Differences in macroglia of the spinal cord in various cold-blooded and warm-blooded animals

Certain macroglial differences of the spinal cord in poikilothermal (Rana esculenta, Lacerta agilis) and in homoiothermal (Columba livia, Felis domesticus, Macaca rhesus) animals have been revealed. A greater amount of glial satellites, surrounding neurons, motor centers of the spinal cord and appearance of new variety of astrocytes and oligodendrocytes are observed in the homoiothermal animals. It is supposed that the phenomenon mentioned indirectly reflects the evolutionary process of a more distinct functional differentiation of macroglia.     

Disinhibition and its role in central nervous system activity]

The review concerning neuronal mechanisms of disinhibition and its participation in activities of the spinal cord, cerebellum, reticulo-thalamo-cortical system, basal ganglia and cerebral cortex is presented.     

Higher-Order Thalamocortical Inputs Gate Synaptic Long-Term Potentiation via Disinhibition

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Disinhibition Mediates a Form of Hippocampal Long-Term Potentiation in Area CA1

The hippocampus plays a central role in memory formation in the mammalian brain. Its ability to encode information is thought to depend on the plasticity of synaptic connections between neurons. In the pyramidal neurons constituting the primary hippocampal output to the cortex, located in area CA1, firing of presynaptic CA3 pyramidal neurons produces monosynaptic excitatory postsynaptic potentials (EPSPs) followed rapidly by feedforward (disynaptic) inhibitory postsynaptic potentials (IPSPs). Long-term potentiation (LTP) of the monosynaptic glutamatergic inputs has become the leading model of synaptic plasticity, in part due to its dependence on NMDA receptors (NMDARs), required for spatial and temporal learning in intact animals. Using whole-cell recording in hippocampal slices from adult rats, we find that the efficacy of synaptic transmission from CA3 to CA1 can be enhanced without the induction of classic LTP at the glutamatergic inputs. Taking care not to directly stimulate inhibitory fibers, we show that the induction of GABAergic plasticity at feedforward inhibitory inputs results in the reduced shunting of excitatory currents, producing a long-term increase in the amplitude of Schaffer collateral-mediated postsynaptic potentials. Like classic LTP, disinhibition-mediated LTP requires NMDAR activation, suggesting a role in types of learning and memory attributed primarily to the former and raising the possibility of a previously unrecognized target for therapeutic intervention in disorders linked to memory deficits, as well as a potentially overlooked site of LTP expression in other areas of the brain.     

Extended Flight Bouts Require Disinhibition from GABAergic Mushroom Body Neurons

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Reductions in Internal Disinhibition During Weight Loss Predict Better Weight Loss Maintenance

The construct of disinhibition, as measured by the Eating Inventory, was recently found to have two factors: internal disinhibition (eating in response to cognitive and emotional cues) and external disinhibition (eating in response to environmental cues). This study examined whether early changes in disinhibition that occurred during a weight loss program predicted later weight loss maintenance. Participants were adults enrolled in a weight loss treatment study (n = 81, 16% men, BMI = 38.4 ± 6.5 kg/m²). Two‐thirds of participants were African Americans. Participants received a uniform, meal‐replacement‐based weight loss program in months 1–3 and one of four nutritionally focused programs for weight loss maintenance in months 4–12. Disinhibition and weight were assessed at clinic visits. Change in internal disinhibition from months 1–3 (i.e., the weight loss period) significantly predicted change in weight from month 4 to 12 (i.e., the weight maintenance period); this remained significant when treatment group, age, gender, ethnicity, baseline weight, baseline depression, baseline internal disinhibition, and initial weight loss were controlled for (P = 0.03). A comparable analysis examining change in external disinhibition found that it was not a significant predictor of weight maintenance (P = 0.43). Participants who experienced the biggest decreases in internal disinhibition during the initial phase of treatment had the most success maintaining their weight loss in the next phase of treatment. Long‐term weight loss outcomes may be improved by spending sufficient treatment time teaching strategies for reducing eating in response to internal cues.     

Disinhibition of female sexual behavior by a CRH receptor antagonist in Syrian hamsters

Several conditions that inhibit female sexual behavior are thought to be associated with altered corticotropin-releasing hormone (CRH) activity in the brain. The present experiments examined the hypothesis that endogenous CRH receptor signaling mediates the inhibition of estrous behavior by undernutrition and in other instances of sexual dysfunction. Intracerebroventricular (ICV) infusion of CRH or urocortin inhibited estrous behavior in ovariectomized steroid-primed hamsters. Conversely, ICV infusion of the CRH receptor antagonist astressin prevented the suppression of estrous behavior by food deprivation or by ICV administration of neuropeptide Y. Astressin treatment also induced sexual receptivity in nonresponders, animals that do not normally come into heat when treated with hormones, and this effect persisted in subsequent weekly tests in the absence of any further astressin treatment. Activation of the hypothalamo-pituitary-adrenocortical axis was neither necessary nor sufficient to inhibit estrous behavior, indicating that this phenomenon is due to other central actions of CRH receptor agonists. This is the first direct evidence that CRH receptor signaling may be a final common pathway by which undernutrition and other conditions inhibit female sexual behavior.     

Head-butting as an Early Indicator of Reproductive Disinhibition in the Termite Zootermopsis nevadensis

In lower termites, functionally sterile larval helpers are totipotent—capable of becoming reproductively active with the loss of their colony’s king or queen. Full reproductive development may take several weeks, but initiation of this developmental response most likely occurs shortly after colony members detect when a reproductive-specific signal is missing. We investigated the early response of termite helpers to the removal of their king and queen in the basal termite species Zootermopsis nevadensis. Within 6–12 h after reproductives were removed, helpers displayed an increase in head-butting—a behavior associated with dominance in other termite species as well as in closely related roaches. The loss of just one reproductive, either the king or queen, was also sufficient to cause an increase in head-butting. We did not find evidence, however, that this response was sex-specific: males and females were equally likely to increase head-butting independent of the sex of the reproductive that was removed. Finally, we discovered that reproductive-specific compounds present on the cuticle of king and queen termites were also present in their feces, but the presence of the feces did not seem sufficient to inhibit the increased head-butting after the reproductives were removed. Collectively, these results indicate that termite workers readily detect the loss of reproductives in their colony and that they at least initially respond in a non sex-specific manner.     

Disinhibition as a mechanism of tuning of cross-like figures in the visual cortex neurons

A discrete neural net was used for simulation of cross-sensitivity in 40% of neurones of the cat visual cortex' area 17th. It is based on disinhibition of the end-stopping inhibition in receptive field from the side-disinhibitory zone. Highly selective or invariant sensitivity of the simulated neurone in respect to shape and orientation of a cross-like figure was observed under changes of location, size and weight of the receptive field zones. The disinhibitory mechanism seems to be critically involved in the selection of the second-order features of the images in the primary visual cortex.