Hypothalamo-hypophysial neurosecretory system of the Indian mud-eel Amphipnous cuchia (Ham.) with a note on the regeneration of the pituitary stalk after hypophysectomy.

The nucleus preopticus (NPO) of Amphipnous cuchia is in the shape of an inverted-L-; the dorsal half of which constituted by the large neurons is the pars magnocellularis (PMC) and the ventral half formed of small cells is called pars parvocellularis (PPC). These cells are stained with aldehyde fuchsin, lead haematoxylin, chrome-alum-haematoxylin and alcian blue. The neurons of the NPO and nucleus lateralis tuberis (NLT) are positive to ascorbic acid test and axons could be traced into both anterior and posterior neurohypophysis. As the NLT neurons lie on the pathway of preoptico-neurohypophysial tract, they come in close contact with NPO axons. The axonal tract entering the pituitary ramifies into the adenohypophysis; more extensively in the pars intermedia where they have perivascular endings. Hypothalamo-hypophysial neurosecretory tract could be demonstrated with Golgi-Cox impregnation technique also. However, all the AF-positive axons do not seem to react positively to Golgi-Cox. In some cases, hypophysectomy is followed by the reorganisation of the proximal cut end of the stalk into a neurohypophysislike organ which is directed backwards. Occasionally some of the cut axons exhibited apparent uncontrolled growth. Hypophysectomy is accompanied by degeneration of some neurons in the PMC.