COVID-19's impact on type 1 diabetes management: A mixed-methods study exploring the Peruvian experience

INTRODUCTION

The COVID-19 pandemic has negatively impacted health services, especially in low-and-middle-income countries, where care for chronic conditions such as diabetes was disrupted. Our study aims to describe the challenges faced by people living with Type 1 diabetes mellitus (T1DM) to access care during the COVID-19 pandemic in Peru.

METHODS

A sequential explanatory mixed-method study was conducted between May and September 2020 including health professionals involved in T1DM care, people with T1DM and their caregivers. The study consisted of a quantitative strand to gather general information through electronic surveys and a qualitative strand that involved in-depth interviews.

RESULTS

For the quantitative study, we included 105 people with T1DM, 50 caregivers and 76 health professionals. The qualitative study included a total of 31 interviews; 16 people with T1DM, 14 health care professionals, and one representative from the Peruvian Ministry of Health (MoH). People with T1DM faced difficulties accessing consultations, insulin, monitoring devices and laboratory testing during the pandemic. Different phases of the Peruvian health system response were found. Firstly, an initial informal response to addressing T1DM care during the pandemic characterised by local initiatives to ensure continuity of care for people with T1DM. Following from this, a formal response was implemented by the MoH which focussed on reinforcing the primary level of care. Measures included teleconsultations and delivery of medicines, although these were not implemented in all health care establishments. Throughout the pandemic patient associations played an important role in organising and helping to counteract the impact of COVID-19 on people with T1DM.

CONCLUSIONS

The Peruvian health care system slowly adapted to the COVID-19 pandemic to provide care for people with T1DM. However, people with T1DM had difficulties to access care. Thus, reinforcement of interventions such as communication between levels of care, teleconsultations and delivery of medicines was urgently needed. Patient associations' capacity to respond should be considered by local authorities and civil society should be part of the health system response.

Evaluation of Breed and Parity Order Effects on the Lipid Composition of Porcine Colostrum

Porcine colostrum lipid classes and fatty acids (FA) were characterized in 6 pools (from 69 samples) from 3 sow breeds (Italian Large White, Italian Landrace, and Italian Duroc) and different parity orders (only Large White). Triacylglycerols (TAG; 94.44 expressed as g/100 g of fat) were the most abundant lipid class, followed by diacylglycerols (DAG; 3.36 g/100 g of fat), free fatty acids (FFA; 0.98 g/100 g of fat), and cholesterol (0.84 g/100 g of fat). The main FAs found in swine colostrum were palmitic (27.29%, expressed as g/100 g of total FA), oleic (28.81%), and linoleic (23.39%) acids. Both the breed of sow and parity order affected the FA and lipid composition. The results suggest that the FA composition of swine colostrum is similar to that of human colostrum and could represent a new source of nutrients for human infants, after further assessment of hygienic and quality aspects. The swine model could be an opportunity for a better understanding of colostrum effects on newborns.

Prevalence and risk factors of gestational diabetes mellitus: findings from a universal screening feasibility program in Lima, Peru

Background

Gestational diabetes mellitus (GDM) is a global public health concern with potential implications for the health of a mother and her offspring. However, data on the prevalence and risk factors of GDM in Latin America are scarce.

The study was designed to estimate the prevalence of GDM and identify maternal risk factors among Peruvian women.

Methods

A cross-sectional study was conducted among 1300 pregnant women attending a prenatal clinic in Lima, Peru. GDM was diagnosed using an Oral Glucose Tolerance Test (OGTT) performed between 24 and 28 gestational weeks using the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. Depression status was assessed using the Patient Health Questionnaire-9. Multivariate logistic regression models were used to identify risk factors of GDM.

Results

Approximately 16% of pregnant women were diagnosed with GDM. The prevalence of obesity and depression were 24.4 and 10.6%, respectively. After adjusting for confounders, mid-pregnancy obesity was associated with a 1.64-fold increased odds of GDM (OR: 1.64; 95% CI: 1.03–2.61). Participants with a family history of diabetes had a 1.5-fold increased odds of developing GDM (OR: 1.51, 95% CI: 1.10–2.07) as compared to women without this family history. Depression was associated with a 1.54-fold increased odds of GDM (OR: 1.54; 95% CI:1.09–2.17).

Conclusions

GDM is highly prevalent and was associated with maternal obesity, family history of diabetes and antepartum depression among Peruvian women. Intervention programs aimed at early diagnoses and management of GDM need to take maternal obesity, family history of diabetes and antepartum depression into account.

Electronic supplementary material

The online version of this article (10.1186/s12884-018-1904-0) contains supplementary material, which is available to authorized users.

Nitric oxide assisted C60 secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers

RATIONALE

Secondary ion mass spectrometry (SIMS) with polyatomic primary ions provides a successful tool for molecular depth profiling of polymer systems, relevant in many technological applications. Widespread C60 sources, however, cause in some polymers extensive damage with loss of molecular information along depth. We study a method, based on the use of a radical scavenger, for inhibiting ion-beam-induced reactions causing sample damage.

METHODS

Layered polystyrene sulfonate and polyacrylic acid based polyelectrolyte films, behaving differently towards C60 beam-induced damage, were selected and prepared as model systems. They were depth profiled by means of time-of-flight (TOF)-SIMS in dual beam mode, using fullerene ions for sputtering. Nitric oxide was introduced into the analysis chamber as a radical scavenger. The effect of sample cooling combined with NO-dosing on the quality of depth profiles was explored.

RESULTS

NO-dosing during C60-SIMS depth profiling of >1 micrometer-thick multilayered polyelectrolytes allows detection, along depth, of characteristic fragments from systems otherwise damaged by C60 bombardment, and increases sputtering yield by more than one order of magnitude. By contrast, NO has little influence on those layers that are well profiled with C60 alone. Such leveling effect, more pronounced at low temperature, leads to a dramatic improvement of profile quality, with a clear definition of interfaces.

CONCLUSIONS

NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems.

High risk for obstructive sleep apnea and other sleep disorders among overweight and obese pregnant women

BACKGROUND

Obstructive sleep apnea (OSA), a common and serious disorder in which breathing repeatedly stops during sleep, is associated with excess weight and obesity. Little is known about the co-occurrence of OSA among pregnant women from low and middle-income countries.

METHODS

We examined the extent to which maternal pre-pregnancy overweight or obesity status are associated with high risk for OSA, poor sleep quality, and excessive daytime sleepiness in 1032 pregnant women in Lima, Peru. The Berlin questionnaire was used to identify women at high risk for OSA. The Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) were used to examine sleep quality and excessive daytime sleepiness, respectively. Multinomial logistic regression procedures were employed to estimate odds ratios (aOR) and 95% confidence intervals (CI) adjusted for putative confounding factors.

RESULTS

Compared with lean women (<25 kg/m(2)), overweight women (25-29.9 kg/m(2)) had 3.69-fold higher odds of high risk for OSA (95% CI 1.82-7.50). The corresponding aOR for obese women (≥30 kg/m(2)) was 13.23 (95% CI: 6.25-28.01). Obese women, as compared with their lean counterparts had a 1.61-fold higher odds of poor sleep quality (95% CI: 1.00-2.63).

CONCLUSION

Overweight or obese pregnant women have increased odds of sleep disorders, particularly OSA. OSA screening and risk management may be indicated among pregnant women in low and middle income countries, particularly those undergoing rapid epidemiologic transitions characterized by increased prevalence of excessive adult weight gain.

Multi-site, multi-country evaluation of analytical and operational performance of a low-mid volume chemiluminescent immunoassay analyzer

BACKGROUND

A new automated immunoassay low-mid volume (< or = 250 immunoassays/day) chemiluminescent analyzer, Abbott Architect i1000sR, was evaluated by seven laboratories around the world (4 in Europe, one each in Canada, Japan, and the U.S.A.) to demonstrate equivalent performance for key operating characteristics (e.g., precision, turn around time, limit of detection, functional sensitivity, and linearity).

METHODS

The laboratories followed standard protocols to assess precision, limit of detection (LoD), functional sensitivity, assay linearity, method comparison, and sample carryover. Turn around time for three stat assays (beta-hCG, BNP, and CK-MB) and the time required to complete workloads of 50 and 100 tests with a mixture of 75% routine tests and 25% stat tests was also evaluated.

RESULTS

Total precision was typically < 5% CV for nine immunoassays. Analytical performance met design goals and demonstrated equivalency to package insert data for assays on market and in use for an existing high volume immunoassay system. Stat turn around times were consistent with the fixed analytical time of 15.6 minutes and met the expectations of the laboratories. Measured test throughput ranged from 47 - 54 tests per hour and demonstrated that the analyzer was fit for the intended purpose of supporting a laboratory that performs < or = 250 immunoassays per day.

CONCLUSIONS

A multisite, international analyzer familiarization study is a practical means of confirming that a new instrument meets both a manufacturer's design specifications and users' real world expectations and provides a pragmatic test for the system. The experience of investigators at seven sites around the world indicates that a new fully automated chemiluminescent system is suitable for use.

Effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in Santo Daime members

The use of the hallucinogenic brew ayahuasca, obtained from infusing the shredded stalk of the malpighiaceous plant Banisteriopsis caapi with the leaves of other plants such as Psychotria viridis, is growing in urban centers of Europe, South and North America in the last several decades. Despite this diffusion, little is known about its effects on emotional states. The present study investigated the effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in members of the Santo Daime, an ayahuasca-using religion. Standard questionnaires were used to evaluate state-anxiety (STAI-state), trait-anxiety (STAI-trait), panic-like (ASI-R) and hopelessness (BHS) in participants that ingested ayahuasca for at least 10 consecutive years. The study was done in the Santo Daime church, where the questionnaires were administered 1h after the ingestion of the brew, in a double-blind, placebo-controlled procedure. While under the acute effects of ayahuasca, participants scored lower on the scales for panic and hopelessness related states. Ayahuasca ingestion did not modify state- or trait-anxiety. The results are discussed in terms of the possible use of ayahuasca in alleviating signs of hopelessness and panic-like related symptoms.

Anxiogenic effects in the rat elevated plus-maze of 5-HT(2C) agonists into ventral but not dorsal hippocampus

The effect of the non-selective 5-HT2C receptor agonist trifluoromethyl-phenylpiperazine (TFMPP, 0.75, 1.5 and 3.0 microg) and the preferential 5-HT2C agonist 6-chloro-2(1-piperazinyl)pyrazine (MK-212, 0.1, 0.3 and 1.0 microg) microinjected into the ventral or dorsal hippocampus was investigated in anxiety measures of rats exposed to the elevated plus-maze test. Ventral hippocampal (VH) microinjections of the 0.75 or 1.5 microg doses of TFMPP reduced open-arm exploration without affecting the number of closed-arm entries, indicating a selective anxiogenic profile. The highest dose (3.0 microg) reduced open- and closed-arm entries, suggesting interference in locomotor activity. The 0.1 microg dose of MK-212 also caused a selective anxiogenic effect when microinjected into the ventral hippocampus, without disturbing locomotor activity. Microinjections of the two higher doses of MK-212 (0.3 or 1.0 microg) into the ventral hippocampus led to a decrease of exploration in both arms of the maze. In contrast to the anxiogenic effect observed in the VH, neither TFMPP nor MK-212 significantly changed anxiety measures when microinjected into the dorsal hippocampus. These results suggest that activation of 5-HT2C postsynaptic receptors located in the ventral, but not in the dorsal, hippocampus play an important role in anxiety triggered by the elevated plus-maze test.

Neuroanatomical and neuropharmacological study of opioid pathways in the mesencephalic tectum: effect of μ1- and κ-opioid receptor blockade on escape behavior induced by electrical stimulation of the inferior colliculus

Deep layers of the superior colliculus (DLSC), the dorsal and ventral periaqueductal gray matter (PAG), and inferior colliculus (IC) are midbrain structures involved in the generation of defensive behavior. beta-Endorphin and Leu-enkephalin are some neurotransmitters that may modulate such behavior in mammals. Light microscopy immunocytochemistry with streptavidin method was used for the localization of the putative cells of defensive behavior with antibodies for endogenous opioids in rat brainstem. Midbrain structures showed positive neurons to beta-endorphin and Leu-enkephalin in similar distributions in the experimental animals, but we also noted the presence of varicose fibers positive to endogenous opioids in the PAG. Neuroanatomical techniques showed varicose fibers from the central nucleus of the inferior colliculus to ventral aspects of the PAG, at more caudal levels. Naloxonazine and nor-binaltorphimine, competitive antagonists that block mu(1)- and kappa-opioid receptors, were then used in the present work to investigate the involvement of opioid peptide neural system in the control of the fear-induced reactions evoked by electrical stimulation of the neural substrates of the inferior colliculus. The fear-like responses were measured by electrical stimulation of the central nucleus of the inferior colliculus, eliciting the escape behavior, which is characterized by vigorous running and jumping. Central administration of opioid antagonists (2.5 microg/0.2 microl and 5.0 microg/0.2 microl) was performed in non-anesthetized animals (Rattus norvegicus), and the behavioral manifestations of fear were registered after 10 min, 2 h, and 24 h of the pretreatment. Naloxonazine caused an increase of the defensive threshold, as compared to control, suggesting an antiaversive effect of the antagonism on mu(1)-opioid receptor. This finding was corroborated with central administration of nor-binaltorphimine, which also induced a decrease of the fear-like responses evoked by electrical stimulation of the inferior colliculus, since the threshold of the escape behavior was increased 2 and 24 h after the blockade of kappa-opioid receptor. These results indicate that endogenous opioids may be involved in the modulation of fear in the central nucleus of the inferior colliculus. Although the acute treatment (after 10 min) of both naloxonazine and nor-binaltorphimine causes nonspecific effect on opioid receptors, we must consider the involvement of mu(1)- and kappa-opioid receptors in the antiaversive influence of the opioidergic interneurons in the dorsal mesencephalon, at caudal level, after chronic (2-24 h) treatment of these opioid antagonists. The neuroanatomical study of the connections between the central nucleus of the inferior colliculus and the periaqueductal gray matter showed neuronal fibers with varicosities and with terminal bottons, both in the pericentral nucleus of the inferior colliculus and in ventral and dorsal parts of caudal aspects of the periaqueductal gray matter.

Mesenteric cyst neoformation. A case report

Mesenteric cysts are rare lesions, with 1 case per 100,000 hospital admission reported. They have to be differentiated from ovarian cysts, gastrointestinal duplications and desmoid cysts. The symptoms are variable, ranging from asymptomatic cases with incidental discovery to chronic abdominal discomfort and acute abdomen. They are usually correlated to the location and the size of the lesion. Abdominal ultrasonography and computed tomography may lead to a correct diagnosis, which is regularly made at the time of abdominal exploration. Surgery is the treatment of choice, consisting with the removal of the cyst, eventually associated with bowel resection. It has to be radical in order to prevent the recurrence of the disease. A case of mesenteric cyst in a sixty-nine-years-old woman hospitalized for chronic abdominal pain is reported. In this case the cyst has been enucleated from the mesentery with open surgery without the need for bowel resection.

Phase IB study on prevention of surgery-induced immunodeficiency with preoperative administration of low-dose subcutaneous interleukin-2 in gastric cancer patients

BACKGROUND AND OBJECTIVES

Low count of total and T helper lymphocytes predicts a poor prognosis in cancer patients and surgical trauma can worsen cancer-related immunodeficiency. Aim of this phase IB study is to verify toxicity and biological effects of interleukin-2 (IL-2) at 9 million IU/day subcutaneously (sc.) administered one, two or three preoperative days in patients with gastric cancer undergoing radical surgery.

METHODS

Absolute value of total and T-helper (CD4) lymphocytes were measured at baseline and at 7th, 14th, and 50th postoperative days in 12 gastric cancer patients, who preoperatively received IL-2 at 9 million IU/day sc. as follows: group A (4 pts) 1-day; group B (4 pts) 2-days; group C (4 pts) 3-days administration. T and total lymphocytes count were recorded and retrospectively analyzed in a historical control-group of 22 consecutive patients, age and stage-matched.

RESULTS

Toxicity consisted of fever grade I. In group A (1 day) T helper lymphocytes count decreased at 7th and at 14th postoperative day; in group B (2 days) and group C (3 days) no decrease of neither total nor T helper lymphocyte count occurred postoperatively, whereas in the historical group these parameters decreased significantly postoperatively and recovered only at 50th day.

CONCLUSIONS

Two- and three-day schedules of sc. IL-2 preoperative administration at 9 million IU/daily prevented postoperative lymphocytopenia, whereas one-day administration did not. Since the IL-2 dose was so tolerable, that it could be given safely as outpatient, based on the previous results on survival observed in colorectal cancer patients with 3-days schedule we suggest that a 3-day schedule of Interleukin-2 as outpatient preoperative treatment seems advisable for further studies in gastric cancer patients.

[Gallbladder carcinoma and laparoscopic cholecystectomy. An emergent problem]

BACKGROUND

Gallbladder cancer (GC) is reported in 1.5-3% of cholecystectomies. Since the introduction of laparoscopic surgery, cholecystectomies have increased and occult GC may therefore be more frequent.

METHODS

Here we conduct a retrospective study on a series of 1200 LC performed between January 1991 and December 1998 at our Institution, to determine whether there was an increase in GC. We also evaluated the risk factors for this outcome and the possibilities of treatment, in case of unsuspected GC discovered after LC at histological examination. Seven cases of GC undiagnosed before surgery (0.6% of the study population) were submitted to LC (against 0.3% GC discovered after open surgery). The clinical course depended on the histopathologic stage of the cancer.

RESULTS

After a median follow-up of 18 months (range 12-48), 2 pT1 patients were alive and well, 2 pT2 patients were alive and disease free (in 1 case after a surgical removal of a trocar site metastasis appeared 6 months after LC). The other 3 patients died, 2 (1 pT2 and 1 pT3) after an additional resection of the liver bed with lymph node dissection, due to peritoneal dissemination of the disease. In 2 cases we found a gallbladder polyp pre and intraoperatively, which proved to be a carcinoma.

CONCLUSIONS

Undiagnosed GC is on the increase with the introduction of LC. Polypoid lesions of the gallbladder, age > 70 years: a long history of stones and a thickened gallbladder wall all represent significant risk factors. If one or more is present, examination of the gallbladder and a frozen section are recommended.

Effects of microinjections of mu and kappa receptor agonists into the dorsal periaqueductal gray of rats submitted to the plus maze test

Several lines of evidence have shown that aversive states are under the influence of opioid mechanisms in the dorsal periaqueductal gray (DPAG). In order to characterize the type of opioid receptors involved in these effects in this work we injected DAMGO and U50,488H, mu and kappa selective agonists, respectively, directly in this structure. Rats implanted with chemitrode in the DPAG were submitted to the elevated plus maze test for 5 min. The effects of DAMGO (0.1-1 nmol/0.2 microliter) and U50,488H (1-10 nmol/0.2 microliter) following administration into DPAG were studied. Low doses of DAMGO (0.1 and 0.3 nmol) caused dose-dependent increases in the number of entries and time spent in the open arms while an overall deficit in the exploratory activity was produced by the higher dose used (1.0 nmol). Clear aversive effects were observed following the administration of U50,488H in the DPAG. The antiaversive effects of 0.3 nmol DAMGO were inhibited by the intraperitoneal administration of the mu receptor antagonist naltrexone (2.0 mg/kg, IP) whereas the aversive effects of 5.0 nmol U50,488H were antagonized by the selective kappa receptor antagonist nor-binaltorphimine (1.0 mg/kg, IP). It is suggested that activation of mu receptors inhibit and kappa receptors enhance the neural substrate of aversion in the DPAG.

Behavioral and pharmacological validation of the elevated plus maze constructed with transparent walls

In this study we compared the performance of male Wistar rats, weighing 250-300 g, submitted to the standard plus maze (vertical surfaces of the closed arms with opaque walls) to their performance in a modified maze with raised Plexiglas edges in the closed arms (transparent walls). The animals (N = 12 for each group) continued to show a clear preference for the closed arms with transparent walls of the modified elevated plus maze. In addition, exploratory activity was higher in the open arms of the modified plus maze (4.25 +/- 0.42 entries and 53.50 +/- 5.10 s) as compared to that of the standard plus maze (2.10 +/- 0.25 entries and 24.00 +/- 4.91 s). Intraperitoneal injection of midazolam produced an increase in the number of entries (6.40 +/- 1.21 and 8.50 +/- 1.15 for 1.0 and 2.0 mg/kg, respectively) and in the time spend in the open arms (85.32 +/- 14.56 and 125.50 +/- 22.16 s for 1.0 and 2.0 mg/kg, respectively) while pentylenetetrazole caused a decrease in the number of entries (3.68 +/- 0.54 and 2.33 +/- 0.62 for 5.0 and 10 mg/kg, respectively) and in the time spent in the open arms of the modified maze (39.60 +/- 6.67 and 23.60 +/- 6.40 s for 5.0 and 10 mg/kg, respectively). The anxiolytic effect of midazolam and the anxiogenic effect of pentylenetetrazole were similar to those usually reported in the literature by authors using the standard test. These results behaviorally and pharmacologically validate the elevated plus maze with transparent walls and suggest that this test could be a useful tool for the study of anxiolytic drugs and the neurobiology of anxiety.

Neural substrate of defensive behavior in the midbrain tectum

It has been shown that the gradual increase in the intensity of electrical stimulation of the dorsal periaqueductal gray (DPAG), deep layers of the superior colliculus (DLSC) and inferior colliculus of rats induces, in a progressive manner, characteristic aversive responses such as arousal, freezing, and escape behavior. The DPAG-DLSC together with the periventricular gray substance of the diencephalon, amygdala and the inferior colliculus, constitute the neural substrate of aversion in the brain. In general, the behavioral responses induced by midbrain tectum stimulation are accompanied by increases in the mean arterial blood pressure, heart rate, and respiration. Both the behavioral and autonomic consequences of electrical stimulation of the mesencephalic tectum have been shown to be attenuated by minor tranquilizers, probably through enhancement of GABAergic neurotransmission. Besides GABAergic mechanisms several lines of evidence have clearly implicated opioid, serotonergic, and excitatory amino acids-mediated mechanisms in the control of the neural substrates commanding defensive behavior in the brain aversive system.

Chronic Effects of Subcutaneous Interleukin-2 Therapy on Soluble Interleukin-2 Receptors in Advanced Small Cell Lung Cancer

The increase in IL-2 receptor serum levels is one of the most typical changes in immune parameters during IL-2 cancer immunotherapy. To better define the effects of prolonged IL-2 injection on SIL-2R levels, we evaluated 7 advanced small cell lung cancer patients who received IL-2 subcutaneously at a daily dose of 9x106 IU/m2/12h for two days followed by 3x106 IU/m2/12h for 18 days (5 days/week for 4 weeks). Moreover, four patients were also evaluated during the second IL-2 cycle. Venous blood samples were drawn before and at weekly intervals during IL-2 therapy. Mean SIL-2R serum levels rapidly increased with the start of IL-2 injection, and they were signicantly higher than the baseline levels throughout the immunotherapy cycle. The increase in mean SIL-2R levels was higher in patients with progressive disease than in those with response or stable disease, but the difference was not significant. Finally, the increase in mean SIL-2R concentrations during the second IL-2 cycle was not significantly different from that seen during the first one. The present study confirms that IL-2 administration determines an evident increase in SIL-2R levels; moreover, it would demonstrate that re-exposure to IL-2 after a rest period does not induce a more pronounced SIL-2R release.

Aversive and antiaversive effects of morphine in the dorsal periaqueductal gray of rats submitted to the elevated plus-maze test

The dorsal periaqueductal gray (DPAG) is a well-known region for processing defensive behavior in the brainstem. Rats implanted with cannulae in the DPAG were submitted to the elevated plus-maze test for 5 min. The effects of morphine following systemic (0.1-1.0 mg/kg) or DPAG administration (5-30 nmol) were compared with the benzodiazepine compound midazolam injected similarly (1-10 mg/kg, IP, and 10-80 nM, DPAG). Morphine and midazolam caused dose-dependent increases in the number of entries and time spent in the open arms. A systemic injection of naloxone in doses that block mu-opioid receptors reversed the effects of centrally administered morphine. Higher doses of morphine (70 nmol) induced a non-naloxone-reversible "fearful" hyperreactivity. It is suggested that low doses of morphine inhibit the neural substrate of aversion in the DPAG, probably through activation of mu-receptors, and that microinjections of higher doses of morphine cause proaversive actions not mediated by these opioid receptors.

Effects of blockade of 5-HT2 receptors and activation of 5-HT1A receptors on the exploratory activity of rats in the elevated plus-maze

Acute administration of gepirone, a 5-HT1A agonist, caused a dose dependent (1-10 mg/kg, IP) reduction in the locomotor activity (open and closed arms) of rats tested in the elevated plus-maze. However, rats housed in individual cages and submitted to chronic treatment with gepirone (10 mg/kg PO) showed a marked increase in the percentages of number and time spent in the open arms as compared to controls. These results are compatible with the idea that the antiaversive effect due to long-term treatment with 5-HT1A agonists is the result of a progressive desensitization of the somatodendritic 5-HT autoreceptor with the consequent recovery of firing rate of 5-HT neurons along with an activation of normosensitive postsynaptic 5-HT neurons. Ketanserin caused a biphasic effects on the exploratory behavior of rats in the plus-maze. The lower dose (0.5 mg/kg) decreased the aversion to the open arms and the higher dose (1.0 mg/kg) caused an unspecific decrease in the overall activity of the animals. Ketanserin is supposed to have antagonistic action on 5-HT2 and on alpha-adrenergic receptors. As prazosin (0.5-1.0 mg/kg), an alpha-adrenergic receptor blocker, did not present any significant effect in the present work it is suggested that the effects of the lower dose of ketanserin was due to its high antagonistic action on 5-HT2 receptors.