My thoughts are pretty different from Mr. Devendra.
When interest rates are lowered, following things are expected to happen:
1. Corporates can raise cheaper debts which lowers their interest costs and thereby increases their profitability. This increased profitability pulls investors to markets and thus sens*x rises.
2. When interest rates are high, investors get good returns from Bank FDs. Thus, they dont invest in equities. But when interest rates are lowered, they have to come to equity markets to get good returns. Thus, the sens*x rises.
People borrowing to invest in equities is primarily a bad idea. I am not saying that people are not doing it, but the percentage of people doing so is very low. Thus, the main reasons for rise in sens*x could be as stated above.
Regards