Early postnatal development of electrophysiological and histological properties of sensory sural nerves in male rats that were maternally deprived and artificially reared: Role of tactile stimulation

Early adverse experiences disrupt brain development and behavior, but little is known about how such experiences impact on the development of the peripheral nervous system. Recently, we found alterations in the electrophysiological and histological characteristics of the sensory sural (SU) nerve in maternally deprived, artificially reared (AR) adult male rats, as compared with maternally reared (MR) control rats. In the present study, our aim was to characterize the ontogeny of these alterations. Thus, male pups of four postnatal days (PND) were (1) AR group, (2) AR and received daily tactile stimulation to the body and anogenital region (AR‐Tactile group); or (3) reared by their mother (MR group). At PND 7, 14, or 21, electrophysiological properties and histological characteristics of the SU nerves were assessed. At PND 7, the electrophysiological properties and most histological parameters of the SU nerve did not differ among MR, AR, and AR‐Tactile groups. By contrast, at PND 14 and/or 21, the SU nerve of AR rats showed a lower CAP amplitude and area, and a significant reduction in myelin area and myelin thickness, which were accompanied by a reduction in axon area (day 21 only) compared to the nerves of MR rats. Tactile stimulation (AR‐Tactile group) partially prevented most of these alterations. These results suggest that sensory cues from the mother and/or littermates during the first 7–14 PND are relevant for the proper development and function of the adult SU nerve. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 351–362, 2018     

The effects of early rearing environment on the hormonal induction of maternal behavior in virgin rats

The present study investigated the effects of isolation rearing, through the artificial rearing paradigm (AR), on the hormonal induction of maternal behavior (MB) in female Sprague-Dawley rats. Between postnatal days (PND) 4 and 18, rat pups were raised either with their mothers (MR) or artificially, without their mothers (AR). As well, some of the AR pups were provided with additional maternal-like licking stimulation (AR-MAX) while the others were not given any additional stimulation (AR-MIN). At PND 60-100, AR (n = 28) and MR (n = 25) animals were ovariectomized (OVX). One week after the surgery, rats were either treated with a 2-week estrogen (E2) and progesterone (P) hormonal regimen or not treated with the hormone replacement. Maternal behavior testing with foster pups commenced 24 h following the removal of P treatment. Results demonstrated that MR animals showed increased pup licking and hover-crouching in comparison to AR animals and that hormonally primed groups became maternal more quickly than non-primed groups, regardless of the rearing history. There was also a significant interaction between the rearing condition (MR vs. AR) and hormonal treatment on the quality of maternal behavior exhibited. The highest level of licking and crouching was shown by the hormone-treated MR group. Mechanisms for these effects are discussed.     

Le comportement du Chevrotain africain,Hyemoschus aquaticus Ogilby (Artiodactyla,Ruminantia)

The purpose of this study was to test the influence of social isolation during infancy on learning behavior in rats. Rats, reared isolated (n = 55) or paired (n = 60) for a period of 50 days following weaning, were tested on different learning tasks in an operant conditioning chamber. Isolation rearing produced significantly better learning when the training period directly followed the different housing conditions. After a 28 day period of social isolation for the subjects raised paired during infancy no differences in learning between isolated and paired reared animals could be observed. The differences are discussed in relation to the effects of stimulus deprivation.     

Habituation of object contact in socially-reared and isolated rats (Rattus norvegicus)

Rats reared in social isolation were found to contact fewer novel objects in an open-field than their socially reared litter mates. They also contacted a smaller variety of objects, and contacted them in different ways. Social animals showed more manipulatory behaviour than the isolates, but there were no differences in sniffing. In a second experiment, employing a longer session, it was found that social animals showed more rapid habituation of object contact. This may account for previous claims that isolates show heightened levels of exploration.     

Early social environment interferes with the development of NADPH–diaphorase‐reactive neurons in the rodent orbital prefrontal cortex

The influence of early parental deprivation on the development of NADPH–diaphorase–(NO‐synthase) reactive neuron numbers in subregions of the orbital prefrontal cortex (ventrolateral orbital, lateral orbital, and agranular insular cortex) was quantitatively investigated in the precocious lagomorph Octodon degus. Forty‐five‐day‐old degus from three groups were compared: (1) repeated parental separation: degus that were repeatedly separated from their parents during the first three postnatal weeks and thereafter raised in undisturbed social conditions; (2) chronic isolation: degus that were raised under undisturbed social conditions until postnatal day 21, and then were reared in chronic social isolation; and (3) control: degus that were reared undisturbed in their families. Compared to the control animals the ventrolateral orbital prefrontal cortex and agranular insular cortex of the two deprived groups displayed significantly decreased density of NADPH–diaphorase‐reactive neurons (down to 62% in the ventrolateral orbital prefrontal cortex of males, 70% in the agranular insular cortex, and in the lateral orbital prefrontal cortex 80% in both genders). These results confirm that early changes of social environment interferes with the development of limbic circuits, which might determine normal or pathological behaviors in later life. © 2004 Wiley Periodicals, Inc. J Neurobiol, 2005     

The effects of early rearing environment on the hormonal induction of maternal behavior in virgin rats

The present study investigated the effects of isolation rearing, through the artificial rearing paradigm (AR), on the hormonal induction of maternal behavior (MB) in female Sprague–Dawley rats. Between postnatal days (PND) 4 and 18, rat pups were raised either with their mothers (MR) or artificially, without their mothers (AR). As well, some of the AR pups were provided with additional maternal-like licking stimulation (AR-MAX) while the others were not given any additional stimulation (AR-MIN). At PND 60–100, AR (n = 28) and MR (n = 25) animals were ovariectomized (OVX). One week after the surgery, rats were either treated with a 2-week estrogen (E2) and progesterone (P) hormonal regimen (Bridges, R.S., 1984. A quantitative analysis of the roles of dosage, sequence, and duration of estradiol and progesterone exposure in the regulation of maternal behavior in the rat. Endocrinology 114, 930–940) or not treated with the hormone replacement. Maternal behavior testing with foster pups commenced 24 h following the removal of P treatment. Results demonstrated that MR animals showed increased pup licking and hover-crouching in comparison to AR animals and that hormonally primed groups became maternal more quickly than non-primed groups, regardless of the rearing history. There was also a significant interaction between the rearing condition (MR vs. AR) and hormonal treatment on the quality of maternal behavior exhibited. The highest level of licking and crouching was shown by the hormone-treated MR group. Mechanisms for these effects are discussed.     

Disruption of behavior and brain metabolism in artificially reared rats

Early adverse life stress has been associated to behavioral disorders that can manifest as inappropriate or aggressive responses to social challenges. In this study, we analyzed the effects of artificial rearing on the open field and burial behavioral tests and on GFAP, c‐Fos immunoreactivity, and glucose metabolism measured in anxiety‐related brain areas. Artificial rearing of male rats was performed by supplying artificial milk through a cheek cannula and tactile stimulation, mimicking the mother's licking to rat pups from the fourth postnatal day until weaning. Tactile stimulation was applied twice a day, at morning and at night, by means of a camel brush on the rat anogenital area. As compared to mother reared rats, greater aggressiveness, and boldness, stereotyped behavior (burial conduct) was observed in artificially reared rats which occurred in parallel to a reduction of GFAP immunoreactivity in somatosensory cortex, c‐Fos immunoreactivity at the amygdala and primary somatosensory cortex, and lower metabolism in amygdala (as measured by 2‐deoxi‐2‐[¹⁸fluoro]‐d ‐glucose uptake, assessed by microPET imaging). These results could suggest that tactile and/or chemical stimuli from the mother and littermates carry relevant information for the proper development of the central nervous system, particularly in brain areas involved with emotions and social relationships of the rat. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1413–1429, 2017     

Direct visualization of membrane architecture of myelinating cells in transgenic mice expressing membrane‐anchored EGFP

Myelinogenesis is a complex process that involves substantial and dynamic changes in plasma membrane architecture and myelin interaction with axons. Highly ramified processes of oligodendrocytes in the central nervous system (CNS) make axonal contact and then extrapolate to wrap around axons and form multilayer compact myelin sheathes. Currently, the mechanisms governing myelin sheath assembly and axon selection by myelinating cells are not fully understood. Here, we generated a transgenic mouse line expressing the membrane‐anchored green fluorescent protein (mEGFP) in myelinating cells, which allow live imaging of details of myelinogenesis and cellular behaviors in the nervous systems. mEGFP expression is driven by the promoter of 2'‐3'‐cyclic nucleotide 3'‐phosphodiesterase (CNP) that is expressed in the myelinating cell lineage. Robust mEGFP signals appear in the membrane processes of oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system (PNS), wherein mEGFP expression defines the inner layers of myelin sheaths and Schmidt‐Lanterman incisures in adult sciatic nerves. In addition, mEGFP expression can be used to track the extent of remyelination after demyelinating injury in a toxin‐induced demyelination animal model. Taken together, the membrane‐anchored mEGFP expression in the new transgenic line would facilitate direct visualization of dynamic myelin membrane formation and assembly during development and process remodeling during remyelination after various demyelinating injuries. genesis 52:341–349, 2014. © 2014 Wiley Periodicals, Inc.     

Early social environment interferes with the development of NADPH-diaphorase-reactive neurons in the rodent orbital prefrontal cortex

The influence of early parental deprivation on the development of NADPH-diaphorase-(NO-synthase) reactive neuron numbers in subregions of the orbital prefrontal cortex (ventrolateral orbital, lateral orbital, and agranular insular cortex) was quantitatively investigated in the precocious lagomorph Octodon degus. Forty-five-day-old degus from three groups were compared: (1) repeated parental separation: degus that were repeatedly separated from their parents during the first three postnatal weeks and thereafter raised in undisturbed social conditions; (2) chronic isolation: degus that were raised under undisturbed social conditions until postnatal day 21, and then were reared in chronic social isolation; and (3) control: degus that were reared undisturbed in their families. Compared to the control animals the ventrolateral orbital prefrontal cortex and agranular insular cortex of the two deprived groups displayed significantly decreased density of NADPH-diaphorase-reactive neurons (down to 62% in the ventrolateral orbital prefrontal cortex of males, 70% in the agranular insular cortex, and in the lateral orbital prefrontal cortex 80% in both genders). These results confirm that early changes of social environment interferes with the development of limbic circuits, which might determine normal or pathological behaviors in later life.     

Effects of social deprivation from birth or weaning on the development of the genital tract, on plasma testosterone, and on fertility in the male mouse

Male mice were placed in one of the following 5 types of rearing conditions: group I: 3 males and 3 females in cohabitation from birth to sacrifice; group II: without littermates from birth to sacrifice; group III: isolated from weaning to sacrifice; groups IV, V: males of groups II, III placed in cohabitation with 5 mature females, from 40 to 90 days. All animals were weaned at 20 days and sacrificed from 20 to 90 days. Plasma testosterone was radioimmunologically determined. Male mice reared in various types of social deprivation showed transient or definitive modifications in body, testicular and seminal vesicle weights as well as in plasma testosterone. Fertility was not affected. Mechanisms of these modifications are unknown.     

The weight of the clan: Even in insects, social isolation can induce a behavioural syndrome

Social isolation has dramatic consequences on the development of individuals of many vertebrate species, and it induces a set of behavioural disturbances rending them unable to process environmental as well as social stimuli appropriately. We hypothesized that isolation syndrome is a ubiquitous trait of social life that can be observed in a wide array of species, including invertebrates. Here we report that gregarious cockroaches (Blattella germanica) reared in isolation showed (i) stronger exploration-avoidance, (ii) reduced foraging activity, (iii) reduced willingness to interact socially, and (iv) reduced ability to assess mating partner quality than conspecifics reared in groups. We demonstrate the occurrence of a behavioural syndrome induced by social isolation, similar to syndromes described in vertebrates, revealing the importance of social interactions and group-living in this non-eusocial insect species. We suggest that investigating social isolation effects on individual development should provide interesting results to assess social cohesion of species and thus constitute an additional tool for comparative studies focusing on the evolution of social life.     

The ultrastructural organization of peripheral nerves in two insect species (Periplaneta americana and Schistocerca gregaria)

The ultrastructural organization of various peripheral nerves, including the crural nerve, has been investigated in the locust and cockroach. In some cases the larger nerves are ensheathed by a fat body layer which is not always complete. However, like many nervous connectives, they do possess a continuous acellular neural lamella and a perineurial cell layer which surround the glial-axonal mass. Adjacent perineurial cells are associated with one another by septate desmosomes, gap junctions and tight junctions. These last may represent the morphological basis of the ‘blood-brain barrier’ observed electrophysiologically in these peripheral nerves in another report. Very small nerves of the cockroach, however, although lying embedded in a neural lamella, do not possess a specialized perineurial layer displaying junctional complexes, unless they contain one or more large axons. If they have only one or more small axons, these small nerves may either appear naked, or display a single glial cell process loosely enveloping them; in either case there is no structural basis for a ‘barrier’ system. Various comparisons have been made between locust crural nerve and the cockroach central nervous connectives in an attempt to correlate some aspects of their ultrastructural organization with relevant electrophysiological information.     

The presence of the dam affects the efficiency of gentling and feeding on the early establishment of the stockperson-lamb relationship

This experiment investigates how the maternal presence influences the effect of additional human contact in early age on the reaction of lambs to their stockperson. Forty twin-born lambs were involved in this experiment during their first 4 days of life. Ten pairs of twins were reared artificially from 12h of age. One of each litter (AF, n=10) received 6.5+/-0.7 sessions of 30min of separation from the twin (with a wire fence) with 5min of gentling and feeding (suckling from a bottle and from a bucket fitted with a rubber teat). The other twin was not treated. Ten pairs of twins were reared with their dam and received 6.6+/-0.7 sessions of treatment. One twin (MAF, n=10) received the same treatment as AF. The other twin (M, n=10) was separated for 30min from the dam and had no human contact. From the age of 70+/-7h, lambs were tested in a social isolation test (alone for 1min, with the familiar stockman for 2min, alone again for 1min), in a Preference test (2min) between an unfamiliar maternal ewe and the familiar stockman, and, for the AF lambs only, in a Preference test (2min) between their familiar and an unfamiliar stockman. Eight AF lambs learned to suck on their own from the bucket of milk by the end of the experiment compared to only one MAF (P<0.001). AF lambs approached the human more (P<0.01), vocalised less (P<0.01) and walked less (P<0.01) during the social isolation test than animals reared with their mother (M and MAF). AF did not show any preference between the stockman and the unfamiliar maternal ewe while M and MAF lambs chose the ewe (P<0.05). AF lambs discriminated the familiar from an unfamiliar stockman only if they had learned to suck from the bucket during the treatment. Nevertheless MAF lambs vocalised less than M (P<0.05) in the presence of the stockman during the social isolation test, indicating a possible reduction of isolation distress. These results show that artificially reared lambs are preferentially motivated to interact with a familiar human after only a few days of contact. Moreover, they highlight the difficulty in using a feeding reward to improve the human-lamb relationship when lambs are reared permanently with their dams. However, the results suggest that early gentling improves the human-animal relationship whatever the maternal environment.     

Stressful animal housing conditions and their potential effect on sympathetic neurotransmission in mice

Although the sympathetic nervous system (SNS) plays a major role in mediating the peripheral stress response, due consideration is not usually given to the effects of prolonged stress on the SNS. The present study examined changes in neurotransmission in the SNS after exposure of mice (BALB/c) to stressful housing conditions. Focal extracellular recording of excitatory junction currents (EJCs) was used as a relative measure of neurotransmitter release from different regions of large surface areas of the mouse vas deferens. Mice were either group housed (control), isolation housed (social deprivation), group housed in a room containing rats (rat odor stress), or isolation housed in a room containing rats (concurrent stress). Social deprivation and concurrent stressors induced an increase of 30 and 335% in EJC amplitude, respectively. The success rate of recording EJCs from sets of varicosities in the concurrent stressor group was greater compared with all other groups. The present study has shown that some common animal housing conditions act as stressors and induce significant changes in sympathetic neurotransmission.     

Pulsed magnetic fields enhance the rate of recovery of damaged nerve excitability

Pulsed magnetic fields (PMFs) have well‐known beneficial effects on nerve regeneration. However, little research has examined the nerve conduction characteristics of regenerating peripheral nerves under PMF. The main goal of this study was to examine the conduction characteristics of regenerating peripheral nerves under PMFs. The sucrose‐gap recording technique was used to examine the conduction properties of injured sciatic nerves of rats exposed to PMF. Following the injury, peripheral nerves were very sensitive to repetitive stimulation. When the stimulation frequency was increased, the amplitude of the compound action potential (CAP) decreased more at 15 days post‐crush injury (dpc) than at 38 dpc. PMF treatment for 38 days after injury caused significant differences in the conduction of CAPs. Moreover, application of PMF ameliorated the abnormal electrophysiological activities of nerves such as hyperpolarizing afterpotentials and delayed depolarizations that were revealed by 4‐aminopyridine (4‐AP). Consequently, characteristic findings in impulse conduction of recovered nerves under PMF indicate that the observed abnormalities in signaling or aberrant ion channel functions following injury may be restored by PMF application. Bioelectromagnetics 32:200–208, 2011. © 2010 Wiley‐Liss, Inc.     

Geographical distribution of morphological abnormalities and wing color pattern modifications of the pale grass blue butterfly in northeastern Japan

The pale grass blue butterfly Zizeeria maha has been used as an environmental indicator to evaluate the biological impacts of the Fukushima nuclear accident. A high morphological abnormality rate (AR) of this butterfly was detected in 2011 from radioactively contaminated areas at 37–38°N. However, the geographical AR distribution has not been documented for the entirety of northeastern Japan. Additionally, the geographical distribution of the wing color pattern modification rate (MR) of temperature‐shock type remains undocumented. Here, we collected adult butterflies from many localities in northeastern Japan in 2014 and examined the local AR and MR. Both AR and MR were generally low throughout the 44 local populations surveyed. Latitudinal AR and MR distributions indicated a gap zone at approximately 39°N. The mean AR and the mean MR of the populations south of the gap zone were low (AR = 3.0%, MR = 1.1%), whereas those of the northern populations were relatively high (AR = 10.6%, MR =10.3%). Logistic regression analyses revealed that abnormalities and modifications were associated with temperature‐related variables. We conclude that abnormalities and modifications are generally rare, but that their rates are higher in the northern populations than in the southern ones. These results, along with evidence from other studies, strongly suggest that the high AR detected in 2011 from contaminated areas was induced by anthropogenic radioactive mutagens. This study presents a basic dataset of the current wildlife state of Z. maha in northeastern Japan, which facilitates a future use of this butterfly species as an environmental indicator.     

FMRF-amide-like immunoreactive efferent fibers and FMRF-amide suppression of pacemaker neurons in eyes of Bulla

The eyes of certain marine gastropods including Aplysia and Bulla, contain circadian pacemakers, which produce a circadian rhythm of autogenous compound action potential (CAP) activity. The CAPs are generated by the synchronous spike discharge of a distinctive population of retinal pacemaker neurons whose axons convey the CAP activity to the CNS. When CAP activity is recorded from a preparation with eyes attached to the CNS, the CAP activity is modulated by efferent activity. In this study we have identified FMRF-amide-like immunoreactive efferent axons in the optic nerves of Bulla. These axons arborize in the basal retinal neuropil adjacent to the pacemaker neurons and are in a position to make synaptic contacts with their dendrites. Similar immunoreactive fibers are not observed in Aplysia eyes. Exogenous FMRF-amide at micromolar concentrations suppresses ongoing CAP activity in isolated eyes but does not suppress the ERG or phase shift the circadian rhythm of CAP activity. Intracellular recordings from the retinal pacemaker neurons reveal that FMRF-amide hyperpolarizes the membrane potential, suppresses spike discharge, and decreases the input resistance, suggesting that a K conductance is increased. Electrical stimulation of the region of the cerebral ganglion that contains FMRF-amide immunoreactive neurons suppresses ongoing CAP activity. All these results are consistent with the idea that the FMRF-amide immunoreactive central neurons and their axons provide a pathway for efferent modulation of the CAP rhythm generated by the retinal pacemaker neurons.     

Effect of the melanostatin analogue alaptide on dopamine-dependent behavior in rats reared in isolation

The effects of alaptide, a new analog of melanostatine, on self-stimulation of the lateral hypothalamus, rotation behavior in rotometer, and stereotypy were studied in rats bred in social isolation from other animals beginning from the 17th day of birth and rats bred in groups. Alaptide potentiated amphetamine-stimulated behavior only in rats reared in social isolation. This effect was lateralized: the left rotation dominated. In rats reared in isolation and in groups the effects of alaptide on self-stimulation were oppositely directed: in the former it increased and in the latter decreased the rate of self-stimulations with oppositely directed changes in pedal pressing duration. At the same time, alaptide suppressed the effects of amphetamine on self-stimulation of rats reared in isolation. The central dopamine mechanisms of melanostatine action are discussed.     

Increased Drinking following Social Isolation Rearing: Implications for Polydipsia Associated with Schizophrenia

Primary polydipsia, excessive drinking without known medical cause, is especially associated with a diagnosis of schizophrenia. We used animal models of schizophrenia-like symptoms to examine the effects on schedule-induced polydipsia: post-weaning social isolation rearing, subchronic MK-801 treatment (an NMDA-receptor antagonist) or the two combined. Male, Sprague-Dawley rats reared in groups or in isolation beginning at postnatal day 21 were further divided to receive subchronic MK-801 (0.5 mg/kg twice daily) or saline for 7 days beginning on postnatal day 62. Following a 4-day withdrawal period, all groups were trained on a schedule-induced polydipsia paradigm. Under food-restriction, animals reared in isolation and receiving food pellets at 1-min intervals developed significantly more drinking behavior than those reared with others. The addition of subchronic MK-801 treatment did not significantly augment the amount of water consumed. These findings suggest a predisposition to polydipsia is a schizophrenia-like behavioral effect of post-weaning social isolation.     

Motor innervation of muscle fibers in thyrotoxic myopathy]

In patients and test animals similar changes in innervation have been revealed. Degeneration of some preterminal axons has been shown. The most manifested feature's increased ramification of distal axons. No signs of real reinnervation have been found. New collateral branches of preterminal, terminal and ++ultra-terminal axons usually have their ends at the same muscle fiber in the form of additional nervous terminals. Decreased average diameter of motor end-plates, revealed in the test animals, depends not on their degeneration, but on formation of new small motor end plates as a result of immature axonal ramification of distal axons. Acetylcholinesterase activity in the end-plates is decreased. A suggestion is made that excess of thyroid hormones in the skeletal muscle disturbs both the system of cyclic nucleotides and mechanisms of muscular contraction, connected with it and axoplasmic transport, respectively. The changes of the terminal intramuscular innervation revealed, structures of the motor end-plates with a decrease of acetylcholinesterase activity are supposed to result from disturbances of neurotrophic regulation of the muscle fibers because of the disturbances of the axoplasmic current as the excess of thyroid hormones.