Effects of sex steroids on the concentrations of some brain neurotransmitters in male and female rats: some new observations.

ABSTRACT

Concentrations of some neurotransmitters, viz. noradrenaline (NA), 5-hydroxytryptamine (5-HT), dopamine (DA), histamine (H) and gamma aminobutyric acid (GABA) in a part of brain consisting of medulla, pons, mid brain, thalamus and hypothalamus were measured in ovariectomized (OVx), intact (+Te) and castrated male (Tex) rats both without injecting estrogen (E) or E and progesterone (P) as well as after E and E+P administration. Some effects, (which, as far as we are aware of) have not been previously reported, were noted (in addition to other already documented observations). These include (i) castration in males causes a fall of the level of GABA, NA, 5-HT and DA, (ii) E therapy also causes fall of the levels of GABA, NA and 5-HT and thus E therapy produces similar results like those of bilateral orchidectomy, (iii) P therapy not only reverses the fall of (GABA) but raises it more than the normal value, (iv) P therapy, it appears (although faintly), retrieve to some extent the fall of NA level due to E therapy, (v) Like the OVx rats, castrated as well as intact rats also showed a fall in the 5-HT level with E treatment but showed a rise when treated by E followed by P, (vi) In between the castrated males and castrated females, the concentrations of all these brain neurotransmitters differ. The probable significances have been discussed.