Figure 9.

Schematic diagram of the proposed mechanism of action of β-endorphin to inhibit LHRH release by suppressing the activity of NOS and activating the release of GABA that by GABA_A receptors blocks the stimulatory action of NO on the LHRH terminals. For further explanation see text. βEn, β-endorphin neuron; NOn, NOergic neuron; NEn, noradrenergic neuron; GABAn, GABAergic neuron; LHRHn, LHRH neuron; GC, guanylyl cyclase; Cyclo, cyclooxygenase; PV, hypophyseal portal vessel, + or ↑, stimulates; −, inhibits.