Delta sleep inducing peptide inhibits somatostatin release via a dopaminergic mechanism

The Kallmann's syndrome variant (KSV) model of the schizophrenias

The KSV model of the schizophrenias proposes that up to 70% of schizophrenics have a pathogenic allele, or abnormal expression, of the KALIG-1 gene which is located at Xp22.3. This gene encodes a nerve-cell adhesion molecule (N-CAM) like protein, and is deleted in 66% of patients with Kallmann's syndrome, anosmia with secondary hypogonadism. Although superficially distinct, the schizophrenias and Kallmann's syndrome show numerous parallel trait defects which occur with a similar sex distribution. These defects are usually more profound in Kallmann's syndrome. Occasionally, Kallmann's patients exhibit additional defects, such as ichthyosis, which are due to the further deletion or translocation of adjacent genes. Since schizophrenics exhibit virtually all known trait defects in Kallmann's except these, it suggests that the aberrant genes are defective, but not deleted in schizophrenia. It also appears that compensatory mechanisms, involving serine proteases, are active in schizophrenia, which largely preserve fertility, but at the expense of an increased vulnerability to develop a psychosis by an episodic disruption of the blood-CSF barrier. Consequently, schizophrenia is rare in Kallmann's patients, while most schizophrenics are capable of reproduction.

Delta sleep-inducing peptide administration does not influence growth hormone and prolactin secretion in normal women

The aim of this study was to analyze the effects of delta sleep-inducing peptide (DSIP) on growth hormone (GH) and prolactin (PRL) secretion in eight healthy women with normal cycles (aged 17-36 years). GH and PRL secretion was studied in five women after DSIP (25 micrograms/kg bw IV over 30 min), arginine chlorhydrate (0.5 g/kg bw IV over 30 min) and simultaneous DSIP plus arginine chlorhydrate administration. In three other women the circadian rhythm of GH and PRL was studied during DSIP (25 micrograms/kg bw from 2130h to 2230h) and placebo IV infusion. Serum GH and PRL levels were normal under basal conditions and no effects were noted after the infusion of DSIP. The GH and PRL circadian rhythm was not modified by DSIP administration. DSIP did not influence GH and PRL responsiveness to arginine chlorhydrate. We found that at dosages which are known to modify ECG patterns, DSIP is unable to modify spontaneous or arginine chlorhydrate-induced GH and PRL secretion.

Immunohistochemical localization of delta sleep-inducing peptide-like immunoreactivity in the central nervous system and pituitary of the frog Rana ridibunda

The purpose of the present study was to investigate the distribution of delta sleep-inducing peptide in the brain and pituitary of the frog Rana ridibunda and to determine the possible effect of this nonapeptide on adrenocorticotropic hormone and corticosteroid secretion. Delta sleep-inducing peptide-like immunoreactive fibres were observed throughout the brain of the frog. These fibres generally exhibited the characteristics of glial cell processes. Scarce delta sleep-inducing peptide-positive fibres were seen in the olfactory bulb and in the periventricular areas of the telencephalon. In the diencephalon, numerous delta sleep-inducing peptide-containing processes were noted in the preoptic nucleus, the infundibular nuclei and the median eminence. A few cerebrospinal fluid-contacting cells were visualized in the ventral nucleus of the infundibulum. Delta sleep-inducing peptide-positive fibres were also observed in the mesencephalon, radiating through the different layers of the tectum. In the cerebellum, all Purkinje cells exhibited delta sleep-inducing peptide-like immunoreactivity. More caudally, numerous delta sleep-inducing peptide-positive fibres were noted in the vestibular nucleus of the rhombencephalon. A dense network of delta sleep-inducing peptide-containing fibres was seen in the pars nervosa of the pituitary. In the distal lobe, a population of endocrine cells located in the anteroventral region contained delta sleep-inducing peptide-immunoreactive material. Labelling of consecutive sections of the pituitary by delta sleep-inducing peptide and adrenocorticotropic hormone antiserum revealed that a delta sleep-inducing peptide-related peptide is expressed in corticotroph cells. The possible role of delta sleep-inducing peptide in the control of adrenocorticotropic hormone and corticosteroid release was studied in vitro, using the perifusion system technique. Administration of graded doses of delta sleep-inducing peptide (from 10(-8) to 10(-6) M) to perifused frog anterior pituitary cells did not affect the spontaneous release of adrenocorticotropic hormone. In addition, prolonged infusion of delta sleep-inducing peptide (10(-6) M) did not alter the stimulatory effect of corticotropin-releasing factor (10(-7) M) on adrenocorticotropic hormone secretion. Similarly, exposure of frog interrenal slices to delta sleep-inducing peptide did not induce any modification of spontaneous or adrenocorticotropic hormone-evoked secretion of corticosterone and aldosterone. Our results provide the first evidence for the presence of a delta sleep-inducing peptide-related peptide in lower vertebrates. The occurrence of delta sleep-inducing peptide-like immunoreactivity in specific areas of the brain suggests that the peptide may act as a neuromodulator.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of delta-sleep-inducing peptide-evoked release of Met-enkephalin from brain synaptosomes in rats

Delta-sleep-inducing peptide (DSIP) stimulates the release of Met-enkephalin (Met-ENK) from superfused slices of the rodent lower brainstem in vitro. In our present study, DSIP (10(-10)-10(-9) M) induced a significant release of Met-ENK from medullary synaptosomes of rats. This DSIP-evoked release of Met-ENK was Ca2+ dependent and tetrodotoxin (TTX) insensitive. Furthermore, DSIP (10(-11)-10(-9) M) significantly increased 45Ca2+ uptake in medullary synaptosomes. These results demonstrate that DSIP acts directly on the nerve endings of Met-ENK-containing neurons to release this pentapeptide by generating a Ca2+ influx into these neurons. Effects of DSIP on Met-ENK release in other discrete brain regions were also studied. Significant DSIP-evoked Met-ENK release from synaptosomes was observed in the cortex, hypothalamus, and midbrain (at concentrations of 10(-10) and 10(-9) M) and in the hippocampus and thalamus (only at 10(-9) M), but not in the striatum. In the hypothalamus, the release of Leu-enkephalin from its synaptosomes was slightly, but not significantly, enhanced by DSIP (10(-10)-10(-8) M). Our findings demonstrate that DSIP triggered a Ca2+ influx in nerve endings to induce a subsequent release of Met-ENK from neurons in only certain brain regions.

The effect of delta sleep-inducing peptide (DSIP) and phosphorylated DSIP (P-DSIP) on the apomorphine-induced hypothermia in rats

Delta sleep-inducing peptide (DSIP) and P-DSIP, phosphorylated analogue, were found to have enhancing effects on hypothermia induced by i.p. injection of apomorphine (2 mg/kg), a dopamine agonist. Further, the action of P-DSIP appeared and diminished more quickly than that of DSIP. A minimal effective dose of these peptides was 10 ng and the dose-response relationship exhibited an inverted bell-shape with a maximal effective dose of 1 microgram. By the pretreatment of anti-DSIP the enhancing effect of DSIP but not P-DSIP, was totally abolished and the action of both peptides was antagonized by haloperidol. These findings suggest that DSIP and P-DSIP have a close relation to the dopaminergic system on the thermoregulatory mechanisms.

Methods for the study of somatostatin

It is clear from the above that there are a number of methods for study of SRIF release. From the standpoint of convenience, the in vitro static incubation of ME is the most practical technique at the present time. Using this preparation SRIF release has been found to be modified by a number of neurotransmitters and peptides, and studies on the mechanism of release of the peptide have been initiated. There is no doubt that such studies should be complemented by perifusion studies, by studies involving larger pieces of the hypothalamus which encompass the entire somatostatinergic neuron, and by in vivo studies to determine the correlation of in vivo and in vitro release. Among the in vivo techniques which have been utilized, the push-pull cannula technique employing cannulae implanted in hypothalamus or anterior pituitary gland offers the most promise. A summary of the effects of some neurotransmitters and neuropeptides on hypothalamic SRIF secretion is reported in Table. I.

Delta sleep-inducing peptide (DSIP)-like immunoreactivity in gut: coexistence with known peptide hormones

Delta sleep-inducing peptide-like immunoreactivity (DSIP-LI) has previously been demonstrated in brain neurons and in endocrine cells of the pituitary and the adrenal medulla. By means of three different antisera against synthetic DSIP we now describe the occurrence and distribution of DSIP-LI in several gut endocrine cells. The human gut was the richest source, where DSIP-LI was located in gastrin/CCK, secretin and PYY/glicentin cells. The rat and pig gut harbour a moderate number of immunoreactive cells in the antral mucosa but in the intestines DSIP-LI-containing cells were very few. By radioimmunoassay, the concentration of DSIP-LI was determined in extracts of various gut regions from man, pig and rat. The highest concentrations were found in all human specimens compared with corresponding samples in the pig and rat. In all three species, high-performance liquid chromatography revealed a single peak of DSIP-like material with approximately the same retention time as DSIP 3-9. Taken together, the present results provide evidence for the presence of DSIP-LI in gut endocrine cells in man, pig and rat; the human gut seems to be the richest source of DSIP-like peptides.

Immunohistochemical colocalization of delta sleep-inducing peptide and luteinizing hormone-releasing hormone in rabbit brain neurons

The anatomical distributions of luteinizing hormone-releasing hormone and delta sleep-inducing peptide immunoreactivity in the rabbit brain were studied by indirect immunofluorescence technique. The comparison of adjacent serial sections, one being immunolabeled with an antiserum to luteinizing hormone-releasing hormone, the other with an antiserum to delta sleep-inducing peptide, showed that the respective distribution patterns of immunoreactivity exhibited a remarkable overlap through the basal forebrain and hypothalamic regions. A sequential double-immunolabelling (elution-restaining method) clearly indicated that all the luteinizing hormone-releasing hormone-immunoreactive cell bodies displayed delta sleep-inducing peptide immunoreactivity. These cell bodies were sparse and mainly located throughout the septal-preoptico-suprachiasmatic region and the ventrolateral hypothalamus. The colocalization of luteinizing hormone-releasing hormone and delta sleep-inducing peptide immunoreactivity was also observed in many fibres supplying all these brain regions and terminal areas such as the organum vasculosum of the lamina terminalis, the subfornical organ, the median eminence and the pituitary stalk. These neuroanatomical findings are suggestive of interaction between delta sleep-inducing peptide and luteinizing hormone-releasing hormone in various brain areas including some circumventricular organs.

Reduction of immunoreactive ACTH in plasma following intravenous injection of delta sleep-inducing peptide in man

Eleven healthy male volunteers, ages 25-39 years, received a single dose of synthetic delta sleep-inducing peptide (DSIP) (25 nmol/kg BW) or saline intravenously in a randomized cross-over, double-blind study. The concentrations of neuropeptides related to the hypothalamic pituitary-adrenal (HPA) axis and cortisol were examined in serial plasma samples. In addition, cortisol and monoamine metabolites were determined in urine. A significant reduction of ACTH-like immunoreactivity (ACTH-LI) in plasma was detected for at least 3 hr after the DSIP injection, compared to the control subjects, in whom a slightly elevated concentration of ACTH-LI occurred. Plasma cortisol levels were unaffected and followed the normal diurnal decline. No differences in urinary cortisol or monoamine metabolite concentrations occurred between the two groups. The results indicate an inhibitory action of DSIP on ACTH secretion in man, as previously suggested by animal experiments.

Evidence for a role of delta sleep-inducing peptide in slow-wave sleep and sleep-related growth hormone release in the rat

To examine the role of delta sleep-inducing peptide (DSIP) in sleep-related growth hormone (GH) release, male rats were deprived of sleep for 4 hr by placing them on a slowly rotating wheel. Sleep deprivation by this method caused a significant increase in GH release, as indicated by the increase in plasma GH concentrations (P less than 0.01), and also in the amount of slow-wave sleep (SWS) (P less than 0.001) above initial values after removal of the animals from the rotating wheel. These increases were blocked by microinjection into the third cerebral ventricle of highly specific antiserum to DSIP. In control rats receiving an equal volume of normal rabbit serum, the significant increase in plasma GH as well as SWS remained after removal of the rats from the wheel. The increased release of endogenous DSIP in the sleep-deprived animals may have caused an increase in SWS as well as plasma GH. Since DSIP increases plasma GH after its injection into the third cerebral ventricle and since passive immunization against DSIP blocks the increase in SWS and GH release that follows the 4 hr of sleep deprivation, the results suggest that DSIP can be a physiological stimulus for sleep-related GH release as well as for the induction of SWS.

Delta sleep inducing peptide (DSIP) stimulates the release of LH but not FSH via a hypothalamic site of action in the rat

Long term ovariectomized (OVX) Sprague-Dawley rats were injected intraventricularly (3rd ventricle) with 5 micrograms (2 microliter) of DSIP. This caused a significant elevation (p = 0.01) of LH levels within 30 min. The values remained elevated for 2 hr; however, FSH levels remained unchanged. The minimal effective dose of DSIP to evoke this effect was 1 microgram. If plasma PH was lowered by pretreatment of the animals with estradiol, the 5 micrograms dose evoked an even greater effect to elevate LH significantly at 30 and 60 min following its intraventricular injection. To determine the site of action of DSIP, dispersed, overnight cultured pituitary cells from OVX rats were incubated with varying concentrations (10(-7) to 10(-12) M) of DSIP in an in vitro system. There was no response to DSIP from the cells in the above system. To evaluate its possible action on the hypothalamus, median eminence (ME) fragments from male rats were incubated in vitro with DSIP in varying concentrations from 10(-7) to 10(-10) M. There was a significant (p less than 0.001) increase in LHRH released from the ME at a concentration of DSIP of 10(-7) M. A sleep-related increase in LH release is seen during puberty in man. It is possible that DSIP released within the hypothalamus may play a physiological role in sleep-related LH release.