2015: IR: Social isolation is associated with reduced neurogenesis, impaired spatial working memory performance, and altered anxiety levels in male rats

Famitafreshi, Hamidreza; Karimian, Morteza; Fanaei, Hamed; Attari, Fatemeh; Sulail Fatima.  Open Access Animal Physiology; Macclesfield Vol. 7, (2015): 87-95. DOI:10.2147/OAAP.S84327

Abstract:

"Background: Social isolation has some adverse behavioral effects. It has been shown that neurogenesis is essential for improvement of behavioral function. The aim of this study was to examine the effects of social isolation on neurogenesis, brain-derived neutrotrophic factor levels, learning abilities, and anxiety levels in rats.

Methods: Twenty male Sprague-Dawley rats were randomly divided into two groups, ie, an isolated group and a socialized group. After a 7-day adaption period, the animals received intraperitoneal bromodeoxyuridine (BrdU) 50 mg/kg for 14 days. Two types of memories were examined: spatial working memory using the Morris water maze and short-term memory using the Y-maze. Anxiety levels were examined using the elevated plus maze. Neurogenesis was assessed by immunostaining brain sections with anti-BrdU antibody.

Results: Neurogenesis was significantly reduced in the isolated group (10 cells/400×) as compared with the socialized group (232 cells/400×). Memory performance was markedly reduced in isolated animals than in socialized animals (working memory 50.87 seconds vs 31.71 seconds; reference memory 55.44 seconds vs 39.73 seconds; and in probe trials 24.72 seconds vs 18.11 seconds). Y-maze performance remained unchanged between the two groups (71.41 seconds vs 64.97 seconds). Anxiety levels were reduced in isolated animals, as indicated by more time spent in the open arms (73 seconds vs 11 seconds) and a higher number of entries into the open arms (4.1 vs 1.4) of the elevated maze. BDNF levels decreased significantly more in the isolated group than in the socialized group (467±37.69 vs 370.7±12.19, P=0.0311).

Conclusion: These results show that social isolation has adverse effects on the hippocampus and learning abilities, and may make one more susceptible to brain diseases like depression and Alzheimer’s disease."