The development of differential mabQ113-immunoreactivity in the rat habenular complex.

Monoclonal antibody mabQ113 selectively labels a subset of Purkinje cells which are arranged in parasagittal bands throughout the vermis and hemispheres of the rat cerebellar cortex. No other cerebellar cell types are immunoreactive. By contrast, in the remainder of the brain the mabQ113 epitope is located primarily in glial cells. In general, the glial immunoreactivity is not differentially distributed. An exception is that mabQ113 densely and uniformly stains the lateral habenula (LHb) but gives no labelling of the medial habenula (MHb). During cerebellar development, the mabQ113 epitope is expressed in three stages. Before postnatal day 7 (P7) all Purkinje cells are negative. Secondly, all Purkinje cells become mabQ113+ between P7 and P12. The parasagittal bands are created between P12 and P30 by selective suppression of epitope expression. To explore whether epitope suppression is also responsible for differential staining patterns in other brain regions the ontogenic development of mabQ113 immunoreactivity has been mapped in the habenular complex. Neither the MHb nor the LHb express the mabQ113 epitope prenatally. P1 is the first age at which the LHb is stained. During the next few days the intensity of staining within the LHb steadily increases until the adult pattern is attained at P6. At no time is there expression of the mabQ113 antigen in the MHb. This also confirms that the two classes of habenular astrocytes, mabQ113-/GFAP+ and mabQ113+/GFAP+, are intrinsically different throughout postnatal life.