effects of de-whiskering and congenital hypothyroidism on the development of nitrergic neurons in rat primary somatosensory and motor cortices

Objective: The aim of the present study is to investigate the effects of chronic whisker deprivation on possible alterations to the development of nitrergic neurons in the whisker part of the somatosensory [wS1] and motor [wM1] cortices in offspring with congenital hypothyroidism [CH]

Materials and Methods: In the experimental study, CH was induced by adding propylthiouracil to the rats drinking water from embryonic day 16 to postnatal day [PND] 60. In whisker-deprived [WD] pups, all the whiskers were trimmed from PND 1 to 60. Nitrergic interneurons in the wS1/M1 cortices were detected by NADPH-diaphorase histochemistry staining technique in the control [Ctl], Ctl+WD, Hypo and Hypo+WD groups

Results: In both wS1 and wM1 cortices the number of nitrergic neurons was significantly reduced in the Hypo and Hypo+WD groups compared to Ctl and Ctl+WD groups, respectively [P<0.05] while bilateral whisker deprivation had no remarkable effect. The mean soma diameter size of NADPH-d labeled neurons in the Ctl+WD and Hypo+WD groups was decreased compared to the Ctl and Hypo groups, respectively. A similar patterns of decreased NADPH-d labeled neurons in the wS1/M1 cortices occur in the processes of nitrergic neurons in both congenital hypothyroidism and whisker deprivation

Conclusion: Our results suggest that both congenital hypothyroidism and whisker deprivation may disturb normal development of the wS1 and wM1 cortical circuits in which nitrergic neurons are involved

A role for endocannabinoids in acute stress-induced suppression of the hypothalamic-pituitary-gonadal axis in male rats / 대한생식의학회지

OBJECTIVE: Stress is known to be an inhibitor of the reproductive hypothalamic-pituitary-gonadal (HPG) axis. However, the neural and molecular connections between stress and reproduction are not yet understood. It is well established that in both humans and rodents, kisspeptin (encoded by the kiss1 gene) is a strong stimulator of the HPG axis. In the present study we hypothesized that endocannabinoids, an important neuromodulatory system in the brain, can act on the HPG axis at the level of kiss1 expression to inhibit reproductive function under stress. METHODS: Adult male Wistar rats were unilaterally implanted with an intracerebroventricular cannula. Afterwards, the animals were exposed to immobilization stress, with or without the presence of the cannabinoid CB1 receptor antagonist AM251 (1 microg/rat). Blood samples were collected through a retro-orbital plexus puncture before and after stress. Five hours after the stress, brain tissue was collected for reverse transcriptase-quantitative polymerase chain reaction measurements of kiss1 mRNA. RESULTS: Immobilization stress (1 hour) resulted in a decrease in the serum luteinizing hormone concentration. Additionally, kiss1 gene expression was decreased in key hypothalamic nuclei that regulate gonadotrophin secretion, the medial preoptic area (mPOA), and to some extent the arcuate nucleus (ARC). A single central administration of AM251 was effective in blocking these inhibitory responses. CONCLUSION: These findings suggest that endocannabinoids mediate, at least in part, immobilization stress-induced inhibition of the reproductive system. Our data suggest that the connection between immobilization stress and the HPG axis is kiss1 expression in the mPOA rather than the ARC.

effects of lidocaine reversible inactivation of the dorsal raphe nucleus on passive avoidance learning in rats

Introduction: The role of serotonergic fibers in avoidance learning is controversial. Involvement of the dorsal raphe nucleus [DRN], the main source of hippocampal projecting serotonergic fibers in acquisition, consolidation and retrieval of passive avoidance [PA] learning, was investigated by functional suppression of this area. Materials and Methods: DRN functional inactivation was done by lidocaine [0.5µl, 2%] injection into the DRN, 5 min before training [n=10]; and 5 [n=9], 90 [n=10] and 360 min [n=9] after acquisition trial. In the last experiment, lidocaine was injected into the DRN 5 min before the retrieval test, which was 48 h after the training [n=10]. Results: Our results showed that PA learning was not impaired by DRN inactivation 5 min before training nor 5 and 360 min after training. Lidocaine injected 90 min after the acquisition trial significantly reduced avoidance of the dark compartment [P<0.001]. Intra-DRN injection of lidocaine before retrieval significantly increased PA retention [P<0.001]. Therefore, it seems that DRN has opposite effects on consolidation and retrieval of passive avoidance learning, but it has no effect on PA acquisition. Discussion: It is suggested that functional ablation of DRN may disrupt integrity of subcortical circuits participating in PA consolidation, but DRN inactivation by increasing brain awareness may affect PA retrieval in rats

Morphology and synaptic organization of non-dopaminergic nigral projections to the medio dorsal thalamic nucleus of the rat, a study by anterograde transport of PHA-L

Mediodorsal [MD] thalamic nucleus, which is considered to take place between extra pyramidal and limbic feedback circuit, receives projective fibers from ventrolateral neurons of reticular part of substantia nigra [SNr]. In order to better understand the influence and chemical reaction of these fibers upon MD nucleus, the morphology and synaptology of them were examined in the present study. Phaseolous vulgaris-leucoagglutin [PHA-L] was injected into substantia nigra pars reticulate. After 3-4 days, the sections of SNr injection site and MD nucleus were prepared. Then, we examined organization, morphology and, synaptology of PHA-L labeled SNr fibers that go to caudal and lateral part of MD thalamic nucleus. At the electron microscopic level, the SNr terminals made synapses predominantly with the medium to small dendrites and far less frequently with soma and large dendrites. These terminals were packed with polymorphic synaptic vesicles and formed symmetrical synapses; furthermore, it has been already recognized that cortico straital fibers from sensory-motor cortex go to region of the SNr that give rise to the nigrothalamic fibers. This data suggest that upon the synaptic organization, morphology and chemical nature of GABAergic, SNr fibers may have different inhibitory influence on MD neurons regulating the thalamic output from MD to cerebral cortex in the control of limbic and extra pyramidal feedback system

Reversible inactivation and excitation of nucleus raphe magnus can modulate tail blood flow of male wistar rats in response to hypothermia

The nucleus raphe magnus [NRM] is involved in thermoregulatory processing. There is a correlation between changes in the firing rates of the cells in the NRM and the application of the peripheral thermal stimulus. We examined the effect of reversible inactivation and excitation of NRM on mechanisms involved in tail blood flow [TBF] regulation in hypothermia. Hypothermia was induced in Male Wistar rats and cannula was implanted above the NRM. To evaluate the effect of nucleus inactivation on TBF, the amount of TBF was measured by Laser Doppler in hypothermic rats, before and after lidocaine microinjection into NRM. TBF was also measured after glutamate microinjection to assess the effect of nucleus excitation in hypothermic rats. Results indicated that after dropping TBF by hypothermia, microinjection of lidocaine into NRM significantly decreased TBF from 54.43 +/- 5.7 to 46.81 +/- 3.4, whereas glutamate microinjection caused a significant increase from 44.194 +/- 0.6 to 98 +/- 10.0 Conclusion: These data suggest that NRM have thermoregulatory effect in response to hypothermia

Opioid receptors of the central amygdala and morphine-induced antinociception

The amygdala is a forebrain region, which is known as a modulator of pain sensation. The amygdala, particularly the central nucleus, has high concentrations of enkephalins relative to dynorphins and has high concentrations of opioid receptors. We here studied the role of central nuclei of amygdala in morphine antinociception. In this study, we used 130 male Wistar rats [200- 250g]. Bilateral two guide cannula were inserted into central nuclei of amygdala. The drugs were administrated via intra central- amygdala and intraperitoneal. The antinociceptive effect was measured by formalin test. Bilateral microinjections of morphine [50 and 100 micro g/rat] into the central nuclei of amygdala elicited powerful suppression of nociceptive behaviors in both phases of formalin test. The intraperitoneal administration of naloxone [1 and 2 mg/kg] decreased significantly the antinociception induced by the intra-amygdaloid injection of morphine. Our data also showed that microinjection of naloxone [50 and 100 micro g/rat] into the central nuclei of amygdala could reduce the analgesic effects of systemic morphine [7 mg/kg]. On the other hand, bilateral neurotoxic lesions of the central nuclei of amygdala attenuated the antinociception induced by subcutaneous or intra-amygdaloid injection of morphine. These findings suggest that morphine analgesia in the formalin test depends on ascending connections to the forebrain, probably the amygdala

effect of nucleus tractus solitarius nitric oxidergic neurons on blood pressure in diabetic rats

It has been shown that nitric oxide is synthesized in the central nervous system as well as in vascular endothelial cells. Recently, it was reported that nitric oxide was involved in central cardiovascular regulation, baroreflex modulation, and involved in a reciprocal release with excitatory amino acids in the nucleus tractus solitarii of rats. The purpose of the present study was to investigate the possible interaction of nitric oxide and glucose in the nucleus tractus solitarii on blood pressure regulation. Male Wistar stereptozotocin induced diabetic rats were anesthetized with urethane. A cannula was inserted above the nucleus tractus solitarii and blood pressure was monitored intra-arterially. Unilateral microinjection of L-glutamate [2.3 nmol/60 nL] into the nucleus produced a decrease in blood pressure in diabetic rats. Microinjection of lidocaine [0.5 Mul%2] increased blood pressure. Unilateral microinjection of sodium nitroprusside [100 mmoV6O nL] into the nucleus increased blood pressure in diabetic rats. After microinjection of sodium nitroprusside, the depressive responses to glutamate were significantly attenuated. These results demonstrated the probable role of glucose on blood pressure regulation in diabetic animals affecting on nitric oxidergic neurons and so it implicates an interaction between nitric oxide and glucose in central cardiovascular regulation

Effect of thyroid hypofunction on the masseter motor innervation pattern in developing rats

The thyroid hormones have profound effects on the development of neuromuscular system. These hormones exert their influence on both muscle fibers and related motoneurons during development. The masseter is one of the most important muscles for mastication in mammals. We attempted to evaluate the effect of thyroid hormone deficiency on the morphological characteristics of masseteric motoneurons in the period of alteration from sucking to biting and chewing in the rat Material and To induce hypothyroidism, timed pregnant dams received 50 ppm antithyroid drug propylthiouracil [PTU] in their drinking water and PTU was administered to the pups during suckling period. Horseradish peroxidase [HRP] was injected into the masseter [0.5-5 mecro lit, 40%] of normal and prenatal hypothyroid pups on postnatal days of 1, 5, 13, and 21 [n=24]. 24 to 48 hours later, following transcardial perfusion and fixation the brainstem blocks were cut to 50 micro m thick sections. After TMB histochemical reaction the morphological characteristics of HRP labeled motoneurons and their HRP labeling intensity was evaluated. Student's t-test and two-way analysis of variance [ANOVA] were used for statistical analysis.No significant morphological differences were observed at the end of first week of life. On day 15, hypothyroid labeled masseteric motoneurons consisted of 70% small and 30% medium neurons versus 40% and 60% in normal pups respectively [p<0.05].At the time of weaning, the number of large motoneurons dropped to 30% of normal value [p<0.001] with few, short, and disoriented dendrites The alteration in particular patterns of masseteric motoneuron morphology and a severe delay in size transition could affect the development and plasticity of oral motor behavior under congenital hypothyroidism

Effect of intrathecal transplantation of adrenal medullary tissue on the sciatic nerve regeneration following chronic constriction injury in the rat

It has been demonstrated that the adrenal medullary transplants into the spinal subarachnoid space can alleviate neuropathic pain behaviors. The aim of the present study was to test the possibility that histological changes of the sciatic nerve in a neuropathic model as well as sensory dysfunction are repaired by adrenal medullary transplantation. Left sciatic nerve was ligated in three groups of rats by 4 loose ligatures [CCI]. After one week of nerve constriction, rats of first group were implanted with adrenal medullary tissue [CCI + adrenal medulla] and rats of the second group with striated muscle at the level of L1-L2 [CCI + muscle]. The third group received only left ligature [CCI] and in the fourth group the sciatic nerve was exposed and then muscle and skin sutured [sham]. Behavioral assessment was evaluated before surgery and 2, 4, 7, 10, 14, 21, 28, 42, and 56 days after the onset of experiment. According to behavioral results, 4 rats in each group were anesthetized and then the distal part of sciatic nerve were isolated and prepared for histological quantitative investigation of nerve regeneration. The results showed that CCI was accompanied with hyperalgesia and morphological changes in the distal part of sciatic nerve. In animals with adrenal medullary transplantation, not only hyperalgesia was markedly reduced or even eliminated, but also the number of myelinated fibers in the distal segment of nerve increased to nearly normal. Our findings showed that the implantation of adrenal medullary tissue might have caused regeneration of ligated nerves as well as alleviation of pain behavior

organization of non - dopaminergic nigral projection to the thalamic nucleus of the rat

Nigrotnalamocortical tract is one of the important outputs of the basal ganglia, but its role in motor disturbances is still vauge, because there is little informations on its connection structure. Some electrophysiological and pharmacological studies report that non-dopaminergic outputs originate from reticular part of substatia nigra to thalamus. In this study the topographical and organization connection of substantia nigra pars reticulata [SNR] with thalamic MD nucleus was investigated using HRP tracer. 25 male rats received injection of 33 percent HRP into the ipsilateral MD nucleus of thalamus stereotaxically. 48 hours later the animals were perfused transcardially, and the brain tissue was fixed. 40 micrometer sections were prepared from diencephalon and midbrain. Following enzymatic reactions of TMB, the sections were stained by neutral red. The light microscopic study showed that there is a high concentration of neurons which project to the MD nucleus from the rostro-lateral part and middle parts of pars reticulata [SNR] and the number of labeled cells decrease in the caudal parts. Other labeled neurons are located at the border of SNC, SNR and VTA, especially close to the passage of III cranial nerve. In general, the size of neurons was mostly medium; and they were multipolar in shape. Any labeled cells were observed in the SNR controlateral to injection site. Our findings show that the SNR connection to the MD arise mainly from lateral and dorsomedial part of SNR. It seems that these connections may influence the limbic system in orientating behaviour