GABA antagonists reverse the somatostatin dependent attenuation of rat locomotor activity

Somatostatin infusion in rat ventral pallidum (VP) led to the attenuation of locomotor activity (Marazioti, A., Kastellakis, A., Antoniou, K., Papasava, D., Thermos, K., 2005. Somatostatin receptors in the ventral pallidum/substantia innominata modulate rat locomotor activity. Psychopharmacology 181, 319-326). In the present study, we investigated the putative circuitry involved in somatostatin's actions by examining the involvement of GABAergic neurotransmission in locomotor activity subsequent to somatostatin's infusion into the VP. Male Sprague-Dawley rats, 300-350 g, were used for all experiments. Saline or somatostatin (240 ng/0.5 microl/side) in the absence or presence of bicuculline (GABA-A antagonist; 5 mg/kg/ml, i.p.; 120 ng/side nucleus accumbens (NAc)) or phaclofen (GABA-B antagonist; 10 mg/kg/ml, i.p.; 120 ng/side NAc) were infused bilaterally, and the locomotor activity measured for 60 min using a rectangular activity cage. Somatostatin infused in the VP decreased the locomotor activity of the rat in a statistically significant manner. Bicuculline (i.p., and in the NAc) and phaclofen (only i.p.) reversed SRIF's actions, when administered prior to somatostatin's infusion in the VP. The present study provides further information on somatostatin's involvement in the VP-NAc circuitry, and implicates the GABAergic system in somatostatin's actions in the VP.