What digital health technology types are used in mental health prevention and intervention? Review of systematic reviews for systematization of technologies.

Digital health technology has been widely applied to mental health interventions worldwide. Using digital phenotyping to identify an individual's mental health status has become particularly important. However, many technologies other than digital phenotyping are expected to become more prevalent in the future. The systematization of these technologies is necessary to accurately identify trends in mental health interventions. However, no consensus on the technical classification of digital health technologies for mental health interventions has emerged. Thus, we conducted a review of systematic review articles on the application of digital health technologies in mental health while attempting to systematize the technology using the Delphi method. To identify technologies used in digital phenotyping and other digital technologies, we included 4 systematic review articles that met the inclusion criteria, and an additional 8 review articles, using a snowballing approach, were incorporated into the comprehensive review. Based on the review results, experts from various disciplines participated in the Delphi process and agreed on the following 11 technical categories for mental health interventions: heart rate estimation, exercise or physical activity, sleep estimation, contactless heart rate/pulse wave estimation, voice and emotion analysis, self-care/cognitive behavioral therapy/mindfulness, dietary management, psychological safety, communication robots, avatar/metaverse devices, and brain wave devices. The categories we defined intentionally included technologies that are expected to become widely used in the future. Therefore, we believe these 11 categories are socially implementable and useful for mental health interventions.

Induction of Fos expression in the rat brain after intragastric administration of dried bonito dashi.

Objectives: Dried bonito dashi, a traditional Japanese fish broth made from dried bonito tuna, enhances food palatability due to its specific umami flavor characteristics. However, the pattern of brain activation following dashi ingestion has not been previously investigated.Methods: We mapped activation sites of the rat brain after intragastric loads of dried bonito dashi by measuring neuronal levels of the Fos protein, a functional marker of neuronal activation.Results: Compared to intragastric saline, intragastric dashi administration produced enhanced Fos expression in four forebrain regions: the medial preoptic area, subfornical organ, habenular nucleus, and central nucleus of the amygdala. Interestingly, the medial preoptic area was found to be the only feeding-related hypothalamic area responsive to dashi administration. Moreover, dashi had no effect in the nucleus accumbens and ventral tegmental area, two connected sites known to be activated by highly palatable sugars and fats. In the hindbrain, dashi administration produced enhanced Fos expression in both visceral sensory (caudal nucleus of the solitary tract, dorsal part of the lateral parabrachial nucleus, and area postrema) and autonomic (rostral ventrolateral medulla, and caudal ventrolateral medulla) sites.Discussion: The results demonstrate the activation of discrete forebrain and hindbrain regions following intragastric loads of dried bonito dashi. Our data suggest that the gut-brain axis is the principal mediator of the postingestive effects associated with the ingestion of dashi.

Increased oxytocin-monomeric red fluorescent protein 1 fluorescent intensity with urocortin-like immunoreactivity in the hypothalamo-neurohypophysial system of aged transgenic rats.

To visualize oxytocin in the hypothalamo-neurohypophysial system, we generated a transgenic rat that expresses the oxytocin-monomeric red fluorescent protein 1 (mRFP1) fusion gene. In the present study, we examined the age-related changes of oxytocin-mRFP1 fluorescent intensity in the posterior pituitary (PP), the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of transgenic rats. The mRFP1 fluorescent intensities were significantly increased in the PP, the SON and the PVN of 12-, 18- and 24-month-old transgenic rats in comparison with 3-month-old transgenic rats. Immunohistochemical staining for urocortin, which belongs to the family of corticotropin-releasing factor family, revealed that the numbers of urocortin-like immunoreactive (LI) cells in the SON and the PVN were significantly increased in 12-, 18- and 24-month-old transgenic rats in comparison with 3-month-old transgenic rats. Almost all of urocortin-LI cells co-exist mRFP1-expressing cells in the SON and the PVN of aged transgenic rats. These results suggest that oxytocin content of the hypothalamo-neurohypophysial system may be modulated by age-related regulation. The physiological role of the co-existence of oxytocin and urocortin in the SON and PVN of aged rats remains unclear.

GABA Signaling and Neuroactive Steroids in Adrenal Medullary Chromaffin Cells.

Gamma-aminobutyric acid (GABA) is produced not only in the brain, but also in endocrine cells by the two isoforms of glutamic acid decarboxylase (GAD), GAD65 and GAD67. In rat adrenal medullary chromaffin cells only GAD67 is expressed, and GABA is stored in large dense core vesicles (LDCVs), but not synaptic-like microvesicles (SLMVs). The α3ß2/3γ2 complex represents the majority of GABAA receptors expressed in rat and guinea pig chromaffin cells, whereas PC12 cells, an immortalized rat chromaffin cell line, express the α1 subunit as well as the α3. The expression of α3, but not α1, in PC12 cells is enhanced by glucocorticoid activity, which may be mediated by both the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR). GABA has two actions mediated by GABAA receptors in chromaffin cells: it induces catecholamine secretion by itself and produces an inhibition of synaptically evoked secretion by a shunt effect. Allopregnanolone, a neuroactive steroid which is secreted from the adrenal cortex, produces a marked facilitation of GABAA receptor channel activity. Since there are no GABAergic nerve fibers in the adrenal medulla, GABA may function as a para/autocrine factor in the chromaffin cells. This function of GABA may be facilitated by expression of the immature isoforms of GAD and GABAA receptors and the lack of expression of plasma membrane GABA transporters (GATs). In this review, we will consider how the para/autocrine function of GABA is achieved, focusing on the structural and molecular mechanisms for GABA signaling.

Maternal dietary restriction alters offspring's sleep homeostasis.

Nutritional state in the gestation period influences fetal growth and development. We hypothesized that undernutrition during gestation would affect offspring sleep architecture and/or homeostasis. Pregnant female mice were assigned to either control (fed ad libitum; AD) or 50% dietary restriction (DR) groups from gestation day 12 to parturition. After parturition, dams were fed AD chow. After weaning, the pups were also fed AD into adulthood. At adulthood (aged 8-9 weeks), we carried out sleep recordings. Although offspring mice displayed a significantly reduced body weight at birth, their weights recovered three days after birth. Enhancement of electroencephalogram (EEG) slow wave activity (SWA) during non-rapid eye movement (NREM) sleep was observed in the DR mice over a 24-hour period without changing the diurnal pattern or amounts of wake, NREM, or rapid eye movement (REM) sleep. In addition, DR mice also displayed an enhancement of EEG-SWA rebound after a 6-hour sleep deprivation and a higher threshold for waking in the face of external stimuli. DR adult offspring mice exhibited small but significant increases in the expression of hypothalamic peroxisome proliferator-activated receptor α (Pparα) and brain-specific carnitine palmitoyltransferase 1 (Cpt1c) mRNA, two genes involved in lipid metabolism. Undernutrition during pregnancy may influence sleep homeostasis, with offspring exhibiting greater sleep pressure.

Expression of the c-fos-monomeric red fluorescent protein 1 fusion gene in the spinal cord and the hypothalamic paraventricular nucleus in transgenic rats after nociceptive stimulation.

We generated transgenic rats expressing the c-fos and monomeric red fluorescent protein 1 (mRFP1) fusion gene in the central nervous system after adequate stimulation. In the present study, the time-course of the induction patterns of mRFP1 fluorescence in the spinal cord and the paraventricular nucleus (PVN) was compared with that of Fos-like immunoreactivity (LI) within 24 h after subcutaneous (s.c.) injection of 0.9% saline and 5% formalin in both hind paws. Control rats were not treated. In the control and saline/formalin injected rats, scattered mRFP1 fluorescence in the spinal cord and the PVN was observed at 0 min, though there was little Fos-LI in the same region. The mRFP1 fluorescence in the spinal cord and the PVN was increased at 3h after formalin. On the other hand, the changes of Fos-LI in the spinal cord and the PVN were relatively shorter than those of the mRFP1 fluorescence after formalin. These results suggest that the c-fos-mRFP1 fusion gene expression is slightly upregulated in normal conditions and nociceptive stimulation-induced induction of the fusion gene may be maintained longer than the endogenous c-fos gene expression in the spinal cord and the PVN. Next, nocifensive behavior and mRFP1 fluorescence and Fos-LI in the spinal cord and the PVN after s.c. injection of formalin, 4α-phorbol 12,13-didecanoate (4α-PDD) and saline were compared. Although the 4α-PDD injected rats seldom displayed nocifensive behaviors like s.c. saline injection, 4α-PDD injection caused mRFP1 fluorescence and Fos-LI significantly in the spinal cord and the PVN unlike s.c. saline injection.

Water deprivation induces appetite and alters metabolic strategy in Notomys alexis: unique mechanisms for water production in the desert.

Like many desert animals, the spinifex hopping mouse, Notomys alexis, can maintain water balance without drinking water. The role of the kidney in producing a small volume of highly concentrated urine has been well-documented, but little is known about the physiological mechanisms underpinning the metabolic production of water to offset obligatory water loss. In Notomys, we found that water deprivation (WD) induced a sustained high food intake that exceeded the pre-deprivation level, which was driven by parallel changes in plasma leptin and ghrelin and the expression of orexigenic and anorectic neuropeptide genes in the hypothalamus; these changed in a direction that would stimulate appetite. As the period of WD was prolonged, body fat disappeared but body mass increased gradually, which was attributed to hepatic glycogen storage. Switching metabolic strategy from lipids to carbohydrates would enhance metabolic water production per oxygen molecule, thus providing a mechanism to minimize respiratory water loss. The changes observed in appetite control and metabolic strategy in Notomys were absent or less prominent in laboratory mice. This study reveals novel mechanisms for appetite regulation and energy metabolism that could be essential for desert rodents to survive in xeric environments.

Molecular characterization and biological function of neuroendocrine regulatory peptide-3 in the rat.

Neuroendocrine regulatory peptide (NERP)-3, derived from the neurosecretory protein VGF (non-aconymic), is a new biologically active peptide identified through peptidomic analysis of the peptides secreted by an endocrine cell line. Using a specific antibody recognizing the C-terminal region of NERP-3, immunoreactive (ir)-NERP-3 was identified in acid extracts of rat brain and gut as a 30-residue NERP-3 with N-terminal pyroglutamylation. Assessed by radioimmunoassay, ir-NERP-3 was more abundant in the brain, including the posterior pituitary (PP), than in the gut. Immunohistochemistry demonstrated that ir-NERP-3 was significantly increased in the suprachiasmatic nucleus, the magnocellular division of the paraventricular nucleus, and the external layer of the median eminence, but not in the supraoptic nucleus, after dehydration. The immunoreactivity was, however, markedly decreased in all of these locations after chronic salt loading. Intracerebroventricular administration of NERP-3 in conscious rats induced Fos expression in a subset of arginine vasopressin (AVP)-containing neurons in the supraoptic nucleus and the magnocellular division of the paraventricular nucleus. On in vitro isolated rat PP preparations, NERP-3 caused a significant AVP release in a dose-related manner, suggesting that NERP-3 in the PP could be an autocrine activator of AVP release. Taken together, the present results suggest that NERP-3 in the hypothalamo-neurohypophyseal system may be involved in the regulation of body fluid balance.

Induction of arginine vasopressin-enhanced green fluorescent protein expression in the locus coeruleus following kainic acid-induced seizures in rats.

Seizure causes autonomic, neuroendocrine and stress responses. We examined the effects of kainic acid (KA)-induced seizures on the expression of the arginine vasopressin (AVP)-enhanced green fluorescent protein (eGFP) in the locus coeruleus (LC), an area known to contain noradrenergic cells, in AVP-eGFP transgenic male and female rats, with the rationale to identify stressors which induce AVP synthesis in the LC. Subcutaneous (s.c.) administration of KA caused a progressive development of seizure behavior within 24 h. AVP-eGFP fluorescence in the LC was detected 6, 24, and 48 h and 1 week after administration of KA (12 mg/kg). From a nearly undetectable level, it reached a maximum at 48 h after s.c. administration of KA and returned to the basal levels after 2 weeks. AVP-eGFP fluorescence in the LC after s.c. administration of KA was significantly reduced by the pretreatment with MK-801 (nonselective N-methyl-D-aspartate (NMDA) receptor antagonist). In the KA-administered rats, immunohistochemistry for tyrosine hydroxylase (TH) revealed that the eGFP fluorescence was co-localized with TH-immuno-reactivity in the LC. These results suggest that the synthesis of AVP-eGFP is potentially up-regulated in noradrenergic neurons in the LC after KA-induced seizures through the activation of NMDA receptors.

Upregulation of arginine vasopressin synthesis in the rat hypothalamus after kainic acid-induced seizures.

We examined the effects of kainic acid (KA)-induced seizures on arginine vasopressin (AVP) gene expression in the paraventricular (PVN) and the supraoptic nuclei (SON) of normal rats using in situ hybridization histochemistry. We also investigated the expression of the AVP-enhanced green fluorescent protein (eGFP) fusion gene after KA-induced seizures in transgenic rats. AVP heteronuclear (hn) RNA levels in the PVN and the SON were significantly increased at 3h and 24h after subcutaneous (s.c.) administration of KA in normal rats. AVP mRNA levels in the PVN and the SON did not change significantly at 3h, 24h and 1 week after s.c. administration of KA in normal rats. In KA-administered transgenic rats, AVP-eGFP fluorescence in the magnocellular and parvocellular divisions of the PVN and the SON were significantly stronger compared to vehicle-administered transgenic rats. By pretreatment with MK-801 (nonselective N-methyl-D-aspartate, NMDA, receptor antagonist), AVP-eGFP transgenic rats after administration of KA did not show preconvulsive symptoms or convulsions and AVP-eGFP fluorescence in the magnocellular and parvocellular divisions of the PVN and the SON of these rats was significantly reduced. These results suggested that KA-induced increases in AVP transcripts and AVP were prevented by MK801 because seizure activity was prevented or reduced.

Possible contribution of pannexin channel to ATP-induced currents in vitro in vasopressin neurons isolated from the rat supraoptic nucleus.

Release of arginine vasopressin (AVP) from magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) is controlled by the electrical activity of these neurons. ATP plays a crucial role in the regulation of SON MNCs by activating the purinergic P2X and P2Y receptors. Recent reports of interaction between P2X receptors and pannexin channels have provided new insights into the physiology of the central nervous system; however, the function of pannexin channels has not been assessed in AVP neurons. In the present study, we examined the possible contribution of the pannexin channel in ATP-induced responses in SON AVP neurons. We used the whole-cell patch-clamp technique in isolated rat SON MNCs that express an AVP-enhanced green fluorescent protein transgene. The ATP-induced current was inhibited in a concentration-dependent manner by pannexin channel blockers carbenoxolone and mefloquine, whereas the connexin channel blockers flufenamic acid and lanthanum had no effect. Multi-cell reverse transcriptase-polymerase chain reaction experiments confirmed the existence of pannexin-1 mRNA in AVP neurons. The involvement of the ATP-activated transient receptor potential vanilloid and acid-sensing ion channels was excluded. These results suggest that pannexin channels in SON AVP neurons are involved in the regulatory mechanisms of neuronal activity.

Highly visible expression of an oxytocin-monomeric red fluorescent protein 1 fusion gene in the hypothalamus and posterior pituitary of transgenic rats.

We have generated rats bearing an oxytocin (OXT)-monomeric red fluorescent protein 1 (mRFP1) fusion transgene. The mRFP1 fluorescence was highly visible in ventral part of the supraoptic nucleus (SON) and the posterior pituitary in a whole mount. mRFP1 fluorescence in hypothalamic sections was also observed in the SON, the paraventricular nucleus (PVN), and the internal layer of the median eminence. Salt loading for 5 d caused a marked increase in mRFP1 fluorescence in the SON, the PVN, the median eminence, and the posterior pituitary. In situ hybridization histochemistry revealed that the expression of the mRNA encoding the OXT-mRFP1 fusion gene was observed in the SON and the PVN of euhydrated rats and increased dramatically after chronic salt loading. The expression of the endogenous OXT and the arginine vasopressin (AVP) genes were significantly increased in the SON and the PVN after chronic salt loading in both nontransgenic and transgenic rats. These responses were not different between male and female rats. Compared with nontransgenic rats, euhydrated and salt-loaded male and female transgenic rats showed no significant differences in plasma osmolality, sodium concentration, OXT, and AVP levels. Finally, we succeeded in generating a double-transgenic rat that expresses both the OXT-mRFP1 fusion gene and the AVP-enhanced green fluorescent protein fusion gene. Our new transgenic rats are valuable new tools to study the physiology of the hypothalamo-neurohypophysial system.

Angiotensin II type 1 receptor signaling regulates feeding behavior through anorexigenic corticotropin-releasing hormone in hypothalamus.

The activation of renin-angiotensin system contributes to the development of metabolic syndrome and diabetes as well as hypertension. However, it remains undetermined how renin-angiotensin system is implicated in feeding behavior. Here, we show that angiotensin II type 1 (AT(1)) receptor signaling regulates the hypothalamic neurocircuit that is involved in the control of food intake. Compared with wild-type Agtr1a(+/+) mice, AT(1) receptor knock-out (Agtr1a(-/-)) mice were hyperphagic and obese with increased adiposity on an ad libitum diet, whereas Agtr1a(-/-) mice were lean with decreased adiposity on a pair-fed diet. In the hypothalamus, mRNA levels of anorexigenic neuropeptide corticotropin-releasing hormone (Crh) were lower in Agtr1a(-/-) mice than in Agtr1a(+/+) mice both on an ad libitum and pair-fed diet. Furthermore, intracerebroventricular administration of CRH suppressed food intake both in Agtr1a(+/+) and Agtr1a(-/-) mice. In addition, the Crh gene promoter was significantly transactivated via the cAMP-responsive element by angiotensin II stimulation. These results thus demonstrate that central AT(1) receptor signaling plays a homeostatic role in the regulation of food intake by maintaining gene expression of Crh in hypothalamus and suggest a therapeutic potential of central AT(1) receptor blockade in feeding disorders.

Allyl isothiocyanates and cinnamaldehyde potentiate miniature excitatory postsynaptic inputs in the supraoptic nucleus in rats.

Allyl isothiocyanates (AITC) and cinnamaldehyde are pungent compounds present in mustard oil and cinnamon oil, respectively. These compounds are well known as transient receptor potential ankyrin 1 (TRPA1) agonists. TRPA1 is activated by low temperature stimuli, mechanosensation and pungent irritants such as AITC and cinnamaldehyde. TRPA1 is often co-expressed in TRPV1. Recent study showed that hypertonic solution activated TRPA1 as well as TRPV1. TRPV1 is involved in excitatory synaptic inputs to the magnocellular neurosecretory cells (MNCs) that produce vasopressin in the supraoptic nucleus (SON). However, it remains unclear whether TRPA1 may be involved in this activation. In the present study, we examined the role of TRPA1 on the synaptic inputs to the MNCs in in vitro rat brain slice preparations, using whole-cell patch-clamp recordings. In the presence of tetrodotoxin, AITC (50µM) and cinnamaldehyde (30µM) increased the frequency of miniature excitatory postsynaptic currents without affecting the amplitude. This effect was significantly attenuated by previous exposure to ruthenium red (10µM), non-specific TRP channels blocker, high concentration of menthol (300µM) and HC-030031 (10µM), which are known to antagonize the effects of TRPA1 agonists. These results suggest that TRPA1 may exist at presynaptic terminals to the MNCs and enhance glutamate release in the SON.

Hypothalamic vasopressin response to stress and various physiological stimuli: visualization in transgenic animal models.

Arginine vasopressin (AVP) is involved in the homeostatic responses numerous life-threatening conditions, for example, the promotion of water conservation during periods of dehydration, and the activation of the hypothalamo-pituitary adrenal axis by emotional stress. Recently, we generated new transgenic animals that faithfully express an AVP-enhanced green fluorescent protein (eGFP) fusion gene in the paraventricular nucleus (PVN), the supraoptic nucleus (SON) and the suprachiasmatic nucleus (SCN) of the hypothalamus. In these transgenic rats, marked increases in eGFP fluorescence and fusion gene expression were observed in the magnocellular division of the PVN and the SON, but not the SCN, after osmotic challenges, such as dehydration and salt loading, and both acute and chronic nociceptive stimuli. In the parvocellular division of the PVN, eGFP expression was increased after acute and chronic pain, bilateral adrenalectomy, endotoxin shock and restraint stress. In the extra-hypothalamic areas of the brain, eGFP expression was induced in the locus coeruleus after the intracerebroventricular administration of colchicine. Next, we generated another transgenic rat that expresses a fusion gene comprised of c-fos promoter-enhancer sequences driving the expression of monomeric red fluorescent protein 1 (mRFP1). In these transgenic rats, abundant nuclear fluorescence of mRFP1 was observed in the PVN, the SON and other osmosensitive areas after acute osmotic stimulation. Finally, we generated a double transgenic rat that expresses both the AVP-eGFP and c-fos-mRFP1 fusion genes. In this double transgenic rat, we have observed nuclear mRFP1 fluorescence in eGFP-positive neurons after acute osmotic stimulation. These unique transgenic rats provide an exciting new tool to examine neuroendocrine responses to physiological and stressful stimuli in both in vivo and in vitro preparations.

Similar changes of hypothalamic feeding-regulating peptides mRNAs and plasma leptin levels in PTHrP-, LIF-secreting tumors-induced cachectic rats and adjuvant arthritic rats.

Parathyroid hormone-related protein (PTHrP) is a causative factor of humoral hypercalcemia in malignancy. However, it is difficult to explain the mechanism of anorexia/cachexia with PTHrP secretion in detail. Previously, we demonstrated that the expressions of orexigenic peptides increased and anorexigenic peptides decreased under cachectic conditions in rats carrying tumors secreting PTHrP. In this study, we investigated whether such changes in the expression of hypothalamic feeding-regulating peptides can be solely attributed to PTHrP or are a general response under cachectic conditions. Cachectic syndromes were induced in rats by: (i) inoculation of human lung cancer LC-6 cells that secreted PTHrP, (ii) inoculation of human melanoma SEKI cells that secrete not PTHrP but LIF1, (iii) injection of heat-killed Mycobacterium leading to arthritis (AA) and (iv) oral administration of a high dose of 1α,25(OH)(2)D(3) that resulted in hypercalcemia. The LC-6-bearing rats and AA rats were treated with or without anti-PTHrP antibody and indomethacin, respectively, and the expression of the hypothalamic feeding-regulating peptide mRNAs were examined by in situ hybridization histochemistry. The orexigenic peptide mRNAs, such as neuropeptide Y and agouti-related protein, were significantly increased, and that of anorexigenic peptide mRNAs, such as proopiomelanocortin, cocaine- and amphetamine-regulated transcript and corticotropin-releasing hormone were significantly decreased when they developed cachectic syndromes and AA. A high dose of 1α,25(OH)(2)D(3) caused hypercalcemia and body weight loss but did not affect the expression of hypothalamic feeding-regulating peptide mRNAs. The expressions of the hypothalamic feeding-regulating peptides change commonly in different chronic cachectic models without relating to serum calcium levels.

Modulators of BK and SK channels alter electrical activity in vitro in single vasopressin neurons isolated from the rat supraoptic nucleus.

Release of arginine vasopressin (AVP) from magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) is controlled by the electrical activities of the MNCs. Ca(2+)-activated K(+) channels, such as the BK and SK channels, are K(+)-selective ion channels that are activated in response to increased intracellular calcium concentrations. Intrinsic affinities for Ca(2+) permit these channels to exert a negative feedback effect on cellular excitability. In the present study, we used the whole-cell patch-clamp technique to examine the effects of BK or SK channel modulators on neuronal activity in single isolated rat SON MNCs that express an AVP-enhanced green fluorescent protein (eGFP) transgene. Application of BK or SK channel activators abolished the action potentials and induced hyperpolarization. In contrast, the number of action potentials was significantly increased after application of BK or SK channel blockers. Our results suggest that BK and SK channels in AVP neurons may play a role in the regulatory mechanisms of neural activity.

Diurnal changes of arginine vasopressin-enhanced green fluorescent protein fusion transgene expression in the rat suprachiasmatic nucleus.

We have recently developed a new transgenic rat line expressing an arginine vasopressin (AVP)-enhanced green fluorescent protein (eGFP) fusion gene. The AVP-eGFP transgene is expressed in the paraventricular (PVN) and supraoptic (SON) nuclei and the suprachiasmatic nucleus (SCN) of the hypothalamus. Transgene expression in the PVN and SON showed an exaggerated response to salt loading and nociceptive stimulation. However, the expression of the AVP-eGFP transgene in the SCN did not change under these stressful conditions. Here, we examined daily profiles of the expression of the AVP-eGFP transgene in the SCN in comparison with the endogenous AVP and Period (Per1 and Per2) genes. While all of these genes elicited diurnal patterns of expression in the SCN, the rate of rhythmic change of transgene expression was significantly greater than that of the endogenous AVP gene. We also examined the effect of a light stimulus on the expression of the AVP-eGFP, AVP, Per1 and Per2 genes in the SCN of transgenic rats. Ninety minutes after a light stimulus, AVP-eGFP mRNA and AVP hnRNA levels in the SCN were significantly decreased, while Per2 mRNA levels were significantly increased. In addition, we observed the eGFP fluorescence in the SCN and recorded the electrophysiological properties of a dissociated SCN eGFP-positive neuron. The AVP-eGFP transgenic rat is a useful animal model to study the diurnal change and dynamics of the AVP system, and enables the facile identification of SCN AVP neurons both in vivo and in vitro.

REVIEW: Oxytocin: Crossing the bridge between basic science and pharmacotherapy.

Is oxytocin the hormone of happiness? Probably not. However, this small nine amino acid peptide is involved in a wide variety of physiological and pathological functions such as sexual activity, penile erection, ejaculation, pregnancy, uterus contraction, milk ejection, maternal behavior, osteoporosis, diabetes, cancer, social bonding, and stress, which makes oxytocin and its receptor potential candidates as targets for drug therapy. In this review, we address the issues of drug design and specificity and focus our discussion on recent findings on oxytocin and its heterotrimeric G protein-coupled receptor OTR. In this regard, we will highlight the following topics: (i) the role of oxytocin in behavior and affectivity, (ii) the relationship between oxytocin and stress with emphasis on the hypothalamo-pituitary-adrenal axis, (iii) the involvement of oxytocin in pain regulation and nociception, (iv) the specific action mechanisms of oxytocin on intracellular Ca²(+) in the hypothalamo neurohypophysial system (HNS) cell bodies, (v) newly generated transgenic rats tagged by a visible fluorescent protein to study the physiology of vasopressin and oxytocin, and (vi) the action of the neurohypophysial hormone outside the central nervous system, including the myometrium, heart and peripheral nervous system. As a short nine amino acid peptide, closely related to its partner peptide vasopressin, oxytocin appears to be ideal for the design of agonists and antagonists of its receptor. In addition, not only the hormone itself and its binding to OTR, but also its synthesis, storage and release can be endogenously and exogenously regulated to counteract pathophysiological states. Understanding the fundamental physiopharmacology of the effects of oxytocin is an important and necessary approach for developing a potential pharmacotherapy.

Induction of the arginine vasopressin-enhanced green fluorescent protein fusion transgene in the rat locus coeruleus.

We examined the effects of intracerebroventricular (i.c.v.) administration of colchicine on the expression of the arginine vasopressin (AVP)-enhanced green fluorescent protein (eGFP) fusion gene in rats. In rats administered i.c.v. vehicle (control), eGFP fluorescence was observed in the supraoptic nucleus (SON), the magnocellular division of the paraventricular nucleus (PVN), the suprachiasmatic nucleus (SCN), the median eminence (ME) and the posterior pituitary. Two days after i.c.v. administration of colchicine, eGFP fluorescence was markedly increased in the SON, the magnocellular and parvocellular divisions of the PVN, the SCN, the ME and the locus coeruleus (LC). Immunohistochemical staining for eGFP confirmed the distribution of fluorescence in both groups. In the colchicines-administered groups, immunohistochemistry for tyrosine hydroxylase (TH) revealed that the eGFP fluorescence was co-localised with TH-immunoreactivity in the LC. Similarly, in situ hybridization histochemistry for eGFP mRNA revealed a significant increase in gene expression in the LC, the SON and the PVN 12-48 h after administration of colchicine. Our results indicate that the synthesis of AVP-eGFP is upregulated in noradrenergic neurones in the LC after colchicine administration. This implies that AVP and noradrenaline, originating from LC neurones, might play a role in response to chronic stress.