Role of the pineal gland in neuroendocrine responses to conditioned fear stimuli in rats

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ROLE OF THE PINEAL GLAND IN NEUROENDOCRINE

RESPONSES TO CONDITIONED

FEAR

STIMULI IN RATS

KMJI YAGI, TATSUSHI ONAKA

Department of Physiology, Jichi Medical School, Minamikawachi-machi,

Tochigi-ken 329-0498

Conditioned fear stimuli inhibit vasopressin (VP) and facilitate oxytocin (OT) or prolactin (PRL) release from the pituitary. To determine the role of pineal gland in these neuroendocrine fear responses, we conducted experiments with pinealectomy, melatonin administrations and electrical lesions of the suprachiasmatic nucleus in male rats. Rats of Wistar strain were trained with foot shocks (0.8 mA, I s) and tested, on the following day, with environmental

stimuli in the box where they had

received shocks, Conditioned fear stimuli decreased plasma VP and increased OT concentrations in pinealectomised as well as sham-operated control rats. Melatonin injected i.p. 20 min before testing stimuli at a dose of 0.3 mg per kg body weight did not impair VP or OT responses to conditioned fear stimuli. Lesion of the suprachiasmatic nucleus. however, prevented VP but not OT or PRL responses to conditioned fear stimuli. The results suggest that the pineal gland does not play an essential role in neuroendocrine

responses to conditioned fear stimuli. Impairment of VP responses after suprachismatic nucleus lesions

might have been due to destruction of passing-through fibres rather than neurones in the suprachiasmatic nucleus.

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RELATIONSHIP HORMONES

YIMU YANG’, HITOSHI ‘Dept.

of Anatomy

Kamigyo-ku,

and

OF NADPH-DIAPHORASE

ACTIVITY

IN THE RAT HYPOTHALAMUS OZAWA’, KAZUNARI Neurobiology,

Kyoto 602-0841,

Kyoto

‘Dept of Anotomy,

WITH POSTERIOR

OF POSTNATAL

YURI’, and MITSUHIRO Prefectural

Univ

of

PITUITARY

DEVELOPMENT

KAWATA’ Medicine.,

Kochi Univ of Medicine., Okatoyo-cho,

Kawaramachi-Hirokoji, Nangoku 783-0043

Recently it has been suggested that nitric oxide (NO) Plays an important role in developing central nerve system. To elucidate the functional role of NO in developing brain, we studied the relationship between NADPH-diaphorase activity (NADPH-d) and vasopressin (AVP) or oxytocin (OXT) containing neurons in the postnatal (P) rat of the hypothalamus using combinations with enzyme histochemistry and immunohistochemistry in adjacent sections. Coexistence of NADPH-d with AVP or OXT was not detected until P14 in the supraoptic nucleus (SON) nor in the paraventricullar nucleus (PVN). However, 20% of NADPH-d positive neurons were immunopositive to AVP, and 28% of those were immunopositive to OXT in the SON at P21 as the same pattern of adult rats. On the other hand, 22% of NADPH-d positive neurons exhibited the AVP-immunoreactivity at the P21 in the PVN, being similar to adult (23.1%). Moreover, the coexistence of NADPH-d and OXT-immunoreactivity was about 34% in the PVN. These results indicate that NADPH-d activity may be related to OXT secretory function but not involved in AVP secretory function in postnatal development of the hypothalamus.

515

DISTRIBUTIONS OF FOS AND NADPH-D POSITIVE NEURONS OF RAT HYPOTHALAMlC PARAVENTRICULAR NUCLEUS AFTER TNTRAPERITONFAL ADMINISTRATION OF IL-l D

KAZUNARI TODAKA’, YASUSHI ISHIDAl, YUTA ISHIZUKA’~~, TOSHIKAZU NISHIMORl* AND HIROSHI KANNAN3 1Depts. of Psychiatry, *Biology, 3Physiology. Miyazaki Medical College, Kiyotake-cho, Miyazak-gun,

Miyazaki 889-

1692 Double staining for Fos and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) was used to investigate the distribution of activated neurons that synthesize nitric oxide in the hypothalamic paraventricular nucleus (PVN) after intraperitoneal administration of interleukin- 1D (IL- IO; 4 pg/kg). The Fos positive neurons were detected predominantly in the parvocellular part, while the NADPH-d neurons were detected predominantly in the magnocellular part of PVN. In a quantitative analysis, the number of Fos positive neurons significantly increased, whereas the number of NADPH-d neurons did not change after IL-la administration. Furthermore, the percentage of neurons positive to both NADPH-d and Fos within the PVN was significantly increased. The data suggest that a part of NADPH-d neurons was activated after systemic administration of IL-1 g, however, most of activated neurons were negative to NADPH-d in the parvocellular part of PVN.