# name
Phenotyping of sigma-1 receptor knock-out rodents

# metadata.dc.contributor.other[].value
Universitat de Barcelona. Departament de Farmacologia, Toxicologia i Química Terapèutica

# metadata.dc.description.abstract[].value
[eng] The  sigma-1  receptor  is  a  chaperone  that  is  primarily  expressed  in  the  mitochondria-associated endoplasmic reticulum (MAM). It was cloned years ago from different tissues of various species and its structure has been recently elucidated.In  2003,  our  laboratory  generated  the  first  knock-out  (KO)  mouse  for  the  sigma-1 receptor. These mice served to demonstrate the involvement of the sigma-1 receptor in acute and chronic pain. In addition to pain, the sigma-1 receptor has been implicated in other  physiological  processes  and  pathological  conditions  including  depression  and  addiction.  The  sigma-1  receptor  has  also  been  shown  to  be  associated  with  the  regulation of other proteins, including dopamine (DAT) transporter. In  this  work,  the  generation  of  a  sigma-1  receptor  KO rat  model  is  reported.   The behavioural  response  of  sigma-1  KO  mice  in  two  models  of  depression  has  been  characterized,  and  the  physiological  and  behavioural  phenotyping  of  sigma-1  KO  rats  has been carried out, with special attention to the possible effects of the absence of the receptor in models of depression and addiction. By  means  of  CRISPR  /  Cas9  technology,  two  KO  strains  for  the  sigma-1  receptor  with  deletions  of  218bp  and 7bp were  obtained.  Wild-type  (WT)  and  the  two  KO  strains  showed no significant differences in the Irwin test, spontaneous locomotor activity, open field  test,  startle  response,  or  pre-pulse  inhibition.  In  contrast,  the  results  obtained  in  response to mechanical or thermal stimulation led us to select the strain with a deletion of 218bp. Using this strain, WT (+/+), KO heterozygous (+/-) and KO homozygous (-/-) rats were phenotyped. No significant differences were found in growth or survival curves, nor  in  most  of  the  assessed  physiological  or  behavioural  parameters.  Regarding  depression, no significant difference was found in the acute study after administration of fluoxetine  (an  antidepressant  with  sigma-1  affinity)  or  venlafaxine  (without  sigma-1 affinity) on the day of the test. This was an expected outcome, based on the literature and  previous  findings  regarding  the  ineffectiveness  of  antidepressants  in  an  acute  treatment.  In  the  sub-acute  study,  the  tendency  for  lower  immobility  during  training  observed  in  mice  was  confirmed.  On  test  days  1  and  7,  neither  fluvoxamine  nor  venlafaxine showed any efficacy in reducing immobility. In contrast, at day 14, the two antidepressants significantly reduced immobility only in KO rats. Given that there is no sigma-1 receptor in these rats and that both antidepressants showed activity, regardless of  whether  they  had  sigma-1  affinity,  it  seems  that  the  efficacy  may  be  due  to  some  change in their action on SERT.Regarding locomotor activity, as a surrogate measure of addictive potential, the set of results seems to indicate a greater role of the sigma-1 receptor in the rearing activity, especially as stereotyped behaviour, rather than its merely exploratory activity, being the difference  between  the  two  genotypes  mainly  at  high  doses.  There  have  been  fewer  differences   in   locomotor   activity   and,   surprisingly,   no   differences   after   cocaine   administration, that has a sigma-1 affinity. Differences between mobility and rearing can be assigned to the dopaminergic pathways involved, meso-limbic for mobility, and nigro-striatal for stereotypes.In conclusion, in rats, deletion of the gene encoding the sigma-1 receptor generates a viable  phenotype  very  similar  to  the  WT  strain  under  normal  conditions.  Behavioural  response  under  conditions  of  environmental  stimulation  and  /  or  pharmacological  treatment,  reveals  some  differences  between  WT  and  KO,  in  both  mice  and  rats.  The  absence of the receptor seems to lead to the adaptation of other proteins. The results further  support  the  concept  that  the  sigma-1  receptor  may  be  involved  in  the  development of depression and addiction and drugs acting on sigma-1 receptors could be useful in such pathologies.

# metadata.dc.description.abstract[].value
[cat] The  sigma-1  receptor  is  a  chaperone  that  is  primarily  expressed  in  the  mitochondria-associated endoplasmic reticulum (MAM). It was cloned years ago from different tissues of various species and its structure has been recently elucidated.In  2003,  our  laboratory  generated  the  first  knock-out  (KO)  mouse  for  the  sigma-1 receptor. These mice served to demonstrate the involvement of the sigma-1 receptor in acute and chronic pain. In addition to pain, the sigma-1 receptor has been implicated in other  physiological  processes  and  pathological  conditions  including  depression  and  addiction.  The  sigma-1  receptor  has  also  been  shown  to  be  associated  with  the  regulation of other proteins, including dopamine (DAT) transporter. In  this  work,  the  generation  of  a  sigma-1  receptor  KO rat  model  is  reported.   The behavioural  response  of  sigma-1  KO  mice  in  two  models  of  depression  has  been  characterized,  and  the  physiological  and  behavioural  phenotyping  of  sigma-1  KO  rats  has been carried out, with special attention to the possible effects of the absence of the receptor in models of depression and addiction. By  means  of  CRISPR  /  Cas9  technology,  two  KO  strains  for  the  sigma-1  receptor  with  deletions  of  218bp  and 7bp were  obtained.  Wild-type  (WT)  and  the  two  KO  strains  showed no significant differences in the Irwin test, spontaneous locomotor activity, open field  test,  startle  response,  or  pre-pulse  inhibition.  In  contrast,  the  results  obtained  in  response to mechanical or thermal stimulation led us to select the strain with a deletion of 218bp. Using this strain, WT (+/+), KO heterozygous (+/-) and KO homozygous (-/-) rats were phenotyped. No significant differences were found in growth or survival curves, nor  in  most  of  the  assessed  physiological  or  behavioural  parameters.  Regarding  depression, no significant difference was found in the acute study after administration of fluoxetine  (an  antidepressant  with  sigma-1  affinity)  or  venlafaxine  (without  sigma-1 affinity) on the day of the test. This was an expected outcome, based on the literature and  previous  findings  regarding  the  ineffectiveness  of  antidepressants  in  an  acute  treatment.  In  the  sub-acute  study,  the  tendency  for  lower  immobility  during  training  observed  in  mice  was  confirmed.  On  test  days  1  and  7,  neither  fluvoxamine  nor  venlafaxine showed any efficacy in reducing immobility. In contrast, at day 14, the two antidepressants significantly reduced immobility only in KO rats. Given that there is no sigma-1 receptor in these rats and that both antidepressants showed activity, regardless of  whether  they  had  sigma-1  affinity,  it  seems  that  the  efficacy  may  be  due  to  some  change in their action on SERT.Regarding locomotor activity, as a surrogate measure of addictive potential, the set of results seems to indicate a greater role of the sigma-1 receptor in the rearing activity, especially as stereotyped behaviour, rather than its merely exploratory activity, being the difference  between  the  two  genotypes  mainly  at  high  doses.  There  have  been  fewer  differences   in   locomotor   activity   and,   surprisingly,   no   differences   after   cocaine   administration, that has a sigma-1 affinity. Differences between mobility and rearing can be assigned to the dopaminergic pathways involved, meso-limbic for mobility, and nigro-striatal for stereotypes.In conclusion, in rats, deletion of the gene encoding the sigma-1 receptor generates a viable  phenotype  very  similar  to  the  WT  strain  under  normal  conditions.  Behavioural  response  under  conditions  of  environmental  stimulation  and  /  or  pharmacological  treatment,  reveals  some  differences  between  WT  and  KO,  in  both  mice  and  rats.  The  absence of the receptor seems to lead to the adaptation of other proteins. The results further  support  the  concept  that  the  sigma-1  receptor  may  be  involved  in  the  development of depression and addiction and drugs acting on sigma-1 receptors could be useful in such pathologies.

# metadata.dc.source[].value
Tesis Doctorals - Departament - Farmacologia, Toxicologia i Química Terapèutica

# metadata.dc.title[].value
Phenotyping of sigma-1 receptor knock-out rodents