TY - JOUR
T1 - Social enrichment attenuates nigrostriatal lesioning and reverses motor impairment in a progressive 1-methyl-2-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease
AU - Goldberg, Natalie R.S.
AU - Fields, Victoria
AU - Pflibsen, Lacey
AU - Salvatore, Michael F.
AU - Meshul, Charles K.
N1 - Funding Information:
Support was from the Department of Veterans Affairs Merit Review Program to CKM, and the Edward P Stiles Trust Fund – LSUHSC – Shreveport and Biomedical Research Foundation of NW Louisiana to MFS. We also thank Deborah Finn for consultation regarding statistical analyses.
PY - 2012/3
Y1 - 2012/3
N2 - Environmental enrichment has been shown to be both neuroprotective and neurorestorative in 1-methyl-2-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models of Parkinson's disease (PD). However, whether social interaction or novel physical stimulation is responsible for this recovery is controversial. In the current study, we have investigated the effects of only social enrichment (SocE) in progressively MPTP-lesioned mice. After mice were lesioned using a progressively increased dose (4. mg/kg, 8. mg/kg, 16. mg/kg and 32. mg/kg; each dose daily for 5. days), the MPTP-induced behavioral deficits, after the 32. mg/kg dose, were reversed with acute l-DOPA. This acute behavioral recovery suggests that this progressive MPTP-induced neurodegeneration is an appropriate murine model of PD. Mice were housed four per cage for the first 2. weeks of progressive lesioning or vehicle treatment. After the 8. mg/kg MPTP dose (prior to SocE intervention) mice showed a significant decrease in rearing and foot fault behaviors (FF/BB) compared to the vehicle group. Additionally, there was a 38% decrease in mean number of tyrosine hydroxylase immunoreactive (TH-ir) substantia nigra pars compacta (SNpc) neurons/section, and a 50% decrease in the optical density of TH-ir dorsolateral caudate putamen (CPu) terminals compared to the vehicle group. Mice were then housed either two (socially limited environment; SLE) or twelve (SocE) mice per cage during continued MPTP lesioning for the next 2. weeks at 16. mg/kg and 32. mg/kg MPTP. MPTP treatment was then discontinued, while mice remained in the SLE or SocE cages for an additional week. Rearing behavior was further impaired in SLE-MPTP mice following progressive MPTP, accompanied by additional decreases in the mean number of TH-ir SNpc neurons/section and CPu TH-ir terminals. CPu TH and dopamine transporter (DAT) protein expression, as well as dopamine tissue and TH protein levels was significantly decreased compared to either vehicle group. However, the deficit in rearing behavior in SLE-MPTP mice was reversed with acute l-DOPA following the intervention period. SocE-MPTP mice showed rearing and FF/BB behaviors similar to vehicle levels, although FF/BB was not significantly different from pre-intervention levels. The reversal from pre-intervention rearing deficits was correlated with an attenuated decrease in the mean number of SNpc TH-ir neurons/section and CPu TH and DAT protein, and with a blocked decrease in CPu TH-ir terminals compared to pre-intervention levels. Our findings show that SocE mice not only resist further nigrostriatal lesioning and FF/BB deficit, but rearing behavior is recovered to the level of the vehicle group despite continued MPTP treatment. In contrast, SLE mice showed continued loss of nigrostriatal TH-ir and decline of motor behaviors with progressive MPTP. The data suggest that non-pharmacological intervention that started at an early stage of dopamine loss is effective at slowing or blocking further nigrostriatal degeneration.
AB - Environmental enrichment has been shown to be both neuroprotective and neurorestorative in 1-methyl-2-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models of Parkinson's disease (PD). However, whether social interaction or novel physical stimulation is responsible for this recovery is controversial. In the current study, we have investigated the effects of only social enrichment (SocE) in progressively MPTP-lesioned mice. After mice were lesioned using a progressively increased dose (4. mg/kg, 8. mg/kg, 16. mg/kg and 32. mg/kg; each dose daily for 5. days), the MPTP-induced behavioral deficits, after the 32. mg/kg dose, were reversed with acute l-DOPA. This acute behavioral recovery suggests that this progressive MPTP-induced neurodegeneration is an appropriate murine model of PD. Mice were housed four per cage for the first 2. weeks of progressive lesioning or vehicle treatment. After the 8. mg/kg MPTP dose (prior to SocE intervention) mice showed a significant decrease in rearing and foot fault behaviors (FF/BB) compared to the vehicle group. Additionally, there was a 38% decrease in mean number of tyrosine hydroxylase immunoreactive (TH-ir) substantia nigra pars compacta (SNpc) neurons/section, and a 50% decrease in the optical density of TH-ir dorsolateral caudate putamen (CPu) terminals compared to the vehicle group. Mice were then housed either two (socially limited environment; SLE) or twelve (SocE) mice per cage during continued MPTP lesioning for the next 2. weeks at 16. mg/kg and 32. mg/kg MPTP. MPTP treatment was then discontinued, while mice remained in the SLE or SocE cages for an additional week. Rearing behavior was further impaired in SLE-MPTP mice following progressive MPTP, accompanied by additional decreases in the mean number of TH-ir SNpc neurons/section and CPu TH-ir terminals. CPu TH and dopamine transporter (DAT) protein expression, as well as dopamine tissue and TH protein levels was significantly decreased compared to either vehicle group. However, the deficit in rearing behavior in SLE-MPTP mice was reversed with acute l-DOPA following the intervention period. SocE-MPTP mice showed rearing and FF/BB behaviors similar to vehicle levels, although FF/BB was not significantly different from pre-intervention levels. The reversal from pre-intervention rearing deficits was correlated with an attenuated decrease in the mean number of SNpc TH-ir neurons/section and CPu TH and DAT protein, and with a blocked decrease in CPu TH-ir terminals compared to pre-intervention levels. Our findings show that SocE mice not only resist further nigrostriatal lesioning and FF/BB deficit, but rearing behavior is recovered to the level of the vehicle group despite continued MPTP treatment. In contrast, SLE mice showed continued loss of nigrostriatal TH-ir and decline of motor behaviors with progressive MPTP. The data suggest that non-pharmacological intervention that started at an early stage of dopamine loss is effective at slowing or blocking further nigrostriatal degeneration.
KW - Dopamine
KW - MPTP
KW - Social enrichment
KW - Striatum
KW - Tyrosine hydroxylase
UR - http://www.scopus.com/inward/record.url?scp=84856574257&partnerID=8YFLogxK
U2 - 10.1016/j.nbd.2011.12.024
DO - 10.1016/j.nbd.2011.12.024
M3 - Article
C2 - 22198503
AN - SCOPUS:84856574257
SN - 0969-9961
VL - 45
SP - 1051
EP - 1067
JO - Neurobiology of Disease
JF - Neurobiology of Disease
IS - 3
ER -