Somatostatin has been suggested to play a role in the transmission of neurotransmitters and in the modulation of pain. Of the different subtypes of somatostatin receptors 2, sstr2A and sstr2B are important in the modulation and transmission of pain. The present study was carried out to investigate sstr2 immunoreactivity in rat.

Dorsal root ganglia (DRG) cells at the L4-L6 levels of the spinal cord of 10 rats (Sprague-Dawley, 200-250 g) were examined for sstr2 by immunohistochemistry.

In the control group, sstr2A immunoreactivity was strongly positive in the dense network within laminae I and II of the dorsal horn at spinal levels (L4-L6). In contrast to sstr2A, sstr2B immunoreactivity was observed throughout laminae III-VI. In the DRG, sstr2A and sstr2B immunoreactivities were mainly found in medium-sized neurons.

The distribution of sstr2A immunoreactive cells among sstr2 in the dorsal root ganglia (L4-6) resembles that of somatostatin. Incontrast to sstr2A, sstr2B immunoreactivity showed a different distribution. The presence of sstr2A at laminae I and II, and sstr2B at laminae III-VI of the dorsal horn may modulate sensory functions at these different regions of the spinal cord. Considering different actions according to the receptors of the neurotransmitter, the functions of the isoforms of sstr2 appear variable in terms of modulating and transmitting pain.