Differential Effect on Two Immobility Responses by Chronic Administration of 1,3-di-o-Tolyl-Guanidine (Sigma Receptor Agonist) in Rats with Neonatal Ventral Hippocampal Lesion

The effect of chronic administration of the sigma agonist: 1,3-di-o-tolyl-guanidine (DTG), in neonatal ventral hippocampal lesioned (nVHL) rats, on the immobility by clamping and dorsal immobility, were investigated. The nVHL increases the duration of immobility by clamping, but does not affect the duration of the dorsal immobility. We found that DTG augments the duration of the dorsal immobility in the unlesioned rats, but does not modify the duration of immobility induced by clamping the neck. DTG also counteracts the increase in the duration of the immobility by clamping produced by nVHL. However, the increase in the duration of the dorsal immobility produced by DTG is counteracted by nVHL. These results are discussed with respect to the differential effect on the two immobility responses tested, suggesting that they are different forms of immobility mediated by different mechanisms although they behaviorally share common characteristics.