first octopamine neurons express their transmitter phenotype at approximately 43% of embryonic development. The last cells show immunostaining at the 3rd larval stage. In the wild, therefore, immunoreactivity in cells appears over a 9-12 month period. In contrast, serotonin-immunoreactive neurons stain early in embryonic development and the last serotonin-immunoreactive cells appear at about the same time the first octopamine-immunoreactive neurons show staining. The pattern of appearance of octopamine-immunoreactive cells is cell type-specific. A pair of brain cells and the descending interneurons stain first. Additional brain cell staining is seen throughout embryonic development. The ascending interneurons appear next, and a general anterior-posterior gradient typifies their emergence over a relatively short portion of embryonic life (E 48-62%). The neurosecretory cell staining appears last, is segment-specific, begins at about 62% development, and continues to the 3rd larval stage. The emergence of immunostaining for amine neurotransmitters within groups of identified neurons at precise times in development may specify possible functional units. With at least one group of cells, this possibility seems plausible: the three pairs of claw octopamine neurosecretory cells show immunostaining as a unit.

Peptide F1, an N-terminally extended analog of FMRFamide, enhances contractile activity in multiple target tissues in lobster.

The physiological actions of lobster peptide F1 (TNRNFLRFamide) have been examined on three different lobster nerve-muscle preparations (exoskeletal, cardiac and visceral). The peptide, which is found at high concentrations in a lobster neurosecretory gland, causes a long-lasting enhancement of contractility in each target tissue. On exoskeletal nerve-muscle preparations, peptide F1 has the following actions: (1) it potentiates transmitter release from nerve terminals innervating exoskeletal muscle, leading to an increase in both spontaneous and nerve-evoked release of transmitter; (2) it acts directly on the muscle, in the absence of nerve activity, to induce tonic contractions; and (3) it shows a potent desensitization that does not reverse with prolonged washing of the tissue. On each of the types of muscle examined, peptide F1 is active at nanomolar concentrations and is 3-4 orders of magnitude more potent than FMRFamide. These findings suggest that peptide F1 is a neurohormone with widespread myogenic actions throughout lobster peripheral tissues. The molecular mechanism(s) by which the peptide acts are not yet known, but do not appear to involve cyclic AMP or cyclic GMP.

A quantitative analysis of agonistic behavior in juvenile American lobsters (Homarus americanus L.).

In these studies a quantitative analysis of agonistic (fighting) behavior in lobsters in presented as a first step in our attempt to relate patterns of behavior to underlying neurobiological mechanisms. The agonistic behavior of juvenile American lobsters (Homarus americanus L.) was studied in laboratory tanks at the New England Aquarium. Using video analyses and statistical techniques: (1) an ethogram of agonistic behavior was constructed; and (2) the temporal structure of the behavior was identified. We demonstrated that fighting in juvenile lobsters proceeds according to strict rules of conduct. All animals exhibit six common behavioral patterns in a stereotypical manner. A temporal sequence of these patterns was evident, representing an increase in intensity during confrontations. The typical scenario of an encounter begins with extensive threat displays upon first contact, continues with periods of ritualized aggression and restrained use of the claws, and terminates in a brief session of unrestrained combat. Predictions of game theory (i.e. assessment strategies) provide a useful framework for the understanding of fighting in lobsters. The presence of a highly structured behavioral system may reduce the potential for damage in fights among conspecifics, and may prove useful in attempts to study the neurobiological causes of complex behavioral patterns such as aggression.

A voltage-sensitive cation channel present in clusters in lobster skeletal muscle membrane.

The single channel properties of a voltage-sensitive cation channel are described in a study of ion channel activity in enzymatically induced blebs of lobster skeletal muscle membrane. This cation channel, one of several that are spontaneously active in excised patches from bleb membrane, can be distinguished from other channels on the basis of its large single channel conductance (293 pS), voltage-sensitive gating properties, the presence of a subconductance state of the fully open channel, and a weak selectivity for K > Na. At hyperpolarizing voltages, this channel displays flickering or bursting behavior, and a single state of the fully open channel is observed. At depolarizing voltages, the mean channel open time increases and a second longer-lived open state is observed. The voltage dependence of the mean channel open time and the linear i-V relation of this channel predict that the macroscopic current carried through this cation channel would be outwardly rectifying. Channels of this type are infrequently observed in this preparation, but when present in the patch are often present in multiple copies. We describe a statistical test for examining the clustering of ion channels in excised patches of membrane. The result of this test shows that the cation channels appear in clusters in the blebs.