Figure 6. Summary of factors known for their ability to modulate LHRH neuronal activity from either LHRH cell bodies or nerve terminals. These factors however do not necessarily all have direct influence on LHRH neurons because of the absence of neuronal projections surrounding these cells. They can indirectly modulate the activity of the neurons responsible of the reproductive function via other neuronal pathways. Filled red arrows, stimulatory effect; Dashed blue arrows, inhibitory effect. The dual effect described for some factors is essentially dependent on the circulating sex steroid levels. AII, angiotensin II; AVP, vasopressin; b-END, b-endorphin; CRF, corticotropin-releasing factor; DA, dopamine; DSIP, d-sleep-inducing peptide; DYN, dynorphin; E, epinephrine; EOP, endogenous opioid peptides; GABA, gamma-aminobutyric acid; GAL, galanin; 5-HT, serotonin; IL-1, interleukin-1; NE, norepinephrine; NPY, neuropeptide Y; OT, oxytoxin; SP, subtance P; SRIF, somatotropin release-inhibiting factor; VIP, vasoactive intestinal peptide.