Neuroscience
-
This study was done to investigate the effects of acute intermittent hypoxia (IH) on metabolic factors associated with energy balance and body weight, and on hypothalamic satiety-inducing pathways. Adult male Sprague-Dawley rats were exposed to either 8h IH or normoxic control conditions. Food intake, locomotion and body weights were examined after IH. ⋯ In addition, POMC-expressing neurons were activated as determined by immediate early gene FRA-1/2 expression. Finally, ERK1/2 and its phosphorylation were reduced in response to IH. These data suggest that IH induces significant alterations to body energy balance through changes in the secretion of leptin which exert effects on satiety-inducing pathways within the hypothalamus.
-
In rodents as well as in many other mammalian and non-mammalian species, the arginine-vasopressin (AVP) system includes a parvocellular sexually dimorphic portion located within the bed nucleus of the stria terminalis (BST), the medial amygdaloid nucleus (MeA) and the lateral septum. In this system, males have more cells and denser projections than females, neurons show androgen and estrogen receptors, and gonadal hormones are required for the activation. However, the role of these hormones for the differentiation of the system is not clear. ⋯ To elucidate the role of androgens on differentiation and functioning of AVP parvocellular system, we compared male and female rats with a non-functional mutation of androgen receptor (Tfm, testicular feminization mutation) to their control littermates. Our data show that the lack of a functional androgen receptor significantly decreases the expression of AVP immunoreactivity within the BST and MeA of male Tfm. Thus supporting the hypothesis that androgens, through the action of their receptor, should have a relevant role in the organization and modulation of the AVP parvocellular sexually dimorphic system.
-
Although surgical trauma activates the anterior pituitary gland and elicits an increase in prolactin (PRL) serum levels that can modulate nociceptive responses, the role of PRL and the PRL-receptor (PRL-R) in thermal and mechanical hyperalgesia in postoperative pain is unknown. Acute postoperative pain condition was generated with the use of the hindpaw plantar incision model. Results showed endogenous PRL levels were significantly increased in serum, operated hindpaw and spinal cords of male and female rats 24h after incision. ⋯ Studies in KO mice showed no effect of PRL and PRL-R gene ablation on heat and cold hyperalgesia in male mice, while heat hyperlgesia were reduced 3-72 h post-surgery in female PRL and PRL-R KO mice. In contrast, PRL and PRL-R ablations significantly attenuated mechanical allodynia 3-72 h post-surgery in both male and female mice. Overall, we found elevated PRL levels in serum, hindpaws and spinal cords after incision, and identify a contributory role for the PRL system in postoperative pain responses to thermal stimuli in females and to mechanical stimuli in both males and females.
-
Strychnine-sensitive glycine receptors are activated by glycine and facilitate chloride influx into neurons. Glycinergic transmission might be either mediated by synaptic or extrasynaptic glycine receptors. While phasic neurotransmission is provided by a synaptic pathway, activation of extrasynaptic glycine receptors induces tonic inhibition. The glycine transporter 2 (GlyT2) regulates the uptake of glycine into presynaptic boutons. It is not determined yet, whether inhibition of GlyT2 by ALX 1393 can produce inhibition of spinal motoric networks and, whether phasic or tonic glycinergic inhibition is mostly enhanced. ⋯ GlyT2 inhibition induced glycinergic tonic currents, which might be the underlying mechanism for the observed suppression of spontaneous action potential activity by ALX 1393 in the spinal ventral horn. Silencing neuronal action potential activity by blocking GlyT2 might be a novel principle to inhibit locomotor circuits in the ventral horn area and to induce muscle relaxation.
-
Reconsolidation refers to the destabilization/re-stabilization process upon memory reactivation. However, the parameters needed to induce reconsolidation remain unclear. Here we evaluated the capacity of memory retrieval to induce reconsolidation of object recognition memory in rats. ⋯ We observed that ani impaired reconsolidation in the absence of retrieval. Therefore, stored memory underwent reconsolidation even though it was not recalled. These results indicate that retrieval and reconsolidation of object recognition memory are independent processes.