It is generally acknowledged that humans display highly variable sensitivity to pain, including variable responses to identical injuries or pathologies. The possible contribution of genetic factors has, however, been largely overlooked. An emerging rodent literature documents the importance of genotype in mediating basal nociceptive sensitivity, in establishing a predisposition to neuropathic pain following neural injury, and in determining sensitivity to pharmacological agents and endogenous antinociception. One clear finding from these studies is that the effect of genotype is at least partially specific to the nociceptive assay being considered. In this report we begin to systematically describe and characterize genetic variability of nociception in a mammalian species, Mus musculus. We tested 11 readily-available inbred mouse strains (129/J, A/J, AKR/J, BALB/cJ, C3H/HeJ, C57BL/6J, C58/J, CBA/J, DBA/2J, RIIIS/J and SM/J) using 12 common measures of nociception. These included assays for thermal nociception (hot plate, Hargreaves' test, tail withdrawal), mechanical nociception (von Frey filaments), chemical nociception (abdominal constriction, carrageenan, formalin), and neuropathic pain (autotomy, Chung model peripheral nerve injury). We demonstrate the existence of clear strain differences in each assay, with 1.2 to 54-fold ranges of sensitivity. All nociceptive assays display moderate-to-high heritability (h2 = 0.30-0.76) and mediation by a limited number of apparent genetic loci. Data comparing inbred strains have considerable utility as a tool for understanding the genetics of nociception, and a particular relevance to transgenic studies.

Clinical pain syndromes, and experimental assays of nociception, are differentially affected by manipulations such as drug administration and exposure to environmental stress. This suggests that there are different 'types' of pain. We exploited genetic differences among inbred strains of mice in an attempt to define these primary 'types'; that is, to identify the fundamental parameters of pain processing. Eleven randomly-chosen inbred mouse strains were tested for their basal sensitivity on 12 common measures of nociception. These measures provided for a range of different nociceptive dimensions including noxious stimulus modality, location, duration and etiology, among others. Since individual members of inbred strains are identical at all genetic loci, the observation of correlated strain means in any given pair of nociceptive assays is an index of genetic correlation between these assays, and hence an indication of common physiological mediation. Obtained correlation matrices were subjected to multivariate analyses to identify constellations of nociceptive assays with common genetic mediation. This analysis revealed three major clusters of nociception: (1) baseline thermal nociception, (2) spontaneously-emitted responses to chemical stimuli, and (3) baseline mechanical sensitivity and cutaneous hypersensitivity. Many other nociceptive parameters that might a priori have been considered closely related proved to be genetically divergent.

The evoked expression of the immediate early gene (IEG)-encoded proteins c-Fos and Krox-24 was used to monitor spinal visceronociceptive processing that results from cyclophosphamide cystitis in behaving rats. Animals received a single dose of 100 mg/kg i.p. of cyclophosphamide and survived for 30 min to 5 h. Longer survival times were not considered because of ethical considerations. Cyclophosphamide-injected animals developed characteristic behavioral signs in parallel with development of bladder lesions and spinal evoked expression of IEG-encoded proteins. Histological examination of the urinary bladder was used to evaluate the degree of cystitis and as a criterion for selection of groups of animals to be quantitatively analyzed. Controls consisted of freely behaving animals including control (un-injected), sham (saline-injected) or diuretic (furosemide-injected) animals. Behavioral modifications consisted of lacrimation, piloerection, assumption of a peculiar "rounded-back" posture, which was accompanied by head immobility and various brief "crises" (tail hyperextension, abdominal retractions, licking of the lower abdomen, backward withdrawal movements). Abnormal behaviors, which first appeared (lacrimation, piloerection) at the end of postinjection hour 1, progressively increased in severity (rounded-back posture) over the following 90 min to reach a plateau at about postinjection hour 2; the rounded-back posture was maintained up to time of death. Histological modifications of bladder tissue were assessed using a 4-grade scale in a blind setting. The 1st grade consisted of control or sham animals with no bladder lesion; 2nd grade, animals with simple chorionic edema; 3rd grade, animals with chorionic edema associated with mucosal abrasion, fibrin deposit, and onset of polymorphonuclear leukocyte infiltration; 4th grade, animals with complete cystitis corresponding to an increase in severity and spread of all the signs of cystitis described above plus petechial hemorrhage. Simple chorionic edema was observed from 30 min to 3 h postinjection, but with a progressive increase in severity over time. Edema accompanied by epithelial abrasion was observed for animals that survived 3-4 h postinjection; complete inflammation was observed in animals that survived 4-5 h postinjection. The study of c-Fos- and Krox-24-encoded protein expression demonstrated that few lumbosacral spinal areas were specifically involved in the processing of visceral inputs in response to bladder stimulation. These areas were the parasympathetic column (SPN), the dorsal gray commissure (DGC as the caudal extent of lamina X), and superficial layers of the dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS)

The simple and automatable nature of CP cystitis using hypolocomotion as a dependent measure renders it an attractive model in which to investigate the genetic and physiological bases of visceral pain. Comparison of strain sensitivity to CP induced hypolocomotion with other nociceptive assays suggests that genes specific to visceral nociception may exist.

Olfactory neurons (ON) which are located in the olfactory epithelium are responsible of odorous molecule detection. A unique feature of these cells is their continuous replacement throughout life due to the proliferation and differentiation of local neural precursors, the basal cells. Thus, experimental destruction of all ON induces a stimulation of basal cell division followed by tissue regeneration. The fact that ON precursors display such proliferative and neurogenic activity in adults makes these cells particularly attractive as a potential tool for nervous system repair. However, basal cell proliferation and, thus, ON production, decrease in relation to age; mostly during the first months of life. Therefore, we aimed to seek whether the ability of ON precursors to yield new functional ON in regenerative conditions was consequently impaired in adult. ZnSO4 intranasal perfusion administered to young (1 month) and adult (6 months) mice leads in a few days to total ON destruction and to hyposmia. Tissue and function restoration occurred in the following weeks in both mice groups and was preceded by a transient peak of cell division. In adults, although neurogenesis in the impaired olfactory epithelium was less efficient than in young mice, neural precursors retain their ability to provide new functional ON as indicated by the butanol detection recovery. This was achieved more rapidly than total ON regeneration, suggesting that a reduced number of reconnected ON may be sufficient for odor discrimination.

The evoked expression of the immediate early gene-encoded proteins c-Fos and Krox-24 was used to study activation of hindbrain neurons as a function of the development of cyclophosphamide (CP) cystitis in behaving rats. CP-injected animals received a single dose of 100 mg/kg i.p. under transient volatile anesthesia and survived for 1 to 4 h in order to cover the whole postinjection period during which the disease develops. CP-injected groups included: (1) animals with minor simple chorionic edema, an early characteristic of inflammation (1 h postinjection); (2) animals with well-developed simple chorionic edema (2 h postinjection); (3) animals with mild inflammation (chorionic edema accompanied by epithelial cleavage; 3 h postinjection); and (4) animals with complete inflammation (4 h postinjection). In addition to onset of chorionic edema, the earliest postinjection period also included the general aspects of the nervous reaction consecutive to the injection process (handling, transient volatile anesthesia and postanesthesia awakening, abdominal pinprick, CP-blood circulating effects). Controls included both noninjected animals and saline-injected animals surviving for the same times as CP-injected ones. Quantitative results come from c-Fos expression. It has been shown that: (1) saline injection is a significant stimulus for only nucleus O and central gray pars alpha and nucleus medialis of the dorsal vagal complex; (2) all structures driven by CP injection (nucleus O and central gray pars alpha, locus coeruleus, Barrington's nucleus and parabrachial area mostly in its ventral and lateral subdivisions, dorsal vagal complex, ventrocaudal portion of lateral bulbar reticular formation) responded vigorously shortly after injection, but only two (dorsal vagal complex, ventrocaudal portion of lateral bulbar reticular formation) showed increased or renewed activity when cystitis completely developed, i.e., when noxious visceral inputs reached highest levels. Regarding the sequential activation of these structures in relation to postinjection time, evidence is given that: (1) a large variety of hindbrain structures are differentially involved in either the general reaction consecutive to the injection process or to various degrees of cystitis; (2) these structures extend from the brain-spinal cord to the pons-mesencephalon transitional junction levels; (3) the two structures most powerfully driven by visceronociceptive inputs are also the most caudal ones, being located at the brain-spinal cord junction level; and (4) the dorsal vagal complex could be the main hindbrain visceral pain center, with three particular subdivisions, the nucleus medialis, nucleus commissuralis, and ventralmost part of area postrema, being involved.

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Macroautophagy is a highly conserved cellular degradation process, regulated by autophagy-related (atg) factors, in which a double membrane autophagosome engulfs cytoplasmic components to target them for degradation. In yeast, the Atg8 protein is indispensable for autophagosome formation. In mammals, this is complicated by the presence of six Atg8 homologues grouped into the GABARAP and MAP1LC3 subfamilies. Although these proteins share a high similarity, their transcript expression, regulation and protein interactions differ, suggesting they may display individual properties and specific functions. GABARAPL1/GEC1 is a member of the GABARAP subfamily and its mRNA is the most highly expressed Atg8 homologue in the central nervous system. Consequently, we performed an in depth study of GABARAPL1 distribution in the developing and adult murine brain. Our results show that GABARAPL1 brain expression is visible as early as embryonic day 11 and progressively increases to a maximum level in the adult. Immunohistochemical staining was detected in both fibers and immature neurons in embryos but was restrained to neurons in adult tissue. By E17, intense punctate-like structures were visible and these accumulated in cortical primary neurons treated with the autophagosome/lysosome fusion inhibitor Bafilomycin A1 (Baf A1), suggesting that they represent autophagosomes. Finally, GABARAPL1 expression was particularly intense in motoneurons in the embryo and in neurons involved in somatomotor and neuroendocrine functions in the adult, particularly in the substantia nigra pars compacta, a region affected in Parkinson's disease. Our study of cerebral GABARAPL1 protein expression provides insight into its role in the development and homeostasis of the mouse brain.