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

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.