Ismael Jiménez-Estrada

The transfection of BDNF to dopamine neurons potentiates the effect of dopamine D3 receptor agonist recovering the striatal innervation, dendritic spines and motor behavior in an aged rat model of Parkinson's disease.

The progressive degeneration of the dopamine neurons of the pars compacta of substantia nigra and the consequent loss of the dopamine innervation of the striatum leads to the impairment of motor behavior in Parkinson’s disease. Accordingly, an efficient therapy of the disease should protect and regenerate the dopamine neurons of the substantia nigra and the dopamine innervation of the striatum. Nigral neurons express Brain Derived Neurotropic Factor (BDNF) and dopamine D3 receptors, both of which protect the dopamine neurons. The chronic activation of dopamine D3 receptors by their agonists, in addition, restores, in part, the dopamine innervation of the striatum. Here we explored whether the over-expression of BDNF by dopamine neurons potentiates the effect of the activation of D3 receptors restoring nigrostriatal innervation. Twelve-month old Wistar rats were unilaterally injected with 6-hydroxydopamine into the striatum. Five months later, rats were treated with the D3 agonist 7-hydroxy-N,N-di-n-propy1-2-aminotetralin (7-OH-DPAT) administered i.p. during 4½ months via osmotic pumps and the BDNF gene transfection into nigral cells using the neurotensin-polyplex nanovector (a non-viral transfection) that selectively transfect the dopamine neurons via the high-affinity neurotensin receptor expressed by these neurons. Two months after the withdrawal of 7-OH-DPAT when rats were aged (24 months old), immunohistochemistry assays were made. The over-expression of BDNF in rats receiving the D3 agonist normalized gait and motor coordination; in addition, it eliminated the muscle rigidity produced by the loss of dopamine. The recovery of motor behavior was associated with the recovery of the nigral neurons, the dopamine innervation of the striatum and of the number of dendritic spines of the striatal neurons. Thus, the over-expression of BDNF in dopamine neurons associated with the chronic activation of the D3 receptors appears to be a promising strategy for restoring dopamine neurons in Parkinson’s disease.

Neuropeptides as neuroprotective agents: Oxytocin a forefront developmental player in the mammalian brain

Oxytocin (OT) plays a major role in the establishment of social bonds. Social bonds are linked to the activation of cell signaling pathways that promote neurotrophic and synaptic maturation, plasticity and memory changes. Anti-social behavior is often associated with abnormalities of cell signaling pathways and/or defective function of brain neurotransmitters within behavioral CNS circuits due to unproper environmental and social factors, such as, diet, stress, chemical, air pollution, and noise, during gestational period or/and during early postnatal development. OT exerts an important regulatory functions in maternity and parental behaviors, lactation, attachment, bonding, trust, and sensorial functions such as: homeostatic cardiovascular control, satiety, touch, pain, analgesia and sexual behavior. Noteworthy, OT displays important neuroprotective properties against fetal programmed hypertension when administered during early postnatal life, added to its known anabolic properties shown in adult rats, e.g. body weight control, reduces blood pressure, and increases analgesia. This review focuses on the new evidences supporting OTs role as a major neuroprotective nonapeptide provided by its quality to reverse hypertension programmed in utero by undernutrition.

Effect of multiparity on morphometry and oestrogen receptor expression of pelvic and perineal striated muscles in rabbits: is serum oestradiol relevant?

OBJECTIVE To determine changes in morphometry and expression of oestrogen receptors (OR) in the pubococcygeus and bulbospongiosus muscles, and the concentration of serum oestradiol associated with multiparity. STUDY DESIGN Twelve chinchilla-breed female rabbits were divided into multiparas who had undergone four consecutive deliveries and age-matched virgin nulliparas. Pubococcygeus and bulbospongiosus muscles were surgically removed from each rabbit and processed histologically. Fibre cross-sectional area, number of peripheral nuclei, and expression of ORα and ORβ were measured for each muscle. Serum samples were obtained and the concentration of serum oestradiol was quantified. RESULTS Multiparity increased (p ≤ 0.05) fibre cross-sectional area and the number of peripheral nuclei per fibre in pubococcygeus muscle, but not in bulbospongiosus muscle. Expression of both ORα and ORβ was high (p ≤ 0.05) in both muscles from multiparous rabbits. A rise in serum oestradiol was measured at the end of the second pregnancy, which was absent (p ≤ 0.05) at the end of the fourth pregnancy. The concentration of serum oestradiol was similar (p > 0.05) in nulliparous and multiparous rabbits. CONCLUSIONS Multiparity caused morphometric changes in pubococcygeus muscle but not in bulbospongiosus muscle. As OR expression was high for both muscles, some properties related to fibre composition or muscle physiology could be affected. The finding that serum oestradiol was not elevated at the end of the fourth pregnancy could be related to changes in pelvic and perineal muscles associated with multiparity.

Hypothyroidism affects differentially the cell size of epithelial cells among oviductal regions of rabbits.

Oviductal regions show particular histological characteristics and functions. Tubal pathologies and hypothyroidism are related to primary and secondary infertility. The impact of hypothyroidism on the histological characteristics of oviductal regions has been scarcely studied. Our aim was to analyse the histological characteristics of oviductal regions in control and hypothyroid rabbits. Hypothyroidism was induced by oral administration of methimazole (MMI) for 30 days. For both groups, serum concentrations of thyroid and gonadal hormones were determined. Sections of oviductal regions were stained with the Massons trichrome technique to analyse both epithelial and smooth muscle layers. The percentage of proliferative epithelial cells (anti-Ki67) in diverse oviductal regions was also quantified. Data were compared with Student t-test, Mann-Whitney U-test, or Fischers test. In comparison with the control group, the hypothyroid group showed: (i) a low concentration of T3 and T4, but a high level of TSH; (ii) similar values of serum estradiol, progesterone and testosterone; (iii) a large size of ciliated cells in the ampulla (AMP), isthmus (IST) and utero-tubal junction (UTJ); (iv) a large size of secretory cells in the IST region; (v) a low percentage of proliferative secretory cells in the fimbria-infundibulum (FIM-INF) region; and (vi) a similar thickness of the smooth muscle layer and the cross-sectional area in the AMP and IST regions. Modifications in the size of the oviductal epithelium in hypothyroid rabbits could be related to changes in the cell metabolism that may impact on the reproductive functions achieved by oviduct.

Early social isolation provokes electrophysiological and structural changes in cutaneous sensory nerves of adult male rats

Sensory and social deprivation from the mother and littermates during early life disturbs the development of the central nervous system, but little is known about its effect on the development of the peripheral nervous system. To assess peripheral effects of early isolation, male rat pups were reared artificially in complete social isolation (AR); reared artificially with two same‐age conspecifics (AR‐Social); or reared by their mothers and with littermates (MR). As adults, the electrophysiological properties of the sensory sural (SU) nerve were recorded. We found that the amplitude and normalized area (with respect to body weight) of the compound action potential (CAP) response provoked by single electrical pulses of graded intensity in the SU nerves of AR animals were shorter than the CAP recorded in SU nerves from MR and AR‐Social animals. The slope of the stimulus‐response curve of AR SU nerves was smaller than that of the other nerves. The histological characterization of axons in the SU nerves was made and showed that the myelin thickness of axons in AR SU nerves was significant lower (2–7µm) than that of the axons in the other nerves. Furthermore, the area and axon diameter of SU nerves of both AR and AR‐Social animals were significant lower than in MR animals. This is the first report to show that maternal and littermate deprivation by AR disturbs the development of the myelination and electrophysiological properties of axons in the SU nerve; the replacement of social cues prevents most of the effects.

Fiber type characterization of striated muscles related to micturition in female rabbits

Pelvic and perineal striated muscles are relevant for reproduction and micturition in female mammals. Damage to these muscles is associated with pelvic organ prolapse and stress urinary incontinence. The fiber type composition of skeletal muscle influences the susceptibility for damage and/or regeneration. The aim of the present study was to determine the fiber type composition of a perineal muscle, the bulbospongiosus, and a pelvic muscle, the pubococcygeus. Both muscles were harvested from adult female rabbits (8-10 months old). NADH-TR (nicotinamide adenine dinucleotide tetrazolium reductase) histochemistry was undertaken to identify oxidative and glycolytic muscle fibers. Alkaline (pH 9.4) ATP-ase (actomyosin adenosine triphosphatase) histochemistry was used to classify type I, type IIb or type IIa/IId muscle fibers. Results showed that the content of glycolytic fibers in the bulbospongiosus muscle was higher than that of oxidative fibers. Meanwhile, the opposite was true for the pubococcygeus. In the bulbospongiosus muscle, the content of type IIb muscle fibers was higher than that of type I, but was similar to that of type IIa/IId. In contrast, the content of each fiber type was similar in the pubococcygeus muscle. The relative proportion of fibers in bulbospongiosus and pubococcygeus muscles is consistent with their function during voiding and storage phases of micturition.

Effect of chronic undernourishment on the cord dorsum potentials and the primary afferent depolarization evoked by cutaneous nerves in the rat spinal cord.

The effect of chronic undernourishment on the cord dorsum potentials (CDPs) and the dorsal root potential (DRP), closely related to primary afferent depolarization (PAD) and presynaptic inhibition in the spinal cord of the rat, was analyzed in this study. Single electrical pulses applied to the sural nerve (SU) of control (n=14) and chronically undernourished (n=16) Wistar rats produced CDPs, which are composed of four components: afferent volley (AV), two negative components (N(1) and N(2)), and one positive component (P wave) and negative DRPs recorded in a small rootlet of the L6 segment of the rat. The CDPs of the control and undernourished rats with AV components of comparable amplitude (U(AV)/C(AV)=0.96), showed N(1) components of similar amplitude (U(N1)/C(N1)=0.94), but smaller P wave (U(PW)/C(PW)=0.23). A comparable reduction in the amplitude of the DRPs was obtained in the undernourished rats (U(DRP)/C(DRP)=0.36). When normalized as a function of the body mass of the animals, the CDPs and DRPs produced in undernourished rats were of significantly smaller normalized amplitude than those evoked in the control. According to these results, it is suggested that chronic undernourishment induce a depressive effect on the mechanisms generating the P wave component in the CDP and the DRPs either by decreasing the sensory input and/or the excitability of the dorsal horn neurones involved in the generation of PAD and presynaptic inhibition in the spinal cord of the rat.

Cord Dorsum Potentials Evoked by Electroacupuncture Applied to the Hind Limbs of Rats

The longitudinal distribution of the cord dorsum potentials (CDPs) produced by electroacupuncture (EA) stimulation at acupuncture points (APs) located on the hind limbs of rats was analyzed in this study. Single electrical pulses (0.05 ms, 1 Hz) applied to the bladder (BL) and the gallbladder (GB) APs produced CDPs on several spinal segments and were composed of the following four components: an afferent volley, two negative components (N1 and N2), and one positive component (P wave). The larger evoked CDPs differed in their rostrocaudal distributions depending on the stimulated AP site, with those evoked by GB32-33 (at L3) and GB36-37 (at L4) being more caudal than those generated by BL58-59 (at L5) and BL37-38 (at L6). The CDPs produced by stimulating nonacupoints (NAPs) showed similar components and rostrocaudal distributions that were smaller in amplitude than those evoked by stimulating APs. The CDPs produced by stimulating NAPs located on a meridian acupuncture area were similar in amplitude and longitudinal distribution to those produced by stimulating APs. Our results suggest that the specificity of EA stimulation for CDPs responses is mainly related to an activation of meridian pathways associated with peripheral nerve routes rather than to a restricted point specificity of APs.

The effect of chronic undernourishment on the synaptic depression of cutaneous pathways in the rat spinal cord

The aim of this study was to determine the effect of chronic undernourishment on the amplitude depression of the first negative component in the cord dorsum potentials (N(1)-CDPs) caused by the conditioning stimulation of sensory cutaneous nerves in the rat spinal cord. Single electrical pulses (1Hz; 2 times threshold) applied to the sural (SU) nerve of control rats (n=14) produced CDPs with a first negative component (N(1)-CDPs) larger in amplitude (14.2±1.3%, p<0.01) than those recorded in chronically undernourished rats (n=14; 3 times threshold). The conditioning stimulation of the SP nerve (4 shocks at 300Hz, 3×T) in the control rats (n=5) evoked a long-lasting (~200ms) depression of the N(1)-CDP (60.2±7.2%). In contrast such depression was smaller in magnitude (42.5±5.7%, p<0.01) and time course (100-120ms) in undernourished rats (n=7). The systemic application of picrotoxin (PTX) reduced, but did not abolish the conditioned depression of the N(1)-CDPs and DRPs in both the control and undernourished rats. By assuming that the depression of the N(1)-CDPs is representative of presynaptic mechanisms, it is proposed that chronic undernourishment influence the activation of presynaptic neuronal pathways that regulate the transmitter release of cutaneous afferent fibers in the spinal cord and such effect could act as a compensatory mechanism that counterbalances the decreased activation of spinal neurons by the reduced afferent input in the rat.

Fiber type composition of pubococcygeus and bulbospongiosus striated muscles is modified by multiparity in the rabbit

We analyzed the effect of multiparity on the fiber type composition of two skeletal muscles involved in the maintenance of the micturition process, the pelvic pubococcygeus (Pc) and perineal bulbospongiosus (Bs) muscles in nulliparous and multiparous rabbits (Oryctolagus cuniculus).